Topochemistry. Part XXIV. The luminescence properties of N-salicylideneaniline and related anils in solution

Abstract

The N-salicylideneanilines studied all luminesce in solution on irradiation with near-ultraviolet light. The intensity of the emission is very low at room temperature in most cses, but becomes appreciable at low temperatures (e.g., below –100°) even when the solvent is still fluid. The intensity is greater in polar than in non-polar solvents. The anils exist in solution in two interconvertible forms; this is indicated by the presence in the absorption spectrum of two bands, lying in the ultraviolet and visible, respectively, the relative intensities of which vary with the experimental conditions. The emission is the “mirror” of the long-wavelength absorption band, irrespective of the wavelength of the exciting light. When the long-wavelength absorption is vanishingly small the result is an apparently anomalously large Stokes shift. An attempt to find a long-lived component in the total luminescence was unsuccessful.