Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Country：Japan

Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d3cc02297h

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/d3dt01491f

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Donor-pi-acceptor fluorophores that consist of an electron-donating amino group and an electron-accepting triarylborane moiety generally exhibit substantial solvatochromism in their fluorescence while retaining high fluorescence quantum yields even in polar media. Herein, we report a new family of this compound class, which bears ortho-P(=X)R-2-substituted phenyl groups (X=O or S) as a photodissociative module. The P=X moiety that intramolecularly coordinates to the boron atom undergoes dissociation in the excited state, giving rise to dual emission from the corresponding tetra- and tricoordinate boron species. The susceptibility of the systems to photodissociation depends on the coordination ability of the P=O and P=S moieties, whereby the latter facilitates dissociation. The intensity ratios of the dual emission bands are sensitive to environmental parameters, including temperature, solution polarity, and the viscosity of the medium. Moreover, precise tuning of the P(=X)R-2 group and the electron-donating amino moiety led to single-molecule white emission in solution.

DOI： 10.1002/anie.202303725

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)  

The visualization of complex biological events in living cells is highly reliant on the development of sophisticated fluorescent probes with multiple functions. Herein, we report a general synthetic strategy for the synthesis of near-infraredemissive phospharhodamines (PORs) bearing various types of aryl groups on their bridging phosphorus atoms. This versatile approach utilizes a Ni-catalyzed P-arylation that allows for the design of POR-based multi-functionalized fluorescent probes. We found that PORs substituted with an aminophenyl group exhibited pH-responsive fluorescence intensity, where photo-induced electron transfer occurs to quench the fluorescence. The combination of our new approach with conventional modification at the 9-position of the xanthene skeleton facilitates the development of multi-functionalized fluorescent probes. As one demonstration of this method, we synthesized a fluorescence probe that can selectively visualize the lysosomes that result from endosomal maturation.

DOI： 10.1246/bcsj.20230082

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/jacs.2c08372

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Language：English  

DOI： 10.1002/anie.202209391

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.3389/fchem.2022.990918

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DOI： 10.1002/chem.202103584

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DOI： 10.1002/ijc.33770

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/anie.202107647

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Language：Japanese  

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DOI： 10.1039/c6tc05208h

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DOI： 10.1002/anie.201404867

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Language：Japanese  

DOI： 10.1021/ja9071173

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Language：Japanese  

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DOI： 10.1002/chem.200601098

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Language：Japanese  

DOI： 10.1351/pac200678071413

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DOI： 10.1021/ja038487+

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.15252/embj.2022112573

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/anie.202302714

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

Abstract

Fullerenes are compelling molecular materials owing to their exceptional robustness toward multi-electron reduction. Although scientists have attempted to address this feature by synthesizing various fragment molecules, the origin of this electron affinity remains unclear. Several structural factors have been suggested, including high symmetry, pyramidalized carbon atoms, and five-membered ring substructures. To elucidate the role of the five-membered ring substructures without the influence of high symmetry and pyramidalized carbon atoms, we herein report the synthesis and electron-accepting properties of oligo(biindenylidene)s, a flattened one-dimensional fragment of fullerene C₆₀. Electrochemical studies corroborated that oligo(biindenylidene)s can accept electrons up to equal to the number of five-membered rings in their main chains. Moreover, ultraviolet/visible/near-infrared absorption spectroscopy revealed that oligo(biindenylidene)s exhibit enhanced absorption covering the entire visible region relative to C₆₀. These results highlight the significance of the pentagonal substructure for attaining stability toward multi-electron reduction and provide a strategy for the molecular design of electron-accepting π-conjugated hydrocarbons even without electron-withdrawing groups.

DOI： 10.1038/s41467-023-38300-3

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Other Link： https://www.nature.com/articles/s41467-023-38300-3

Language：English   Publishing type：Research paper (scientific journal)  

We report the thermodynamic and kinetic aqueous self-assembly of a series of amide-functionalized dithienyldiketopyrrolopyrroles (TDPPs) that bear various hydrophilic oligoethylene glycol (OEG) and hydrophobic alkyl chains. Spectroscopic and microscopic studies showed that the TDPP-based amphiphiles with an octyl group form sheet-like aggregates with J-type exciton coupling. The effect of the alkyl chains on the aggregated structure and the internal molecular orientation was examined via computational studies combining MD simulations and TD-DFT calculations. Furthermore, solvent and thermal denaturation experiments provided a state diagram that indicates the formation of unexpected nanoparticles during the self-assembly into nanosheets when longer OEG side chains are introduced. A kinetic analysis revealed that the nanoparticles were obtained selectively as an on-pathway intermediate state toward the formation of thermodynamically controlled nanosheets. The metastable aggregates were used for seed-initiated supramolecular assembly, which allowed establishing control over the assembly kinetics and the aggregate size. The sheet-like aggregates prepared using the seeding method exhibited coherent vibration in the excited state, indicating a well-ordered orientation of the TDPP units. These results underline the significance of fine tuning of the hydrophobic/hydrophilic balance in the molecular design to kinetically control the assembly of amphiphilic π-conjugated molecules into two-dimensional nanostructures in aqueous media.

DOI： 10.1021/jacs.2c07299

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/anie.202209394

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/chem.202200728

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The design of magnetic topological states due to spin polarization in an extended pi carbon system has great potential in spintronics application. Although magnetic zigzag edges in graphene nanoribbons (GNRs) have been investigated earlier, real-space observation and manipulation of spin polarization in a heteroatom substituted system remains challenging. Here, we investigate a zero-bias peak at a boron site embedded at the center of an armchair-type GNR on a AuSiX/Au(111) surface with a combination of low-temperature scanning tunneling microscopy/spectroscopy and density functional theory calculations. After the tip-induced removal of a Si atom connected to two adjacent boron atoms, a clear Kondo resonance peak appeared and was further split by an applied magnetic field of 12 T. This magnetic state can be relayed along the longitudinal axis of the GNR by sequential removal of Si atoms.

DOI： 10.1021/acsnano.2c04563

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

We report on the fluorescence properties of a new class of emissive and stable pi-radicals that contain a boron atom at a position distant from the radical center. A fully planarized derivative exhibited an intense red fluorescence with high fluorescence quantum yields (Phi(F) > 0.67) even in polar solvents. To elucidate the origin of this phenomenon, we synthesized another boron-stabilized radical that contains a bulky aryl group on the boron atom. A comparison of these derivatives, as well as with conventional donor-rr-acceptor (D-pi-A)-type emissive pi-radicals, unveiled several characteristic features in their photophysical properties. A theoretical analysis revealed that the SOMO-LUMO electronic transition generates an emissive D-1 state. Unlike conventional D-pi-A-type pi-radicals, this state does not undergo significant structural relaxation. The boron-stabilized pi-radicals demonstrated promising potential for organic light-emitting diodes as an emitting material.

DOI： 10.1002/anie.202201965

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1038/s41467-022-30153-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

The asymmetric oxidation of a sulfur-containing nine-membered heterocycle was achieved for the late-stage introduction of chirality to the substituents of π-electron systems.

DOI： 10.1039/d1cc06996a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Planarized triarylboranes are attracting increasing attention not only as models of boron-doped graphenes, but also as promising materials for organic optoelectronics. In particular, polycyclic aromatic hydrocarbon (PAH) skeletons with embedded boron atom(s) in the inner positions are of importance in light of their high chemical stability and pi-stacking ability derived from their planar geometries. Herein, we disclose a robust synthesis of such fully fused boron-doped PAHs and their self-assembly behavior in aqueous media to explore their potential utility in biological applications. The synthesis using in situ-generated planar diarylboranes as a key precursor afforded a series of fully fused boron-doped PAHs, even including an amphiphilic derivative with hydrophilic side chains. These compounds exhibited red emission in solution, and slight structural modification resulted in increased fluorescence brightness. While these compounds showed relatively low Lewis acidity compared to their partially ring-fused counterparts, their Lewis acidities were slightly increased in polar solvents compared to those in nonpolar solvents. In addition, their B-N Lewis acid-base adducts, even those with a strong, charge-neutral Lewis base such as N,N-dimethylaminopyridine (DMAP), exhibited photo-dissociation behavior in the excited state. The amphiphilic derivative showed significant spectral changes with increased water content in DMSO/H2O mixed media and formed sheet-like aggregates. The disassembly and assembly processes of the aggregates were externally controlled by the addition of DMAP and an acid, accompanied by a change in the fluorescence intensity.

DOI： 10.1039/d1sc06710a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Wiley  

DOI： 10.1002/anie.202114230

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/anie.202114230

Language：English   Publishing type：Research paper (scientific journal)  

Understanding the transmission of nanoscale forces in the pico-to-nanonewton range is important in polymer physics. While physical approaches have limitations in analyzing the local force distribution in condensed environments, chemical analysis using force probes is promising. However, there are stringent requirements for probing the local forces generated before structural damage. The magnitude of those forces corresponds to the range below covalent bond scission (from 200 pN to several nN) and above thermal fluctuation (several pN). Here, we report a conformationally flexible dual-fluorescence force probe with a theoretically estimated threshold of approximately 100 pN. This probe enables ratiometric analysis of the distribution of local forces in a stretched polymer chain network. Without changing the intrinsic properties of the polymer, the force distribution was reversibly monitored in real time. Chemical control of the probe location demonstrated that the local stress concentration is twice as biased at crosslinkers than at main chains, particularly in a strain-hardening region. Due to the high sensitivity, the percentage of the stressed force probes was estimated to be more than 1000 times higher than the activation rate of a conventional mechanophore.

DOI： 10.1038/s41467-022-27972-y

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

DOI： 10.1021/acs.chemmater.1c02072

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Electron-deficient heteroacenes that contain two tricoordinate boron atoms in their acene skeletons and planarized phenyl ether moieties at their periphery were synthesized via the borylation of silicon-bridged precursors. X-ray crystallographic analysis revealed quinoidal structures, which give rise to two-step reversible redox processes for both the reduction and oxidation. These compounds exhibit intense absorption and sharp fluorescence bands with vibronic structures in the near-infrared (NIR) region. These properties originate from the push-pull effect along the long axis of the molecule derived from the electron-donating ether moieties and the electron-accepting boron moieties. Of particular note is the NIR emission of the thienothiophene-centered heteroacene, which has a maximum at 952 nm with a narrow band width of 309 cm(-1) in cyclohexane. A Franck-Condon analysis revealed the crucial role of the sterically less-hindered thienothiophene spacer in achieving this sharp emission band.

DOI： 10.1002/anie.202106642

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society ({ACS})  

DOI： 10.1021/jacs.1c04251

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

<p>A series of NIR-emissive phospha-xanthene dyes bearing an ethynyl group are reported. The late-stage functionalisation of the NIR dyes enables creation of multi-functionalised fluorescent probes that can be designed to target organelles of interest.</p>

DOI： 10.1039/d1sc01705e

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The use of donor-pi-acceptor (D-pi-A) skeletons is an effective strategy for the design of fluorophores with red-shifted emission. In particular, the use of amino and boryl moieties as the electron-donating and -accepting groups, respectively, can produce dyes that exhibit high fluorescence and solvatochromism. Herein, we introduce a dithienophosphole P-oxide scaffold as an acceptor-spacer to produce a boryl- and amino-substituted donor-acceptor-acceptor (D-A-A) pi-system. The thus obtained fluorophores exhibit emission in the near-infrared (NIR) region, while maintaining high fluorescence quantum yields even in polar solvents (e.g. lambda(em) = 704 nm and phi(F) = 0.69 in CH3CN). A comparison of these compounds with their formyl- or cyano-substituted counterparts demonstrated the importance of the boryl group for generating intense emission. The differences among these electron-accepting substituents were examined in detail using theoretical calculations, which revealed the crucial role of the boryl group in lowering the nonradiative decay rate constant by decreasing the non-adiabatic coupling in the internal conversion process. The D-A-A framework was further fine-tuned to improve the photostability. One of these D-A-A dyes was successfully used in bioimaging to visualize the blood vessels of Japanese medaka larvae and mouse brain.

DOI： 10.1039/d1sc00827g

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier {BV}  

DOI： 10.1016/j.cclet.2020.12.013

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Herein, we report the first example of two pure organic polymorphs with stimuli-responsive single/dual phosphorescence transformation. By analyzing the crystal structures and theoretical results, it could be understood that efficient intermolecular interactions could restrict the molecular movements and lock distinct molecular conformations, leading to different phosphorescence behaviors. Besides, single/dual phosphorescence could transform into each other by heating or under solvent vapor conditions. Considering such unique properties, logical sensors (AND gate and OR gate) were built by providing different emission colors as inputs. Our work provides not only important information for understanding the dual RTP mechanism but also unique stimuli-responsive pure organic phosphorescent materials to enrich material fields.

DOI： 10.1039/d0tc05468b

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report the kinetically controlled supramolecular polymerization of boron-containing p-conjugated molecules, which was enabled by a seeding method based on dual trapping of a metastable state by synergistic intramolecular hydrogen bonding and Lewis acid-based complexation. Planarized triarylborane-based 1, which bears a diamide chain with chiral alkyl groups, was synthesized. Upon cooling, the solution of monomer 1 afforded a supramolecular polymerization in a cooperative manner to form helical supramolecular nanostructures with intense J-type aggregate emission. In the presence of pyridine, the triarylborane moiety formed a Lewis acid-base complex, which enhances the stabilization of the metastable monomeric state. An assembly incompetent structure with a folded diamide chain conformation and a pyridine moiety axially coordinated to the boron atom is responsible for slowing the spontaneous aggregation. The seeding method was successfully applied to the solution to produce homogeneous nanofibers even at a high (millimolar-level) concentration. This unprecedented kinetic control via dual trapping provides an effective method to achieve seed-initiated polymerization under concentrated conditions.

DOI： 10.1021/jacs.0c13353

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The synthesis and photophysical properties of a soluble amide-embedded coronene is reported. The key step in this synthesis is the twofold C-H activation of diazaperylene by a rhodium(III)Cp* catalyst. This unprecedented structural motif shows intense fluorescence in the near infrared region with a small Stokes shift and a distinct vibronic structure, which exhibits a slight extent of negative solvatochromism. Comparison of this compound with some relevant compounds revealed the importance of the amide incorporation in the peripheral concave region including an angular position to retain high aromaticity reflecting that of parent coronene. Treatment of this compound with Lewis acid B(C6F5)(3) formed a bis-adduct, which exhibited enhanced aromaticity as a consequence of the increased double bond character of the amide C-N bonds.

DOI： 10.1002/chem.202004080

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Language：English   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/chem.202004897

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Lipid droplets (LDs) are essential organelles in most eukaryotes, and tracking intracellular LD dynamics using synthetic small molecules is crucial for biological studies. However, only a limited number of fluorescent markers that satisfy all requirements, such as the selective staining of LDs, high photostability, and sufficient biocompatibility, have been developed. Herein, we report a series of donor-p-acceptor dyes based on the thiophene-containing fused polycyclic scaffold [1]benzothieno[3,2-b][1]benzothiophene (BTBT), in which either or both thiophene rings are oxidized into thiophene-S,S-dioxide to form an electron-accepting building block. Among these dyes, LAQ1 satisfied all the aforementioned requirements and allowed us to capture ultrasmall LDs on the endoplasmic reticulum (ER) membrane by stimulation emission depletion (STED) microscopy with a super-resolution below the diffraction limit of light. Moreover, the extremely high photostability of LAQ1 enabled recording the lipolysis of LDs and the concomitant lipogenesis, as well as long-term trajectory analysis of micro-LDs at the single-particle level in living cells.

DOI： 10.1021/acsmaterialslett.0c00451

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Dithieno[a,e]penalenes (DTPs) with various substituents were synthesized as a class of antiaromatic compounds. Annulation of thiophene rings imparts the pentalene moiety with high thermal stability even without bulky substituents, while retaining antiaromaticity. The higher magnitude of antiaromaticity in DTPs, in addition to the differences in the electronic structures of the fused aromatic rings, resulted in a narrower HOMO-LUMO gap than that of the corresponding dibenzo[a,e]pentalene analog, giving rise to red-shifted electronic absorption that reaches the near-infrared region. Moreover, systematic investigations on the solid-state packing structure revealed that DTPs prefer offset face-to-face packing motifs rather than face-centered pi-pi stacking. In particular, the thienyl-substituted DTP bearing hydrophilic side chains exhibited thermochromic behavior in polar solvents, which was ascribed to the formation of aggregates.

DOI： 10.1002/chem.202004244

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Language：Japanese   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/acs.orglett.0c03771

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Seeded supramolecular polymerization of cystine-based dimeric diamides with aromatic substituents at the C- and N-termini was achieved in aqueous media. Theoretical and spectroscopic studies reveal that the terminal groups play crucial roles in slowing spontaneous assembly through formation of a folded conformation and guiding molecular alignment in the aggregated state.

DOI： 10.1039/d0cc05255h

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：OXFORD UNIV PRESS INC  

Synthetic chemical fluorescent dyes promise to be useful for many applications in biology. Covalent, targeted labeling, such as with a SNAP-tag, uses synthetic dyes to label specific proteins in vivo for studying processes such as endocytosis or for imaging via super-resolution microscopy. Despite its potential, such chemical tagging has not been used effectively in plants. A major drawback has been the limited knowledge regarding cell wall and membrane permeability of the available synthetic dyes. Of 31 synthetic dyes tested here, 23 were taken up into BY-2 cells, while eight were not. This creates sets of dyes that can serve to measure endocytosis. Three of the dyes that were able to enter the cells, SNAP-tag ligands of diethylaminocoumarin, tetramethylrhodamine, and silicon-rhodamine 647, were used to SNAP-tag alpha-tubulin. Successful tagging was verified by live cell imaging and visualization of microtubule arrays in interphase and during mitosis in Arabidopsis (Arabidopsis thaliana) seedlings. Fluorescence activation-coupled protein labeling with DRBG-488 was used to observe PIN-FORMED2 (PIN2) endocytosis and delivery to the vacuole as well as preferential delivery of newly synthesized PIN2 to the actively forming cell plate during mitosis. Together, the data demonstrate that specific self-labeling of proteins can be used effectively in plants to study a wide variety of cellular and biological processes.Multicolor imaging with SNAP-tagged tubulin and monitoring of PIN2 endocytosis with a chemical dye demonstrate that specific self-labeling of proteins can be used effectively in plants.

DOI： 10.1105/tpc.20.00439

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER PHYSICAL SOC  

Graphene nanoribbons (GNRs), low-dimensional platforms for carbon-based electronics, show the promising perspective to also incorporate spin polarization in their conjugated electron system. However, magnetism in GNRs is generally associated with localized states around zigzag edges, difficult to fabricate and with high reactivity. Here we demonstrate that magnetism can also be induced away from physical GNR zigzag edges through atomically precise engineering topological defects in its interior. A pair of substitutional boron atoms inserted in the carbon backbone breaks the conjugation of their topological bands and builds two spin-polarized boundary states around them. The spin state was detected in electrical transport measurements through boron-substituted GNRs suspended between the tip and the sample of a scanning tunneling microscope. First-principle simulations find that boron pairs induce a spin 1, which is modified by tuning the spacing between pairs. Our results demonstrate a route to embed spin chains in GNRs, turning them into basic elements of spintronic devices.

DOI： 10.1103/PhysRevLett.125.146801

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Near infrared (NIR)-emissive polymers are attractive luminescent materials due to their utilities in biological, optoelectronic, and telecommunication applications. Herein we report the use of a dialkylamine-strapped dithienylpyrrole (DTP) as an excited-state intramolecular proton transfer (ESIPT) building block for producing NIR-emissive pi-conjugated polymers. The study of a series of model compounds showed that the extension of pi-conjugation with a moderately electron-accepting comonomer unit, dithientyl-substituted thiazolo[5,4-d]thiazole (TzTz), effectively stabilizes the zwitterionic ESIPT state while increasing the oscillator strength for the electronic transition from the ESIPT state. Consequently, a polymer consisted of DTP and TzTz units exhibited a significantly red-shifted emission, exceeding 750 nm, from the ESIPT state in polar solvents.

DOI： 10.1002/ajoc.202000234

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The field of supramolecular polymers is rapidly expanding; however, the exploitation of these systems as functional materials is still elusive. To become competitive, supramolecular polymers must display microstructural order and the emergence of new properties upon copolymerization. To tackle this, a greater understanding of the relationship between monomers' design and polymer microstructure is required as well as a set of functional monomers that efficiently interact with one another to synergistically generate new properties upon copolymerization. Here, we present the first implementation of frustrated Lewis pairs into supramolecular copolymers. Two supramolecular copolymers based on p-conjugated O-bridged triphenylborane and two different triphenylamines display the formation of B-N pairs within the supramolecular chain. The remarkably long lifetime and the circularly polarized nature of the resulting photoluminescence emission highlight the possibility to obtain an intermolecular B-N charge transfer. These results are proposed to be the consequences of the enchainment of B-N frustrated Lewis pairs within 1D supramolecular aggregates. Although it is challenging to obtain a precise molecular picture of the copolymer microstructure, the formation of random blocklike copolymers could be deduced from a combination of optical spectroscopic techniques and theoretical simulation.

DOI： 10.1021/jacs.0c06921

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Super-resolution imaging techniques have become increasingly important tools to visualize suborganelle structures and dynamic processes in living cells on the nanoscale. However, the utility of these imaging techniques is currently limited by the availability of advanced fluorescent probes that enable the specific labeling of the organelle of interest and provide the absorption/emission properties required for super-resolution imaging techniques. Herein, LysoPB Yellow is presented as a new small-molecule fluorescent probe that can selectivity stain the lysosomal membrane. Its outstandingly high photostability and long fluorescence lifetime are beneficial for its use in super-resolution stimulated emission depletion (STED) microscopy. A lysosomal membrane stained with LysoPB Yellow was successfully visualized by STED imaging in living cells with a full width at half maximum (FWHM) of 70 nm, which is substantially below the diffraction limit of light. Additionally, LysoPB Yellow displayed excellent retention ability and negligible cytotoxicity. Consequently, long-term time-lapse confocal imaging of living cells was successfully conducted, which demonstrates the practical utility of LysoPB Yellow in fluorescence imaging.

DOI： 10.1021/acsmaterialslett.0c00147

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A series of phosphine oxide-bridged rhodamines (P-rhodamines) bearing various acyclic and cyclic amine moieties, including dimethyl- and diethylamine, azetidine, pyrrolidine and 7-azabicyclo[2,2,1]heptane (7ABH), have been synthesized. The photophysical properties as well as chemical and photostability of these dyes have been studied in detail. Among these dyes, the 7ABH-substituted dye shows stronger fluorescence in the near-infrared (NIR) region, relative to the other P-rhodamines. This dye could be applied to live-cell imaging, wherein lysosomes were selectively stained in a pH-independent manner. It was also found that the ring fusion of the amine moieties gives rise to remarkably redshifted spectra, with absorption and emission maxima at 770 and 820 nm, respectively, spectrally close to that of indocyanine green (ICG). Importantly, the ring-fused P-rhodamines showed much higher photostability than ICG, indicative of their promising utility as the NIR-emissive dyes.

DOI： 10.1002/chem.202000957

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Dimesitylboron-functionalized stilbene derivatives have been found to undergo an unusual regioselective photoisomerization upon irradiation at 365 nm. Using NMR to follow the photoreaction, the structures of key reaction intermediates and the final products were established. This photoisomerization occurs in four steps: trans-cis isomerization, Diels-Alder reaction, di-pi-methane rearrangement, and ring opening with [1,3]-H migration. This results in the formation of a rare structure with three fused five-membered rings and a six-membered one.

DOI： 10.1021/acs.orglett.0c01042

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

An N-phenylbenzimidazole constrained in a coplanar fashion with a methylene tether (IMAC) was designed and used to prepare a series of emitters exhibiting thermally activated delayed fluorescence (TADF). Four novel TADF emitters using 9,9-dimethylacridine, phenoxazine, phenothiazine, and bis(di-ptolylamino)carbazole as the donor group were designed and synthesized using IMAC as the acceptor. Additionally, two deepblue fluorescent emitters were prepared with carbazole and tercarbazole as the donor moieties. The twisted conformation between donor and acceptor in these molecules resulted in effective spatial separation of the HOMO and LUMO and small singlet-triplet energy gaps. Crystallographic properties, electronic structures, thermal stabilities, photophysical properties, and energy levels were studied systematically. Ultimately, these findings provide a promising opportunity for the design and synthesis of highly efficient TADF materials based on IMAC derivatives.

DOI： 10.1021/acs.joc.9b02283

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The hydrophobicity and CH/pi-interaction-driven self-assembly of an amphiphile that contains a biphenylanthracene group furnishes two-dimensional aggregates in dilute aqueous solution. A windmill-shaped molecular packing structure that arises from multiple intermolecular CH/pi interactions of the aromatic hydrocarbons is the key motif for the self-assembly into micrometer-scale nanosheets.

DOI： 10.1039/c9cc08070h

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The chemistry of the boron cation has been revitalized in the past decade due to its newfound application in stoichiometric and catalytic organic reactions. To extend the frontier of boron cation catalysis, we came to discover that a mesityl-substituted eta(5)-Cp*-coordinated boron cation could serve as a powerful Lewis acid for organic catalytic transformations. The boron cation [Cp*B-Mes][B(C6F5)(4)] ([1] [B(C6F5)(4)]) stabilized in a boronium-like electronic structure binds to Et3PO readily and displays an acceptor number exceeding that of B(C6F5)(3) on the Gutmann-Beckett acidity scale. The steric and electronic stabilization exerted by the electron-donating Cp* renders the highly Lewis acidic boron cation an easy-to-handle catalyst for hydrodeoxygenation of aryl ketones at ambient temperature. The exceptional catalytic performance of [1](+) implies that the incorporation of a coordinatively flexible substituent at boron is critical in bringing catalytic activity and stability to boron cation catalysts.

DOI： 10.1021/acs.organomet.9b00671

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Two different chromophores, namely a dipolar and an octupolar system, were prepared and their linear and nonlinear optical properties as well as their bioimaging capabilities were compared. Both contain triphenylamine as the donor and a triarylborane as the acceptor, the latter modified with cationic trimethylammonio groups to provide solubility in aqueous media. The octupolar system exhibits a much higher two-photon brightness, and also better cell viability and enhanced selectivity for lysosomes compared with the dipolar chromophore. Furthermore, both dyes were applied in two-photon excited fluorescence (TPEF) live-cell imaging.

DOI： 10.1002/chem.201902461

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Bora-fluoresceins (BFs), fluorescein analogues containing a tricoordinate boron atom instead of an oxygen atom at the 10-position of the fluorescein skeleton, were synthesized as a new family of fluorescein analogues. The deprotonated BFs exhibited absorption and fluorescence in the near-infrared region, which were significantly red-shifted relative to those of hitherto-known heteroatom-substituted fluorescein analogues on account of the orbital interaction between the tricoordinate boron atom and the fluorescein skeleton. BFs also showed multi-stage changes resulting from a Lewis acid-base equilibrium at the boron center in combination with a Bronsted acid-base equilibrium at the phenolic hydroxy group.

DOI： 10.1039/c9sc02314c

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The air-water interface, which is the boundary of two phases with a large difference in polarity, gives a distinct environment compared with bulk water or air. Since the interface provides a field for various biomolecules to work, it is important to understand the molecular behaviors at the interface. Here, polarity-independent flapping viscosity probes (FLAP) equipped with hydrophobic/hydrophilic substituents have been synthesized and studied at the air-water interface. In situ fluorescence (FL), which is related to the internal motion and orientation, of three different FLAPs were investigated at the interface, and the internal motion of the molecule was indicated to be suppressed at the interface. In addition, the molecular response was compared with that of conventional viscosity probes (molecular rotors), which indicates the different behaviors of FLAP probably due to the distinct molecular orientation as well as molecular motion.

DOI： 10.1002/asia.201900769

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATL ACAD SCIENCES  

Stimulation emission depletion (STED) microscopy enables ultrastructural imaging of organelle dynamics with a high spatiotemporal resolution in living cells. For the visualization of the mitochondria! membrane dynamics in STED microscopy, rationally designed mitochondrial fluorescent markers with enhanced photostability are required. Herein, we report the development of a superphotostable fluorescent labeling reagent with long fluorescence lifetime, whose design is based on a structurally reinforced naphthophosphole fluorophore that is conjugated with an electron-donating diphenylamino group. The combination of long-lived fluorescence and superphotostable features of the fluorophore allowed us to selectively capture the ultrastructures of the mitochondria! cristae with a resolution of similar to 60 nm when depleted at 660 nm. This chemical tool provides morphological information of the cristae, which has so far only been observed in fixed cells using electron microscopy. Moreover, this method gives information about the dynamic ultrastructures such as the intermembrane fusion in different mitochondria as well as the intercristae mergence in a single mitochondrion during the apoptosis-like mitochondrial swelling process.

DOI： 10.1073/pnas.1905924116

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PubMed

Language：Japanese   Publisher：AMER CHEMICAL SOC  

Incorporation of main group elements into the it-conjugated frameworks is a sophisticated strategy to alter the fundamental nature of the parent conjugated pi systems, giving rise to attractive electronic and photophysical properties that are otherwise inaccessible with classic carbon- or metal-based materials. Out of all irconjugated heterocycles, those that are structurally constrained by tethered aryl substituents surrounding the main group center deserve a great deal of attention because not only do they commonly possess the maximum efficiency of it -conjugation and intermolecular interaction, but they also enjoy remarkable thermal and morphological stabilities that are especially crucial for solid-state performances. In certain cases, elucidation of the behavior of such compounds may additionally provide sufficient perspective toward graphene materials doped with main group elements, which are widely considered as potential next -generation optoelectronic materials. In this review, we will specifically focus on historical developments of structurally constrained polycyclic it -electron systems particularly of those with boron, nitrogen, silicon, or phosphorus atoms annulated directly into the center of 2r -conjugated systems.

DOI： 10.1021/acs.chemrev.8b00637

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A B,N-diphenyl-5,10-dihydro-dibenzo-1,4-azaborine, in which both phenyl groups on the boron and nitrogen atoms are planarized to generate a carbazole substructure, was synthesized. The structral constraint around the boron and nitrogen atoms alters the pi-conjugation mode and thus the photophysical and electrochemical properties. Specifically, this structurally constrained dibenzoazaborine showed an intense blue emission with a narrow full width at half maximum. One of its derivatives exhibited near infrared absorption in the one-electron-oxidized state.

DOI： 10.1039/c9ob00934e

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The stability of tetracationic triarylboranes in dilute aqueous solution was investigated by tuning the steric demand of the linker in a (para-(N,N,N-trimethylammonio)xylyl)(2)B-(linker)-B(para-(N,N,N-trimethylammonio)xylyl)(2) structure. With increasing steric bulk of the linker, namely 1,4-phenylene, 2,2 '''-(3,3 '''-dimethyl)-5,2 ':5 ',2 '':5 '',5 '''-quaterthiophene, 9,10-anthracenylene, and 4,4 '''-(5 '-(3,5-dimethylphenyl))(5 ''-(3 ''',5 '''-dimethylphenyl))-2 ',2 ''-bithiophene, the stability of the compounds increased. The anthracene-based chromophore, compound 3M is water-stable for at least 48 h, is nontoxic to cells and exhibits an exceedingly high fluorescence quantum yield of 0.86 in water making it an ideal candidate for confocal live-cell imaging of lysosomes.

DOI： 10.1002/chem.201900723

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PubMed

DOI： 10.1039/c9sc00793h

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The self-assembly of an amide-functionalized dithienyldiketopyrrolopyrrole (DPP) dye in aqueous media was achieved through seed-initiated supramolecular polymerization. Temperature- and time-dependent studies showed that the spontaneous polymerization of the DPP derivative was temporally delayed upon cooling the monomer solution in a methanol/water mixture. Theoretical calculations revealed that an amide-functionalized DPP derivative adopts an energetically favorable folded conformation in the presence of water molecules due to hydration. This conformational change is most likely responsible for the trapping of monomers in the initial stage of the cooperative supramolecular polymerization in aqueous media. However, the monomeric species can selectively interact with externally added fragmented aggregates as seeds through concerted pi-stacking and hydrogen-bonding interactions. Consequently, the time course of the supramolecular polymerization and the morphology of the aggregated state can be controlled, and one-dimensional fibers that exhibit a J-aggregate-like bathochromically shifted absorption band can be obtained.

DOI： 10.1002/chem.201901382

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Language：English   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/acs.orglett.8b03964

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

It is important to understand how solute molecules align in anisotropic media such as liquid crystals and biological membranes. Alignment of fluorescent probes used in polarised fluorescence microscopy is of interest because anisotropy of the medium is indirectly estimated through the fluorescence intensity originating from the transition dipole moments fixed on the molecule. Here we report fluorescence anisotropies of a series of phosphole oxide-based dyes with an elongated pi-conjugated system, along which the transition dipole moment lies, in nematic liquid crystals. We observe that as the number, size and rigidity of substituents protruding from the pi-conjugated plane increase, the transition dipole moment tends to tilt away from the nematic director over the magic angle, similar to 54.7 degrees, showing conspicuous negative fluorescence anisotropy. Analysis of molecular shapes suggests that the substitutions modulate the interaction with the nematic mean field, impacting the direction of the principal molecular axis aligned with the nematic director.

DOI： 10.1038/s42004-018-0055-6

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The sulfur-containing nine-membered heterocycle thiacyclononene (TN) was evaluated as a new type of end-capping group for pi-conjugated systems. A systematic study on TN-capped -oligothiophenes (TNnTs; n=4-7) revealed that the capping with TN, which adopts a bent conformation, imparts the resulting oligothiophenes with drastically increased solubility at approximately 140 degrees C and high electrochemical stability, whereas the electronic structure remains virtually unperturbed. The even-numbered oligothiophenes TN4T and TN6T form characteristic offset herringbone-type packing structures on account of the steric repulsion between the TN rings and the presence of intermolecular nonbonding S center dot center dot center dot S interactions. This packing mode in combination with the high solubility enabled the solution-process fabrication of field-effect transistors based on TN6T, which exhibited a high performance without degradation even upon exposure to air.

DOI： 10.1002/chem.201802656

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A two-step synthesis to prepare tricoordinate organoboron compounds bearing three different aryl groups has been developed. After the first aryl substitution to an aryl boronic ester took place, the intermediate species, that is, bis(diarylborinate) species, was isolated as an air- and moisture-stable solid, which allowed the second aryl substitution to carry out in a selective manner. Subsequently, a series of unsymmetrical triarylboranes possessing a sterically bulky aryl group, triarylamine moiety, and para-functionalized phenyl ring was synthesized. Not only did these triarylboranes exhibit remarkable solvent-dependent fluorescence as expected for donor it acceptor (D-pi-A) systems, they were also accompanied by profound persistence against photoirradiation especially for that bearing a 1,3,5-tri-tert-butylphenyl ring. This survey exemplifies that sufficient electronic and steric modification is key to construct photostable D-pi-A type triarylborane-based fluorophores.

DOI： 10.1021/acs.joc.8b01015

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PubMed

DOI： 10.1021/acs.jpcc.8b05423

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Various fluorescence microscopy techniques require bright NIR-emitting fluorophores with high chemical and photostability. Now, the significant performance improvement of phosphorus-substituted rhodamine dyes (PORs) upon substitution at the 9-position with a 2,6-dimethoxyphenyl group is reported. The thus obtained dye PREX 710 was used to stain mitochondria in living cells, which allowed long-term and three-color imaging in the vis-NIR range. Moreover, the high fluorescence longevity of PREX 710 allows tracking a dye-labeled biomolecule by single-molecule microscopy under physiological conditions. Deep imaging of blood vessels in mice brain has also been achieved using the bright NIR-emitting PREX 710-dextran conjugate.

DOI： 10.1002/anie.201804731

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

High-quality graphene nanoribbons (GNRs) grown by on-surface synthesis strategies with atomic precision can be controllably doped by inserting heteroatoms or chemical groups in the molecular precursors. Here, we study the electronic structure of armchair GNRs substitutionally doped with di-boron moieties at the center, through a combination of scanning tunneling spectroscopy, angle resolved photoemission, and density functional theory simulations. Boron atoms appear with a small displacement toward the surface, signaling their stronger interactions with the metal. We find two boron-rich flat bands emerging as impurity states inside the GNR band gap, one of them particularly broadened after its hybridization with the gold surface states. In addition, the boron atoms shift the conduction and valence bands of the pristine GNR away from the gap edge and leave unaffected the bands above and below, which become the new frontier bands and have a negligible boron character. This is due to the selective mixing of boron states with GNR bands according to their symmetry. Our results depict that the GNR band structure can be tuned by modifying the separation between di-boron moieties.

DOI： 10.1021/acs.jpcc.8b03748

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A B-phenyldibenzo[b,f]borepin planarized with two methylene bridges was synthesized. The structural constraint on the B-phenyl group resulted in a bathochromic shift of the absorption and fluorescence properties as well as enhanced Lewis acidity. A donor--acceptor type derivative based on this scaffold exhibited intense fluorescence irrespective of the solvent polarity.

DOI： 10.1039/c8cc02837k

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Fluorophores that can undergo excited-state intramolecular proton transfer (ESIPT) represent promising scaffolds for the design of compounds that show red-shifted fluorescence. Herein, we disclose new near infrared-emissive materials based on a dialkylamine-strapped 2,5-dithienylpyrrole as an ESIPT scaffold. The introduction of electron-accepting units to the terminal positions of this scaffold generates acceptor-pi-donor-pi-acceptor (A-pi-D-pi-A) type pi-conjugated compounds. Following the ESIPT, the electron-donating ability of the core scaffold increases, which results in a substantially red-shifted emission in the NIR region, while increasing the oscillator strength. The electron-accepting units play a vital role to achieve intense and red-shifted emission from the ESIPT state. The strapped dialkylamine chain that forms an intramolecular hydrogen bond is also essential to induce the ESIPT. Moreover, an extended A-pi-D-pi-A skeleton enables two-photon excitation with the NIR light. One of the derivatives that satisfy these features, i.e., borylethenyl-substituted 5, exhibited an intense NIR emission in polar solvents such as acetone (lambda(em) = 708 nm, phi(F) = 0.55) with a strong two-photon-absorption band in the NIR region.

DOI： 10.1039/c8sc00066b

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Amino acid based diamides are widely used as a substructure in supramolecular polymers and are also key components of polypeptides that help to understand protein folding. The interplay of folding and aggregation of a diamide was used to achieve seed-initiated supramolecular polymerization. For that purpose, a pyrene-substituted diamide was synthesized in which pyrene is used as a tracer to monitor the supramolecular polymerization. Thermodynamics and time-dependent studies revealed that the folding of the diamide moiety, via the formation of intramolecular hydrogen bonds, effectively prevents a spontaneous nucleation that leads to supramolecular polymerization. Under such out-of-equilibrium conditions, the addition of seeds successfully initiates the supramolecular polymerization. These results demonstrate the utility of such amino acid based diamides in programmable supramolecular polymerizations.

DOI： 10.1002/anie.201712119

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The far-red emissive fluorescent probe CaPF-1 based on a phospha-fluorescein scaffold enables the detection of cytosolic calcium ions in living cells. The probe can be excited in the red region (lambda(abs) = 636 nm) and exhibits a sufficiently high fluorescence turn-on response in the far-red region (lambda(em) = 663 nm) upon complexation with calcium ions. The hydrophilic and anionic characteristics of this phospha-fluorescein fluorophore allowed the cytosolic localization of CaPF-1. Moreover, it was possible to visualize histamineinduced calcium oscillation in HeLa cells using CaPF-1.

DOI： 10.1039/c7cc07344e

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

B,B-Dimesityl-substituted dithieno-1,2-dihydro-1,2-diborin was synthesized and its properties and reactivity were studied. Owing to the noticeably electron-deficient and antiaromatic character of the 1,2-dihydro-1,2-diborin ring, this compound was found to homolytically cleave diatomic hydrogen (H-2) gas at ambient temperature under 1 atm to afford a hydrogen-bridged bis(borane). This reaction was accompanied by a dramatic color change from dark green to yellow in addition to a turn-on fluorescence response.

DOI： 10.1246/cl.170812

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Aromaticity of photoexcited molecules is an important concept in organic chemistry. Its theory, Baird's rule for triplet aromaticity since 1972 gives the rationale of photoinduced conformational changes and photochemical reactivities of cyclic pi-conjugated systems. However, it is still challenging to monitor the dynamic structural change induced by the excited-state aromaticity, particularly in condensed materials. Here we report direct structural observation of a molecular motion and a subsequent packing deformation accompanied by the excited-state aromaticity. Photoactive liquid crystal (LC) molecules featuring a pi-expanded cyclooctatetraene core unit are orientationally ordered but loosely packed in a columnar LC phase, and therefore a photoinduced conformational planarization by the excited-state aromaticity has been successfully observed by time-resolved electron diffractometry and vibrational spectroscopy. The structural change took place in the vicinity of excited molecules, producing a twisted stacking structure. A nanoscale torque driven by the excited-state aromaticity can be used as the working mechanism of new photoresponsive materials.

DOI： 10.1021/jacs.7b08021

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The straightforward assembly of various thiophene-fused benzosiloles is accomplished by 2-fold metalation of benzo[b]thiophenes substituted at C3 with ortho-brominated aryl groups followed by electrophilic substitution with dichlorosilanes. The method relies on the innate acidity of the C(sp(2))-H bond at C2 of benzo[b]thiophenes and the halogen-metal exchange of the proximal C(sp(2))-Br bond. The related indole- and benzofuran-annulated systems are also accessible, but these siloles are chemically less stable. An example of a thiophene-fused benzogermole is included as well.

DOI： 10.1021/acs.organomet.7b00619

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Organic neutral pi-monoradicals are promising semiconductors with balanced ambipolar carrier transport abilities, which arise from virtually identical spatial distribution of their singly occupied and unoccupied molecular orbitals, SOMO(alpha) and SOMO(beta), respectively. Herein, we disclose a boron-stabilized triphenylmethyl radical that shows outstanding thermal stability and resistance toward atmospheric conditions due to the substantial spin delocalization. The radical is used to fabricate organic Mott-insulator transistors that operate at room temperature, wherein the radical exhibits well-balanced ambipolar carrier transport properties.

DOI： 10.1021/jacs.7b05471

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A new reaction mode for triarylboranes under photochemical conditions was discovered. Photoirradiation of dimesitylboryl-substituted (hetero)arenes produced spirocyclic boraindanes, where one of the C-H bonds in the ortho-methyl groups of the mesityl substituents was formally added in a syn fashion to a C-C double bond of the (hetero)aryl group. Quantum chemical calculations and laser flash photolysis measurements indicated that the reaction proceeds through a [1,6]-sigmatropic rearrangement. This behavior is reminiscent of the photochemical reaction mode of arylalkenylketones, thus demonstrating the isosteric relation between tricoordinate organoboron compounds and the corresponding pseudo-carbocationic species in terms of pericyclic reactions. Despite the disrupted -conjugation, the resulting spirocyclic boraindanes exhibited a characteristic absorption band at relatively long wavelengths (=370400 nm).

DOI： 10.1002/anie.201706929

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The substitution of an oxygen atom in rhodols with a phosphine oxide (P=O) moiety affords P=O-bridged rhodols as a new type of near-infrared (NIR) fluorophore. This compound class can be readily accessed upon exposure of the corresponding rhodamines to aqueous basic conditions. The electron-withdrawing effect of the P=O group facilitates the hydrolytic deamination, and, moreover, prolonged exposure to aqueous basic conditions generates P=O-bridged fluoresceins, that is, a series of three P=O-bridged xanthene dyes is available in one simple operation. The P=O-bridged rhodols show significant bathochromic shifts of the longest-wavelength absorption maximum (Delta lambda = 125 nm; > 3600 cm(-1)) upon changing the solvent from toluene to water, whereas the emission is shifted less drastically (Delta lambda = 70 nm; 1600 cm @ 1). The hydrogen bonding between the P=O and C=O groups with protic solvents results in substantial stabilization of the LUMO level, which is responsible for the solvatochromism.

DOI： 10.1002/chem.201703456

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Publisher：Wiley-Blackwell  

DOI： 10.1002/ange.201706929

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Seminaphtho-phospha-fluorescein (SNAPF), a phosphine-oxide-containing unsymmetric fluorescein dye, was synthesized based on the consecutive arylation of PhPCl2, followed by Friedel-Crafts cyclization. The resulting SNAPF exhibited several attractive photo-physical properties including an intense fluorescence in the NIR region and a large Stokes shift.

DOI： 10.1039/c7cc04323f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

As stimulated emission depletion (STED) microscopy can provide structural details of cells with an optical resolution beyond the diffraction limit, it has become an indispensable tool in cell biology. However, the intense STED laser beam usually causes rapid photobleaching of the employed fluorescent dyes, which significantly limits the utility of STED microscopy from a practical perspective. Herein we report a new design of super-photostable dye, PhoxBright 430 (PB430), comprising a fully ring-fused pi-conjugated skeleton with an electron-accepting phosphole pi-oxide unit. We previously developed a super-photostable dye C-Naphox by combining the phosphole unit with an electron-donating triphenylamine moiety. In PB430, removal of the amino group alters the transition type from intramolecular charge transfer character to pi-pi* transition character, which gives rise to intense fluorescence insensitive to molecular environment in terms of fluorescence colors and intensity, and bright fluorescence even in aqueous media. PB430 also furnishes high solubility in water, and is capable of labeling proteins with maintaining high fluorescence quantum yields. This dye exhibits outstanding resistance to photoirradiation even under the STED conditions and allows continuous acquisition of STED images. Indeed, using a PB430-conjugated antibody, we succeed in attaining a 3-D reconstruction of super-resolution STED images as well as photostability-based multicolor STED imaging of fluorescently labeled cytoskeletal structures.

DOI： 10.1021/jacs.7b04418

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Structurally simple pyrazole derivatives that exhibit excited-state intramolecular proton transfer (ESIPT) were synthesized. While these compounds displayed deep violet fluorescence in solution, in the crystalline state they showed white emission from the enol and keto forms.

DOI： 10.1039/c7cc03758a

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Diindenosilole Si1, a silicon-bridged fulvalene derivative, was successfully reduced to its dianions using various alkali metals, and the structures were characterized by X-ray crystallographic analysis. Radical anions of Si1 as well as dianions of pi-extended Si3 could also be synthesized, and the structural and physical properties were systematically compared. It was also found that the NMR spectra of dianions Si1(2-) and Si3(2-) show countercation and temperature dependency for their signal broadness, indicating the possible existence of thermal interconversion between closed-shell singlet states and open-shell triplet states.

DOI： 10.1021/acs.organomet.7b00260

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A near-infrared (NIR) polymethine dye (1), consisting of a cyclohepta[1,2-b; 4,3-b'] dithiophene and two phenol moieties, was synthesized. This dye exhibited pH-responsive changes in its photophysical properties due to a two-step acid-base equilibrium that produced a protonated cation (1H(+)) and an anion (1(-)). While 1H(+) showed an intense fluorescence in the red region of the visible spectrum, 1(-) exhibited a strong absorption in the NIR region. The tropylium ion character in 1H(+) induces high pK(a1) and pK(a2) values for 1. Moreover, a stable radical (1(center dot)) was prepared, which showed a NIR absorption band with a maximum at circa 1600 nm. The cyclic voltammogram of 1(center dot) revealed a two-step reversible redox process that produced 1(-) and the cation 1(+), which is different from 1H(+). These redox processes accompany drastic electrochromic changes in the vis-NIR region. Overall, 1 is susceptible to multiple interconversions between five forms, due to the multifaceted character of the cycloheptadithiophene skeleton.

DOI： 10.1002/anie.201702140

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A variety of fluorescent molecular viscosity probes have been widely used for mapping the local viscosity in cells and for monitoring the microenvironments in materials. However, their viscosity-sensing structural design still relies strongly on molecular rotors featuring intramolecular rotational dynamics. Here we report flapping molecules (FLAP) as a ratiometric viscosity-sensing fluorophore that shows polarity-independent dual fluorescence. Viscosity-sensing mechanism is based on a unique V-shaped-to-planar conformational change in the singlet excited state (S-1), in which the flexible motion of an eight-membered ring plays an important role. Fast conformational dynamics have been studied by time-resolved spectroscopies, and the viscochromic properties have been quantitatively analyzed. Application of FLAP to monitoring the curing process of epoxy resins has also been demonstrated, in which other typical environment-sensitive dyes did not work as a local viscosity probe.

DOI： 10.1039/c7tc01533j

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

New P/N-containing -electron systems comprising fully planar biaryl arrays are synthesized by multiple radical phosphanylation. The biaryl moiety in these highly strained planar -systems is rigidified by double P-bridging. The electronic properties of the core biaryl entity are varied by introducing N-donor substituents or by installing N-atoms within the -system, thereby moving to the viologen core structure. The electrochemical and photophysical properties of these compounds are discussed and compared with those of related systems.

DOI： 10.1002/chem.201605272

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Pentalenes represent highly reactive Huckel antiaromatics with 8 pi electrons. Usually, pentalenes are stabilized by incorporation of two benzene rings in a fused fashion. In dibenzo[a,e]pentalenes, however, the high aromaticity of the fused benzene rings compromises the inherent antiaromaticity of the pentalene core. Herein, we disclose that this forfeited antiaromaticity can be restored by fusing four additional aromatic rings onto the peripheral positions of dibenzo[ a, e]pentalenes. Such polycyclic pentalenes were prepared by successive transannular cyclizations via in situ-generated tetrakisdehydro[16]annulenes. The thus obtained compounds showed intriguing properties, for example, characteristic absorptions in the visible-to-near-infrared (NIR) region and low reduction potentials. These results hence afford a design principle to produce highly antiaromatic yet stable pentalenes. The antiaromaticity of the pentalene core can be widely tuned via the degree of aromaticity of the peripherally fused rings.

DOI： 10.1002/anie.201611344

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The development of emissive liquid dyes containing trialkylsilyl groups, and their use in the preparation of fluorescent organic nanoparticles (FONs) are described. A series of trialkylsilyl-substituted pyrenes is synthesized as oils, whose viscosity depends on the nature of the alkyl groups. The neat compounds show intense excimer emission with maxima of around 460-480 nm and quantum yields of 0.5-0.7. The low viscosity (eta = 162 cP) of 2-tri((Z)-3-hexen-1-yl)silylpyrene (1) allows the preparation of spherical nanoparticles (NP1) in the presence of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol. NP1 shows a hydrodynamic diameter of 161 +/- 48 nm and maintains an excimer emission similar to that of neat 1. NP1 in water spontaneously absorbs dopant dyes into its liquid core, and simultaneous doping with two dyes is also possible. When using green-emissive C545T and red-emissive DCJTB dyes as dopants, efficient Forster resonance energy transfer (FRET) occurs from the pyrene excimer to the dyes. Extensive emission color tuning is thus achieved as evident from a plot of the emission colors of doped and undoped NP1 on the CIE 1931 xy chromaticity diagram. These results demonstrate the efficacy of the present design strategy for color-tunable FONs that do not require premixing of dopant dyes.

DOI： 10.1039/c6tc05208h

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© The Royal Society of Chemistry. The development of emissive liquid dyes containing trialkylsilyl groups, and their use in the preparation of fluorescent organic nanoparticles (FONs) are described. A series of trialkylsilyl-substituted pyrenes is synthesized as oils, whose viscosity depends on the nature of the alkyl groups. The neat compounds show intense excimer emission with maxima of around 460-480 nm and quantum yields of 0.5-0.7. The low viscosity (η = 162 cP) of 2-tri((Z)-3-hexen-1-yl)silylpyrene (1) allows the preparation of spherical nanoparticles (NP1) in the presence of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) and cholesterol. NP1 shows a hydrodynamic diameter of 161 ± 48 nm and maintains an excimer emission similar to that of neat 1. NP1 in water spontaneously absorbs dopant dyes into its liquid core, and simultaneous doping with two dyes is also possible. When using green-emissive C545T and red-emissive DCJTB dyes as dopants, efficient Förster resonance energy transfer (FRET) occurs from the pyrene excimer to the dyes. Extensive emission color tuning is thus achieved as evident from a plot of the emission colors of doped and undoped NP1 on the CIE 1931 xy chromaticity diagram. These results demonstrate the efficacy of the present design strategy for color-tunable FONs that do not require premixing of dopant dyes.

DOI： 10.1039/c6tc05208h

Scopus

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Bottom-up chemical reactions of selected molecular precursors on a gold surface can produce high quality graphene nanoribbons (GNRs). Here, we report on the formation of quantum dots embedded in an armchair GNR by substitutional inclusion of pairs of boron atoms into the GNR backbone. The boron inclusion is achieved through the addition of a small amount of boron substituted precursors during the formation of pristine GNRs. In the pristine region between two boron pairs, the nanoribbons show a discretization of their valence band into confined modes compatible with a Fabry-Perot resonator. Transport simulations of the scattering properties of the boron pairs reveal that they selectively confine the first valence band of the pristine ribbon while allowing an efficient electron transmission of the second one. Such band-dependent electron scattering stems from the symmetry matching between the electronic wave functions of the states from the pristine nanoribbons and those localized at the boron pairs.

DOI： 10.1021/acs.nanolett.6b03148

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PubMed

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1021/acs.organomet.6b00800

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A series of thiophene-fused tropylium ions, containing various electron-donating amino groups at the terminal positions, was synthesized. The fusion of the thiophene rings, as well as the presence of the terminal amino groups endows the cationic tropylium ion with excellent stability and high pK(R)(+) values. X-ray crystallographic analysis of these compounds revealed a pronounced quinoidal character for the amino-substituted dithienotropylium skeletons. These compounds exhibit attractive photophysical properties such as strong absorption in the visible region combined with red fluorescence. Theoretical calculations suggested that the 3,3'-bithiophene substructure should be crucial for attaining these photophysical properties.

DOI： 10.1002/chem.201604509

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/anie.201605221

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Liquid crystal (LC) provides a suitable platform to exploit structural motions of molecules in a condensed phase. Amplification of the structural changes enables a variety of technologies not only in LC displays but also in other applications. Until very recently, however, a practical use of LCs for removable adhesives has not been explored, although a spontaneous disorganization of LC materials can be easily triggered by light-induced isomerization of photoactive components. The difficulty of such application derives from the requirements for simultaneous implementation of sufficient bonding strength and its rapid disappearance by photoirradiation. Here we report a dynamic molecular LC material that meets these requirements. Columnar-stacked V-shaped carbon frameworks display sufficient bonding strength even during heating conditions, while its bonding ability is immediately lost by a light-induced self-melting function. The light-melt adhesive is reusable and its fluorescence colour reversibly changes during the cycle, visualizing the bonding/nonbonding phases of the adhesive.

DOI： 10.1038/ncomms12094

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Bright fluorescent molecules with long fluorescence lifetimes are important for the development of lifetime-based fluorescence imaging techniques. Herein, a molecular design is described for simultaneously attaining long fluorescence lifetime (tau) and high brightness (Phi(F) x epsilon) in a system that features macrocyclic dimerization of fluorescent p-conjugated skeletons with flexible linkers. An alkylene-linked macrocyclic dimer of bis(thienylethynyl)anthracene was found to show excimer emission with a long fluorescence lifetime (tau approximate to 19 ns) in solution, while maintaining high brightness. A comparison with various relevant derivatives revealed that the macrocyclic structure and the length of the alkylene chains play crucial roles in attaining these properties. In vitro time-gated imaging experiments were conducted as a proof-of-principle for the superiority of this macrocyclic fluorophore relative to the commercial fluorescent dye Alexa Fluor 488.

DOI： 10.1002/anie.201602239

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We report the first examples of straightforward trans-hydroboration of internal alkynes at room temperature with 9-BBN, producing five-membered BN-heterocycles. Contrary to conventional cis-hydroboration, we demonstrate that the introduction of a pyridyl group switches the stereoselectivity of the reaction. A hydride migration mechanism has been proposed and supported by DFT calculations for the trans-hydroboration. This new hydroboration approach allows facile construction of new blue fluorescent BN-heterocyclic compounds.

DOI： 10.1021/acs.orglett.5b03698

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Phospha-fluorescein (POF), a phosphine oxide-containing analogue of fluorescein, was synthesized and its photophysical properties were examined. Compared with fluorescein and sila-fluorescein, POF displayed significantly red-shifted absorption and fluorescence as well as superior photobleaching resistance, while retaining the pH-responsive characteristics of fluorescein dyes.

DOI： 10.1039/c5cc09345g

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Ladder pi-conjugated materials and also push-pull systems belong to important classes of compounds for the development of organic electronic devices. In this communication, a novel pi-conjugated material that unifies the properties of both of these classes is presented. The material comprises a rigid biphenyl framework, which bears two bridging electron-accepting phosphine oxide moieties as well as two electron-donating amino groups. The structure and photophysical properties of this compound are discussed and compared with those of a related system lacking the second P-moiety.

DOI： 10.1039/c5cc03063c

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A 9-phenylanthracene, constrained in a coplanar fashion by two methylene tethers, was synthesized and its optoelectronic properties were investigated. The rigid planarization increased its electron-donating character and induced a bathochromic shift of its absorption, as well as an increased molar absorption coefficient and intense fluorescence. These properties render this compound a promising building block for fluorescent materials.

DOI： 10.1039/c5cc08259e

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

The preparation of boron-doped nanocarbon scaffolds with well-defined structures is important for the understanding of the impact of boron doping on their properties and behavior at the molecular level. We recently succeeded in the synthesis of a structurally well-defined nanographene molecule, bearing two boron atoms at the central positions. In this study, the characteristic properties and functions of this boron-doped nanographene were investigated in terms of (1) Lewis acidity, (2) redox properties, and (3) electrode performance in a battery. This boron-doped nanographene was susceptible to chemical adsorption with various Lewis bases, resulting in significant changes in the absorption and fluorescence properties, as well as in the conformation of the honeycomb framework. The two-electron reduction of this boron-doped nanographene produced a dianionic species that showed a substantial biradical character with a triplet ground state. A Li battery electrode, composed of a boron-doped nanographene with small peripheral substituents, displayed a stable performance in the 1.5-4.0 V range with a first discharge capacity of 160 mA h g(-1). These results provide important insights into the effect of boron doping on nanocarbon compounds.

DOI： 10.1039/c5sc02246k

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The development of stimulated emission depletion (STED) microscopy represented a major breakthrough in cellular and molecular biology. However, the intense laser beams required for both excitation and STED usually provoke rapid photobleaching of fluorescent molecular probes, which significantly limits the performance and practical utility of STED microscopy. We herein developed a photoresistant fluorescent dye C-Naphox as a practical tool for STED imaging. With excitation using either a lambda = 405 or 488 nm laser in protic solvents, C-Naphox exhibited an intense red/orange fluorescence (quantum yield phi(F) > 0.7) with a large Stokes shift (circa 5900 cm(-1)). Even after irradiation with a Xe lamp (300 W, lambda(ex) = 460 nm, full width at half maximum (FWHM) = 11 nm) for 12 hours, 99.5 % of C-Naphox remained intact. The high photoresistance of C-Naphox allowed repeated STED imaging of HeLa cells. Even after recording 50 STED images, 83 % of the initial fluorescence intensity persisted.

DOI： 10.1002/anie.201507939

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

Fluorophores with intramolecular charge-transfer (ICT) character in the excited state exhibit significant solvatochromism of their fluorescence. Here, we report an example for such compounds, a benzophosphole P-oxide bearing an electron-donating p-(diphenylamino)phenyl group at the 3-position. While this compound shows only subtle dependence of the absorption maximum on the solvent polarity (lambda(max) = 383-392 nm), its emission maximum is significantly red-shifted upon increasing the solvent polarity (cyclohexane: lambda(em) = 457 nm; DNIF: lambda(em) = 598 nm). Most notably, the fluorescence quantum yields gradually increase with increased Stokes shifts, ultimately reaching Phi(F) = 0.28 in DMF. This trend is fundamentally different from that observed for the corresponding 2-(diphenylamino)phenyl-substituted benzophosphole congener, for which applications as a fluorescent bioimaging probe were previously demonstrated. In this study, the origins of this striking difference are examined by a combined experimental and theoretical approach. Our results suggest that the observed difference arises from a significant contribution of quinoidal resonance forms in the ICT excited state, which suppresses nonradiative decay and hence increases the quantum yield in polar solvents.

DOI： 10.1246/bcsj.20150238

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1002/anie.201507939

Language：Japanese   Publisher：CHEMICAL SOC JAPAN  

Boron, a group 13 element, has several characteristic structural and electronic features: 1) trivalent boron compounds usually adopt a trigonal planar geometry; 2) due to the presence of a vacant p-orbital, effective orbital interaction with pi-conjugated compounds is possible; 3) the presence of a vacant p-orbital is furthermore responsible for high Lewis acidity; 4) the boryl group acts as a pi-electron-accepting group particularly in the excited state. The consequent exploitation of these characteristic features of boron in the molecular design enables us to produce sophisticated pi-functional materials with attractive photophysical and electronic properties. This account article illustrates our systematic studies on the molecular design and the development of functional pi-electron materials using boron as a key element.

DOI： 10.1246/bcsj.20150151

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1039/c5sc02246k

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1038/ncomms9098

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1246/bcsj.20150238

Language：English   Publishing type：Research paper (scientific journal)   Publisher：NATURE PUBLISHING GROUP  

Boron is a unique element in terms of electron deficiency and Lewis acidity. Incorporation of boron atoms into an aromatic carbon framework offers a wide variety of functionality. However, the intrinsic instability of organoboron compounds against moisture and oxygen has delayed the development. Here, we present boron-doped graphene nanoribbons (B-GNRs) of widths of N = 7, 14 and 21 by on-surface chemical reactions with an employed organoboron precursor. The location of the boron dopant is well defined in the centre of the B-GNR, corresponding to 4.8 atom%, as programmed. The chemical reactivity of B-GNRs is probed by the adsorption of nitric oxide (NO), which is most effectively trapped by the boron sites, demonstrating the Lewis acid character. Structural properties and the chemical nature of the NO-reacted B-GNR are determined by a combination of scanning tunnelling microscopy, high-resolution atomic force microscopy with a CO tip, and density functional and classical computations.

DOI： 10.1038/ncomms9098

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Heptalene, a nonaromatic, bicyclic 12 -electron system with a twisted structure, is of great interest with regard to its potential Huckel aromaticity in the two-electron oxidized or reduced forms. The synthesis of thiophene-fused heptalene 5 from the reductive transannular cyclization of bisdehydro[12]annulene 4, and its solid-state structure, which was confirmed by X-ray crystallographic analysis, is presented. Chemical reduction of 5 readily generated the corresponding dianion, which was successfully isolated as [(K[2.2.2]cryptand)(+)](2)5(2-). The X-ray crystallographic analysis of the dianion revealed a shallower saddle structure for the heptalene moiety and a lesser degree of bond alternation relative to 5. (HNMR)-H-1 spectroscopy exposed the effect of a diamagnetic ring current on dianion 5(2-), which was corroborated by nucleus-independent chemical shift (NICS) calculations. These results demonstrate that the heptalene dianion, containing 14 -electrons, does indeed exhibit pronounced degrees of Huckel aromaticity.

DOI： 10.1002/anie.201501790

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PubMed

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1039/C5CC03547C

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A discotic liquid-crystalline (LC) material, consisting of a planarized triphenylborane mesogen, was synthesized. X-ray diffraction analysis confirmed that this compound forms a hexagonal columnar LC phase with an interfacial distance of 3.57 angstrom between the discs. At ambient temperature, this boron-centered discotic liquid crystal exhibited ambipolar carrier transport properties with electron and hole mobility values of approximately 10(-3) and 3x10(-5)cm(2)V(-1)s(-1), respectively.

DOI： 10.1002/anie.201502678

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PubMed

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1002/anie.201501790

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1002/anie.201502678

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Electron-donating aryl groups were attached to electron-accepting benzophosphole skeletons. Among several derivatives thus prepared, one benzophosphole oxide was particularly interesting, as it retained high fluorescence quantum yields even in polar and protic solvents. This phosphole-based compound exhibited a drastic color change of its fluorescence spectrum as a function of the solvent polarity, while the absorption spectra remained virtually unchanged. Capitalizing on these features, this phosphole-based compound was used to stain adipocytes, in which the polarity of subcellular compartments could then be discriminated on the basis of the color change of the fluorescence emission.

DOI： 10.1002/anie.201500229

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PubMed

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1002/anie.201500229

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1039/C4SC03849E

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A series of novel benzene centered mono-, bis- and tris-1,3,5-triazapentadiene ligands 6a-e was synthesized and investigated with respect to their reactivity towards triphenylborane. The resulting blue-fluorescent boron complexes 14a-e with a six-membered ring chelate structure show excellent thermal and chemical stability. All title compounds were completely characterized including X-ray diffraction studies for 14a-c and 14e. Whereas the absorption spectra of all three classes of compounds are similar, the fluorescence spectra show distinct differences. Thus, the emission spectra of 14a, b show Stokes shifts of 4100-6700 cm(-1) with low quantum yields both in solution and in the solid state. However, the more bulky compounds 14c-e show markedly larger molar extinction coefficients and smaller bathochromic shifts compared to 14a,b. For all compounds, we observe significantly more intense red-shifted fluorescence in the solid state compared to that in dichloromethane solutions. For the interpretation of the absorption properties TD-DFT studies were performed based on DFT geometry optimizations.

DOI： 10.1039/c5dt00908a

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Scopus

PubMed

Other Link： http://orcid.org/0000-0003-1863-9956

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A cyclic octithiophene containing two beta,beta '-linkages was synthesized. Due to the large structural change in the excited state, this compound exhibited bathochromically shifted fluorescence. It also showed a small difference between the first and second oxidation potentials, indicative of spin delocalization through the beta,beta '-linkage in the one electron-oxidized state.

DOI： 10.1039/c5cc00570a

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We disclose the development of a ratiometric fluorescent probe based on a benzophosphole P-oxide and its application for the detection of intracellular Na+ ions. Excitation by visible light induced red emission from this probe in water, which was subjected to a hypsochromic shift upon complexation with Na+. Based on this change, a ratiometric analysis enabled us to visualise changes in the Na+ concentration in living mammalian cells.

DOI： 10.1039/c5cc03547c

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A reproducible formation of strongly bent crystals was accomplished by structurally restraining macrocyclic pi-conjugated molecules. The model pi-units consist of two 9,10-bis(2-thienylethynyl)anthracenes with a strong propensity for stacking, which are connected in a macrocyclic fashion via two alkylene linkers. The correlation between the crystalline morphology and the macrocyclic structures restrained by a variety of flexible alkylene linker combinations was systematically studied. Bent crystals were obtained only with specific alkylene linkers of appropriate chain length. The alkylene linkers can adopt different conformations in the crystal packing, so as to fill voids within the macrocycle. The ability to form several similar molecular structures with different alkylene conformations gives rise to contaminations of different crystalline phases within a single crystal, and it is these phase contaminations which are responsible for the bending of the crystals.

DOI： 10.1039/c4sc03849e

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The synthesis of a planarized trinaphthylborane with partially fused structure is presented. This compound shows not only high chemical and thermal stability but also sufficient Lewis acidity to form Lewis adducts with pyridine derivatives in solution. The BN Lewis adducts exhibit unprecedented photodissociation behavior in the excited state, reminiscent of the photogeneration of carbenium ions from triarylmethane leuco dyes. Consequently, these BN Lewis adducts exhibit dual fluorescence emission arising from the initial tetracoordinate BN adducts and the photodissociated tricoordinate boranes.

DOI： 10.1021/ja506980p

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The transannular cyclization of dehydroannulenes bearing several alkyne moieties in close proximity is a powerful synthetic method for producing polyc-yclic aromatic hydrocarbons. We report that the reactivity can be switched by the aromaticity of the ring skeletons fused with the dehydroannulene core. Thus, while thiophene-fused bisdehydro[12]annulene 1 was handled as a stable compound in the air at room temperature, the oxidation with m-chloroperbenzoic acid from the aromatic thiophene rings to the nonaromatic thiophene-S,S-dioxides induced the transannular cyclization, even at room temperature, which was completed within 1 day to produce the formal [2 + 2] cycloadduct 3. This is in stark contrast to the fact that the thermal cyclization of 1 itself required heating at 80 C for 9 days for completion. Experimental and theoretical studies indicate that the oxidation of even one thiophene ring in 1 sufficiently decreases the activation barrier for the transannular cyclization that proceeds through the 8 pi and 4 pi electrocyclic reaction sequence. The thiophene-S,S-dioxide-fused biphenylene 3 thus produced exhibits a set of intriguing properties, such as a higher electron affinity (E-1/2 = -1.17 V vs Fc and Fc(+)) and a stronger fluorescence (Phi(F) = 0.20) than the other relevant biphenylene derivatives, which have electron-donating and nonfluorescent characteristics.

DOI： 10.1021/ja503499n

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PubMed

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1021/ja503499n

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A series of nitrogen-containing heterotriangulenes expanded at the bridging positions has been synthesized. Among them, a dibenzo[c,g]fluorenylidene-substituted derivative has a highly twisted conformation for the overcrowded alkene moieties, which impart a highly electron-accepting character to the electron-donating heterotriangulene skeleton and thereby an NIR absorption as well as multiredox properties with a low reduction potential.

DOI： 10.1021/ol501004g

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

4,5-Dimethyl-1,2-bis(1-naphthylethynyl)benzene (12) undergoes a rapid multiple ring-closure reaction upon treatment with the strong boron Lewis acid B(C6F5)(3) to yield the multiply annulated, planar conjugated -system 13 (50% yield). In the course of this reaction, a C6F5 group was transferred from boron to carbon. Treatment of 12 with CH3B(C6F5)(2) proceeded similarly, giving a mixture of 13 (C6F5-transfer) and the product 15, which was formed by CH3-group transfer. 1,2-Bis(phenylethynyl)benzene (8a) reacts similarly with CH3B(C6F5)(2) to yield a mixture of the respective C6F5- and CH3-substituted dibenzopentalenes 10a and 16. The reaction is thought to proceed through zwitterionic intermediates that exhibit vinyl cation reactivities. Some B(C6F5)(3)-substituted species (26, 27) consequently formed by in situ deprotonation upon treatment of the respective 1,2-bis(alkynyl)benzene starting materials (24, 8) with the frustrated Lewis pair B(C6F5)(3)/P(o-tolyl)(3). The overall formation of the C6F5-substituted products formally require HB(C6F5)(2) cleavage in an intermediate dehydroboration step. This was confirmed in the reaction of a thienylethynyl-containing starting material 21 with B(C6F5)(3), which gave the respective annulated pentalene product 23 that had the HB(C6F5)(2) moiety 1,4-added to its thiophene ring. Compounds12-14, 23, and 26 were characterized by X-ray diffraction.

DOI： 10.1002/asia.201400096

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PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1021/ol501004g

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Pyridine N-oxide-BF2CF3 and -BF2C2F5 complexes and their derivatives were synthesized. Most of the complexes show fluorescence both in solution and in the solid state. By expanding the -conjugated skeleton, the color of the fluorescence could be changed dramatically. A fluorophore with a high solvent dependency could also be produced. Since such compounds can be synthesized on a gram scale in high yield, and are stable to oxygen, water, and heat, the complexes hold great potential as organic functional materials.

DOI： 10.1002/asia.201301688

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The hybridization of flexible and rigid -conjugated frameworks is a potent concept for producing new functional materials. In this article, a series of multifluorescent flapping systems that combine a flexible cyclooctatetraene (COT) core and rigid aceneimide wings with various -conjugation lengths has been designed and synthesized, and their structure/properties relationships have been investigated. Whereas these molecules have a V-shaped bent conformation in the ground state, the bent structure changes to a planar conformation in the lowest excited singlet (S-1) state irrespective of the lengths of the aceneimide wings. However, the fluorescence behavior in solution is distinct between the naphthaleneimide system and the anthraceneimide system. The former has a nonemissive S-1 state owing to the significant contribution of the antiaromatic character of the planar COT frontier molecular orbitals, thereby resulting in complete fluorescence quenching in solution. In contrast, the latter anthraceneimide system shows an intense emission, which is ascribed to the planar but distorted S-1 state that shows the allowed transition between the -molecular orbitals delocalized over the COT core and the acene wings. The other characteristic of these systems is the significantly redshifted fluorescence in the crystalline state relative to their monomer fluorescence. The relationship between the packing structures and the fluorescence properties was investigated by preparing a series of hybrid systems with different sizes of substituents on the imide moieties, which revealed the effect of the twofold -stacked structure of the V-shaped molecules on the large bathochromic shift in emission.

DOI： 10.1002/chem.201303955

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PubMed

Web of Science

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/ajoc.201300227

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Other Link： http://orcid.org/0000-0001-9308-153X

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Triphenylboranes planarized with three methylene bridges exhibited dual fluorescence bands around 340 and 400 nm despite their structural constraint. To elucidate the origin, their excited state dynamics were experimentally and theoretically studied. The measurements of fluorescence lifetimes and transient absorption spectra indicated that the planarized triphenylboranes adopt two local minimum structures in the lowest-energy excited singlet (S-1) state. The TD-DFT potential energy surface of the S-1 state possesses at least two minimum energy structures associated with a planar and a bowl-shaped molecular structure. The theoretical S-1-S-0 transition energies at these geometries were in good agreement with the experimentally observed values. These results indicated that the plane-to-bowl structural relaxation in the S-1 state is the origin of the dual fluorescence. Based on the calculated partial atomic charge on the boron atom, the structural deformation to the bowl-shaped structure results in an increase in the electron density on the boron center. Thus, the enhanced intramolecular charge-transfer character plays a role in this structural deformation. Similar behavior was also observed for trigonally pi-expanded planarized borane derivatives. These results provide an important implication that structural constraint in a planar fashion is not only a strategy to construct a rigid skeleton, but also a viable mechanism to impart flexibility to the skeleton.

DOI： 10.1039/c3sc52751d

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Planarized triphenylboranes extended with thiophene or bithiophene spacers were synthesized, which showed intense fluorescences in solution and reversible redox waves for reduction in cyclic voltammetry. Organic light-emitting diodes (OLEDs) using these compounds as an electron-transporting material were fabricated.

DOI： 10.1021/ol403084x

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Various novel N-alkyl and N-benzyl 2-borylbenzaldimines 3 were prepared by condensation of 2-(dimesitylboryl)benzaldehyde (1) with amines. Further functionalization of compound 3e was possible by deprotonation and subsequent regioselective reaction with electrophiles to give compounds 4. Applying similar conditions to 3a led to the unexpected formation of hitherto unknown dimeric compounds (5 and 6). All structural types were fully characterized, including by X-ray diffraction (XRD). Furthermore, quantum chemical calculations on the SCS-MP2 and DFT levels gave insights into the reaction mechanisms and the stereoselectivity. The BIN bonding situation in these molecules was analyzed using Wiberg bond indices. Preliminary UV-vis and fluorescence measurements indicate that the substitution reaction leading to compounds 4 can be utilized to tune the photophysical properties of these compounds.

DOI： 10.1021/jo401748d

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Chemical reduction of the structurally constrained triphenylborane 1 with K produced a radical anion. EPR analysis demonstrated the delocalization of the unpaired electron spin density over the entire pi skeleton to a greater extent than is the case for a nonconstrained Ph3B radical anion. DFT calculations indicated that the coplanarization of the benzene rings with the boron plane and the shortening of the B-C bond lengths by the structural constraint are responsible for the spin delocalization. The geometry optimization also suggested a bowl-shaped conformation as a viable local minimum structure in addition to the planar conformation. X-ray crystal structure analysis indeed revealed the nonplanar structure of the radical anion 1(center dot-).

DOI： 10.1021/om400560u

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201306323

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PubMed

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1039/C3SC52751D

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Smooth and selective: Upon photoirradiation, bis(3-alkenyl-2-thienyl) acetylenes smoothly and selectively undergo double 5-exo-dig cyclization to produce a series of thiophene-fused pentafulvalenes with various aryl substituents. In this fused π-conjugated skeleton, the fused thiophene rings and the aryl substituents significantly modulate the electronic structure of the pentafulvalene skeleton. Copyright © 2013 WILEY-VCH Verlag GmbH &amp
Co. KGaA, Weinheim.

DOI： 10.1002/anie.201303738

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DOI： DOI: 10.1002/anie.201306323

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： DOI: 10.1002/anie.201303738

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Amplified spontaneous emission (ASE) is observed, under optical pump, in polystyrene films doped with two pentathienoacene derivatives functionalised with thienyl-S, S-dioxide groups (compounds 2 and 3). The effect of the dioxide groups on the ASE properties is analysed by comparing the performance with that of its corresponding non-oxidized analogue (1). Films containing either 2 or 3 show ASE at 511 and 574 nm, respectively, when excited directly (at 435 nm) on their absorption bands, showing thresholds and linewidths larger than those obtained from films doped with 1, pumped at 355 nm. ASE is also observed under excitation at 355 nm, in samples containing 1 (host) and either 2 or 3 (guests), due to energy transfer from host to guest. For the blends with 3, the ASE threshold is lower than that obtained when the films are excited directly. Results are interpreted in terms of the photophysical parameters such as absorption capacity, fluorescence efficiency, singlet-to-triplet intersystem crossing leading to triplet-triplet re-absorptions, bimolecular energy-transfer efficiency, efficiency of internal conversion process, etc. State-of-the-art quantum chemical calculations are used in the interpretation of the experimental results.

DOI： 10.1002/adom.201300155

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201303830

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DOI： DOI: 10.1021/ja4055228

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Luminescent mechanochromism has been intensively studied in the past few years. However, the difference in the anisotropic grinding and the isotropic compression is not clearly distinguished in many cases, in spite of the importance of this discrimination for the application of such mechanochromic materials. We now report the distinct luminescent responses of a new organic fluorophore, tetrathiazolylthiophene, to these stresses. The multichromism is achieved over the entire visible region using the single fluorophore. The different mechanisms of a blue shift by grinding crystals and of a red shift under hydrostatic pressure are fully investigated, which includes a high-pressure single-crystal X-ray diffraction analysis. The anisotropic and isotropic modes of mechanical loading suppress and enhance the excimer formation, respectively, in the 3D hydrogen-bond network.

DOI： 10.1021/ja4055228

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Tricoordinate boron-containing pi-electron systems are an attractive class of compounds with intense fluorescence and strong electron-accepting properties. However, the impact of pentacoordination of the boron atoms on their properties has not been determined. We now disclose a B,B'-bis(1,8-dichloro-9-anthryl)-substituted 9,10-dihydro-9,10-diboraanthracene as a new pentacoordinate organoboron compound. In this skeleton, with the aid of the orthogonal arrangement of the anthryl substituent, the B and Cl atoms can form a three-center four-electron (3c-4e) Cl-B-Cl bond. The pentacoordination of the boron atom significantly perturbs the electronic structure and thereby the photophysical and electrochemical properties.

DOI： 10.1021/ja404724f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We have designed and synthesized a pi-conjugated system that consists of a flexible and nonplanar pi joint and two emissive rigid and planar wings. This molecular system exhibits respectively red, green, and blue (RGB) emission from a single-component luminophore in different environments, namely in polymer matrix, in solution, and in crystals. The flexible unit gives rise to a dynamic conformational change in the excited state from a nonplanar V-shaped structure to a planar structure, leading to a dual fluorescence of blue and green colors. The rigid and planar moieties favor the formation of a two-fold pi-stacked array of the V-shaped molecules in the crystalline state, which produces a red excimer-like emission. These E RGB emissions are attained without changing the excitation energy.

DOI： 10.1021/ja404198h

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DOI： DOI: 10.1021/ja404198h

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We have synthesized a series of new fluorescent boron systems 1a-c and 2a-d based on nitrogen (NNN) or nitrogen and oxygen (ONO)-containing tridentate ligands. These novel dyes are characterized by high thermal and chemical stability. They show large Stokes shifts (mostly above 3200 cm(-1)) and quantum yields in solution and in the solid state up to 40%. The easy, modular synthesis facilitates the convenient variation of the axial substituent on the central boron atom, allowing the functionalization of this dye for biochemical use. Introducing a long alkyl chain with a phenyl spacer at this axial position enables the self-assembly of the boron compound 2d to form a fluorescent vesicle, which is able to encapsulate small molecules such as sulforhodamine. Additionally, boron compound 2d was found to serve as a dye for cell imaging since it has the capability of binding to the nuclear membranes of HeLa cells. With phospholipids such as DOPC, giant unilamelar vesicles (GUV) are formed. These results demonstrate the wide applicability of this new boron system in supramolecular and medicinal chemistry.

DOI： 10.1021/jo4003745

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DOI： DOI: 10.1002/anie.201210236

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DOI： 10.1021/ja3126849

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Photoirradiation of bis(bithienyl)acetylenes in the presence of iodine undergoes sequential electrophilic and photochemical cyclizations to produce tetrathienonaphthalenes (TTN) in one pot. The UN framework is readily transformed into cruciform pi-extended derivatives, which form ordered nano/microstructures.

DOI： 10.1021/ol303107y

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Bromo-substituted acyclic thiazole tetramers selectively underwent an 8 pi thermal electrocyclic reaction at high temperatures of 280-300 degrees C without solvent, producing p-extended thiazole-fused cyclooctatetraenes (COTs) in high yields. A quantum chemical study provided a rationale for the lower activation barrier and high selectivity of the 8 pi electrocyclic reaction mode over a competitive 6 pi electrocyclic reaction. The terminal bromine atom acts as a leaving group to trigger the rearomatization of the electrocyclized intermediate, which leads to the formation of the energetically stable COT products. This synthetic protocol enables us to synthesize a series of thiazole-fused COTs, including a derivative that can form loosely stacked columnar arrays in the crystalline state and shows fluorescence in the solid state.

DOI： 10.1039/c3sc52232f

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A sulfur analogue of a Pechmann dye has been synthesized. In addition to long-wavelength absorption and fluorescence, it showed multiple redox processes with low reduction potentials in cyclic voltammetry. The size effect of sulfur is responsible for its enhanced electron-accepting character.

DOI： 10.1039/c3cc41007b

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Other Link： http://orcid.org/0000-0003-1863-9956

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201300871

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

4,4-Difluoro-4-bora-3a, 4a-diaza-s-indacenes (BODIPYs) are fascinating dyes with great potentials for various applications. To establish the design principle for the modification of the BODIPY skeleton, we now investigate the electronic impacts of the introduction of ring-fused structures. The DFT calculations revealed that while the benzene-fusing at the a bond in the BODIPY skeleton increases the HOMO level, the benzene-fusing at the b bond leads to a decreased LUMO level. Based on these results, a benzo[b]fused BODIPY 1 and a fully-fused BODIPY dimer 2 were synthesized. X-ray crystal structure analysis demonstrated that the benzo[b]-fused structure significantly perturbs the pi-conjugation with enhancement of an electron-accepting azafulvene character. In the ring-fused BODIPY dimer 2, the central benzene ring is largely deviated from the aromatic benzene geometry. As a consequence, 2 has a significantly low-lying LUMO delocalized along the periphery. In cyclic voltammograms, the benzene-fused BODIPY 1 and fully-fused dimer 2 indeed showed reversible reduction waves at much less negative potentials (E-1/2 = -1.05 V vs. Fc/Fc(+) for 1, -0.85 V for 2), relative to a non-fused BODIPY 3 (E-1/2 = -1.40 V). In addition, the benzene-fused BODIPYs showed broad and intense absorption bands in the Vis-NIR region. In particular, the BODIPY dimer 2 showed an intense absorption at 629 nm with a broad shoulder band reaching 900 nm. Corresponding to the red-shifted absorption, compounds 1 and 2 showed weak fluorescence in the deep red region (lambda(em) = 690 nm, Phi(F) < 0.01) and in the near-infrared region (940 nm, Phi(F) < 0.01), respectively.

DOI： 10.1039/c2sc21768f

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201210236

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Triplet acceptors such as naphthalene, pyrene, and anthracene have been found to be highly effective in controlling the photoisomerization efficiency of N,C-chelate boryl chromophores, establishing the involvement of a photoactive triplet state in the isomerization of this class of photochromic compounds.

DOI： 10.1021/ol302742g

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DOI： DOI: 10.1002/anie.201206699

Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1039/C2DT32134C

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

We disclose a new planarized triarylborane in which the tri-coordinated boron atom is embedded in a fully fused polycyclic pi-conjugated skeleton. The compound shows high stability toward oxygen, water, and silica gel, despite the absence of steric protection around the B atom. Reflecting the electron-donating character of the pi-skeleton and the electron-accepting character of the B atom, this compound shows broad absorption bands that cover the entire visible region and a fluorescence in the visible/near-IR region. In addition, this compound shows dramatic property changes upon formation of a tetra-coordinated borate, such as thermochromic behavior in the presence of pyridine.

DOI： 10.1021/ja3036042

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A series of diarene-fused 1,2-dihydro-1,2-diborins were prepared as a new B?B-bond-embedded polycyclic p-electron system. The reduction of these compounds with metals produced their corresponding dianions, the p-conjugation modes of which varied from 6p-conjugation within the central 1,2-diborin skeleton to 14p peripheral conjugation over the tricyclic skeleton, depending on the nature of the reduced biaryl framework. Moreover, the countercation to the dianions had a significant effect on the absorption spectra, with a dramatic color change from yellow to deep blue, depending on the distance between the tricyclic dianion skeleton and the countercation.

DOI： 10.1002/asia.201200055

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DOI： DOI: 10.1021/ja3036042

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

2,3-Dihydroboroles are readily formed by treatment of dicyclopropylacetylene with the strongly electrophilic borane B(C6F5)(3). The reaction involves a sequence of 1,1-carboboration reactions and proceeds via dienylborane intermediates. Consistent with this, the reaction of the conjugated enyne 15c with B(C6F5)(3) leads to the formation of a dihydroborole.

DOI： 10.1021/om300065m

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Triphenylborane and 9,10-diphenyl-9,10-dihydro-9,10-diboraanthracene, constrained to a planar arrangement with methylene tethers, were synthesized by intramolecular multi-fold Friedel-Crafts cyclization. These compounds were stable toward air, water, and amines, despite the absence of steric protection in the vertical direction with respect to the B atoms, and showed characteristic structural, electronic, and photophysical properties. In addition, upon treatment with a fluoride ion, these compounds underwent a plane-to-bowl conversion in a controlled manner.

DOI： 10.1021/ja211944q

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Novel N-aryl-substituted 2-borylbenzaldimines 6 and related systems with extended pi-framework 7 based on two borylbenzaldimine units linked by a spacer moiety were synthesized by condensation reactions of 2-(dimesitylboryl)benzaldehyde 3 with various amines 4 and diamines 5. All compounds were completely characterized including X-ray diffraction, especially in view of Lewis acid-base B-O and B-N interactions. The electronic as well as the photophysical properties of bisimines 7 were determined using cyclic voltammetry, UV/vis, and fluorescence spectroscopy and quantum chemistry. These compounds feature large Stokes shifts and reversible reduction waves. Interestingly, UV irradiation experiments unfold enhanced photostability for compounds 7 with an extended pi-skeleton. By use of 1,8-diaminonaphthalene we observed the formation of a hitherto unknown BN-heterocyclic compound 9 fused with a perimidine skeleton. Structural and energetic aspects were evaluated by high level quantum chemical methods (DFT and SCS-MP2-calculations).

DOI： 10.1021/jo202212s

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DOI： DOI: 10.1021/ja211944q

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

N-Boryl-substituted carbazoles (carBR(2)) and (diphenylamino)boranes (Ph2NBR2) with R = Mes (mesityl) and FMes [tris(trifluoromethyl)phenyl] substituents on boron exhibit large UV/vis Stokes shifts. To investigate the substituent effect on the magnitude of the Stokes shifts, we studied the electronic structure and spectroscopic properties of carBR(2) and Ph2NBR2 with R = H, Mes, and FMes using hybrid density functional theory (B3LYP) and time-dependent density functional theory (TD-B3LYP) for ground and low-lying excited states. The lowest lying excited state with a nonvanishing oscillator strength is a twisted internal charge transfer (TICT) (1)A state in the C-2 point group, owing to a single-electron excitation from the nitrogen lone pair to the unoccupied boron p(z) AO, Nlp -> Bp(z). Emission from these (1)A excited states are predicted to be much brighter than from the energetically close B-1 excited states that are not directly related to CT excitation from N to B, due to symmetry. An analysis of geometrical relaxations in the excited state and the state energies relative to the ground state energy of the equilibrium geometry reveals that (a) the carbazole skeleton induces a general red shift in UV/vis spectra, (b) bulky boryl substituents reduce the predicted Stokes shifts of TICT states, and (c) the presence of electron-withdrawing functional groups induces a further general red shift in UV/vis spectra but does not significantly alter Stokes shifts.

DOI： 10.1021/jp209264j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A biphenyl-fused BODIPY was synthesized through a facile oxidative cyclization of peripheral aryl-substituents at the beta-position of the BODIPY unit. The extended pi-system of the fused BODIPY induces near-infrared (NIR) absorption and strong pi-pi interactions in the solid state. These features are beneficial for the application of the dye as a functional material. The biphenyl-fused BODIPY dye was demonstrated to exhibit photocurrent conversion ability on the basis of its n-type semiconducting property.

DOI： 10.1021/ol2033916

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Potassium and lithium salts of anionic B-phenylborataanthracenes, whose phenyl groups were fixed in a coplanar fashion, were synthesized. These compounds exhibited solvent-separated ion pair structures both in the crystalline state and in solution. Planarization of the phenyl moiety had a remarkable impact on the photophysical properties, such as the red-shifted absorption and intense fluorescence.

DOI： 10.1039/c2cc35874c

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201201156

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A series of benzoheteroarene-fused boroles, containing pyrrole, furan, and thiophene as the heteroarene rings, were synthesized and their structures were determined by X-ray crystallographic analysis. Their antiaromaticity was assessed by calculations of the nucleus-independent chemical shift (NICS) values using the geometries derived from their crystal structures. The large NICS(1)(zz) values of the borole ring in the heteroarene-fused structures showed their high antiaromaticity, in contrast to the fact that dibenzoborole has a reduced antiaromaticity. This enhanced antiaromaticity is due to the lower extent of bond alternation in the borole ring with the heteroarene-fused structures compared to that in the parent borole. Theoretical calculations also indicated that the antiaromatic character of the borole is relevant to its LUMO level. Moreover, the experimentally evaluated Lewis acidities of the heteroarene-fused boroles are linearly correlated to their reduction potentials, namely, the LUMO levels. These results shed light on the understanding of how the fused-structures affect the properties and reactivities of the borole moiety. All the heteroarene-fused boroles have broad absorption bands with the comparable absorption maxima around 468-479 nm. In contrast, their reduction potentials are different from one another, dependent on the electronic characteristics of the heteroarene rings.

DOI： 10.1039/c2sc20100c

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A novel thienoacene compound, dihexyl-substituted dibenzo[d,d']thieno[3,2-b;4,5-b']dithiophene (C6-DBTDT), is developed as a p-type organic semiconductor for high-performance organic field-effect transistors. Insertion of an acceptor material at the contact interface enables substantial reduction in the threshold voltage and hysteresis behavior, and the field-effect mobilities of 2.5 and 3.1 cm(2) V-1 s(-1) are achieved for the C6-DBTDT film vacuum-deposited at room temperature and 80 degrees C, respectively.

DOI： 10.1039/c2jm30840a

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201201265

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201107172

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201204050

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Other Link： http://orcid.org/0000-0003-1863-9956

Language：English   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

We studied the UV-vis absorption and fluorescence in solution/solid states of [n]cycloparaphenylene ([n] CPP: n = 9, 12, 14, 15, and 16), and conducted theoretical studies to better understand the experimental results. The representative experimental findings include (i) the most intense absorption maxima (lambda(abs1)) display remarkably close values (338-339 nm), (ii) the longest-wavelength absorption maxima (lambda(abs2)) are blue-shifted with increasing the ring size (395 --> 365 nm), (iii) the emission maxima (lambda(em)) are blue-shifted with increasing the ring size (494 --> 438 nm for longest-wavelength maxima), (iv) the fluorescent quantum yields (Phi(F)) in solution are high (0.73-0.90), (v) the fluorescence lifetimes (tau(s)) of [9]- and [12] CPP are 10.6 and 2.2 ns, respectively, and (vi) the Phi(F) values slightly increase in polymer matrix but significantly decrease in the crystalline state. According to TD-DFT calculations, the longest-wavelength absorption (lambda(abs2)) corresponds to a forbidden HOMO --> LUMO transition and the most intense absorption (lambda(abs1)) corresponds to degenerate HOMO - 1 --> LUMO and HOMO --> LUMO + 1 transitions with high oscillator strength. The interesting and counterintuitive optical properties of CPPs (constant lambda(abs1) and blue shift of lambda(abs2)) could be ascribed mainly to the ring-size effect in frontier molecular orbitals (in particular the increase of the HOMO-LUMO gap as the number of benzene rings increases). On the basis of comparative calculations using hypothetical model geometries, we conclude that the unique behavior of HOMO and LUMO of CPPs is due mainly to their lack of a conjugation length dependence in combination with a significant bending effect (particularly to HOMO) and a torsion effect (particularly to LUMO).

DOI： 10.1039/c2ob25199j

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.201206699

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SOC SYNTHETIC ORGANIC CHEM JPN  

Incorporation of main group elements into pi-conjugated skeletons is a powerful strategy for the development of new pi-electron materials with intriguing properties. An important direction in this chemistry may be to exploit synergistic effects of two or more main group elements, which enables us to construct new skeletons with unusual electronic structures. From this point of view, several kinds of pi-conjugated molecules containing B, N, and P have been synthesized, including B-B bond-containing thiophene-fused 1,2-dihydro-1,2-diborin, B-N bond-incorporated pi-extended 1,2-dihydro-1,2-azaborine, and several ladder-type pi-conjugated compounds containing boron and phosphorus as the bridging moieties. In particular, some of the latter compounds have been synthesized based on newly developed intramolecular double cyclizations from o,o'-disubstituted diphenylacetylene precursors. Investigation on their structure-properties relationships revealed the effect of these main group elements on the electronic structures and thus their properties. Some of these compounds showed high potentials for applications as the electron-transporting materials and two-photon absorption materials.

DOI： 10.5059/yukigoseikyokaishi.69.661

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DOI： 10.1021/ja2019977

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The synthesis of a family of 1,1-dimethyldibenzo-[bf]silepin derivatives, substituted with. donor groups of various donor strength and conjugation length in the positions meta or para to the silepin silicon, is presented. The compounds were characterized by NMR, UV-vis, and fluorescence spectroscopy, as well as with cyclic voltammetry and DFT computations. One of the meta series was characterized by X-ray crystallography. All compounds show red-shifts in onset absorption and emission maxima compared to the parent 1,1-dimethyldibenzo[bf]silepin, but all exhibit blue fluorescence with quantum yields ranging from 0.46 to 0.93 for the meta series and from 0.09 to 0.46 for the para derivatives. The data suggest that, for the meta series, the primary absorption is of pi-pi* character, while in the para series, for strongly donating groups, transitions from low-lying pi orbitals to the LUMO+1 orbital, which has contributions from the C-Si-C sigma* orbitals, are charge-transfer in character. The phenyl-substituted derivatives can be converted to borepins via transmetalation with BBr3, but other strategies are necessary to prepare borepins with other donor groups.

DOI： 10.1021/om2000597

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Phenylene and biphenyl compounds with dibenzophosphole sulfide (DBPS) as an anchoring group for single molecule junctions were synthesized. The conductance measurements revealed that the phosphine sulfide indeed acts as an anchoring group for Au electrodes. Theoretical calculations including metal electrodes demonstrated that the LUMO level of the DBPS-terminated biphenyl is close to the Au Fermi level, leading to the electron conduction of the Au-molecule-Au junction based on the resonance-tunneling mechanism.

DOI： 10.1246/cl.2011.174

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

DOI： 10.1002/anie.201104971

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DOI： 10.1002/anie.201104114

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Electronic tuning of thiazolyl-capped pi-conjugated systems via a coordination/cyclization protocol with B(C6F5)(3) effectively enhances an electron-accepting character giving rise to lower reduction potentials and increases thermal stability.

DOI： 10.1021/ol102282x

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The reaction of N-Bac-protected bis(5-phenyl-2-pyrrolyl)borane with BF3 center dot OEt2 produced 3-(phenylpyrrolyl)-6-phenyl- 1,2-dihydro-1,2-azaborine in moderate yield. This compound showed (117 absorption band at a longer wavelength compared to that of its benzene analogue and also exhibited an intense red-shifted fluorescence with a high quantum yield close to unity. According to the X-ray structural analysis, cyclic voltammetry, and theoretical calculations, the 1,2-dihydro-1,2-azaborine acts not like a benzene analogue but like a cyclohexadiene analogue in the extended pi-conjugated skeleton.

DOI： 10.1021/om100408m

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A series of 2,3,4,5-tetraphenylphosphole oxides with various aryl groups on the phosphorus atoms were synthesized and their fluorescence properties in the crystalline state were investigated. Some of these compounds showed an intense fluorescence with the quantum yields of 0.75-0.91. These intense emissions are attributable not only to the restricted rotation of the peripheral phenyl rings, but also to the long intermolecular distances between the adjacent molecules in the crystal packing.

DOI： 10.1039/c0nj00155d

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DOI： 10.1016/j.crci.2010.04.021

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

This work presents an analysis of the structural, electrochemical, and optical properties of a family of triisopropylsilyl end-capped oligothienoacenes (TIPS-Tn-TIPS, n=4-8) by combining cyclic voltammetry, spectroscopic techniques, and quantum-chemical calculations. TIPS-Tn-TIPS compounds form stable radical cations, and dications are only obtained for the longest oligomers (n=7 and 8). Oxidation leads to the quinoidization of the conjugated backbone, from which electrons are mainly extracted. The absorption and fluorescence spectra show partially resolved vibronic structures even at room temperature, due to the rigid molecular geometry. Two well-resolved vibronic progressions are observed at low temperatures due to the vibronic coupling, with normal modes showing wavenumbers of approximate to 1525 and approximate to 480 cm(-1). Optical absorption bands display remarkable bathochromic dispersion with the oligomer length, indicative of the extent of pi conjugation. The optical properties of the oxidized compounds are characterized by in situ UV/Vis/NIR spectroelectrochemistry. The radical cation species show two intense absorption bands emerging at energies lower than in the neutral compounds. The formation of the dication is only detected for the heptamer and the octamer. and shows a new band at intermediate energies. Optical data are interpreted with the help of density functional theory calculations performed at the B3LYP/6-31G** level, both for the neutral and the oxidized compounds.

DOI： 10.1002/chem.200903343

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Herein, we study the pi-conjugational properties of a homologous series of all-anti oligothienoacenes containing four to eight fused thiophene rings by means of FT Raman spectroscopy and DFT calculations. The theoretical analysis of the spectroscopic data provides evidence that selective enhancement of a very limited number of Raman scatterings is related to the occurrence in these oligothienoacenes of strong vibronic coupling between collective nu(C=C) stretching modes in the 1600-1300 cm(-1) region and the HOMO/LUMO frontier orbitals (HOMO=highest occupied molecular orbital; LUMO=Iowest unoccupied molecular orbital). The correlation of the Raman spectroscopic data and theoretical results for these all-anti oilgothienoacenes with those previously collected for a number of all-syn oligothienohelicenes gives further support to the expectation that cross-conjugation is dominant in heterohelicenes. Fully planar all-anti oligothienoacenes display linear pi conjugation which seemingly does not reach saturation with increasing number of annulated thiophene rings in the oligomeric chain at least up to the octamer.

DOI： 10.1002/cphc.200900440

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

As a B-B bond-containing polycyclic pi-electron system, a dithieno[3,2-c:2',3'-e](1,2-dihydro-1,2-diborin) derivative and its dianion salts were successfully prepared, and their structures were determined by X-ray crystallography. The neutral. dithieno-1,2dihydro-1,2-diborin has a twisted diborin ring in which both the sigma-TT and p-pi* orbital interactions between the bithiophene pi framework and the B-B bond moiety effectively take place, giving rise to an absorption that is significantly red-shifted compared with that of the parent bithiophene. Upon a two-electron reduction, the dithienodiborin pi framework becomes planar and has a characteristic peripheral. pi conjugation through the B-B bond with 14 pi etectrons. Furthermore, the dianion salts show an intriguing countercation effect on their photophysical, properties, indicative of possible etectronic tuning by the countercations.

DOI： 10.1021/ja905007s

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Upon the treatment of bis(arylcarbonyl)diphenylacetylenes with lithium naphthalenide, the carbonyl reduction dominantly occurs over the acetylene reduction. The produced bis(radical anion) intermediate undergoes a synchronous double-radical 5-endo-dig cyclization. This simple reduction procedure produces two intriguing classes of ladder pi-conjugated skeletons, i.e., emissive methylene-bridged stilbenes and dibenzo[a,e]pentalenes regarded as a cyclic 1,4-diphenylbutadiene.

DOI： 10.1021/ol901148p

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Two kinds of the totally alkyl-substituted ladder pi-conjugated compounds, the totally hexyl-substituted silicon-bridged stilbene trimer 1 and the totally propyl-substituted silicon-and carbon-bridged distyrylbenzene 2, were synthesized. X-ray crystallography revealed that both compounds adopt the all-parallel-aligned packing structures through the interpenetration of the alkyl chains with those of the neighboring molecules. The effect of this packing structure on the photophysical properties was investigated. The fluorescence quantum yield measurements showed that both compounds maintained their high quantum yields (Phi(F)) even in the crystalline state (Phi(F) = 0.64 for 1; 0.63 for 2), suggesting the potential effect of the all-parallel alignment for attaining the intense emission in the solid state.

DOI： 10.1002/macp.200900037

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Long-lived exciplex emission is observed in blend films of poly[9,9-dioctylfluorene-co-N-(4-methoxyphenyl)diphenylamine] (TFMO) and the soluble silole derivative 2,5-bis-(2,2-bipyridin-6-yl)-1,1-dimethyl-3,4-diphenylsilacyclopentadiene (PyPySPyPy). The exciplex is characterized by a long-lived (similar to 40-90 ns) component in both the photoluminescence and electroluminescence spectra, which is red-shifted relative to the emission of the pristine materials. In addition to exciplex emission, delayed fluorescence from the TFMO singlet state is observed and is attributed to exciton regeneration through the interfacial exciplex state. Comparing blend films made using chlorobenzene and p-xylene solvents, we find that exciplex lifetime and exciton regeneration in the blend film are sensitive to the choice of solvent and the resulting morphology of the blend film. The exciplex emissive lifetime can be correlated to changes in photoluminescence quenching and efficiency of light-emitting diodes.

DOI： 10.1021/jp808671f

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

5-Aryl-3,3,4,4-tetramethyl-3,4 -dihydro-3H-pyrrol-2-imines, conformationally restrained 1,3-diazabuta-1,3-diene derivatives, were, easily prepared by treating aryllithium species with 2,2,3,3-tetramthylsuccinonitrile (1). Trapping the reaction intermediate with chlorotrimethylsilane gave N-silylaled compounds 2a-e, whereas aqueous workup gave N-H derivatives 3a,b. Pyrenyl-substituted compound 3b was characterised by X-ray diffraction studies, revealing the presence of both intermolecular aromatic face-to-face contacts and the formation of homodimers by twotold H-bonding. N-Silylated derivatives 2a-d were used successfully as nucleophilic components in palladium-catalysed C-N bond-forming reactions to obtain N-arylated compounds 5b-h,j,k,m and 7a-d. The UV spectra of compounds 5 and 7 exhibit long wavelength absorptions up to 462 nm for 7d, thus indicating extended pi-pi* conjugation. Dihydropyrrolimine-based compounds with larger conjugated aryl substituents in the 5-position react. with Bronsted and Lewis acids displaying a significant colour change that could be used to estimate. the pK(1), of 3a to a value of -4.5. Derivatives 2c,e and 3a,b, which are not N-arylated, are fluorescent with a Stokes shift of 107 nm (6034 cm(-1)) for 3a. ((c) Wiley-VCH Verlag GmbH & Co, KGaA, 69451 Weinheim, Germany, 2009)

DOI： 10.1002/ejoc.200900045

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SPRINGER  

Ultraviolet photoemission spectroscopic measurements of bis (benzo)pentathienoacene were carried out in gas and solid phase. For the measurements of solid phase, vacuum deposited films in both amorphous and crystalline phase were prepared on different substrates of HOPG and polycrystalline Au, respectively. The adiabatic ionization energies were determined to be 6.8(4), 5.3(2), and 5.0(8) eV, for gas, amorphous, and crystalline phases, respectively. The spectral lineshapes were interpreted with the aid of the density functional calculations for both isolated molecule and single-crystal structure. The calculated electronic structures were further analyzed in terms of the energy band dispersion and the transport properties of charge carriers.

DOI： 10.1007/s00339-008-5004-2

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：GEORG THIEME VERLAG KG  

Di(heteroaryl)acetylenes having a pyridyl or thiazolyl as the heteroaryl group underwent a reaction with bromodibenzoborole to produce coordination complexes, which were further treated with water to promote the intramolecular cascade double cyclization to produce the dibenzoborolyl-bridged ladder di(heteroaryl)vinylenes. For the thiazolyl derivative, further derivatization at the terminal positions produced a bis(dimesitylboryl)-substituted derivative. The ladder molecules prepared showed ail intense emission in the fluorescence spectra as well as reversible reduction waves at low reduction potentials in the cyclic voltammetry.

DOI： 10.1055/s-0028-1083271

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

Intense blue emissions with a small Stokes' shift both in solution and in the solid state were attained by introducing (pentafluorophenyl) dimethylsilyl groups to a 9,10-diphenylanthracene skeleton as the pi-stacking tethers.

DOI： 10.1039/b901794a

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The intramolecular trans-halophosphanylation of 2-(aminophosphanyl)phenylacetylenes mediated by PBr3 followed by the oxidation with H2O2 produces 3-bromobenzo[b]phosphole oxide derivatives. This cyclization is also used for the synthesis of a 3-iodo derivative by conducting the reaction in the presence of LiI. Based on this synthetic method, various benzophosphole-containing pi-conjugated compounds, including a phosphoryl and methylene-bridged stilbene 10, 2,3,6,7-tetraphenylbenzo[1,2-b:4,5-b']diphosphole-P,P'-dioxides 11, and their phosphine sulfide derivatives 12, are synthesized. The study of the structure-property relationships in a series of the bridged stilbenes, including a bis(methylene)-bridged stilbene 10, and a bis-(phosphoryl)-bridged stilbene, reveals that as the contribution of the phosphoryl groups increased, the absorption and emission maxima substantially shift to longer wavelengths. The intrinsic substituent effects of the phosphoryl group in this skeleton are to decrease the oscillator strength of the electronic transition and thus decrease the radiative decay rate constants from the singlet excited state. Nevertheless, these compounds maintain high fluorescence quantum yields (Phi(F) > 0.8) owing to the significantly retarded non-radiative decay process. In the study of the benzodiphosphole derivatives 11 and 12, their cyclic voltammetry revealed that both of the phosphoryl and phosphine sulfide derivatives have low reduction potentials (-1.7 to -1.8 V vs ferrocene/ferrocenium couple) with the high reversibility of the redox waves. These compounds also showed high thermal stabilities with the high glass transition temperatures of 147-159 degrees C, indicative of their potential utilities as amorphous materials.

DOI： 10.1002/asia.200900303

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A series of 2,5-bis(dimesitylboryl)-1,4-bis(arylethynyl)benzenes 1-6 that contain various p-substituents on the terminal benzene rings, including NPh2 (1), OMe (2), Me (3), H (4), CF3 (5), and CN (6) groups, were synthesized, and the effects of the p-substituents on the absorption and fluorescence properties were investigated both in solution and in the solid state. Linear relationships were obtained not only between the Hammett sigma(+)(p) constants of the p-substituents and the absorption and fluorescence maxima, quantum yields, and excited-state dynamics parameters in solution, but also between the sigma(+)(p) constants and the fluorescence quantum yields in the solid state. An important finding extracted from these results is that the suppressed fluorescence quenching in the solid state is a common feature for the present laterally boryl-substituted pi-conjugated skeletons. Hence, the diborylphenylene can serve as a useful core unit to develop highly emissive organic solids. In fact, most of the derivatives showed more intense emission in the solid state than in solution. In addition to these studies, the titration experiment of 1 by the addition of nBu(4)NF was conducted, which showed the stepwise bindings of two fluoride ions with high association constants as well as a drastic change in the fluorescence spectra, while constantly maintaining high quantum yields (0.61-0.76), irrespective of the binding modes. This result also demonstrated the potential utility of the present molecules as an efficient fluorescent fluoride ion sensor.

DOI： 10.1002/chem.200900864

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Treatment of tetramethylsuccinonitrile 1 with aryl lithium compounds and subsequent quenching with chlorotrimethylsilane yields 5-aryl-3,3,4,4-tetramethyl-N-(trimethylsilyl)-3,4-dihydropyrrol-2-imines 2a-c in 49-71% yield. Attempts to crystallise 2a-c in the presence of wet air yielded the tetraaryl tetradecahydroporphyrazins 3a-c in yields of 4-84% as single diastereomers. X-ray diffraction studies of 3b and c showed that only the isomer with four aryl substituents pointing in the same direction was formed. The resulting four-bladed pinwheel-like structures were characterised by four intramolecular aromatic interactions, in which each phenyl ring points with its edge towards the centre of a neighbouring phenyl moiety, resembling the arrangement of benzene molecules in T-shaped dimers. Temperature-dependent NMR spectra give insight into the dynamic properties of the aryl substituents. Quantum chemical calculations that included dispersion corrections indicated the importance of aryl-aryl interactions for the diastereoselectivity of the reaction and for the structural properties of the single isomers observed.

DOI： 10.1002/chem.200901187

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

A detailed investigation of the optical and electrochemical properties of two pentathienoacene derivatives, 2,6-bis(trimethylsilyl)-alpha-pentathienoacene (TMS-T5-TMS) and 2,6-bis(triisopropylsilyl)-alpha-pentathienoacene (TIPS-T5-TIPS), as the neutral and oxidized species was performed in the temperature range of 80-300 K. The experimental solution UV/Vis and solid-state Raman spectra were interpreted by using time-dependent DFT and DFT quantum chemical calculations at the B3LYP/6-31G** level. Bond lengths, HOMO-LUMO positions, and charge distribution were also predicted by computational methods for both the neutral and oxidized states of each thienoacene. As evidenced by ESR and spectroelectrochemical data, upon oxidation the pentathienoacene derivative with the less sterically hindering trimethylsilyl solubilizing groups, TMS-T5-TMS, undergoes pi dimerization to form [TMS-T5-TMS](2)(2+). In contrast, TIPS-T5-TIPS, with the more bulky triisopropylsilyl solubilizing groups, was oxidized to the radical cation but dimerization was prevented due to steric interactions. These experimental observations are supported by DFT calculations, which were used to investigate [TMS-T5-TMS](2)(2+) and [TIPS-T5-TIPS](2)(2+) pi dimers in the solid state and in solution. The redox potentials and absorption peak locations corresponding to the radical cations and pi dimer of TMS-T5-TMS were identified experimentally.

DOI： 10.1002/chem.200900246

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

Ladder pi-conjugated compounds, which have fully ring-fused polycyclic skeletons, are an important class of materials possessing significant potentials for application in organic electronics. The incorporation of main-group elements, such as B, Si P, S, and Se, into the ladder skeletons as bridging moieties is a powerful strategy to endow unusual electronic structures as well as suitable molecular arrangements in the solid state, giving rise to attractive photophysical and electronic properties. Recent efforts have produced a number of fascinating ladder materials, some of which indeed showed high performance as light-emitting materials and charge carrier transporting materials. This Focus Review is an overview of the progress in this chemistry, focusing on several important pi-conjugated skeletons.

DOI： 10.1002/asia.200900179

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Reductive coupling of a 9,10-dibromo-9,10-disilatriptycene derivative followed by treatment with chlorotrimethylsilane (TMSCI) affords a series of TMS-capped 9, 10-disilatriptycene oligomers DSiT[n]. Each isomer, up to the pentamer (n = 5), can be separated using recycling gel permeation chromatography. The X-ray structural analysis of DSiT[2] shows that the six silicon atoms are linearly aligned in a rigid array structure. While the ultraviolet (UV) absorption maximum remains constant at 230 nm, irrespective of the chain length, the magnetic circular dichroism (MCD) spectra exhibit a red shift band near 245 nm, and the emission maximum steadily shifts from 319 to 337 nm as the number of silicon atom increases. These spectra indicate the occurrence of electronic delocalization along the one-dimensional arrangement of bridge-head disilane moieties.

DOI： 10.1021/om701283e

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：CHEMICAL SOC JAPAN  

A series of red-emissive BODIPY derivatives 2-4 having five to seven phenyl groups on their periphery were synthesized., and their photophysical and electrochemical properties were investigated. While the 8-phenyl-substituted derivatives only have moderate fluorescence quantum yields in solution, they can show intense red fluorescence in the PMMA films. The peripheral phenyl groups also affect the redox reversibility in cyclic voltammetry.

DOI： 10.1246/cl.2008.1094

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：SOC SYNTHETIC ORGANIC CHEM JPN  

Utilization of boron, a group 13 element, as a key element for developing new functional electronic and optoelectronic materials is an important direction in the organoboron chemistry. Boron has several characteristic features, such as trigonal planar geometry for trivalent boron compounds, high Lewis acidity, and effective orbital interaction with pi-conjugated frameworks through the vacant p-orbital (i.e., p(pi)-pi* conjugation). Exploiting these features of the boron element for molecular designs allows us to create sophisticated pi-electron materials having attractive photophysical and electronic properties. We here present some progress in our chemistry, including B,B',B"-trianthrylborazine (B3N3)-based molecular bundles, boryl-substituted thienylthiazole pi-electron systems with intramolecular B-N coordination, borole- and dibenzoborole-based pi-conjugated compounds, and boryl-substituted emissive organic solids.

DOI： 10.5059/yukigoseikyokaishi.66.858

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The reaction of pentathienoacene (f-5T) with mCPBA produced a series of oxidized derivatives containing one or two thiophene-S,S-dioxide rings. The regioselectivity of the oxidation reflects the aromaticity of each thiophene ring in the f-5T skeleton, and the extent of the oxidation significantly affects the fluorescence and redox properties.

DOI： 10.1021/ol801136k

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Facile photochemical exocyclic [2 + 2 + 2] cycloaddition produced a series of electron-donating 1,1'-bi(isobenzofuran)s having various aryl groups at the 3,3' positions. The 1,1'-bi(isobenzofuran) skeleton with a highly coplanar structure is a useful building unit to construct the narrow bandgap pi-conjugated systems with low oxidation potentials.

DOI： 10.1021/ol801358c

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A series of l-aryl-2,3,4,5-tetraphenylboroles [Ph(4)C(4)BAr] [Ar = p-MeC(6)H(4) (2), p-Me(3)SiC(6)H(4)(3), p-FC(6)H(4) (4)] were synthesized. The X-ray crystallography of 2-4 revealed that they have short distances between the borole boron atom and the phenyl rings of the neighboring molecules, suggesting the existence of certain intermolecular interaction. Despite this interaction, the borole rings in 2-4 remain planar and contain substantial bond alternation in the butadiene skeleton, which is consistent with the theoretically optimized structures of the singlet boroles. These results demonstrated that the boroles still have antiaromatic character in the crystalline state. Compound 3 and pentaphenylborole [Ph(4)C(4)BPh] (5) were further reacted with potassium or potassium graphite to form potassium borole dianion salts [K(2){Ph(4)C(4)B(p-Me(3)SiC(6)H(4)))] (6) and [K(2){Ph(4)C(4)BPh)] (7), respectively. In their X-ray crystal structures, compounds 6 and 7 are polymeric and have two K(+) ions lying on both sides of the borole plane With eta(5)-coordination.

DOI： 10.1021/om8002812

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Bis-phosphoryl-bridged stilbenes have been synthesized using an intramolecular cascade cyclization. They show intense blue fluorescences at longer wavelengths with higher quantum yields compared to those of the known element-bridged stilbenes. In addition, they have much lower reduction potentials due to the inductive effect of phosphoryl groups. The incorporation of the phosphoryl moiety is an effective way for the construction of highly electron-accepting pi-conjugated systems.

DOI： 10.1021/ol7030608

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

DOI： 10.1002/anie.200801834

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-BLACKWELL  

We report the synthesis and photophysical properties of poly(aryleneethynylene)s (PAEs) containing disilyl- or tetrasilyl-substituted phenylene as the key building unit. The fluorescence spectra of one of the PAEs, consisting of the diethynylbis(trimethylsilyl)phenylene and fluorenylene units, shows an intense blue emission with the maximum at 428 nm. The absolute quantum yield (0,) and the fluorescence lifetime (Phi(F)) are 0.92 and 0.39 ns, respectively. The calculated radiative decay rate constant (k(r)) from the singlet excited state, based on Phi(F) and tau(s), is 2.4 x 10(9) s(-1), which is extremely large for organic molecules. A series of silyl-substituted PAEs, including a tricyclic tetrasilylphenylene-containing polymer, also show intense emissions with large k(r) values. Theoretical calculations of the model systems with the bis(phenylethynyl)benzene skeleton reveal the general substituent effect of the silyl groups attached to the PAE skeleton.

DOI： 10.1002/asia.200800125

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DOI： 10.1002/anie.200802026

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOC CHEMISTRY  

A synthetic route to a dibenzoborole, kinetically stabilized by the 2,4,6-tri-tert-butylphenyl group, was developed, and a series of pi-extended derivatives were synthesized, which show orange-red emissions and stable electrochemical redox properties.

DOI： 10.1039/b716107g

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

The silicon analogues of the oligo(p -phenylenevinylene)s (Si-OPVs) with highly planar structures have been synthesized using a newly developed ligand, the 1,1,3,3,5,5,7,7-octaethyl-s -hydrindacen-4-yl (Eind) group. Their X-ray crystal structures and spectroscopic data demonstrate that the pi-conjugation effectively extends over the Si-OPV framework. Notably, tetrasiladistyrylbenzene exhibits an orange fluorescence even at room temperature both in solution and in the solid state, which is attributable to the effective extension of conjugation. To the best of our knowledge, the tetrasiladistyrylbenzene is the first emissive Si=Si derivative even at room temperature.

DOI： 10.1021/ja0764207

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In this article, we report the characterization of a series of thiophene- and selenophene-based heteroacenes, materials with potential applications in organic electronics. In contrast to the usual alpha-oligothiophenes, these annelated oligomers have a larger band gap than most semiconductors currently used in the fabrication of organic field-effect transistors (OFETs) and therefore they are expected to be more stable in air. The synthesis of these fused-ring molecular materials was motivated by the notion that a more rigid and planar structure should reduce defects (such as torsion about single bonds between alpha-linked units or S-syn defects) and thus improve pi-conjugation for better charge-carrier mobility. The conjugational properties of these heteroacenes have been investigated by means of FT-Raman spectroscopy, revealing that pi-conjugation increases with the increasing number of annelated rings. DFT and TDDFT quantum chemical calculations have been performed, at the B3LYP/6-31G** level, to assess information regarding the minimum-energy molecular structure, topologies, and absolute energies of the frontier molecular orbitals around the gap, vibrational normal modes related to the main Raman features, and vertical one-electron excitations giving rise to the main optical absorptions.

DOI： 10.1021/jp067262t

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ROYAL SOCIETY  

Conjugated polymers undergo facile exciton diffusion. Different molecular structures were examined to study the role of the excited state lifetimes and molecular conformations on energy transfer. There is a clear indication that extended fluorescence lifetimes give enhanced exciton diffusion as determined by fluorescence depolarization measurements. These results are consistent with a strong electronic coupling or Dexter-type energy transfer as the dominating mechanism. The control of polymer conformations in liquid crystal solvents was also examined and it was determined that more planar conformations gave enhanced energy transfer to emissive low band-gap endgroups.

DOI： 10.1098/rsta.2007.2033

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ma0702997

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER INST PHYSICS  

Recently synthesized benzoannulated fused oligothiophenes and oligoselenophenes are introduced as air-stable organic semiconductors for high-performance organic field-effect transistors. To evaluate electronic mobility intrinsic to the materials, the technique of single-crystal transistors is employed for two representative compounds of benzoannulated pentathienoacene f-B5TB and its selenium analog f-BT3STB. High mobility of approximately 1.1 cm(2)/V s is achieved for the selenium compound due to its considerable Se---Se orbital interactions. The materials simultaneously bear features of high mobility and high duration in ambient atmosphere. (c) 2007 American Institute of Physics.

DOI： 10.1063/1.2535617

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A cascade-type anionic double cyclization of (o-silylphenyl)(o-halophenyl)acetylenes via lithiation followed by treatment with elemental chalcogen produces silicon and chalcogen-bridged stilbenes. Based on this reaction, a series of silicon and sulfur- or silicon and selenium-bridged ladder distyrylbenzenes have been synthesized. Their chemical modification by oxidation, crystal structures, and photophysical properties are described.

DOI： 10.1021/ol062615s

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200604935

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Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

The intramolecular double cyclization of bis(3-bromo-2-thienyl)acetylenes though a lithium-halogen exchange reaction with tBuLi followed by treatment with elemental sulfur produces two thiophene-fused thieno[3,2-c](1,2-dithiin)s. The subsequent dechal-cogenation from the 1,2-dithiins with copper nanopowder affords tetrathienoacenes. On the basis of this two-step procedure, a series of trialkylsilyl-terminated, fused oligothiophenes, including hexathienoacene (a six thiophene-fused system) and octathienoacene (an eight thiophene-fused system), were synthesized. In the UV/Vis absorption and fluorescence spectra of the fused oligothiophenes, the absorption and emission maxima shift to longer wavelengths, as the pi-conjugation length increases. Their maximum wavenumbers have linear relationships with the reciprocal number of thiophene rings consisting of the it-conjugated frameworks. In the cyclic voltammograms, all the compounds show reversible oxidation waves, the first oxidation potential of which shifts to less positive as the conjugation length increases. Among them, the octathienoacene also shows a reversible second oxidation process. Indeed, its chemical oxidation with an excess amount of NO+SbF6- produces the dication as a golden crystal. The crystal structures of the neutral octathienoacene and its dication were determined by X-ray crystallography. While in the neutral state, the octathienoacene has a benzenoid structure with a large bond alternation of about 0.04 angstrom, its dication has a quinoid structure in which two cationic charges are mainly localized on the terminal rings.

DOI： 10.1002/chem.200601064

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PubMed

Publishing type：Research paper (international conference proceedings)  

Recently synthesized benzo-annulated fused oligothiophenes and oligoselenophenes are introduced as air-stable organic semiconductors for high-performance organic field-effect transistors. To evaluate electronic mobility intrinsic to the materials, single-crystal transistors are prepared for two representative compounds of benzo-annulated pentathienoacene f-B5TB and its selenium analogue f-BT3STB. High mobility of more than 1 cm2/Vs is achieved for the selenium compound, due to its considerable Se- - -Se orbital interactions. The transistor performances have been stable for two months, indicating high duration of the compound in the ambient atmosphere. Copyright © 2007 Materials Research Society.

Scopus

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ja0637550

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PubMed

Language：English   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

In noncoordinating solvents, meso-cinchomeronimide appended Zn(II) porphyrin 2 forms a cyclic trimer, while diporphyrins 7 exhibit high-fidelity self-sorting assembling to form discrete cyclic trimer, tetramer, and pentamer with large association constants from 7(in-in), 7(in-out), and 7(out-out), respectively, through almost perfect discrimination of enantiomeric and conformational differences of the meso-cinchomeronimide substituents. In the latter self-sorting processes, the dihedral angles dictated by the two pyridyl nitrogen atoms control the size of the aggregates; the trimer from 7(in-in), the tetarmer from 7(in-out), and the pentamer from 7(out-out). Cyclic structures of (2) 3 and (R-7(out-out)) 5 have been determined by single-crystal X-ray diffraction analysis.

DOI： 10.1021/ja0611137

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PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

Bis(thieno[3,2-b]thiophene)-fused 1,2-dithiin reacts with a stoichiometric amount of Ni(cod)(2)/2PPh(3) to produce a dimeric Ni(II) complex via the oxidative addition of the disulfide bond in the 1,2-dithiin skeleton to the Ni(0) center. An X-ray crystal structure analysis revealed that this complex has a dimeric structure in which one sulfur atom derived from the disulfide bond bridges two metal centers. The resultant Ni complex undergoes desulfurization at elevated temperature to produce a fully fused thiophene-based heteroacene.

DOI： 10.1021/om051000g

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：INT UNION PURE APPLIED CHEMISTRY  

Ladder-type pi-conjugated skeletons are promising building units for new materials for organic electronics, wherein their annelated coplanar structures enhance the pi-conjugation, leading to a set of desirable properties such as intense fluorescence and high carrier mobility. As a new entry into this class of skeletons, we now disclose two series of ladder molecules, i.e., silicon- and carbon-bridged oligo(p-phenylenevinylene)s and thiophene- and selenophene-based heteroacenes. The former ladder molecules contain the silole substructure in which the silicon bridges affect the electronic structure and thus photophysical properties through the sigma*-pi* conjugation. The latter heteroacenes can be recognized as the heteroatom analogs of acenes and may be promising materials for organic thin film transistors. These two series of molecules have been synthesized based on newly developed intramolecular cyclizations of acetylenic compounds.

DOI： 10.1351/pac200678040721

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：WILEY-V C H VERLAG GMBH  

DOI： 10.1002/anie.200504391

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Language：English  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE SA  

A series of partially or fully fused ladder oligo(p-phenylenevinylene)s (LOPVs) and related pi-electron systems has been synthesized. Thus, the intramolecular reductive cyclization of o-silyl-substituted bis(phenylethynyl)benzenes with lithium naphthalenide produces partially silicon-bridged bis(styryl)benzenes consisting of silaindene or disilaindacene skeletons. By combining this cyclization with the Friedel-Crafts type electrophilic cyclization, a homologous series of the fully fused LOPVs and related compounds, bearing silicon and carbon bridges, has been synthesized in fairly good yields. The longest example of the LOPVs is the 13-ring-fused system that has a nearly flat pi-conjugated framework with a length of 2.9 nm, as proven by X-ray crystallography. All the produced ladder pi-electron systems show intense fluorescence in the visible region with high quantum yields as well as relatively small Stokes shifts. As the silicon contents increase or the disilaindacene skeleton is incorporated, the emission maxima shift to the longer wavelengths and the fluorescent quantum yields slightly decrease. These trends can be rationalized as due to the sigma* effect of silicon, wherein the silicon bridges contribute to the electronic structure through sigma*-pi* orbital interaction that cause the red-shifts ill the emission maxima and suppress the radiative decay process from the singlet excited state. (c) 2005 Elsevier B.V. All rights reserved.

DOI： 10.1016/j.jorganchem.2005.05.019

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Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

A new intramolecular triple cyclization of bis(o-haloaryl)diacetylenes, via dilithiation followed by reaction with chalcogen elements, produces pi-conjugated compounds containing heterole-1,2-dichalcogenin-heterole fused tricyclic skeletons. The subsequent dechalcogenation with copper metal affords a series of thiophene- and selenophene-based heteroacenes.

DOI： 10.1021/ol0523650

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PubMed

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：SOC SYNTHETIC ORGANIC CHEM JPN  

The intramolecular reductive cyclization of bis(o-silylphenyl)acetylenes with lithium naphthalenide produces bis-silicon-bridged stilbenes. Based on this new cyclization, a series of silicon-bridged ladder pi-conjugated systems consisting of the p-phenylenevinylene framework have been synthesized, including the partially or fully silicon-bridged bis (styryl) benzenes, extended ladder oligo(p-phenylenevinylene)s, and bis-silicon-bridged stilbene-based pi-conjugated polymers. All the ladder pi-electron systems show intense fluorescence in the visible region. The detailed elucidation of their photophysical properties revealed the significant effect of the silicon moieties on the fluorescence properties.

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DOI： 10.1021/ja0537171

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PubMed

DOI： 10.1016/j.jcis.2005.01.003

PubMed

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

DOI： 10.1021/ja042964m

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PubMed

DOI： 10.1246/cl.2005.2

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Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：English   Publishing type：Research paper (scientific journal)  

Language：Japanese   Publishing type：Research paper (scientific journal)   Publisher：AMER CHEMICAL SOC  

pi-Conjugated polymers containing the bis-silicon-bridged stilbene (5,10-dihydro-5,10-disilaindeno[2,1-a]indene) skeleton in the main chain have been synthesized. Our synthesis uses 3,8-dimethoxy derivatives (2) and 3,8-difluoro derivatives (3) of the bis-silicon-bridged stilbene as the key precursors. Thus, their regioselective ortho-metalation reactions with appropriate bases (sec-butyllithium for 2 and (LiBu2ZnTMP)-Bu-t for 3) followed by quenching with electrophiles afford various 2,7-difunctionalized bis-silicon-bridged stilbenes. By using the 2,7-difunctionalized derivatives as starting materials, a series of pi-conjugated polymers, including homopolymers of the bis-silicon-bridged stilbene skeleton and copolymers between the bis-silicon-bridged stilbene unit and other types of monomer units, such as bithiophene and diethynylbenzene, have been synthesized by cross-coupling methodologies. While all the homopolymers of the bis-silicon-bridged stilbene skeleton exhibit an intense blue to greenish-blue emission, the copolymers with the bithiophene and diethynylbenzene units show green and orange emissions, respectively, suggesting easy tuning of the emission colors over a wide range.

DOI： 10.1021/ma0486546

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Language：Japanese  

DOI： 10.1021/ol0486932

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PubMed

Language：Japanese  

DOI： 10.1021/om049695t

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DOI： 10.1039/b310655a

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PubMed

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1246/cl.2003.1104

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Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1002/anie.200250648

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PubMed

DOI： 10.1002/anie.200250788

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PubMed

DOI： 10.1021/ja026689k

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PubMed

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DOI： 10.1021/om020124f

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