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Calculated electronic spectra of model ferric cytochrome P450 complexes
Author(s) -
Waleh Ahmad,
Collins Jack R.,
Loew Gilda H.,
Zerner M. C.
Publication year - 1986
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560290547
Subject(s) - chemistry , ferrous , protonation , ferric , spectral line , ground state , molecular orbital , open shell , computational chemistry , inorganic chemistry , molecule , atomic physics , organic chemistry , physics , ion , astronomy
Restricted open‐shell ground state properties and electronic spectra of two closely related low‐spin, ferric, 6‐coordinate, model cytochrome P450 complexes, one with a methyl mercaptide and the other a mercaptan as the second axial ligands, have been calculated with a newly modified, semiempirical INDO‐SCF‐CI method. The sensitivity of the calculated spectra to protonation of the sixth axial ligand, and the ability of the method to predict characteristic spectral features for the complexes investigated, are determined. Assignment of transitions, including xy ‐ and z ‐polarized transitions, are made and compared with experimental observations where available. In particular, the origin of the anomalous split Soret spectrum observed in low‐spin ferric complexes with mercaptide but not a mercaptan is investigated. Finally, a two part hypothesis is presented which provides a general explanation for the origin of both the observed split Soret and the red‐shifted normal Soret in various ferrous and ferric P450 complexes in terms of the ground state orbital characters and simple symmetry considerations.