Table of Contents
Laser Chemistry
Volume 9, Issue 4-6, Pages 317-337
http://dx.doi.org/10.1155/LC.9.317

Laser Induced Fluorescence of 4-N,N-Dimethylaminobenzonitrile (DMABN) and Related Compounds

The Royal Institution, 21 Albemarle Street, London W1X 4BS, UK

Received 20 May 1988

Copyright © 1988 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 role of polar solvent in determining the photophysics of normal (b*) and anomalous (a*) fluorescence from 4-N,N-dimethylaminobenzonitrile (DMABN) and related compounds has been investigated by means of picosecond time-resolved fluorescence studies in non-polar/polar solvent mixtures, and by electronic spectroscopic studies on complexes of 1:1 stoichiometry prepared by nozzle expansion. The solution phase results indicate clearly that a DMABN-polar solvent complex is formed initially in either ground or excited state, and that this rearranges to a geometry from which the b* to a* state transition can occur. Specific solvent-solute interactions are clearly indicated by this work, and these lead to the necessity of modelling b* state decay kinetics in solution by a distribution of decay times.

Laser induced fluorescence studies of jet-cooled solvated complexes of DMABN and the related molecule 4-aminobenzonitrile (4-ABN) provide evidence for the existence of 1:1 complexes involving interaction of a protic solvent molecule with either the cyano group or the amino group. In the case of 4-ABN both types of complex are fluorescent whereas in the case of DMABN, those complexes involving interaction with the dimethylamino group appear to be non-emissive. This behaviour may be due to formation of DMABN-solvent exciplex which constitutes a dark state under jet-cooled conditions. Neither the DMABN bare molecule nor the observed 1:1 solvated complexes exhibit a* emission in the jet.