Vibronic spin-orbit interactions in heteroaromatic molecules. II. phosphorescence of quinoxaline and other diazanaphthalenes

Abstract

Solvent effects on phosphorescence and its polarization characteristics indicate that the two major spin-orbit coupling mechanisms through which the 3B2(ππ*) state of quinoxaline acquires dipole-allowed character via nπ* states are 1B 1(nπ*)↔so3B2 (ππ*) and 1A1 (ππ*) ↔b1vib1B1 (nπ*) ↔so3B2 (ππ*). The deuterium isotope effect on the emission characteristic and the intensity of vibronic bands of the n→π* absorption suggest that the perturbing vibration (s) is an out-of-plane C-H bending mode(s).