A pulse radiolysis and pulsed laser study of the pyrromethene 567 triplet state

The triplet state of pyrromethene 567, a molecule with potential as a solid state laser dye, has been characterized in benzene by pulse radiolysis in terms of its absorption spectrum, lifetime, self-quenching, electronic exci tation energy, triplet-triplet extinction coefficient and oxygen quenching rate constant. The use of laser flash photolysis has then allowed determina tion of the triplet quantum yield, efficiency of formation of singlet oxyge n ((1)Delta(g)), and the rate constant for reaction of the latter species w ith the ground state. The affects of oxygen on the fluorescence and triplet yields demonstrate that oxygen-induced intersystem crossing is important, the sum of these parameters being unity within experimental error. The mech anism of reaction of P-567 with (1)Delta(g) in benzene is predominantly phy sical in character with only a small (similar to 6%) contribution from chem ical reaction. (C) 2000 Elsevier Science S.A. All rights reserved.