Photophysics of meso-substituted anthracenes. Part 2.—Temperature effects in the solution and vapour phases

Abstract

The temperature-dependent photophysical properties of anthracene and three meso-substituted derivatives have been studied in both the solution and gas phases. In solution the S₁ state of all four compounds have single-exponential decay with pre-exponential factors of opposite signs. The fluorescence decay of 9,10-diphenylanthracene changes from single- to dual-exponential kinetics at a temperature of ca. 230 °C, whilst 9-vinylanthracene has single-exponential decay throughout the range studied. Rate and energy parameters have been calculated and interpreted in terms of a model of level inversion between S₁ and T₂ in the vapour phase and thermally activated reverse intersystem crossing from T₂ and S₁. Evidence is presented for temperature-dependent internal conversion in relaxed vapours of 9,10-diphenylanthracene and 9-cyanoanthracene.