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担当区分：筆頭著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

The redox state of the metallomonooxygenases is finely tuned by imposing specific coordination environments on the metal center to reduce the activation energy for the generation of active-oxygen species and subsequent substrate oxygenation reactions. In this study, copper(II) complexes supported by a series of linear tetradentate ligands consisting of a rigid 6-, 7-, or 8-membered cyclic diamine with two pyridylmethyl (-CH2Py) side arms (L6Pym2, L7Pym2, and L8Pym2) are employed to examine the effects of the coordination environment on the reactivity of their acylperoxide adduct complexes. The UV-vis and electron paramagnetic resonance spectroscopic data indicate that the ligand-field splitting between the dx2-y2 and dz2 orbitals of the starting copper(II) complexes increase with an increase of the ring size of the diamine moiety (L6Pym2 → L7Pym2 → L8Pym2). In the reaction of these copper(II) complexes with m-chloroperbenzoic acid (m-CPBA), the L6Pym2 complex gives a stable m-CPBA adduct complex, whereas the L7Pym2 and L8Pym2 complexes are immediately converted to the corresponding m-chlorobenzoic acid (m-CBA) adducts, indicating that the reactivity of the copper(II) acylperoxide complexes largely depends on the coordination environment induced by the supporting ligands. Density functional theory (DFT) calculations on the m-CPBA adduct complexes show that the ligand-field-splitting energy increases with an increase of the ring size of the diamine moiety, as in the case of the starting copper(II) complexes, which enhances the reactivity of the m-CPBA adduct complexes. The reasons for such different reactivities of the m-CPBA adduct complexes are evaluated by using DFT calculations.

DOI： 10.1021/acs.inorgchem.1c00475

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

Hydroxylation of cyclohexane with m-chloroperbenzoic acid was examined in the presence of an iron(III) complex supported by a trianionic planar tetradentate ligand. The present reaction system shows a high turnover number of 2750 with a high product selectivity of alcohol (93%). The turnover frequency was 0.51 s-1, and the second-order rate constant (k) for the C-H bond activation of cyclohexane was 1.08 M-1 s-1, which is one of the highest values among the iron complexes in the oxidation of cyclohexane so far reported. The present catalytic system can be adapted to the hydroxylation of substrates having only primary C-H bonds such as 2,2,3,3-tetramethylbutane as well as gaseous alkanes such as butane, propane, and ethane. The involvement of an iron(III) acyl peroxido complex as the reactive species was suggested by spectroscopic measurements of the reaction solution.

DOI： 10.1021/acs.inorgchem.0c03469

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Bulletin of the Chemical Society of Japan  

The rhodium (III) complexes supported by a di-deprotonated o-phenylenediamido ligand, ([Cp*RhIII(C6H4N2tBu2Ph221)] ([Cp*RhIII(L21)], 1), and one-electron and two-electron oxidized ligands, [Cp*RhIII(C6H4N2tBu2Ph2•1)(CN)] ([Cp*RhIII(L•1)(CN)], 2) and [Cp*RhIII(C6H4N2tBu2Ph20)(CN)]+ ([Cp*RhIII(L0)(CN)]+, 3) (H2L = H2C6H4N2tBu2Ph2 = N,N-di-(3,5-di-tert-butylphenyl)benzene-1,2-diamine)), have been synthesized and characterized by 1H NMR, ESImass, EPR, UVvis spectroscopic methods, and cyclic voltammetry as well as single-crystal structure analysis. In complexes 2 and 3, a cyanide ion coordinates to each rhodium(III) center to stabilize the six-coordinate structures. Catalytic activity of these complexes has been examined in the intramolecular CH amination of trisylazide (2,4,6-triisopropylphenylsulfonyl azide) to find that complex 2 shows the highest activity. The result suggests that single-electron transfer takes place from the anion radical ligand C6H4N2tBu2Ph2•1 of 2 to trisylazide to form a nitrene radical bound rhodium(III) active species for the CH amination.

DOI： 10.1246/BCSJ.20190291

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

A mononuclear copper complex bearing a ‘histidine brace’ is synthesised and characterised as an active-site model of mononuclear copper monooxygenases such as lytic polysaccharide monooxygenases (LPMOs) and particulate methane monooxygenase (pMMO). The complex has similar structural and functional features to the active sites of the enzymes.

DOI： 10.1039/d0cc01392g

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemistry - A European Journal  

A tetrahedral CuII alkylperoxido complex [CuII(TMG3tach)(OOCm)]+ (1OOCm) (TMG3tach={2,2′,2′′-[(1s,3s,5s)-cyclohexane-1,3,5-triyl]tris-(1,1,3,3-tetramethyl guanidine)}, OOCm=cumyl peroxide) is prepared and characterized by UV/Vis, cold-spray ionization mass spectroscopy (CSI-MS), resonance Raman, and EPR spectroscopic methods. Product analysis of the self-decomposition reaction of 1OOCm in acetonitrile (MeCN) indicates that the reaction involves O−O bond homolytic cleavage of the peroxide moiety with concomitant C−H bond activation of the solvent molecule. When an external substrate such as 1,4-cyclohexadiene (CHD) is added, the O−O bond homolysis leads to C−H activation of the substrate. Furthermore, the reaction of 1OOCm with 2,6-di-tert-butylphenol derivatives produces the corresponding phenoxyl radical species (ArO.) together with a CuI complex through a concerted proton-electron transfer (CPET) mechanism. Details of the reaction mechanisms are explored by DFT calculations.

DOI： 10.1002/chem.201902669

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Communications Chemistry  

銅錯体配位子のわずかな構造の違いが、その酸素錯体（スーペルオキソ錯体: 02[•–]）の反応性に与える効果を明らかにした論文です。具体的には、先行研究では、メチレン鎖ひとつ分の違いによって銅–スーペルオキシド種の求核性が大きく高まり、アルドール反応を触媒するようになることが分かりました。

DOI： 10.1038/s42004-019-0115-6

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Angewandte Chemie - International Edition  

ポルフィリンの一電子酸化体を配位子として持つ鉄四価オキシド錯体 [Fe(IV)(O)(Por·+)] （下の図、右）は、微生物から人間、植物に至るまで、幅広い生物の代謝過程における重要な化学種です。この化学種は活性が高すぎるがゆえ、反応溶媒ですら瞬時に酸化してしまいます。これまでの研究では、-60°Cといった極低温条件を用いることで、なんとかその観察を行っていました。<br />
我々は、種々の溶媒を試した結果、トリフルオロトルエンを用いて実験を行うことによって、Fe(IV)(O)(Por·+) の分解が顕著に抑えられることを見出しました。これまでの最長記録と比べ、700倍以上も寿命が伸び、室温付近（30°C）でも、活性種を観測することに成功しました。<br />
また、これまでのFe(IV)(O)(Por·+) についての研究では、溶媒の酸化が基質の酸化徒競走して進行してしまうがゆえに、基質は酸化されやすいものに限定されていました。溶媒の酸化を抑えることによって、実験に用いることができる基質が大きく広がりました。結果として、通常の反応では活性化することが困難な、アルカンの末端炭素のC–H結合を酸化することができるようになり、反応の様子を世界で初めて直接的に観測することに成功しました（下図、左）。<br />
高い酸化活性を持つ化学種の反応機構は、分厚いカーテンに隠されていますが、それを開く方法が分かって来ました。この成果を手がかりに、より酸化の難しい物質を、より温和な条件で選択的に酸化する方法の発展が期待されます。

DOI： 10.1002/anie.201901608

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担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1002/ange.201802779

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

DOI： 10.1002/ejic.201800436

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：European Journal of Organic Chemistry  

A tyrosinase-mediated arylation towards a variety of different building blocks is presented. Utilizing phenol or simple substituted phenols, the corresponding quinones are synthesized in a two-step procedure by an enzyme-catalyzed oxidation (tyrosinase from Aspergillus oryzae). The activated intermediates undergo a 1,4-addition with selected β-dicarbonyl compounds. Starting from phenol, yields of isolated product for the hydroxylation-oxidation-arylation sequence range from 43–77 %, whereas substituted acceptors provided 9–55 %, only. Different substitution patterns on phenol revealed that electron donating functionalities are preferentially accepted to electron withdrawing ones, whereas ortho-substituted phenols are not accepted at all.

DOI： 10.1002/ejoc.201800188

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Zeitschrift fur Anorganische und Allgemeine Chemie  

A copper(I) complex, [CuI(TIPT2aped)(CH3CN)]ClO4 (1), and two copper(II) complexes, [CuII(TIPT2aped)(Cl)]PF6 (2) and [CuII(TIPT2aped)(ClO4)]ClO4 (3), were synthesized and characterized. The reaction of 1 with dioxygen in acetone at –90 °C gave an end-on superoxide copper(II) complex 4. The superoxide copper(II) complex 4 reacted with 2,2,6,6-tetramethylpiperidin-1-ol (TEMPO-H) and 2,6-di-tert-butyl-4-methoxyphenol (DTBMP) to generate a hydroperoxide copper(II) complex 6. These copper-oxygen adducts were thoroughly characterized by UV/Vis, resonance Raman, EPR, and NMR spectroscopic techniques. Complex 6 was also synthesized from the copper(II) complex 3 in the presence of hydrogen peroxide and triethylamine. The reaction of 4 with TEMPO-H showed a relatively large kinetic deuterium isotope effect (kH/kD = 5.8) and a largely negative activation enthalpy (ΔH‡). Based on the kinetic data, the reaction mechanism for the conversion of 4 to 6 is discussed.

DOI： 10.1002/zaac.201800083

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：European Journal of Inorganic Chemistry  

Copper(I) and copper(II) complexes supported by a bulky tetradentate N4 ligand, [CuI(TIPT3tren)(CH3CN)]ClO4 (1) and [CuII(TIPT3tren)Cl]BF4 (2), were synthesized and characterized, where TIPT is 2,2′′,6,6′′-tetraisopropyl-1,3′:5′,1′′-terphenyl and tren is tris(2-aminoethyl)amine. The copper(II) chloride complex 2 exhibits a trigonal-bipyramidal structure, as usually observed for the tren ligand system, in which the chloride ligand occupies an axial position and is encapsulated in an isolated cavity consisting of three TIPT substituents. Such a trigonal-bipyramidal structure is stabilized in acetone, in which hydrogen-bonding interactions between the anilino N–H groups and the oxygen atom of the acetone molecules, entrapped in the hydrophobic clefts between the TIPT substituents, play an important role. The reaction of copper(I) complex 1 and O2 in an acetone-containing solvent at –110 °C gave end-on copper(II) superoxide complex 3 together with putative side-on copper(III) peroxide complex 4, as was evident from detailed studies by variable-temperature UV/Vis, resonance Raman, and 1H and 2H NMR spectroscopy. The formation of 3 and 4 was also validated by DFT calculations.

DOI： 10.1002/ejic.201800029

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Wiley  

酸化反応の活性種である、二核ニッケル(III)錯体の結晶構造と、そのスピン状態を決定した論文です。近年、酸化反応活性種の反応特性について、その電子状態から理解してゆこうという試みが進められています。その中で、電位や立体の因子に加え、スピン状態についても注目が集まっています。本、論文のニッケル錯体は非常に不安定な錯体でしたが、その結晶構造解析およびSQUIDやEPRを用いたキャラクタリゼーションに成功しました。その結果、高い酸化数を持つ金属酸素二核錯体としては極めて珍しく、強磁性的に相互作用した（スピンの向きが揃った）錯体であることがわかりました。電子相関の寄与を正確に見積もる必要のある錯体分子の計算は、一般には非常に難しいのですが、構造と電子状態のデータがしっかり取れていたので細かく議論することが出来ました。

DOI： 10.1002/anie.201802779

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganica Chimica Acta  

This mini-review article summarizes the O2-reactivity of copper(I) complexes supported by a series of 2-(2-pyridyl)ethylamine (Pye) based ligands, which was developed by Karlin and his coworkers for biomimetic copper-oxygen chemistry. Oxygenation reaction of the copper(I) complexes supported by simple bis[2-(2-pyridyl)ethyl]amine tridentate ligands (R′Pye2R) mainly provided (μ-η2:η2-peroxido)dicopper(II) complex 5, but the reaction rates were significantly altered by the ligand substituents R and R′. The peroxide complex 5 induced aliphatic hydroxylation at the benzylic position of the ligand sidearm, when R = –CH2CH2Ph. Mechanistic studies on the aliphatic ligand hydroxylation revealed that the real reactive intermediate was a bis(μ-oxido)dicopper(III) speceis 6 generated in situ by the O–O bond homolysis of 5. On the other hand, peroxide complex 5 induced direct hydroxylation of phenolate derivatives to the corresponding catechols via electrophilic aromatic substitution mechanism, which can be regarded as a model reaction of tyrosinase. When the reaction of copper(I) complexes and O2 was conducted by using 2-(2-pyridyl)ethylamine didentate ligands (R″Pye1R,R′), not only the (μ-η2:η2-peroxido)dicopper(II) complex 5, but also the bis(μ-oxido)dicopper(III) speceis 6 and a mixed-valent bis(μ3-oxido)tricopper(II,II,III) complex 7 were generated, the product type of which was also controlled by the ligand substituents (R, R′ and R″). Reactivities of the generated complexes supported by the didentate ligands R″Pye1R,R′ were also explored. Notably, a tridentate ligand consisting with 2-(2-pyridyl)ethylamine (Pye1) and 8-membered cyclic diamine (RL8Pye) gave a mononuclear copper(II) endo-on superoxide complex 1, when the supported copper(I) complex and O2 was reacted at a low temperature. Such a unique ligand effect of the RL8Pye system were examined using a series of related tridentate ligands. Furthermore, asymmetric (μ-η1:η2-peroxido)dicopper(II) complex 8 was successfully obtained by using a newly designed penta-pyridine ligand (Pye2PyPye2).

DOI： 10.1016/j.ica.2017.09.017

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Chemical Society ({ACS})  

トシルアジドを酸化剤&amp;アミンソースとして、アルキル基のアミノ化を行った論文です。酸化還元活性を有する配位子を持つロジウム(III)錯体を触媒として用いています。前の報告では、ロジウム上のアミンがなかなか外れなかったのですが、軸配位子をクロライドとし、アニオン錯体としてやることによって、一般的には置換不活性なロジウムの配位子交換が加速されました。触媒反応系中から藤田くんは、配位子が部分的に開裂し、アミノフェノールのラジカル体となったものも単離してきました。DFTとEPRのパートを担当しました。

DOI： 10.1021/acs.inorgchem.8b00289

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganica Chimica Acta  

To discuss the relationship between the structure and the oxygen reduction reaction (ORR) activity of pyridylmethylamine copper complexes containing carboxy groups, CuII complexes of a N,N-bis(2-pyridylmethyl)phenylmethylamine tridentate ligand (L1) or its carboxy derivatives (2-{[bis(2-pyridylmethyl)amino]methyl}benzoic acid: L2, 3-{[bis(2-pyridylmethyl)amino]methyl}benzoic acid: L3, or 4-{[bis(2-pyridylmethyl)amino]methyl}benzoic acid: L4) were synthesized and characterized. The X-ray crystal structures of mononuclear CuII complexes ligated by L2–L4 were obtained as dichloride complexes, and a crystallographic analysis revealed that all of them have a square pyramidal geometry. The ESR spectroscopy showed that these complexes also had a square pyramidal geometry in a neutral aqueous solution. Cyclic voltammetry analysis in a neutral aqueous solution suggested that only the CuII complex of L2 shows intramolecular interaction between the carboxy group and copper ion in the aqueous solution. The introduction of a carboxy group dramatically increased the amount of the CuII complexes adsorbed on carbon black, which can slightly increase the ORR activity.

DOI： 10.1016/j.ica.2017.10.031

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier {BV}  

Copper(II) complexes supported by N3-tridentate ligands, consisting of a rigid cyclic diamine (8-membered cyclic-diamine; L8 or 7-membered cyclic-diamine; L7) and a 2-(2-pyridyl)ethyl (-CH2CH2Py) group, were synthesized and structurally characterized. Reaction of the copper(II) complexes and cumene hydroperoxide (CmOOH) in the presence of triethylamine in CH3CN gave the corresponding cumylperoxide complexes L8CuIIOOCm and L7CuIIOOCm. The UV–vis and EPR spectra suggested that L8CuIIOOCm takes a tetrahedrally distorted structure, whereas L7CuIIOOCm has a planar geometry in solution. Resonance Raman spectra of these alkylperoxide complexes indicated that the O-O stretching vibration energy of L8CuIIOOCm (νO–O = 878 cm− 1) is somewhat lower than that of L7CuIIOOCm (νO–O = 881 cm− 1). Such a difference in O-O bond strength is reflected to the reactivity difference of these two alkylperoxide complexes. Namely, the reactivity L8CuIIOOCm toward CHD (1,4-cyclohexadiene) as well as solvent molecule (CH3CN) is higher than that of L7CuIIOOCm due to the weaker O-O bond of the former complex as compared to that of the latter complex. Geometric effects on the reactivity induced by the supporting ligands are discussed.

DOI： 10.1016/j.jinorgbio.2017.08.016

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

A new tridentate N3 ligand (TMG3tach) consisting of cis,cis-1,3,5-triaminocyclohexane (tach) and three N,N,N′,N′-tetramethylguanidino (TMG) groups has been developed to prepare copper complexes with a tetrahedral geometry and a labile coordination site. Treatment of the ligand with CuIIX2 (X = Cl and Br) gave copper(II)-halide complexes, [CuII(TMG3tach)Cl]+ (2Cl) and [CuII(TMG3tach)Br]+ (2Br), the structures of which have been determined by X-ray crystallographic analysis. The complexes exhibit a four-coordinate structure with C3v symmetry, where the labile halide ligand (X) occupies a position on the trigonal axis. 2Br was converted to a methoxido-copper(II) complex [CuII(TMG3tach)(OMe)](OTf) (2OMe), also having a similar four-coordinate geometry, by treating it with an equimolar amount of tetrabutylammonium hydroxide in methanol. The methoxido-complex 2OMe was further converted to the corresponding phenolato-copper(II) (2OAr) and thiophenolato-copper(II) (2SAr) complexes by ligand exchange reactions with the neutral phenol and thiophenol derivatives, respectively. The electronic structures of the copper(II) complexes with different axial ligands are discussed on the basis of EPR spectroscopy and DFT calculations.

DOI： 10.1021/acs.inorgchem.7b01154

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Dalton Transactions  

A stable nickel(ii)-aminoxyl radical complex was generated by the reaction of a nickel(ii) complex supported by a tren ligand (tris(2-aminoethyl)amine) having bulky m-terphenyl substituents (TIPT: 3,5-bis(2,6-diisopropylphenyl)phenyl) and m-CPBA (m-chloroperoxybenzoic acid). The formation mechanism of the nickel(ii)-aminoxyl radical complex was examined.

DOI： 10.1039/c7dt01789h

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

Werner type six-coordinate rhodium(iii) complexes coordinated by a planar trianionic ligand and two axial aniline ligands are synthesised. The trianionic ligand behaves as a redox-active ligand to form a ligand radical species upon one-electron oxidation of the complex. The rhodium(iii) complexes catalyse C-H amination of external substrates such as xanthene with tosylazide as the nitrene source. DFT-calculation and kinetic deuterium isotope effects indicate that a di-radical rhodium(iii) complex formed by one-electron transfer from the redox-active ligand to the nitrene group works as a reactive intermediate to induce aliphatic C-H activation.

DOI： 10.1039/c7cc01840a

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記述言語：英語  

DOI： 10.1039/c7cc90176c

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

Thermally stable TM1459 cupin superfamily protein from Thermotoga maritima was repurposed as an osmium (Os) peroxygenase by metal-substitution strategy employing the metal-binding promiscuity. This novel artificial metalloenzyme bears a datively bound Os ion supported by the 4-histidine motif. The well-defined Os center is responsible for not only the catalytic activity but also the thermodynamic stability of the protein folding, leading to the robust biocatalyst (T m ≈ 120 °C). The spectroscopic analysis and atomic resolution X-ray crystal structures of Os-bound TM1459 revealed two types of donor sets to Os center with octahedral coordination geometry. One includes trans-dioxide, OH, and mer-three histidine imidazoles (O 3 N 3 donor set), whereas another one has four histidine imidazoles plus OH and water molecule in a cis position (O 2 N 4 donor set). The Os-bound TM1459 having the latter donor set (O 2 N 4 donor set) was evaluated as a peroxygenase, which was able to catalyze cis-dihydroxylation of several alkenes efficiently. With the low catalyst loading (0.01% mol), up to 9100 turnover number was achieved for the dihydroxylation of 2-methoxy-6-vinyl-naphthalene (50 mM) using an equivalent of H 2 O 2 as oxidant at 70 °C for 12 h. When octene isomers were dihydroxylated in a preparative scale for 5 h (2% mol cat.), the terminal alkene octene isomers was converted to the corresponding diols in a higher yield as compared with the internal alkenes. The result indicates that the protein scaffold can control the regioselectivity by the steric hindrance. This protein scaffold enhances the efficiency of the reaction by suppressing disproportionation of H 2 O 2 on Os reaction center. Moreover, upon a simple site-directed mutagenesis, the catalytic activity was enhanced by about 3-fold, indicating that Os-TM1459 is evolvable nascent osmium peroxygenase.

DOI： 10.1021/jacs.7b00675

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemistry - A European Journal  

A new CeIV complex [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)2] (1), bearing a dianionic pentadentate ligand with an N3O2 donor set, has been prepared by treating (NH4)2Ce(NO3)6 with the sodium salt of ligand L1. Complex 1 in the presence of TEMPO and 4 Å molecular sieves (MS4 A) has been found to serve as a catalyst for the oxidation of arylmethanols using dioxygen as an oxidant. We propose an oxidation mechanism based on the isolation and reactivity study of a trivalent cerium complex [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)(THF)] (2), its side-on μ-O2 adduct [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)]2(μ-η2:η2-O2) (3), and the hydroxo-bridged CeIV complex [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)]2(μ-OH)2 (4) as key intermediates during the catalytic cycle. Complex 2 was synthesized by reduction of 1 with 2,5-dimethyl-1,4-bis(trimethylsilyl)-1,4-diazacyclohexadiene. Bubbling O2 into a solution of 2 resulted in formation of the peroxo complex 3. This provides the first direct evidence for cerium-catalyzed oxidation of alcohols under an O2 atmosphere. Cerium-catalyzed alcohol oxidation: A new CeIV complex [Ce{NH(CH2CH2N=CHC6H2-3,5-(tBu)2-2-O)2}(NO3)2] (1) has been shown to serve as a catalyst for the oxidation of arylmethanols using dioxygen as an oxidant in the presence of TEMPO and molecular sieves MS4 A (see scheme). CeIII complex 2, obtained by reduction of 1 with 2,5-dimethyl-1,4-bis(trimethylsilyl)-1,4-diazacyclohexadiene, reacted with O2 to give the peroxo complex 3. This provides the first direct evidence for operation of the peroxo mechanism in the cerium-catalyzed oxidation of alcohols under O2 atmosphere.

DOI： 10.1002/chem.201503846

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記述言語：日本語   出版者・発行元：化学同人  

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

The reaction of [CuI(TIPT3tren) (CH3CN)]ClO4 (1) and cumene hydroperoxide (C6H5C(CH3)2OOH, ROOH) at -60°C in CH2Cl2 gave a CuII-alkylperoxide/anilino radical complex 2, the formation of which was confirmed by UV-vis, resonance Raman, EPR, and CSI-mass spectroscopy. The mechanism of formation of 2, as well as its reactivity, has been explored.

DOI： 10.1021/jacs.5b04104

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

Selective hydroxylation of benzene to phenol has been achieved using H<inf>2</inf>O<inf>2</inf> in the presence of a catalytic amount of the nickel complex [Ni^II(tepa)]²⁺ (2) (tepa = tris[2-(pyridin-2-yl)ethyl]amine) at 60°C. The maximum yield of phenol was 21% based on benzene without the formation of quinone or diphenol. In an endurance test of the catalyst, complex 2 showed a turnover number (TON) of 749, which is the highest value reported to date for molecular catalysts in benzene hydroxylation with H<inf>2</inf>O<inf>2</inf>. When toluene was employed as a substrate instead of benzene, cresol was obtained as the major product with 90% selectivity. When H<inf>2</inf>¹⁸O<inf>2</inf> was utilized as the oxidant, ¹⁸O-labeled phenol was predominantly obtained. The reaction rate for fully deuterated benzene was nearly identical to that of benzene (kinetic isotope effect = 1.0). On the basis of these results, the reaction mechanism is discussed.

DOI： 10.1021/jacs.5b01814

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記述言語：英語   掲載種別：論文集(書籍)内論文   出版者・発行元：Chemical Science of Electron Systems  

Recent studies of redox non-innocence of β-diketiminate ligands are introduced. Reduction of Yb3+ and Al3+ as well as Li+ and Be2+ complexes using strong electron-transfer reductants induces the ligand-based one- and/or two-electron reduction, whereas electron-transfer oxidation of bis(β-diketiminato)-Ni2+ complexes gives Robin and Day class III mixed-valence complexes, having an unpaired electron completely delocalized between the two ligands. Furthermore, a new trianionic tetradentate ligand is developed by introducing two phenolate moieties on the nitrogen atoms of a β-diketiminate ligand to mimic the active site of galactose oxidase. In the copper(II) complex of this ligand, oxidation reaction also takes place at the ligand moiety to provide phenoxyl–copper(II) complexes.

DOI： 10.1007/978-4-431-55357-1_42

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of Porphyrins and Phthalocyanines  

A new type of nickel and palladium complexes with non-innocent β-diketiminate ligand having redox active phenol groups, 2,4-di-tert-butyl-6-(((1E,2E)-3-((3,5-di-tert-butyl-2-hydroxyphenyl) amino)-2-nitroallylidene)amino)phenol (LH3, fully protonated form) have been developed, and the structure, physical properties, and reactivity of their one-electron and two-electron oxidized complexes, [MII(L•2-)] and [MII(L-)]+ (M = NiII or PdII) have been examined in detail. The two-electron oxidized forms of both complexes, [MII(L-)]+, exhibited hydrogen atom abstraction ability from 1,4-cyclohexadiene (CHD) comparable to its copper analog [CuII(L-)]+ (Dalton Trans. 2013; 42: 2438-2444). The oneelectron oxidized form of palladium complex, [PdII(L•2-)], was also found to oxidize CHD, whereas the nickel analog, [NiII(L•2-)], exhibited photo-induced oxidation ability of CHD.

DOI： 10.1142/S1088424615500248

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：European Journal of Inorganic Chemistry  

A functionalized β-dialdimine was prepared, bearing a 3,3-dimethylindoleninyl group at the meso-position and two Nphenolic groups. The structure contains three labile protons, which can be lost or migrate through tautomerism to provide an N2O2 coordination core. A number of divalent and trivalent metal ions (CuII, NiII, CoII/III, and MnIII) were accommodated inside the core, forming a series of intensely colored products consisting of a tricyclic MN2O2 chelate. In the resulting divalent metal complexes, the dialdimine ligand is deprotonated only at the two phenolic oxygen atoms and is thus dianionic, whereas in the trivalent metal complexes, the dialdiminato ligand is triply deprotonated. The copper and nickel complexes adopt square-planar geometries, whereas in the trivalent cobalt and manganese complexes, two neutral ancillary ligands complete an octahedral geometry around the metal center. In each case, the denticity of the diimino-diiminato ligand is four. The electrochemical oxidation of the copper and nickel complexes was studied by cyclic voltammetry.

DOI： 10.1002/ejic.201402745

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

Copper(I) complexes supported by a series of N3-tridentate ligands bearing a rigid cyclic diamine framework such as 1,5-diazacyclooctane (L8, eight-membered ring), 1,4-diazacycloheptane (L7, seven-membered ring), or 1,4-diazacyclohexane (L6, six-membered ring) with a common 2-(2-pyridyl)ethyl side arm were synthesized and their reactivity toward O2 were compared. The copper(I) complex of L8 preferentially provided a mononuclear copper(II) end-on superoxide complex S as reported previously [Itoh, S., et al. J. Am. Chem. Soc. 2009, 131, 2788-2789], whereas a copper(I) complex of L7 gave a bis(μ-oxido)dicopper(III) complex O at a low temperature (-85 °C) in acetone. On the other hand, no such active-oxygen complex was detected in the oxygenation reaction of the copper(I) complex of L6 under the same conditions. In addition, O2-reactivity of the copper(I) complex supported by an acyclic version of the tridentate ligand (LA, PyCH2CH 2N(CH3)CH2CH2CH2N(CH 3)2; Py = 2-pyridyl) was examined to obtain a mixture of a (μ- η2:η2-peroxido)dicopper(II) complex SP and a bis(μ-oxido)dicopper(III) complex O. Careful inspection of the crystal structures of copper(I) and copper(II) complexes and the redox potentials of copper(I) complexes has revealed important geometric effects of the supporting ligands on controlling nuclearity of the generated copper active-oxygen complexes. © 2014 American Chemical Society.

DOI： 10.1021/ic501461n

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

Nickel complexes of a series of β-diketiminate ligands ( RL-, deprotonated form of 2-substituted N-[3-(phenylamino)allylidene]aniline derivatives RLH, R = Me, H, Br, CN, and NO2) have been synthesized and structurally characterized. One-electron oxidation of the neutral complexes [NiII( RL-)2] by AgSbF6 or [Ru III(bpy)3](PF6)3 (bpy = 2,2′-bipyridine) gave the corresponding metastable cationic complexes, which exhibit an EPR spectrum due to a doublet species (S = 1/2) and a characteristic absorption band in near IR region ascribable to a ligand-to-ligand intervalence charge-transfer (LLIVCT) transition. DFT calculations have indicated that the divalent oxidation state of nickel ion (NiII) is retained, whereas one of the β-diketiminate ligands is oxidized to give formally a mixed-valence complex, [NiII( RL-)(RL•)]+. Thus, the doublet spin state of the oxidized cationic complex can be explained by taking account of the antiferromagnetic interaction between the high-spin nickel(II) ion (S = 1) and the organic radical (S = 1/2) of supporting ligand. A single-crystal structure of one of the cationic complexes (R = H) has been successfully determined to show that both ligands in the cationic complex are structurally equivalent. On the basis of theoretical analysis of the LLIVCT band and DFT calculations as well as the crystal structure, the mixed-valence complexes have been assigned to Robin-Day class III species, where the radical spin is equally delocalized between the two ligands to give the cationic complex, which is best described as [NiII(RL 0.5•-)2]+. One-electron reduction of the neutral complexes with decamethylcobaltocene gave the anionic complexes when the ligand has the electron-withdrawing substituent (R = CN, NO2, Br). The generated anionic complexes exhibited EPR spectra due to a doublet species (S = 1/2) but showed no LLIVCT band in the near-IR region. Thus, the reduced complexes are best described as the d9 nickel(I) complexes supported by two anionic β-diketiminate ligands, [NiI(RL -)2]-. This conclusion was also supported by DFT calculations. Substituent effects on the electronic structures of the three oxidation states (neutral, cationic, and anionic) of the complexes are systematically evaluated on the basis of DFT calculations. © 2014 American Chemical Society.

DOI： 10.1021/ic5006693

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

Oxidative C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by a nonheme iron(IV)-oxo complex, [(N4Py)Fe IV(O)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl) methylamine), were remarkably enhanced by the presence of triflic acid (HOTf) and Sc(OTf)3 in acetonitrile at 298 K. All the logarithms of the observed second-order rate constants of both the oxidative C-H bond cleavage and sulfoxidation reactions exhibit remarkably unified correlations with the driving forces of proton-coupled electron transfer (PCET) and metal ion-coupled electron transfer (MCET) in light of the Marcus theory of electron transfer when the differences in the formation constants of precursor complexes between PCET and MCET were taken into account, respectively. Thus, the mechanisms of both the oxidative C-H bond cleavage of toluene derivatives and sulfoxidation of thioanisole derivatives by [(N4Py)FeIV(O)]2+ in the presence of HOTf and Sc(OTf)3 have been unified as the rate-determining electron transfer, which is coupled with binding of [(N4Py)FeIV(O)]2+ by proton (PCET) and Sc(OTf)3 (MCET). There was no deuterium kinetic isotope effect (KIE) on the oxidative C-H bond cleavage of toluene via the PCET pathway, whereas a large KIE value was observed with Sc(OTf)3, which exhibited no acceleration of the oxidative C-H bond cleavage of toluene. When HOTf was replaced by DOTf, an inverse KIE (0.4) was observed for PCET from both toluene and [Ru II(bpy)3]2+ (bpy =2,2′-bipyridine) to [(N4Py)FeIV(O)]2+. The PCET and MCET reactivities of [(N4Py)FeIV(O)]2+ with Brønsted acids and various metal triflates have also been unified as a single correlation with a quantitative measure of the Lewis acidity. © 2014 American Chemical Society.

DOI： 10.1021/ic403124u

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

Rates of formation of a non-heme iron(IV)-oxo complex, [Fe IV(O)(N4Py)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2- pyridyl)methylamine), via electron-transfer oxidation of [FeIII(OH) (N4Py)]2+ in acetonitrile (MeCN) containing H2O (0.56 M) were accelerated as much as 390-fold by addition of proton acceptors such as CF3COO-, TsO- (p-MeC6H 4SO3-), NsO- (o-NO2C 6H4SO3-), DNsO- (2,4-(NO2)2C6H3SO3-), and TfO- (CF3SO3-). The acceleration effect of proton acceptors increases with increasing basicity of the proton acceptors. The one-electron oxidation potential of [Fe III(OH)(N4Py)]2+ was shifted from 1.24 to 0.96 V vs SCE in the presence of TsO- (10 mM). The electron-transfer oxidation of FeIII-OH complex was coupled with the deprotonation process by proton acceptors in which deuterium kinetic isotope effects were observed when H 2O was replaced by D2O. © 2013 American Chemical Society.

DOI： 10.1021/ic302573x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

Evidence of an autocatalytic radical chain pathway has been reported in formation of a non-heme iron(iv)–oxo complex by oxidation of an iron(ii) complex with dioxygen and isopropanol in acetonitrile at 298 K. The radical chain reaction is initiated by hydrogen abstraction from isopropanol by the iron(iv)–oxo complex. © 2013 The Royal Society of Chemistry.

DOI： 10.1039/c3cc38727e

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

The rate of oxidation of 2,5-dimethoxybenzyl alcohol (2,5-(MeO) 2C6H3CH2OH) by [Fe IV(O)(N4Py)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2- pyridyl)methylamine) was enhanced significantly in the presence of Sc(OTf) 3 (OTf- = trifluoromethanesulfonate) in acetonitrile (e.g., 120-fold acceleration in the presence of Sc3+). Such a remarkable enhancement of the reactivity of [FeIV(O)(N4Py)] 2+ in the presence of Sc3+ was accompanied by the disappearance of a kinetic deuterium isotope effect. The radical cation of 2,5-(MeO)2C6H3CH2OH was detected in the course of the reaction in the presence of Sc3+. The dimerized alcohol and aldehyde were also produced in addition to the monomer aldehyde in the presence of Sc3+. These results indicate that the reaction mechanism is changed from one-step hydrogen atom transfer (HAT) from 2,5-(MeO)2C6H3CH2OH to [Fe IV(O)(N4Py)]2+ in the absence of Sc3+ to stepwise Sc3+-coupled electron transfer, followed by proton transfer in the presence of Sc3+. In contrast, neither acceleration of the rate nor the disappearance of the kinetic deuterium isotope effect was observed in the oxidation of benzyl alcohol (C6H5CH2OH) by [FeIV(O)(N4Py)]2+ in the presence of Sc(OTf) 3. Moreover, the rate constants determined in the oxidation of various benzyl alcohol derivatives by [FeIV(O)(N4Py)]2+ in the presence of Sc(OTf)3 (10 mM) were compared with those of Sc 3+-coupled electron transfer from one-electron reductants to [Fe IV(O)(N4Py)]2+ at the same driving force of electron transfer. This comparison revealed that the borderline of the change in the mechanism from HAT to stepwise Sc3+-coupled electron transfer and proton transfer is dependent on the one-electron oxidation potential of benzyl alcohol derivatives (ca. 1.7 V vs SCE). © 2012 American Chemical Society.

DOI： 10.1021/ic3016723

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出版者・発行元：Journal of the American Chemical Society  

Sulfoxidation of thioanisoles by a non-heme iron(IV)-oxo complex, [(N4Py)Fe IV(O)] 2+ (N4Py = N,N-bis(2-pyridylmethyl)-N- bis(2-pyridyl)methylamine), was remarkably enhanced by perchloric acid (70% HClO 4). The observed second-order rate constant (k obs) of sulfoxidation of thioaniosoles by [(N4Py)Fe IV(O)] 2+ increases linearly with increasing concentration of HClO 4 (70%) in acetonitrile (MeCN)at 298 K. In contrast to sulfoxidation of thioanisoles by [(N4Py)Fe IV(O)] 2+, the observed second-order rate constant (k et) of electron transfer from one-electron reductants such as [Fe II(Me 2bpy) 3] 2+ (Me 2bpy = 4,4-dimehtyl-2,2′-bipyridine) to [(N4Py)Fe IV(O)] 2+ increases with increasing concentration of HClO 4, exhibiting second-order dependence on HClO 4 concentration. This indicates that the proton-coupled electron transfer (PCET) involves two protons associated with electron transfer from [Fe II(Me 2bpy) 3] 2+ to [(N4Py)Fe IV(O)] 2+ to yield [Fe III(Me 2bpy) 3] 3+ and [(N4Py)Fe III(OH 2)] 3+. The one-electron reduction potential (E red) of [(N4Py)Fe IV(O)] 2+ in the presence of 10 mM HClO 4 (70%) in MeCN is determined to be 1.43 V vs SCE. A plot of E red vs log[HClO 4] also indicates involvement of two protons in the PCET reduction of [(N4Py)Fe IV(O)] 2+. The PCET driving force dependence of log k et is fitted in light of the Marcus theory of outer-sphere electron transfer to afford the reorganization of PCET (λ = 2.74 eV). The comparison of the k obs values of acid-promoted sulfoxidation of thioanisoles by [(N4Py)Fe IV(O)] 2+ with the k et values of PCET from one-electron reductants to [(N4Py)Fe IV(O)] 2+ at the same PCET driving force reveals that the acid-promoted sulfoxidation proceeds by one-step oxygen atom transfer from [(N4Py)Fe IV(O)] 2+ to thioanisoles rather than outer-sphere PCET. © 2012 American Chemical Society.

DOI： 10.1021/ja211641s

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：AMER CHEMICAL SOC  

Sulfoxidation of thioanisoles by a non-heme iron(IV)-oxo complex, [(N4Py)Fe-IV(O)](2+) (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine), was remarkably enhanced by perchloric acid (70% HClO4). The observed second-order rate constant (k(obs)) of sulfoxidation of thioaniosoles by [(N4Py)Fe-IV(O)](2+) increases linearly with increasing concentration of HClO4 (70%) in acetonitrile (MeCN) at 298 K In contrast to sulfoxidation of thioanisoles by [(N4Py)-Fe-IV(O)](2+), the observed second-order rate constant (k(et)) of electron transfer from one-electron reductants such as [Fe-II(Me(2)bpy)(3)](2+) (Me(2)bpy = 4,4-dimehty1-2,2'-bipyridine) to [(N4Py)Fe-IV(O)](2+) increases with increasing concentration of HClO4, exhibiting second-order dependence on HClO4 concentration. This indicates that the proton-coupled electron transfer (PCET) involves two protons associated with electron transfer from [Fe-II(Me(2)bpy)(3)](2+) to [(N4Py)Fe-IV(O)](2+) to yield [Fe-III(Me(2)bpy)(3)](3+) and [(N4Py)Fe-III(OH2)](3+). The one-electron reduction potential (E-red) of [(N4Py)Fe-IV(O)](2+) in the presence of 10 mM HClO4 (70%) in MeCN is determined to be 1.43 V vs SCE. A plot of E-red VS log[HClO4] also indicates involvement of two protons in the PCET reduction of [(N4Py)Fe-IV(O)](2+). The PCET driving force dependence of log k(et) is fitted in light of the Marcus theory of outer-sphere electron transfer to afford the reorganization of PCET (lambda = 2.74 eV). The comparison of the kobs values of acid-promoted sulfoxidation of thioanisoles by [(N4Py)Fe-IV(O)](2+) with the k values of PCET from one-electron reductants to [(N4Py)Fe-IV(O)](2+) at the same PCET driving force reveals that the acid-promoted sulfoxidation proceeds by one-step oxygen atom transfer from [(N4Py)Fe-IV(O)](2+) to thioanisoles rather than outer-sphere PCET.

DOI： 10.1021/ja211941s

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Chemical Communications  

Electron-transfer properties of a nonheme Mn(IV)–oxo complex, [(Bn-TPEN)MnIV(O)]2+, reveals that Mn(IV)–oxo complex acts as a stronger one-electron oxidant than the Fe(IV)–oxo analogue. As a result, an electron transfer process in N-dealkylation has been detected by a transient radical cation intermediate, para-Me-DMA-+, in the oxidation of para-Me-DMA by [(Bn-TPEN)MnIV(O)]2+. © 2012 The Royal Society of Chemistry.

DOI： 10.1039/c2cc36291k

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Physical Chemistry Chemical Physics  

Redox inactive metal ions acting as Lewis acids can control electron transfer from electron donors (D) to electron acceptors (A) by binding to radical anions of electron acceptors which act as Lewis bases. Such electron transfer is defined as metal ion-coupled electron transfer (MCET). Mechanisms of metal ion-coupled electron transfer are classified mainly into two pathways, i.e., metal ion binding to electron acceptors followed by electron transfer (MB/ET) and electron transfer followed by metal ion binding to the resulting radical anions of electron acceptors (ET/MB). In the former case, electron transfer and the stronger binding of metal ions to the radical anions occur in a concerted manner. Examples are shown in each case to clarify the factors to control MCET reactions in both thermal and photoinduced electron-transfer reactions including back electron-transfer reactions. This journal is © the Owner Societies 2012.

DOI： 10.1039/c2cp40459a

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Inorganic Chemistry  

Oxidative dimerization of N,N-dimethylaniline (DMA) occurs with a nonheme iron(IV)-oxo complex, [FeIV(O)(N4Py)]2+ (N4Py = N,N-bis(2-pyridylmethyl)-N-bis(2-pyridyl)methylamine), to yield the corresponding dimer, tetramethylbenzidine (TMB), in acetonitrile. The rate of the oxidative dimerization of DMA by [FeIV(O)(N4Py)]2+ is markedly enhanced by the presence of scandium triflate, Sc(OTf)3 (OTf = CF3SO3-), when TMB is further oxidized to the radical cation (TMB•+). In contrast, we have observed the oxidative N-demethylation with para-substituted DMA substrates, since the position of the C-C bond formation to yield the dimer is blocked. The rate of the oxidative N-demethylation of para-substituted DMA by [FeIV(O) (N4Py)]2+ is also markedly enhanced by the presence of Sc(OTf) 3. In the case of para-substituted DMA derivatives with electron-donating substituents, radical cations of DMA derivatives are initially formed by Sc3+ ion-coupled electron transfer from DMA derivatives to [FeIV(O)(N4Py)]2+, giving demethylated products. Binding of Sc3+ to [FeIV(O)(N4Py)]2+ enhances the Sc3+ ion-coupled electron transfer from DMA derivatives to [Fe IV(O)(N4Py)]2+, whereas binding of Sc3+ to DMA derivatives retards the electron-transfer reaction. The complicated kinetics of the Sc3+ ion-coupled electron transfer from DMA derivatives to [FeIV(O)(N4Py)]2+ are analyzed by competition between binding of Sc3+ to DMA derivatives and to [FeIV(O)(N4Py)] 2+. The binding constants of Sc3+ to DMA derivatives increase with the increase of the electron-donating ability of the para-substituent. The rate constants of Sc3+ ion-coupled electron transfer from DMA derivatives to [FeIV(O)(N4Py)]2+, which are estimated from the binding constants of Sc3+ to DMA derivatives, agree well with those predicted from the driving force dependence of the rate constants of Sc3+ ion-coupled electron transfer from one-electron reductants to [FeIV(O)(N4Py)]2+. Thus, oxidative dimerization of DMA and N-demethylation of para-substituted DMA derivatives proceed via Sc3+ ion-coupled electron transfer from DMA derivatives to [FeIV(O)(N4Py)]2+. © 2011 American Chemical Society.

DOI： 10.1021/ic201545a

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

The mechanism of sulfoxidation of thioaniosoles by a non-heme iron(IV)-oxo complex is switched from direct oxygen transfer to metal ion-coupled electron transfer by the presence of Sc 3+. The switch in the sulfoxidation mechanism is dependent on the one-electron oxidation potentials of thioanisoles. The rate of sulfoxidation is accelerated as much as 10 2-fold by the addition of Sc 3+.(Figure Presented) © 2011 American Chemical Society.

DOI： 10.1021/ja200901n

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

Rates of electron transfer from a series of one-electron reductants to a nonheme oxoiron(IV) complex, [(N4Py)FeIV(O)]2+, are enhanced as much as 108-fold by addition of metal ions such as Sc3+, Zn2+, Mg2+, and Ca2+; the metal ion effect follows the Lewis acidity of metal ions. The one-electron reduction potential of [(N4Py)FeIV(O)]2+ is shifted to a positive direction by 0.84 V in the presence of Sc3+ ion (0.20 M). © 2011 American Chemical Society.

DOI： 10.1021/ja109056x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nature Chemistry  

Critical biological electron-transfer processes involving high-valent oxometal chemistry occur widely, for example in haem proteins [oxoiron(IV); FeIV (O)] and in photosystem II. Photosystem II involves Ca 2+ as well as high-valent oxomanganese cluster species. However, there is no example of an interaction between metal ions and oxoiron(IV) complexes. Here, we report new findings concerning the binding of the redox-inactive metal ions Ca2+ and Sc3+ to a non-haem oxoiron(IV) complex, [(TMC)FeIV (O)]2+ (TMC = 1,4,8,11-tetramethyl-1,4,8,11-tetraazacyclotetradecane). As determined by X-ray diffraction analysis, an oxo-Sc3+ interaction leads to a structural distortion of the oxoiron(IV) moiety. More importantly, this interaction facilitates a two-electron reduction by ferrocene, whereas only a one-electron reduction process occurs without the metal ions. This control of redox behaviour provides valuable mechanistic insights into oxometal redox chemistry, and suggests a possible key role that an auxiliary Lewis acid metal ion could play in nature, as in photosystem II. © 2010 Macmillan Publishers Limited. All rights reserved.

DOI： 10.1038/nchem.731

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Journal of the American Chemical Society  

Iron(III)-superoxo intermediates are believed to play key roles in oxygenation reactions by non-heme iron enzymes. We now report that a non-heme iron(II) complex activates O2 and generates its corresponding iron(IV)-oxo complex in the presence of substrates with weak C-H bonds (e.g., olefins and alkylaromatic compounds). We propose that a putative iron(III)-superoxo intermediate initiates the O2-activation chemistry by abstracting a H atom from the substrate, with subsequent generation of a high-valent iron(IV)-oxo intermediate from the resulting iron(III)-hydroperoxo species. © 2010 American Chemical Society.

DOI： 10.1021/ja103903c

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開催年月日： 2022年11月 - 2022年12月

記述言語：英語   会議種別：ポスター発表  

開催地：神戸国際会議場, 兵庫県   国名：日本国  

P-110

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開催年月日： 2022年11月 - 2022年12月

記述言語：英語   会議種別：ポスター発表  

開催地：神戸国際会議場, 兵庫県   国名：日本国  

P-53

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開催年月日： 2022年11月 - 2022年12月

記述言語：英語   会議種別：ポスター発表  

開催地：神戸国際会議場, 兵庫県   国名：日本国  

P-52

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開催年月日： 2022年9月

記述言語：英語   会議種別：口頭発表（一般）  

開催地：九州大学伊都キャンパス, 福岡県   国名：日本国  

2.00E-03

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開催年月日： 2022年9月

記述言語：日本語   会議種別：ポスター発表  

開催地：名古屋大学東山キャンパス, 愛知県   国名：日本国  

P117

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開催年月日： 2022年6月

記述言語：日本語   会議種別：ポスター発表  

開催地：同志社大学京田辺キャンパス夢告館, 京都府   国名：日本国  

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開催年月日： 2022年6月

記述言語：英語   会議種別：シンポジウム・ワークショップ パネル（指名）  

開催地：The Korean Academy of Science and Technology, Seoul   国名：大韓民国  

OP 19

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開催年月日： 2022年5月

記述言語：日本語   会議種別：シンポジウム・ワークショップ パネル（指名）  

開催地：東京大学農学部弥生講堂一条ホール, 東京都   国名：日本国  

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開催年月日： 2022年3月

記述言語：英語   会議種別：口頭発表（一般）  

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開催年月日： 2022年3月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

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開催年月日： 2022年3月

記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

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