Generation of adenosyl radical from S-adenosylmethionine (SAM) in biotin synthase.

A mechanism of the C-S bond activation of S-adenosylmethionine (SAM) in biotin synthase is discussed from quantum mechanical/molecular mechanical (QM/MM) computations. The active site of the enzyme involves a [4Fe-4S] cluster, which is coordinated to the COO(-) and NH(2) groups of the methionine moiety of SAM. The unpaired electrons on the iron atoms of the [4Fe-4S](2+) cluster are antiferromagnetically coupled, resulting in the S=0 ground spin state.

Molybdenum-catalyzed transformation of molecular dinitrogen into silylamine: experimental and DFT study on the remarkable role of ferrocenyldiphosphine ligands.

A molybdenum-dinitrogen complex bearing two ancillary ferrocenyldiphosphine ligands, trans-[Mo(N(2))(2)(depf)(2)] (depf = 1,1'-bis(diethylphosphino)ferrocene), catalyzes the conversion of molecular dinitrogen (N(2)) into silylamine (N(SiMe(3))(3)), which can be readily converted into NH(3) by acid treatment. The conversion has been achieved in the presence of Me(3)SiCl and Na at room temperature with a turnover number (TON) of 226 for the N(SiMe(3))(3) generation for 200 h. This TON is significantly improved relative to those ever reported by Hidai's group for mononuclear molybdenum complexes having monophosphine coligands [J.

How axial ligands control the reactivity of high-valent iron(IV)-oxo porphyrin pi-cation radicals in alkane hydroxylation: a computational study.

The push effect of anionic axial ligands of high-valent iron(IV)-oxo porphyrin pi-cation radicals, (Porp)(+.)Fe(IV)(O)(X) (X=OH(-), AcO(-), Cl(-), and CF(3)SO(3)(-)), in alkane hydroxylation is investigated by B3LYP DFT calculations. The electron-donating ability of anionic axial ligands influences the activation energy for the alkane hydroxylation by the iron(IV)-oxo intermediates and the Fe-O bond distance of the iron-oxo species in transition state.

Participation of multioxidants in the pH dependence of the reactivity of ferrate(VI).

Alcohol oxidation by ferrate (FeO(4)(2)(-)) in water is investigated from B3LYP density functional theory calculations in the framework of polarizable continuum model. The oxidizing power of three species, nonprotonated, monoprotonated, and diprotonated ferrates, was evaluated. The LUMO energy levels of nonprotonated and monoprotonated ferrates are greatly reduced by solvent effects, and as a result the oxidizing power of these two species is increased enough to effectively mediate a hydrogen-atom abstraction from the C-H and O-H bonds of methanol.