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

DOI： https://doi.org/10.5059/yukigoseikyokaishi.78.856

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

DOI： 10.1021/jacs.9b02864

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

DOI： 10.1021/jacs.9b02517

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

DOI： 10.1021/jacs.8b04904

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

The oxidation of organic substrates is of fundamental importance in nature and includes key transformations in organic synthesis and industry. Dioxygen (O2) is potentially the greenest oxidant because O2 is available in air and its reduction product is water, which is environmentally the most benign substance. However, the direct thermal oxidation of organic substrates with O2 is spin-forbidden because the spin state of ground-state O2 is triplet and the spin state of most organic substrates is singlet. Transition metal complexes can react with triplet O2 in the presence of an electron source to produce metal-oxygen intermediates, such as metal-oxo and metal-hydroperoxo complexes, that can oxidize substrates under mild conditions. Various thermal and photocatalytic mechanisms of the oxidation of organic substrates by O2 with transition metal complexes have been critically discussed by focusing on how metal-oxygen intermediates are produced in the presence of an electron source and then react with organic substrates. Metal-oxygen intermediates are more easily produced by the reactions of metal complexes with hydrogen peroxide (H2O2) and act as active catalysts for the oxidation of substrates by H2O2. The photocatalytic oxidation of water by O2 to produce H2O2 has been combined with the catalytic oxidation of organic substrates by H2O2 to achieve the photocatalytic oxidation of organic substrates by O2. The photocatalytic oxidation of organic substrates by O2 with the use of water as an electron source has also been made possible by the use of inorganic and organic photocatalysts, which can be combined with transition metal complexes as catalysts for thermal reaction steps.

DOI： 10.1039/c7gc03387g

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Scopus

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

Classic formulations of aromaticity have long been associated with topologically planar conjugated macrocyclic systems. The theoretical possibility of so-called bicycloaromaticity was noted early on. However, it has yet to be demonstrated by experiment in a simple synthetic organic molecule. Conjugated organic systems are attractive for studying the effect of structure on electronic features. This is because, in principle, they can be modified readily through dedicated synthesis. As such, they can provide useful frameworks for testing by experiment with fundamental insights provided by theory. Here we detail the synthesis and characterization of two purely organic non-planar dithienothiophene-bridged [ 34] octaphyrins that permit access to two different aromatic forms as a function of the oxidation state. In their neutral forms, these congeneric systems contain competing 26 and 34 pi-electronic circuits. When subject to two-electron oxidation, electronically mixed [4n+1]/[4n+1] triplet biradical species in the ground state are obtained that display global aromaticity in accord with Baird's rule.

DOI： 10.1038/NCHEM.2834

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

DOI： 10.1039/c7sc02495a

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

Six-electron oxidation of anthracene to anthraqui-none by a nonheme Mn-IV-oxo complex, [(Bn-TPEN)Mn-IV(O)] (2+), proceeds through a rate-determining electron transfer from anthracene to [(Bn-TPEN) Mn-IV(O)](2+), followed by subsequent fast oxidation reactions to give anthraquinone. The reduced Mn-II complex ([(Bn-TPEN) Mn-II](2+)) is oxidized by [(Bn-TPEN)Mn-IV(O)](2+) rapidly to produce the mu-oxo dimer ([(Bn-TPEN)Mn-III- O-Mn-III(Bn-TPEN)](4+)). The oxygen atoms of the anthraquinone product were found to derive from the manganese-oxo species by the O-18-labelling experiments. In the presence of Sc3+ ion, formation of an anthracene radical cation was directly detected in the electron transfer from anthracene to a Sc3+ ion-bound Mn-IV(O) complex, [(Bn-TPEN)Mn-IV( O)-(Sc(OTf)(3))(2)](2+), followed by subsequent further oxidation to yield anthraquinone. When anthracene was replaced by 9,10-dimethylanthracene, electron transfer from 9,10-dimethylanthracene to [(Bn-TPEN) Mn-IV(O)-(Sc(OTf)(3))(2)](2+) occurred rapidly to produce stable 9,10-dimethylanthracene radical cation. The driving force dependence of the rate constants of electron transfer from the anthracene derivatives to [(Bn-TPEN) Mn-IV(O)](2+) and [(Bn-TPEN) Mn-IV(O)-(Sc(OTf)(3))(2)](2+) was well-evaluated in light of the Marcus theory of electron transfer.

DOI： 10.1002/chem.201700666

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

The reactivity of organic photoredox catalysts in oxidation reactions is enhanced by the addition of Lewis acids, which bind to the catalyst to increase its oxidizing ability. Redox-inactive metal ions, such as Sc3+, also act as Lewis acids and can bind to flavins to increase their one-electron reduction potentials and photocatalytic stability. The Sc3+ ion can bind to acridine and pyrene to enhance their photoredox catalytic activity in the oxidation of substrates by dioxygen. The binding of Lewis acids to radical anions enhances their overall photocatalytic activity by prohibiting a back electron transfer from the radical anions of substrates to the oxidized photocatalysts. The photocatalytic asymmetric oxidation of terminal olefins by using water as the oxygen source with a mononuclear nonheme chiral manganese complex has been made possible by the addition of acetic acid, which is essential to afford the products with high enantioselectivity.

DOI： 10.1002/ajoc.201600576

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

Metal-superoxo species are involved in a variety of enzymatic oxidation reactions, and multi-electron oxidation of substrates is frequently observed in those enzymatic reactions. ACr(III)-superoxo complex, [Cr-III(O-2)(TMC)(Cl)](+) (1; TMC=1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane), is described that acts as a novel three-electron oxidant in the oxidation of dihydronicotinamide adenine dinucleotide (NADH) analogues. In the reactions of 1 with NADH analogues, a Cr-IV-oxo complex, [Cr-IV(O)(TMC)(Cl)](+) (2), is formed by a heterolytic O-O bond cleavage of a putative Cr-II-hydroperoxo complex, [Cr-II(OOH)(TMC)(Cl)], which is generated by hydride transfer from NADH analogues to 1. The comparison of the reactivity of NADH analogues with 1 and p-chloranil (Cl(4)Q) indicates that oxidation of NADH analogues by 1 proceeds by proton-coupled electron transfer with a very large tunneling effect (for example, with a kinetic isotope effect of 470 at 233 K), followed by rapid electron transfer.

DOI： 10.1002/ange.201611709

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

DOI： 10.1002/anie.201602460

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

DOI： 10.1002/asia.201501329

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

DOI： 10.1021/acs.inorgchem.5b02019

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

DOI： 10.1002/anie.201600287

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

DOI： 10.1021/acs.inorgchem.5b01777

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

DOI： 10.1021/ic5030125

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

DOI： 10.1021/jacs.5b00816

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

DOI： 10.1021/jp505860f

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

DOI： 10.1021/ic402121j

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

DOI： 10.1039/c3ee42815j

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

DOI： 10.1039/c2ee21185h

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Event date： 2014.6

Language：English   Presentation type：Poster presentation  

Event date： 2014.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2013.11

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2013.11

Language：English   Presentation type：Poster presentation  

Country：Korea, Republic of  

Event date： 2013.9

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Country：Japan  

Event date： 2013.8

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2013.7

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Country：France  

Event date： 2013.6

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2013.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2012.9

Language：English   Presentation type：Poster presentation  

Country：Japan  

Event date： 2012.3

Language：English   Presentation type：Oral presentation (general)  

Country：Japan  

Event date： 2011.9

Language：English   Presentation type：Poster presentation  

Country：Japan