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Substituent Effects in the Absorption Spectra of Phenol Radical Species: Origin of the Redshift Caused by 3,5-Dimethoxyl Substitution

Authors

  • Lei Zhang,

    1. Centre for Research in Molecular Modeling and Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada
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  • Heidi M. Muchall,

    Corresponding author
    • Centre for Research in Molecular Modeling and Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada
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  • Gilles H. Peslherbe

    Corresponding author
    • Centre for Research in Molecular Modeling and Department of Chemistry and Biochemistry, Concordia University, Montreal, QC, Canada
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Corresponding author email: gilles.peslherbe@concordia.ca (Gilles H. Peslherbe); heidi.muchall@concordia.ca (Heidi M. Muchall)

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.

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