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

Alternately stacked donor-acceptor (DA) complexes con-taining 5,11-dimethyl-5,11-dihydroindolo[3,2-b]carbazole (ICZ-Me) as a donor were synthesized for the first time by crystallization with three different acceptor molecules. Among them, the DA complex with tetracyanoethylene (TCNE) exhibited the largest effective charge transfer integral (ItDAI), degree of charge transfer (& mu;), and electrical conductivity (& BULL;). Designing the noncovalent interaction is important to fix the position of acceptors with respect to ICZ-Me and to control the electronic properties.

DOI： 10.1246/cl.230175

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Here we report the development of an equimolar conjugate of a metal-organic cage (MOC) and DNA (MOC-DNA). Several MOC-DNA conjugates were assembled into a programmed structure by coordinating with a template DNA having a complementary base sequence. Moreover, conjugation with the MOC drastically enhanced the permeability of DNA through the lipid bilayer, presenting great potential as a drug delivery system.

DOI： 10.1039/d3cc00460k

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

We report the synthesis, characterization, and electronic properties of the quinoid-based three-dimensional metal-organic framework [Fe2(dhbq)3]. The MOF was synthesized without using cations as a template, unlike other reported X2dhbq3-based coordination polymers, and the crystal structure was determined by using single-crystal X-ray diffraction. The crystal structure was entirely different from the other reported [Fe2(X2dhbq3)]2-; three independent 3D polymers were interpenetrated to give the overall structure. The absence of cations led to a microporous structure, investigated by N2 adsorption isotherms. Temperature dependence of electrical conductivity data revealed that it exhibited a relatively high electrical conductivity of 1.2 × 10-2 S cm-1 (Ea = 212 meV) due to extended d-π conjugation in a three-dimensional network. Thermoelectromotive force measurement revealed that it is an n-type semiconductor with electrons as the majority of charge carriers. Structural characterization and spectroscopic analyses, including SXRD, Mössbauer, UV-vis-NIR, IR, and XANES measurements, evidenced the occurrence of no mixed valency based on the metal and the ligand. [Fe2(dhbq)3] upon incorporating as a cathode material for lithium-ion batteries engendered an initial discharge capacity of 322 mAh/g.

DOI： 10.1021/acs.inorgchem.2c04313

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

Estimating the coordination environment of non-crystalline metal complexes has been an important issue. In this study, we applied machine learning methods to extract features of coordination number and coordination elements from X-ray absorption near edge structure (XANES) spectra of 44 Ni complexes. The spectra were clearly classified according to the coordination number and coordination elements. The similarity between spectra was visualized as a 2D map by dimensionality reduction using multidimensional scaling (MDS).

DOI： 10.1246/cl.230028

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The use of molecular spins as quantum bits is fascinating because it offers a wide range of strategies through chemical modifications. In this regard, it is very interesting to search for organic radical ions that have small spin-orbit coupling values. On the other hand, the feature of the magnetic relaxation of π-organic radical ions is rarely exploited due to the difficulty of spin dilution, and π-stacking interaction. In this study, we focus on N,N′,N′′-tris(2,6-dimethylphenyl)benzenetriimide (BTI-xy), where three xylene moieties connected to the imide groups cover the π-plane of the BTI core. As a result, BTI-xy radical anions without π-stacking interaction were obtained. This led to the slow magnetization relaxation, which is reported for the first time in organic radicals. Furthermore, the relaxation times in a solution state revealed the importance of spin interaction.

DOI： 10.1039/d2cp06026d

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Authorship：Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

Quasi-one-dimensional (1D) compounds are suitable models to develop future nanodevices. The critical issue is that most of the several hundred reported 1D compounds adopt parallel arrangements. Here, we report the first example of an orthogonal grade-separated arrangement of the halogen-bridged metal complex (MX-Chain) [PtII(en)2][PtIVCl2(en)2][FeIIICl5]2, abbreviated as [Pt(en)2Cl][FeIIICl5] (en = ethylenediamine), which is the first example of that arrangement of molecular single chains. The space group and topology are coincidentally same as alchemists' gold, Hg3-delta AsF6, which aligns as atomic single chains. This molecular nanostructure is very rare and valuable as a three-dimensional (3D) nanowiring model. The hydrogen bond network found in [Pt(en)2Cl][FeIIICl5] represents a new strategy for making such nanostructures. The structural and optical relationships are similar to those of typical Pt(II)/Pt(IV) mixed valent MX-Chains in charge-density-wave (CDW) states. Polarized Raman spectra strongly supported the presence of orthogonal grade-separated chains in CDW states. Thus, this work proved the concept of molecular single-chain grade-separated nanowiring.

DOI： 10.1021/acs.chemmater.2c02720

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

DOI： 10.1002/cphc.202200618

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

DOI： https://doi.org/10.1016/j.ccr.2022.214878

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Benzenetriimide (BTI) is a promising building block for materials chemistry due to its characteristic 3-fold symmetry and redox properties, whereas little is known about its conductive and magnetic properties. In this study, we synthesized three charge-transfer complexes based on N,N',N''-trimethylbenzenetriimide (BTI-Me). One of the complexes contains isolated dimers of BTI-Me radical anion (BTI-Me⋅- ), while the other two have the infinite π-stacked array of BTI-Me with the formal charge of -0.5. The latter two complexes did not show metallic behavior but showed semiconducting behavior probably due to the characteristic insulation in one-dimensional electron system, so-called charge ordering and dimer-Mott insulation. The magnetic susceptibility of the complex in dimer-Mott state exhibits an unusual transition from antiferromagnetic to ferromagnetic spin states with the hysteresis loop of 15 K derived from the structural phase transition around 130 K. These properties were also supported by DFT calculations.

DOI： 10.1002/cphc.202200322

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Research Square Platform {LLC}  

In condensed matter, phase separation is strongly related to ferroelasticity, ferroelectricity, ferromagnetism, electron correlation, and crystallography. These ferroics are important for nano-electronic devices such as non-volatile memory. However, the quantitative information regarding the lattice (atomic) structure at the border of phase separation is unclear in many cases. Thus, to design electronic devices at the molecular level, a quantitative electron-lattice relationship must be established. Herein, we elucidated a PdII-PdIV/PdIII-PdIIIphase transition and phase separation mechanism for [Pd(cptn)2Br]Br2(cptn = 1R,2R-diaminocyclopentane), propagated through a hydrogen-bonding network. Although the Pd···Pd distance was used to determine the electronic state, the differences in the Pd···Pd distance and the optical gap between Mott-Hubbard (MH) and charge-density-wave (CDW) states were only 0.012 Å and 0.17 eV, respectively. The N-H···Br···H-N hydrogen-bonding network functioned as a jack, adjusting the structural difference dynamically, and allowing visible ferroelastic phase transition/separation in a fluctuating N2gas flow. Additionally, the effect of the phase separation on the spin susceptibility and electrical conductivity were clarified to represent the quasi-epitaxial crystals among CDW-MH states. These results indicate that the phase transitions and separations could be controlled via atomic and molecular level modifications, such as the addition of hydrogen bonding.

DOI： 10.1021/acs.inorgchem.2c02078

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

Multi-metallic inorganic alloy materials have attracted great attention recently. Additionally, molecule-based materials have wide designability in terms of their structures and electronic states. These are two different ideas. Here, we report the mixing of Pd(III) and Au(III) ions into a bromide-bridged molecular chain compound [Ni(chxn)2Br]Br2 (chxn: 1R,2R-diaminocyclo-hexane) to form an average formula of [Ni0.853Pd0.142Au0.005(chxn)2Br]Br2, which was synthesized by an electrochemical oxidation method. This trimetallic material is revealed to be a MottHubbard state semiconductor with a one-dimensional electronic system like that of [Ni(chxn)2Br]Br2, whereas it shows a smaller activation energy for conductivity than that of pristine [Ni(chxn)2Br]Br2. This work represents a fusion of the concepts of multi-metallic and molecule-based materials using a 1D compound.

DOI： 10.1246/bcsj.20220137

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

Halogen-bridged linear chain metal complexes (MX-Chains) are fascinating compounds that have a quasi-one-dimensional (1D) electronic system. In this study, we synthesized the first Ni-based MX-Chain compound having hydroxy groups, i.e., [Ni(dabdOH)2Br]Br2·[Ni(dabdOHx)2Br]0.5·(2-PrOH)0.25·(MeOH)0.25(1·solvent, x = ∼0.6, dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol). Single-crystal X-ray diffraction revealed that the MX-Chains in 1·solvent formed sheets and single-chain structures in the superlattice. It suggested an MH-like state, whereas the polarized reflection and Raman spectra suggested a CDW-like state. Magnetic and electron spin resonance measurements revealed that both high-spin Ni(II) (∼15%) and low-spin Ni(III) (∼85%) sites are present in the chain structures, i.e., the metal sites show mixed valency. Therefore, we concluded that 1·solvent adopts an intermediate state between the MH and CDW states. Moreover, a single crystal of 1·solvent exhibited semiconductive characteristics along the chain direction. This finding represents a new structural and electronic state of 1D electronic systems as well as MX-Chains.

DOI： 10.1021/acs.inorgchem.2c00473

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

The coordination polymers (CPs) with binary ligands, including 2,5-dihydroxy-1,4-benzoquinone (H2DHBQ) and 4,4′-bipyridyl (bpy), were synthesized using in situ hydrolysis of 2,5-dimethoxy-1,4-benzoquinone (DMBQ). Three kinds of CPs were obtained depending on the metal ions. For M = Mn and Zn, a 1D zigzag chain structure with cis conformation (cis-1D-M) was obtained, whereas Co, Ni, and Cu compounds afforded a 2D net structure with trans conformation (trans-2D-M) with a 1D pore. A linear chain structure was also obtained for M = Cu. Magnetic susceptibility (χMT) at 300 K in cis-1D-Mn and trans-2D-Co was evaluated to be 4.421 and 2.950 cm3 K mol-1, respectively, indicating that both compounds are in the high-spin state. According to the N2 adsorption isotherms at 77 K, trans-2D-Ni showed microporosity with the BET surface area of 177 m2 g-1, whereas the isomorphic trans-2D-Co rarely adsorbed N2 at 77 K. This phenomenon was explained by the difference of diffusion kinetics of the adsorbent molecules, which was supported by the CO2 adsorption isotherms at 195 K. The optical band gaps of cis-1D-Mn, cis-1D-Zn, trans-2D-Co, and trans-2D-Ni were estimated to be 1.6, 1.8, 1.0, and 1.1 eV, respectively, by using UV-vis-NIR spectroscopy.

DOI： 10.1021/acsomega.1c07077

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Authorship：Last author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Royal Society of Chemistry (RSC)  

Intrinsically electron-conductive metallocycle was synthesized. π-Radicals play a key role in constructing π-stacked columns among molecular hexagons and achieving high electrical conductivity over 10⁻⁴ S cm⁻¹ in polycrystalline pellet.

DOI： 10.1039/d2sc00447j

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Many solids, particularly low-dimensional systems, exhibit charge density waves (CDWs). In one dimension, charge density waves are well understood, but in two dimensions, their structure and their origin are difficult to reveal. Herein, the 2D charge-density-wave atomic structure and stabilization mechanism in the bromide-bridged Pd compound [Pd(cptn)2Br]Br2 (cptn=1R,2R-diaminocyclopentane) is investigated by means of single-crystal X-ray diffraction employing the 3D-Δpair distribution function (3D-ΔPDF) method. Analysis of the diffuse scattering using 3D-ΔPDF shows that a 2D-CDW is stabilized by a hydrogen-bonding network between Br− counteranion and the amine (NH2) group of the cptn in-plane ligand, and that 3D ordering is prevented due to a weak plane to plane correlation. We extract the effective displacements of the atoms describing the atomic structure quantitatively and discuss the stabilization mechanism of the 2D-CDW. Our study provides a method to identify and measure the key interaction responsible for the dimensionality and stability of the CDW that can help further progress of rational design.

DOI： 10.1002/cphc.202100857

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Guest-promoted modulation of the electronic states in metal-organic frameworks (MOFs) has brought about a new field of interdisciplinary research, including host-guest chemistry and solid-state physics. Although there are dozens of studies on guest-promoted enhancement of the electrical conductivity properties, including stoichiometry, conductive carriers and structure-property relationships have been scarcely studied in detail. Herein, we studied the effects of continuous and controlled bromine vapor doping on structural, optical, thermoelectric, and semiconducting properties of Cu[Cu(pdt)2] (pdt = 2,3-pyrazinedithiolate) as a function of bromine stoichiometry. We demonstrated that the same material could act as both p- and n-type semiconductors by tuning the stoichiometry of Br doped in Brx@Cu[Cu(pdt)2], and a change in the charge-carrier type from holes in pristine MOF to electrons upon bromine vapor doping was observed. Bromine molecules acted as an oxidant, causing the selective oxidation of [CuII(pdt)2] in the host framework. In addition, a redox hopping pathway between the partially oxidized CuII/CuIII center contributed to the enhancement of the electrical conductivity of the MOF.

DOI： 10.1021/acs.inorgchem.1c03933

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Current-voltage characteristics and dielectric properties were studied in bromo-bridged one-dimensional compounds, [Pd(en)2Br](Suc-C5)2·H2O, exhibiting mixed-valence and averaged valence (MV-AV) phase transition. In the AV phase, clear nonlinear current-voltage characteristics were observed. This phenomenon was explained by the thermally induced electron-hole separation assisted by an electric field. This mechanism was supported by the dielectric properties of [Pd(en)2Br](Suc-Cn)2·H2O (n = 5 and 6).

DOI： 10.1039/d2cp00051b

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Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

Temperature dependency of the 15N CP-MAS NMR spectrum were examined in quasi-one-dimensional bromo-bridged palladium compound [Pd(en)2Br](Suc-C5)2 H2O (Suc-C5 = dipentylsulfosuccinate), which shows mixed-valence (MV) to averaged-valence (AV) phase transition. Single and double peaks were observed at lower and higher temperature sides from the phase transition temperature, reflecting that they are AVand MV states, respectively. Peak-to-peak interval in the spectra steadily decreased upon cooling, showing the charge-density-wave (CDW) amplitude decreased accompanied by approaching the AV state.

DOI： 10.1246/cl.210804

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

Abstract

The creation of low-dimensional heterostructures for intelligent devices is a challenging research topic; however, macro- and atomic-scale connections in one-dimensional (1D) electronic systems have not been achieved yet. Herein, we synthesize a heterostructure comprising a 1D Mott insulator [Ni(chxn)₂Br]Br₂ (1; chxn = 1R-2R-diaminocyclohexane) and a 1D Peierls or charge-density-wave insulator [Pd(chxn)₂Br]Br₂ (2) using stepwise electrochemical growth. It can be considered as the first example of electrochemical liquid-phase epitaxy applied to molecular-based heterostructures with a macroscopic scale. Moreover, atomic-resolution scanning tunneling microscopy images reveal a modulation of the electronic state in the heterojunction region with a length of five metal atoms (~ 2.5 nm), that is a direct evidence for the atomic-scale connection of 1 and 2. This is the first time that the heterojunction in the 1D chains has been shown and examined experimentally at macro- and atomic-scale. This study thus serves as proof of concept for heterojunctions in 1D electronic systems.

DOI： 10.1038/s41467-022-28875-8

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Other Link： https://www.nature.com/articles/s41467-022-28875-8

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The first interdigitated MX-type chain complex with infinite π-stacked arrays was synthesized. The synchronization between a Pt-Br⋯ chain and π-stacking periodicities led to the longest M-X-M distance (6.6978(15) Å) and nil or negligible intervalence charge transfer, which is essential to realize the Robin-Day class I mixed valence state in MX chains.

DOI： 10.1039/d1dt02996g

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Ohmic contacts are of critical importance to improve the performance of semiconductor devices as well as those of low-dimensional materials. Halogen-bridged metal complexes (MX-Chains) are fascinating quasi-one-dimensional (1D) electronic materials. However, reports on the electrical characteristics of MX-Chains remain elusive. Herein, we report the electrical characteristics of single crystals of [Ni(chxn)2Br]Br2 (chxn: (1R,2R)-(−)-1,2-cyclohexanediamine), which is a 1D Mott insulator, using different probe arrangements. [Ni(chxn)2Br]Br2 was shown for the first time to exhibit Ohmic characteristics on the crystal surface, albeit that the conductivity behavior of the interior of the crystal is nonlinear due to the Joule heating effect. The current flow on the surface is shallow (a few micrometers in depth) despite the millimeter-scale crystal size; this phenomenon is strongly connected to its structural anisotropy. The Ohmic contact revealed in this work should be valuable for the application of MX-Chains as electronic devices in the near future.

DOI： 10.1002/asia.202100637

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Reversible H2storage under mild conditions is one of the most important targets in the field of materials chemistry. Dihydrogen complexes are attractive materials for this target because they possess moderate adsorption enthalpy as well as adsorption without cleavage of the H-H bond. In spite of these advantages, H2adsorption studies of dihydrogen complexes in the solid state are scarce. We herein present H2adsorption properties of the 16-electron precursor complex ([Mo(PCy3)2(CO)3]) in the solid state synthesized by two procedures. One is the direct synthesis under an Ar atmosphere (1), and the other is removal of the N2-adduct under vacuum (2).2showed ideal Langmuir type reversible ad/desorption of H2above room temperature, whereas1showed irreversible adsorption. The adsorption enthalpy of2was larger than that in THF solution. Using DFT calculation, this difference was explained by the absence of the agostic interaction in the solid state.

DOI： 10.1039/d1dt01404h

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Redox-active metal-organic frameworks (MOFs) have great potential for use as cathode materials in lithium-ion batteries (LIBs) with large capacities because the organic ligands can undergo multiple-electron redox processes. However, most MOFs are electrical insulators, limiting their application as electrode materials. Here, we report an electron-conductive MOF with a 2,5-dihydroxy-1,4-benzoquinone (dhbq) ligand, Fe(dhbq). This compound had an electrical conductivity of 5 × 10-6 S cm-1 at room temperature due to d-πinteractions between the Fe ion and the ligand and the permanent microporosity. Fe(dhbq) had an initial discharge capacity of 264 mA h g-1, corresponding to the two-electron redox process of dhbq.

DOI： 10.1021/acsami.1c06571

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Authorship：Last author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

Naphthalenediimide (NDI) is generally a yellowish to reddish chromophore, which shows vapochromism by the alternation of charge-transfer (CT) interactions at the NDI core. On the contrary, we discovered that the deprotonation of N,N - dihydroxy-1,4,5,8-naphthalenetetracarboxdiimide (NDI-(OH)2) gave a bluish organic salt with a hydrochromic property, which has been rare in conventional NDI derivatives. On the basis of the structural analyses and the calculation, the origin of the hydrochromism can be explained by the change of hydrogenbond interaction between the anionic imide group and H2O molecules.

DOI： 10.1246/cl.210275

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A new family of liquid π-donors, lipophilic dihydrophenazine (DHP) derivatives, show remarkably high π-electron-donor property which exhibit supramolecular alternating copolymerization with 7,7,8,8-tetracyanoquinodimethane (TCNQ), giving ionic charge-transfer (ICT) complexes. The ICT complexes form distinct columnar liquid crystalline (LC) mesophases with well-defined alternating molecular alignment as demonstrated by UV-Vis-NIR spectra, IR spectra, and X-ray diffraction (XRD) patterns. These liquid crystalline ICT complexes display unique phase transitions in response to mechanical stress: the columnar ICT phase is converted to macroscopically oriented smectic-like mesophases upon applying shear force. Although there exist reports on the formation of ICT in the crystalline state, this study provides the first rational identification of ICT mesophases based on the spectroscopic and structural data. The liquid crystalline ICT phases are generated by strong electronic interactions between the liquid π-donors and solid acceptors. It clearly shows the significance of simultaneous fulfillment of strong π-donating ability and ordered self-assembly of the stable ICT pairs. The flexible, stimuli-responsive structural transformation of the ICT complexes offer a new perspective for designing processable CT systems with controlled hierarchical self-assembly and electronic structures.

DOI： 10.3389/fchem.2021.657246

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The Pd(iii) oxidation state is unusual and unstable since it strongly tends to disproportionate. We synthesized the quasi-one-dimensional (1D) halogen-bridged Pd(iii)-Cl complex [Pd(dabdOH) Cl]Cl (1-Cl; dabdOH = (2S,3S)-2,3-diaminobutane-1,4-diol) with multiple hydrogen bonds. From single-crystal X-ray diffraction, the bridging Cl ions were located at the midpoint of the Pd-Cl-Pd moieties in the 1D chains, indicating that the Pd ions are in a Pd(iii) average valence (AV) state. Moreover, bright spots for the Pd(iii) d orbitals in the upper Hubbard band above the Fermi level were observed every ∼5 Å using scanning tunnelling microscopy. These results clearly indicate that the Pd ions are in a Pd(iii) AV state in1-Cl. In addition,1-Clhas the highest thermal stability (470 K) among the Pd(iii) complexes reported and the highest electrical conductivity (0.6 S cm at 300 K) among the 1D Pd-Cl chains reported so far. 2 2 z2 − −1

DOI： 10.1039/d0dt03848b

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© 2020 by the authors. Licensee MDPI, Basel, Switzerland. The studies of crystal structures with hydrogen bonds have been actively pursued because of their moderate stabilization energy for constructing unique structures. In this study, we synthesized a molecular conductor based on 2,6-bis(4-pyridyl)-1,4,5,8-tetrathiafulvalene (trans-TTF-py2). Two pyridyl groups were introduced into the TTF skeleton toward the structural exploration in TTF-based molecular conductors involved by hydrogen bonds. In the obtained molecular conductor, (trans-TTF-py2)1.5(PF6)·EtOH, short contacts between the pyridyl group and the hydrogen atom of the TTF skeleton were observed, indicating that hydrogen bonding interactions were introduced in the crystal structure. Spectroscopic measurements and conductivity measurement revealed semiconducting behavior derived from π-stacked trans-TTF-py2 radical in the crystal structure. Finally, these results are discussed with the quantified hydrogen bonding stabilization energy, and the band calculation of the crystal obtained from density functional theory calculation.

DOI： 10.3390/cryst10121081

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© The Royal Society of Chemistry. Preliminary chemical reduction of naphthalenediimide (NDI)-based organic ligands was applied to the synthesis of a porous molecular conductor (PMC) with neutral metal nodes (cobalt(ii) acetylacetonate). The obtained semiconductive PMC (PMC-2) was stable due to the neutral metal nodes, providing an advantage over electrochemical reduction. This journal is

DOI： 10.1039/d0cc03541f

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

© The Royal Society of Chemistry. A flexible coordination polymer with a naphthalenediimide core exhibited reversible desorption-adsorption of solvent molecules and an enhancement of electrical conductivity (∼10-7 S cm-1) upon chemical reduction using hydrazine.

DOI： 10.1039/d0cc03062g

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© The Royal Society of Chemistry 2020. Coexistence of zigzag structure and the uncommon Pd(iii) oxidation state in quasi-1D halogen-bridged metal complexes was realized in a conductive Br-bridged Pd chain complex, [Pd(dabdOH)2Br]SO4·3H2O (2), for the first time. Intra- and interchain hydrogen-bond networks among the (2S,3S)-2,3-diaminobutane-1,4-diol (dabdOH) ligand and SO42−and H2O molecules support this unusual structure and electronic state. The electrical conductivity of2reached 0.05 S cm−1at room temperature.

DOI： 10.1039/d0ce00332h

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DOI： 10.1002/chem.201903934

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/chem.201903934

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DOI： 10.1002/chem.201905439

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Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1002/chem.201905439

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

<p>A tetranuclear Cu^II complex composed of a doubly bpypz⁻ bridged dinuclear Cu^II complex with TCNQ˙⁻ self-assembles into a 3D supramolecular coordination architecture <italic>via</italic> complementary weak coordination bonding and π-stacking interactions.</p>

DOI： 10.1039/c9ce01580a

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

Sensitive chemo-switchable magnetic materials operating at room temperature are one of the most potential candidates for future chemical devices. Here, we report a discrete iron(III) complex that exhibits high-spin/low-spin switching, sensitive even to rare water-vapor atmosphere above room temperature. The transformation of the hydrogen-bonded network triggered by water molecules is closely associated with the spin-state changing.

DOI： 10.1246/cl.190532

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DOI： 10.1039/c9dt01684h

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DOI： 10.1002/chem.201901288

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<p>MX-type one-dimensional complexes containing only an aromatic in-plane ligand were synthesized for the first time.</p>

DOI： 10.1039/c9dt00784a

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DOI： 10.1021/jacs.9b01717

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DOI： 10.1021/acs.inorgchem.8b01910

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© 2019 The Chemical Society of Japan. Porous coordination polymer (PCP) with 2,7-bis(4-pyridyl)-[1]benzothieno[3,2-b][1]benzothiophene (BTBT-4py) ligands was synthesized. The PCP provides both pores and infinite π-stacked columns via the assemblies of linear coordination polymers. The overlap integrals between highest occupied molecular orbitals (HOMOs) of adjacent ligands largely depend on the conformation of BTBT cores. The PCP also showed drastic structural change induced by desolvation. This approach to introduce porosity in organic semiconductor crystal can lead to the development of molecular-based devices, such as porous field-effect transistor.

DOI： 10.1246/cl.190276

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DOI： 10.1002/zaac.201700461

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

MX chains have been widely studied as a 1D mixed-valence system. Although there have been a large number of studies on the boundary between class II and III materials of the Robin-Day classification, there are few studies of compounds at the boundary between classes I and II. In this study, we synthesized a series of Pt- and Pd- MX-chain compounds with perrhenate counterions, [M(en)2][M(en)2X2](ReO4)4 (X = Br for M = Pd and X = Cl, Br, and I for M = Pt). All compounds were isostructural, and the metal-metal distances within the chain exceed 6 Å, which is the longest among MX-chain compounds thus far reported. For [Pt(en)2][Pt(en)2Cl2](ReO4)4 (PtCl), an intervalence charge transfer (IVCT) transition was observed in the UV region at 335 nm (3.7 eV), which is the shortest wavelength for the MX-chain compounds thus far reported, indicating that PtCl is the closest to the Robin-Day class I limit.

DOI： 10.1021/acs.inorgchem.7b03051

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

Hydrostatic (physical) pressure effects on the electrical resistivity of a bromido-bridged palladium compound, [Pd(en)2Br](Suc-C5)2·H2O, were studied. The charge-density-wave to Mott-Hubbard phase transition temperature (TPT) steadily increased with pressure. By a comparison of the effects of the chemical and physical pressures on TPT, it was estimated that the chemical pressure by unit alkyl chain length, i.e., the number of carbon atoms in the alkyl chains within the counterion, corresponded to ca. 1.3 kbar of the physical pressure.

DOI： 10.1021/acs.inorgchem.7b02566

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

We synthesized cyano-bridged three dimensional metal-organic frameworks [M-II(H2O)(2)Pt-IV(CN)(4)Br-2](infinity) center dot n(H2O) (1: M = Co, 2: M = Ni) with an NbO type topology. Although 1 and 2 have no accessible pores, these MOFs were found to undergo reductive elimination of the axial bromides on the Pt-IV ions as well as removal of water molecules upon heating to form porous [(MPtII)-Pt-II(CN)(4)](infinity) (1 ': M = Co, 2 ': M = Ni) with retention of their crystallinity.

DOI： 10.1039/c7cc01766a

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

A Br-bridged Pd chain complex with the Pd ion in an uncommon +3 oxidation state, [Pd(dabdOH)(2)Br]Br-2 (3), was prepared using a new method involving multiple hydrogen bonds. The PdBr chain complex exhibited superior electrical conductivity and thermal stability. An in-plane ligand with an additional hydrogen donor group (hydroxy group), (2S,3S)-2,3-diaminobutane-1,4-diol (dabdOH), was used to create a multiple-hydrogen-bond network, which effectively shrinks the Pd-Br-Pd distance, stabilizing the Pd(III) state up to its decomposition temperature (443 K). 3 shows semiconducting behavior with quite high electrical conductivity (3-38 S cm(-1) at room temperature), which is 10(6) times larger than the previous record for analogous PdBr chains. Indeed, 3 is the most conductive MX-type chain complex reported so far. The precise positional control of ions via a multiple-hydrogen-bond network is a useful method for controlling the electronic states, thermal stability and conductivity of linear coordination polymers.

DOI： 10.1021/jacs.7b02558

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

Self-assembly of Keggin-type polyoxometalates (POMs) with diammonium ions containing oligo(ethylene oxide) units form parallelepiped or octahedral nanocrystals. These structures are tunable depending on the chemical structure of the ammonium ions and preparative conditions. The ether linkages in these ammonium ions exert conformational flexibility, which is essential to achieve long-range regular molecular alignments in the nanocrystals.

DOI： 10.1246/cl.161124

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

Anionic Keggin polyoxometalates (POMs) and ether linkage-enriched ammonium ions spontaneously self-assemble into rectangular ultrathin nanosheets in aqueous media. The structural flexibility of the cation is essential to form oriented nanosheets; as demonstrated by single-crystal X-ray diffraction measurements. The difference in initial conditions exerts significant influence on selecting for self-assembly pathways in the energy landscape. Photoillumination of the POM sheets in pure water causes dissolution of reduced POMs, which allowed site-specific etching of nanosheets using laser scanning microscopy. By contrast, photoetching was suppressed in aqueous AgNO3 and site-selective deposition of silver nanoparticles occurred as a consequence of electron transfer from the photoreduced POMs to Ag+ ions on the nanosheet surface.

DOI： 10.1002/anie.201612473

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

A neutral mononuclear Fe-III complex [Fe-III(H-5-Br-thsa-Me)(5-Br-thsa-Me)]H2O (1; H-2-5-Br-thsa-Me=5-bromosalicylaldehyde methylthiosemicarbazone) was prepared that exhibited a three-step spin-crossover (SCO) with symmetry breaking and a 14K hysteresis loop owing to strong cooperativity. Two ordered intermediate states of 1 were observed, 4HS-2LS and 2HS-4LS, which exhibited reentrant phase-transition behavior. This study provides a new platform for examining multistability in SCO complexes.

DOI： 10.1002/anie.201511281

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

We synthesized a bromo-bridged Pd complex, which underwent as lowering the temperature a charge-density-wave (CDW) to Mott-Hubbard (MH) phase transition, as confirmed by using X-ray diffraction analysis, ESR, FT-IR and Raman spectroscopies. The complex showed a phase-separation phenomenon with a striped pattern over a wide temperature range, and domain propagation was observed using an optical microscope. Moreover, we observed changes in the local electronic state accompanying the phase transition by using scanning tunneling microscopy (STM).

DOI： 10.1002/slct.201600065

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

Quasi-one-dimensional halogen-bridged Pt, Pd, and Ni complexes (MX chains) are a family of materials with potential charge bistability: M(II)-M(IV) mixed valence charge-density-wave (CDW) and M(III) averaged valence Mott-Hubbard (MH) states can form. However, until recently, no examples of MX chains showing charge bistability have been reported. Charge-bistable Pd MX chains, [Pd(en)(2)Br](Y1-C-n)(2)center dot H2O (en = 1,2-diaminoethane; Y1-C-n = dialkyl 2-sulfosuccinate; n = the number of carbon atoms in alkyl chains) and [Pd(en)(2)Br](Y2-C-n)(2)center dot H2O (Y2-C-n = dialkyl alpha-sulfomalonate), both of which showed phase transitions between Pd(III) MH and Pd(II,IV) CDW states, were prepared by utilizing chemical pressure. In addition, [Pd(en)(2)Br](Y1-C-n)(2) center dot H2O underwent pressure- and photo-induced MH-CDW phase transitions. [Pd(en)(2)Br](Y2-C-n)(2)center dot H2O has a higher transition temperature, i.e., higher stability of the MH state, than [Pd(en)(2)Br](Y1-C-n)(2)center dot H2O does due to the difference in the crystal packing. The recent progress will lead to new pressure sensing and optical switching devices.

DOI： 10.1039/c5dt00439j

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

The optical gap in a series of bromo-bridged platinum chain complexes, [Pt(en)(2)Br](C-n-Y)(2).H2O (en = ethylenediamine; Cn-Y = dialkyl sulfosuccinate; n = the number of carbon atoms), was controlled by using chemical pressure. From the single-crystal structure, [Pt(en)(2)Br](C-6-Y)(2).H2O is in a mixed-valence state at 200 K. In addition, Pt-Pt distances decreased with an increase in n or with a decrease in the temperature. Continuous decreases in the optical gaps upon cooling were observed for n = 5, 7. The smallest gap of 1.20 eV was observed for n = 7 at 50 K. For n = 12, the complex was still in a mixed-valence state at 5 K, although the Pt-Pt distance was quite short. This is probably because of the energetic mismatch between 5dz(2) orbitals of the Pt ions and 4pz orbitals of the Br ions.

DOI： 10.1021/ic502071u

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

Electron-transfer-facilitated dissolution, ion insertion, and desorption associated with an MMX-type quasi-one-dimensional iodide-bridged dinuclear Pt complex (MMX chain) have been investigated for the first time. K-2(NC3N)-[Pt-2(pop)(4)1]center dot 4H(2)O (1) (NC3N2+ = (H3NC3H6NH3)(2+); pop = P2H2O52-) is a semiconductor with a three-dimensional coordination-bond and hydrogen-bond network included in the chain. The cyclic voltammetry of 1 was studied by using 1-modified electrodes in contact with acetonitrile solutions containing electrolyte. The chemical reversibility for oxidation of 1 depended on the electrolyte cation size, with large cations such as tetrabutylammonium (Bu4N+) being too large to penetrate the pores formed by the loss of K+ and NC3N2+ upon oxidation. The potential for reduction of 1 decreased as the cation size increased. The presence of the acid induced additional well-defined processes but with gradual solid dissolution, attributed to the breaking of the coordination-bond networks.

DOI： 10.1021/ic402980t

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

MMX-Type quasi-one-dimensional iodide-bridged diplatinum complexes (MMX chains) provide various electronic states and attractive physical properties. In this review, we summarize the recent progress in MMX chains consisting of pyrophosphite (pop) ligands. The MMX chains with binary countercations, which have short Pt-I-Pt distance and robust frameworks, form a new electronic state. They show reversible dehydration-rehydration accompanied by the change of electronic states and electrical conductivity. Relatively high electrical conductivity in the MMX chains with binary countercations enables us to investigate the negative differential resistance (NDR) and electrochemical characteristics in the solid state for the first time in MMX chains.

DOI： 10.1246/cl.130961

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

I-129 Mossbauer spectroscopy was applied to water-vapor-responsive MMX-type quasi-one-dimensional iodide-bridged Pt complexes (MMX chains)in order to investigate their electronic state quantitatively. Two sets of octuplets observed in K-2(H3NC3H6NH3)[Pt-2(pop)(4)I]center dot 4H(2)O (2 center dot 4H(2)O)and one octuplet observed in K-2(cis-H(3)NCH(2)CHvCHCH(2)NH(3))[Pt-2(pop)(4)I]center dot 4H(2)O (1 center dot 4H(2)O)and dehydrated complexes (1 and 2)indicate a unique alternating charge-polarization + charge-density-wave (ACP + CDW)electronic state and a charge-density-wave (CDW)electronic state, respectively. These spectra correspond to their crystal structure and the change of electronic states upon dehydration. Since these complexes consist of an alternating array of positively charged and negatively charged layers, the charge on the iodide ion (rho(IS))was discussed on the basis of the isomer shift (IS). The rho(IS) of the water-vapor-responsive MMX chains was mainly -0.13 to -0.21, which are the smallest of all MMX chains reported so far. Hence, it indicates that the negative charge on the iodide ion is strongly donated to the Pt ion in these complexes. This covalent interaction predominates in the ACP + CDW state as well as in the CDW state. Therefore, the ACP + CDW state is in fact the CDW state with the ACP-type lattice distortion. Because the rho(IS) became smaller with the decreasing Pt-I-Pt distance, it can be concluded that the covalent interaction plays an important role in determining the electronic states of the MMX chains with pop (= P2H2O52-)ligands.

DOI： 10.1039/c4dt00627e

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

Negative differential resistance (NDR) was discovered in MX- and MMX-type iodide-bridged platinum complexes for the first time. The low resistance of the complex observed under the large current cannot be explained only by the Joule heat. The intrinsic charge-ordering states are considered to play an important role in the NDR of these compounds.

DOI： 10.1021/ic402277x

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

MMX-type quasi-one-dimensional iodide-bridged dinuclear Pt complexes (MMX chains) with binary countercations show a new alternating charge-polarization + charge-density-wave (ACP+CDW) electronic state and reversible switching of the electronic states and physical properties upon dehydration and rehydration process. By comparing several MMX chains with various binary countercations with previous chains, we found that the short backbone of the aliphatic diammonium ion was indispensable for realizing the ACP+CDW state because it induces a 2-fold periodicity along the chain axis via twisting of the ligands. Moreover, the reversibility of the changes in the structure and electrical conductivity upon dehydration and rehydration depend on the length of aliphatic diammonium ion. Short diammonium ions support a robust framework, which undergoes reversible structural changes. On the other hand, long and bent aliphatic diammonium ions weaken the framework, which causes partial degradation of the crystal and a decrease in the electrical conductivity when the structure changes. However, the decrease in the activation energy of the electrical conductivity after the dehydration process is independent of the robustness of the complex, indicating that the orbital overlap in MMX chains with binary countercations increases upon dehydration. Controllable electronic states and physical properties provide a platform for designing the multifunctional materials based on MMX chains.

DOI： 10.1021/ic301469u

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

Electron spin resonance (ESR) measurements have been performed on a series of quasi-one-dimensional iodo-bridged diplatinum complexes K-2[C3H5R(NH3)(2)][Pt-2(pop)(4)I]center dot 4H(2)O (pop = P2H2O52-; R = H, CH3, or Cl), where dehydration/ rehydration of the crystalline water switches the electronic state reversibly with retention of single crystallinity. We have observed a nonmagnetic nature in as-grown samples, whereas in the dehydrated samples, a clear enhancement of the spin susceptibility has been observed above similar to 80 K with the activation energy ranging 50-60 meV. The activated spins originate from isolated Pt3+ state on the chain, as confirmed from the principal g values. Concomitantly, the ESR linewidth exhibits a prominent motional narrowing, suggesting that the activated Pt3+ spins are mobile solitons generated in the doubly degenerate charge-density-wave states of the dehydrated salts.

DOI： 10.1103/PhysRevB.85.073104

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

The first MMX-type quasi-one-dimensional (Q1D) Pt chain complex (MMX chain) that contains a mono-protonated diamine as countercation, {o-(H3NC6H4NH2)}(4)[Pt-2(pop)(4)I]center dot H2O (pop = P2H2O52-), was synthesized. According to the crystal structural analysis, -NH2 group was hydrogen-bonded to either lattice H2O molecule or -NH3+ group in addition to typical hydrogen bond between -NH3+ group and pop ligand. To control the partial deprotonation of the countercation will be an important method for achieving the high-conductive MMX-chain polymer by the hole doping.

DOI： 10.3390/polym3041652

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

DOI： 10.1002/anie.200905608

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

The dehydrated vapochromic 1D coordination polymer, (H(3)NC(4)H(8)NH(3))(2)[Pt(2)(pop)(4)I] (1) was synthesized directly from methanol solution. Although vapochromic 1 center dot A 4H (2) O has been synthesized, dehydrated high-temperature structure has never been determined because of lowering the quality of crystal by dehydration. The crystal structure of 1 was determined by X-ray crystal structure analysis, and we confirmed that it was identical to the dehydrated high-temperature structure of 1 center dot A 4H (2) O by comparing the powder X-ray diffraction (XRD) patterns. The Pt-I-Pt distance (d(Pt-I-Pt)) of compound 1 center dot A 4H (2) O was shortened for approximately 1.1 A... by desorption of water to form compound 1, accompanied with phase transition in electronic states. The other crystal including methanol molecule as lattice solvent, 1 center dot A 2MeOH, was also obtained as by-product. The synthesis from various kinds of organic solvent has the great potential to develop the field of vapochromism accompanying phase transition of electronic state.

DOI： 10.1007/s10904-008-9242-8

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

A new charge-ordering (CO) state in quasi-1D iodide-bridged dinuclear Pt complexes (MMX-chains) was developed by introducing two different kinds of countercations. From crystal structure analysis, K(2)(H(3)NCH(2)CHMeCH(2)NH(3))[Pt(2)(pop)(4)I]center dot 4H(2)O (pop = P(2)H(2)O(5)(2-)) had structural features of both ACP (alternating charge-polarization) and CDW (charge-density-wave) states. Therefore, this new CO state was named ACP+CDW state. Remarkably, the structure was three dimensionally ordered, which was verified by the strong superlattice reflections observed in an X-ray oscillation photograph. Using polarized Raman and (31)P MAS NMR spectroscopies, it was shown that there were two different Pt(2) units and four inequivalent P atoms, respectively. These results agreed with the crystal structure analysis and supported the presence of the ACP+CDW state.

DOI： 10.1021/ja807901p

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

Linear-chain iodo-bridged dinuclear Pt mixed-valence compounds with aromatic ammonium countercations, A(4)[Pt2I(POP)(4)]center dot nH(2)O [POP = P2O5H22-, A = benzyl ammonium (n = 2; 1), anilinium (n = 2; 2), and p-methoxy anilinium (n = 2; 3)], that have three-dimensionally ordered structures were synthesized. In the case of 1-3 the aromatic ammonium countercations were located between neighboring Pt chains and stacked in 1D columns. pi-pi Interactions between the phenyl rings and hydrogen bonds between the -NH3+ moieties and the oxygen atoms of the pop ligand link the Pt chains together, thus giving rise to a three-dimensionally ordered CDW state. This is the first observation of this phenomenon in compounds of this type. ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008).

DOI： 10.1002/ejic.200701276

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

This article describes the electronic structure of the Co-III doped Br bridged Ni-III complexes, [Ni(1-x)Co(x)chxn)(2)Br]Br-2 (x = 0.01, 0.02, 0.05, and 0.11) by using a optical spectroscopy, scanning tunneling microscopy (STM), and electron spin resonance spectroscopy. In the optical reflectivity spectrum, the new band was formed at about 0.5 eV, which is reasonably recognized as the d(z)2 band of doped Co-III ions. In the STM images of [Ni1-x,Co-x(chxn)(2)Br]Br-2, the bright spots attributable to the tunnel current from the Fermi level of the STM tip to the conduction band of the sample were observed. In addition, some brighter spots were also observed. Because the number of the brighter spots is in good agreement with that of doped Co species, the brighter spots can be assigned to doped Co-III sites. These are reasonably explained by the tunnel current from the Fermi level of the tip to the d(z)(2) band of Co-III. The Curie spin concentration was gradually increased with increasing Co-III ions, which is explained by the scissions of the S = 1/2 1D antiferromagnetic chains.

DOI： 10.1021/ic7012232

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Language：Japanese   Publishing type：Article, review, commentary, editorial, etc. (trade magazine, newspaper, online media)   Publisher：化学同人  

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Language：English   Publisher：Springer-Verlag Wien  

Pyrophosphito-bridged diplatinum complex is one of the most studied dinuclear complexes in a paddle-wheel structure. The chemistry of pyrophosphito-bridged diplatinum complex began at the discovery of the Pt(II)-Pt(II) complex, K4[Pt2(pop)4]·2H2O (pop = P2H2O 5 2-) by Roundhill et al. in 1977 [1]. Since [Pt2(pop)4]4- shows intense long-lived phosphorescence, photochemistry and excited-state chemistry of [Pt2(pop)4]4- has been attracted much attention (see following early reviews and references therein [2, 3]). Although no chemical bond exist between two Pt(II) atoms in the ground state, 5dσ → 6pσ transition should induce the bonding character between them. This excited-state structure has been confirmed by several optical methods [4-9]. The excited state of [Pt2(pop)4]4- is powerful one-electron reductant, therefore, it can be used as a photochemical catalyst for converting ethanol to acetaldehyde and hydrogen [10] and for the transfer hydrogenation of alkenes and alkynes [11, 12]. The Pt(III)-Pt(III) complex, [Pt2(pop)4H2]4-, is the active species of the catalytic reaction [13].

DOI： 10.1007/978-3-7091-1317-2_10

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