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International Journal of Photoenergy
Volume 2006, Article ID 81896, 6 pages

The dynamics of excited state structural relaxation of 4-dimethylaminobenzonitrile (DMABN) and related compounds

Department of Chemistry, Lomonosov Moscow State University, Moscow 119992, Russia

Received 29 September 2003; Revised 19 July 2005; Accepted 25 July 2005

Copyright © 2006 Valery Volchkov et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The excited state structural relaxation of 4-dimethylaminobenzenes with various para-acceptor substituents having double-band emission, local excited (LE) and charge transfer (CT), has been investigated. Fluorescence measurements at different temperatures and in different solvents have confirmed the existence of viscosity-dependent, temperature, and polarity-activated relaxation. The kinetics analysis has shown that the radiative deactivation rate constants of the individual LE and CT states differ by 7112-fold. The dipole moment changes at the excitation for CT states are significantly larger than those for LE states. The spectral-kinetics behavior of compounds studied agrees with the models AAB or AAB, where A is the local excited planar and B is the relaxed twisted state of the molecule. The rate constants of the twisted state formation have been calculated in the temperature range 29377 K. The activation energies of forward process for compounds studied have been estimated.