Twisted intramolecular charge transfer emission of 2-(4 '-N,N-dimethylaminophenyl)benzimidazole in micelles

Spectral characteristics of 2-(4'N,N-dimethylaminophenyl)benzimidazole have been studied as a function of surfactant concentration and as a function o f acid concentration in three surfactants. Dual fluorescence is observed in all the micelles. Fluorescence intensities of the local emission (B band) and twisted intramolecular charge transfer (A band, TICT) increase by an 17 -30% and 38 to 64% respectively. When dissolved in micelles lifetimes of bo th the states also increase in the presence of micelles. The increase in th e fluorescence intensities is attributed to the decrease in the non-radiati ve decay constant, cmc of the surfactants can be determined from the variat ion in the fluorescence intensity and the lifetime data. The equilibrium co nstants are determined for the prototropic reactions of the fluorophore in all the micelles in S-0 and S-1 states and the values obtained are discusse d. (C) 1999 Academic Press.