Transient-resonance Raman and density functional theory investigation of 4-biphenylylnitrenium, 2-fluorenylnitrenium, and diphenylnitrenium ions

Abstract

We present transient-resonance Raman spectra for the 4-biphenylylnitrenium, diphenylnitrenium, and 2-fluorenylnitrenium ions. These spectra display a number of fundamental vibrational bands whose frequencies exhibit good agreement with those computed using BPW91/cc-PVDZ density functional theory calculations for the singlet ground states of the 4-biphenylylnitrenium, diphenylnitrenium, and 2-fluorenylnitrenium ions. Comparison of these arylnitrenium ions with each other and with previous results for structurally similar biphenyl radical cations indicates that the degree of iminocyclohexadienyl character observed in these arylnitrenium ions depends on the relative orientation of the two phenyl rings, the nature of the nitrenium ion moiety, and the ability of the biphenyl-like group to accommodate positive charge through formation of a more planar-like structure with quinoidal-like character. © Wiley-VCH Verlag GmbH, 2001.