The decomposition mechanisms of NO on Cu-ZSM-5 catalyst models were theoretically investigated. The structure and frequency of adsorbed NO on Cu-ZSM-5 and the poisoning of Cu-ZSM-5 by oxygen can be reproduced by the calculations using the density functional method with Huzinaga's MIDI+P basis set.

Dioxygen binding to the active dinuclear iron site of methane monooxygenase (MMO) is theoretically analyzed with a density functional method. The μ-η1:η1-O2 mode was calculated to be the most favorable binding mode of dioxygen to a supposed active site of MMO that contains two five-coordinate irons(II).

No abstract

No abstract

Time-dependent density functional theory (TDDFT) calculations have been performed on the excitation energies and oscillator strengths of the Q-like bands of three structural isomers of phenylene-linked free-base (FBP) and zinc (ZnP) porphyrin dimers. The TDDFT calculated results on the low-lying excited states of the reference monomers, FBP and ZnP, are in excellent agreement with previously calculated and experimental results. It is found that the 1,3-and 1,4-phenylene-linked dimers have monomerlike Q bands that are slightly red-shifted compared to the monomers and new Q bands comprised of the cross-linked excitations from the FBP (ZnP) ring to the ZnP (FBP) ring at considerably lower energies than the monomer Q bands. For the 1,2-phenylene-linked dimer, the direct π-π interaction between porphyrin rings caused by the van der Waals repulsion between them provides strong mixing of the Q bands with the Q bands, which causes its minimum excitation energy to be red-shifted by 0.05 eV compared to the other isomers. The oscillator strengths of the Q bands are also unexpectedly found to be as strong as those of the Q bands in the dimers.