Temperature dependence of the deactivation of triplet aromatic molecules by metal ions

Abstract

The temperature dependence of the deactivation of triplet anthracene by transition metal ions, and of triplet phenanthrene by lanthanide ions has been studied in methanol/water (9:1) over the range 120–293 K. At high temperatures, the reactions show Arrhenius behaviour, and the rate parameters for the intra-cage interaction have been determined. The large variation in the A-factors of these reactions, and their magnitudes in relation to energy transfer between aromatic molecules, are discussed in terms of the inefficiency of the transmission of the exchange interaction through the ligand molecules. At low temperatures, all the reactions become diffusion-controlled, and follow a temperature dependence similar to that found in the triplet-triplet annihilation reaction of both anthracene and phenanthrene.