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International Journal of Photoenergy
Volume 6 (2004), Issue 2, Pages 69-72
http://dx.doi.org/10.1155/S1110662X04000108

Excited state structural relaxation relaxation of N-(1-anthryl)-2,4,6-trimethyl-pyridinium cation

1Department of Chemistry, M.V. Lomonosov Moscow State University, Vorob'evy Gory, Moscow 119899, Russia
2Institute of Physical and Organic Chemistry, Rostov State University, Stachki str. 194/3, Rostov on Don 344104, Russia

Copyright © 2004 Hindawi Publishing Corporation. 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.

Abstract

The fluorescence spectrum of N-(1-anthryl)-2,4,6-trimethylpyridinium cation (1) has an anomalously high Stokes' shift. The fluorescence spectra of 1 in ethanol and butyronitrile are shifted to shortwavelength region and fluorescence quantum yield increases as the temperature decreases. The fluorescence rate constant of this compound changes considerably (6 times in ethanol and 15 times in butyronitrile) as the temperature decreases from 293 K (relaxed state) to 77 K (mainly nonrelaxed state). It points out that at these temperatures the fluorescence takes place from two species with different structures. It is concluded that anomalously high fluorescence Stokes' shift of 1 is caused by both solvent orientation relaxation and excited state structural relaxation consisting in the mutual rotation of anthracene and pyridinium fragments of the cation and resulting in the formation of a specie with different structure. The rates of these processes are determined by the temperature-dependent viscosity of the medium.