Photochromism of Schiff base compounds derived from N,N′-bis(2-aminophenyl)isophthalamide: Structure and photosensitivity

The photochromic behaviors of four Schiff bases derived from N,N′-bis(2-aminophenyl)isophthalamide were studied to reveal the substituent effect on the photosensitivity. On UV radiation, all of compounds 1–4 exhibit photochromic behavior in solution through intramolecular hydrogen atom transfer, and the tautomerism equilibrium moved toward the keto-form. The solution and solid state fluorescence were also studied. After irradiated by 254 nm UV light, the solution fluorescence emission of compounds 1 and 4 went down, but the fluorescence emission intensified for compound 3. The solid state fluorescence (ss-FL) emission of compound 1 went down after UV irradiation. However, the ss-FL emission of 3 and 4 did not show any observable difference before and after UV irradiation. The influences of solvent, wavelength of irradiation and acidity on the adsorption spectra of the title compounds were also investigated.