title: Substituent effects in the absorption spectra of phenol radical species: origin of the redshift caused by 3,5-dimethoxyl substitution.
abstract: The ground-state equilibrium geometries, electronic structures and vertical excitation energies of methyl- and methoxyl-substituted phenol radical cations and phenoxyl radicals have been investigated using time-dependent density-functional theory (namely TD-B3LYP) and complete-active-space second-order perturbation theory (CASPT2). The "anomalous" large redshifts of the absorption maxima of the phenol radical species observed in the ultraviolet-visible spectral region upon di-meta-methoxyl substitution are reproduced by the calculations. Furthermore, these "anomalous" shifts which were unexplained to date can be rationalized on the basis of a qualitative molecular orbital perturbation analysis.
authors.affiliation: Centre for Research in Molecular Modeling and Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada.
authors.forename: Lei
authors.initials: L
authors.lastname: Zhang
authors.forename: Heidi M
authors.initials: HM
authors.lastname: Muchall
authors.forename: Gilles H
authors.initials: GH
authors.lastname: Peslherbe
mesh_terms: D007700:Kinetics; D008958:Models, Molecular; D010636:Phenols / Q000737:chemistry*; D010696:Phloroglucinol / Q000031:analogs & derivatives* / Q000737:chemistry; D011789:Quantum Theory; D013816:Thermodynamics; D014466:Ultraviolet Rays
chemical_list: D010636:Phenols; C015155:phloroglucinol dimethyl ether; C042329:phenoxy radical; D010696:Phloroglucinol