LASER-INDUCED ABSORPTION AND FLUORESCENCE STUDIES OF PHOTOCHROMIC SCHIFF-BASES

Three photochromic Schiff bases: N-salicylideneaniline (SA), N-salicyl idene-1-naphthylamine (SN), and N,N-bis-(salicylidene)-p-phenylenediam ine (Bsp), were studied in acetonitrile by means of steady-state and t ime-resolved absorption and fluorescence spectroscopy, as well as semi empirical quantum chemical calculations. In all these molecules, the t ransient absorption and two-step laser-induced fluorescence spectra of long-lived transients are remarkably similar. The photochromic specie s is tentatively assigned to the non-hydrogen bonded form of the proto n transfer reaction product with a considerable contribution of zwitte rionic character.