Excited state intramolecular proton transfer in 2-(2 '-benzamidophenyl)benzimidazole: effect of solvents

Excited state intramolecular proton transfer (ESIPT) process in 2-(2'-benza midophenyl)benzimidazole (2-BAPBI) has been studied in different solvents b y means of absorption, fluorescence, fluorescence excitation and time resol ved spectroscopy. Dual fluorescence (normal and tautomer emissions) is obse rved in all the solvents. The quantum yield of the tautomer emission is alw ays larger than that of the normal emission. This is because of the enhance d rate of ESIPT process which arises due to the presence of the electron wi thdrawing benzoyl group as a substituent to one of the hydrogen atom of the amino group in 2-(2'-aminophenyl)benzimidazole (2-APBI). (C) 1999 Elsevier Science B.V. All rights reserved.