Solvent effects on the fluorescence quenching rate constant of an intramolecular exciplex by poly(chlorobenzenes)

Abstract

The fluorescence of the intramolecular exciplex formed by N,N-diethyl-2-(1-naphthyl)ethylamine (I), was quenched by chlorobenzenes in acetonitrile, tetrahydrofuran, ethylacetate and cyclohexane. An electron transfer mechanism was proposed for the quenching process. It was observed that the second-order quenching rate constants, when the process is not diffusionally controlled, markedly increase as the relative permittivity of the solvent decreases. This unusual behaviour is analysed in terms of the Marcus theory of electron transfer reactions. It is suggested that the increase in the rate with decreasing solvent polarity may be explained by a lowering of the solvent barrier.