Abstract

The appearance of a normal band F_N and an anomalous band F_x, to the red of the former, in the fluorescence spectrum of solutions of 4-N,N-diethylaminoethylbenzoate in alkanes has been considered as evidence for the existence of a low energy twisted intramolecular charge transfer (TICT) excited state in electron acceptor substituted aniline derivatives [1]. Objections have been raised against this interpretation of the dual fluorescence [2]. Nevertheless, the TICT state seems to be widely accepted as a reasonable explanation of the phenomenon. Here we will present evidence that the long wavelength band in the spectrum arises from an adiabatic reaction of the molecule on the S₂-surface, in which a conformational change takes place along a reaction coordinate Q_xinvolving a deformation along the inversion coordinate of the amino group as well as an in-plane deformation of the benzene ring.

© 1992 The Author(s)