Luminescence studies of benzamide derivatives at room and low temperatures

In this study the luminescence spectra and fluorescence decay times of benzamide and its three derivatives have been measured at room and low temperatures in MCH, EPA and IP/EE mixtures. The bichromophoric derivatives i.e., N-phenylbenzamide and N,N'-methylphenylbenzamide yield dual fluorescence. The phosphorescence spectra of the molecules under study show a blue shift when nonpolar rigid solvent is replaced with polar one. This effect, and the same lambda(max) values of the phosphorescence bands indicate that the phosphorescence emissions originate from the (n, pi*) state of the benzoic moiety. The small tau values of the S-1(LE) state suggest that the rate constants of the excited state proton-transfer tautomer and TICT isomer creation processes are large. The tau values of molecules in the S-1(LE), S-1'(PT), and S-1"(CT) states differ significantly. (C) 1999 Elsevier Science S.A. All rights reserved.