Charge transfer complexes of benzimidazoles with pi-acceptors

ABSTRACT

Charge transfer complexes play an important role in biological system. Some investigators[1] suggested that the activity of biologically active compounds may depend on their tendencies to form such CT complexes. Benzimidazoles have received much attention because of their biological importance.[2,4] Studies have shown the benzimidazole molecule favours the formation of a CT species [5] The complexes of benzimidazoles depend upon the nature of substituents and also on the nature of the solvent [6] Benzimidazoles have been found to interact strongly in solution with iodine to give 1 1 molecular charge transfer [CT] complexes of the n-sigma type and the donor site was reported to be the nitrogen atom of imidazole ring [7-9] Interaction of some thiazoles and oxazolones derivatives as donors with nitrobenzene derivatives as acceptors have been studied [10-11]The CT complexes of some Schiff bases derivatives with tri-and dinitrobenzenes have been studied, where found to be the electron-acceptor of a molecule depends on the number of the nitro group of the acceptor[12-13] The charge transfer aromatic nitro compounds have been reported with various aromatic amine compounds[14]. In the present work, an attempt has been made to investigate the complexes of benzimidazoles with 4-nitrophenol, 2,4-dinitrophenol and picric acid. Equilibrium constants and molar extinction coefficients of the charge transfer complexes formed are determined at different temperatures and in different solvents