Intramolecular charge transfer in amino-benzonitriles: Requirements for dual fluorescence

Abstract

Dual fluorescence and intramolecular charge transfer (ICT) are observed with aminobenzo-nitriles when two excited state levels (S1 and S2(CT) in DMABN) have an energy gap sufficiently small for vibronic coupling: a solvent-induced pseudo-Jahn-Teller effect. It is argued that the N-inversion of the amino group acts as a promoting mode. These conclusions are based on a comparison of absorption spectra and photostationary and time-resolved fluorescence data. Dual fluorescence is also observed with MMD, in which the dimethylamino group is twisted towards a perpendicular configuration with respect to the phenyl ring. © 1993, Walter de Gruyter. All rights reserved.