Kazunari Yoshizawa

Extended pi-conjugated molecules are interesting materials that have been studied theoretically and experimentally with applications to conducting nanowire, memory, and diode in mind. Chemical understanding of electron transport properties in molecular junctions, in which two electrodes have weak contact with a pi-conjugated molecule, is presented in terms of the orbital concept. The phase and amplitude of the HOMO and LUMO of pi-conjugated molecules determine essential properties of the electro

The direct formation of ammonia from molecular dinitrogen under mild reaction conditions was achieved by using new cobalt dinitrogen complexes bearing an anionic PNP-type pincer ligand. Up to 15.9 equivalents of ammonia were produced based on the amount of catalyst together with 1.0 equivalent of hydrazine (17.9 equiv of fixed nitrogen atoms).

The transfer of electrons in molecules and solids is an essential process both in biological systems and in electronic devices. Devices that take advantage of the unique electronic properties of a single molecule have attracted much attention, and applications of these devices include molecular wire, molecular memory, and molecular diodes. The so-called Landauer formula with Green's function techniques provides a basis for theoretical calculations of coherent electron transport in metal-molecule

Crossing seams between the potential energy surfaces and possible spin inversion processes for the direct conversion of methane to methanol by the bare FeO+ species are discussed by means of the intrinsic reaction coordinate (IRC) approach. There are three crossing seams between the sextet and the quartet potential energy surfaces, and spin inversion should occur twice in the entrance and the exit channels; FeO+(6Σ+)+CH4(1A1)→OFe+(CH4)(6A)→TS1(4A′)→HO–Fe+–CH3(4A)→TS2(4A)→Fe+(CH3OH)(4A)→Fe+(6D)+C

A review of the recent progress in revealing the structures, formation, and reactivity of the active sites in Fe-, Co-, Ni- and Cu-exchanged zeolites as well as outlooks on future research challenges and opportunities is presented.

The entire reaction pathway for the gas-phase methane−methanol conversion by late transition-metal-oxide ions, MnO+, FeO+, and CoO+, is studied using an ab initio hybrid (Hartree−Fock/density-functional) method. For these oxo complexes, the methane−methanol conversion is proposed to proceed via two transition states (TSs) in such a way MO+ + CH4 → OM+(CH4) → [TS1] → HO−M+−CH3 → [TS2] → M+(CH3OH) → M+ + CH3OH, where M is Mn, Fe, and Co. A crossing between high-spin and low-spin potential energy s

Methane hydroxylation at the mononuclear and dinuclear copper sites of pMMO is discussed using quantum mechanical and QM/MM calculations. Possible mechanisms are proposed with respect to the formation of reactive copper-oxo and how they activate methane. Dioxygen is incorporated into the Cu(I) species to give a Cu(II)-superoxo species, followed by an H-atom transfer from a tyrosine residue near the monocopper active site. A resultant Cu(II)-hydroperoxo species is next transformed into a Cu(III)-

The reaction pathways and the energetics for the direct methane−methanol and benzene−phenol conversions that occur on the surface of Fe−ZSM-5 zeolite are analyzed from B3LYP DFT computations. We propose a reasonable model for “α-oxygen”, a surface oxygen species responsible for the catalytic reactivities of Fe−ZSM-5 zeolite. Our model involves an iron−oxo species on the AlO4 surface site of the zeolite as a catalytic active center and as a source of oxygen. The essential features of the reaction

Newly designed and prepared vanadium complexes bearing anionic pyrrole-based PNP-type pincer and aryloxy ligands were found to work as effective catalysts for the direct conversion of molecular dinitrogen into ammonia and hydrazine under mild reaction conditions. This is the first successful example of vanadium-catalyzed dinitrogen reduction under mild reaction conditions.

Mechanisms of dopamine hydroxylation by the Cu(II)-superoxo species and the Cu(III)-oxo species of dopamine beta-monooxygenase (DBM) are discussed using QM/MM calculations for a whole-enzyme model of 4700 atoms. A calculated activation barrier for the hydrogen-atom abstraction by the Cu(II)-superoxo species is 23.1 kcal/mol, while that of the Cu(III)-oxo, which can be viewed as Cu(II)-O*, is 5.4 kcal/mol. Energies of the optimized radical intermediate in the superoxo- and oxo-mediated pathways a

The N≡N bond of molecular dinitrogen bridging two molybdenum atoms in the pentamethylcyclopentadienyl molybdenum complexes that bear ferrocenyldiphosphine as an auxiliary ligand is homolytically cleaved under visible light irradiation at room temperature to afford two molar molybdenum nitride complexes. Conversely, the bridging molecular dinitrogen is reformed by the oxidation of the molybdenum nitride complex at room temperature. This result provides a successful example of the cleavage and for

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTESR of the cationic triradical of 1,3,5-tris(diphenylamino)benzeneKazunari Yoshizawa, Akihisa Chano, Akihiro Ito, Kazuyoshi Tanaka, Tokio Yamabe, Hideo Fujita, Jun Yamauchi, and Motoo ShiroCite this: J. Am. Chem. Soc. 1992, 114, 15, 5994–5998Publication Date (Print):July 1, 1992Publication History Published online1 May 2002Published inissue 1 July 1992https://pubs.acs.org/doi/10.1021/ja00041a013https://doi.org/10.1021/ja00041a013research-articleACS Pub

Two kinds of H-atom abstractions from methane by iron−oxo complexes with different charges are discussed from density functional theory calculations. A concerted H-atom abstraction via a four-centered transition state is shown to be energetically more favorable than a direct H-atom abstraction via a transition state with a linear C−H−O array. Iron(IV)−oxo complexes appear to be the most effective for the cleavage of the C−H bond of alkanes in the concerted mechanism, which is rationalized from q

Abstract We propose possible theoretical reaction paths for the conversion of methane to methanol catalyzed by FeO + . The geometric and electronic structures for the reactant, product, intermediates, and transition states were calculated and analyzed in detail by means of a hybrid Hartree–Fock/density functional method. Sextet and quartet spin states were taken into consideration in the analysis of the reaction paths. The conversion of methane to methanol was shown to proceed through basic conc

A nonradical mechanism for methane hydroxylation by the bare FeO+ complex, Fe-ZSM-5 zeolite, and soluble methane monooxygenase is proposed from quantum chemical calculations. This mechanism is applicable when a metal-oxo species is coordinatively unsaturated. Direct interaction between methane and a metal active center can form a weakly bound methane complex in the initial stages of this reaction. Subsequent C-H bond cleavage to form an intermediate with an HO-Fe-CH3 moiety in a nonradical manne