The Triplet State of 3‐Nitropyrene

Abstract

Abstract 3‐nitropyrene was exposed to a 347.2 nm laser flash in dilute solutions of organic solvents and in aqueous micellar solutions. It was found that the triplet state is formed with a quantum yield of 0.6. The triplet absorption spectrum shows a red shift with increasing polarity of the solvent. Triplet‐triplet energy transfer experiments with anthracene, pyrene and perylene were performed to obtain both the energy (190 ± 10kJ/mol) and the absolute extinction coefficient ((1.0 ± 0.1) 10 4 M −1 cm −1 at 530nm in benzene) of the 3‐nitropyrene triplet. Diffusion‐controlled triplet‐triplet annihilation occurs in ethanol, benzene and hexane solutions. In some micellar solutions and in glycerol, where the bimolecular triplet‐triplet interaction is retarded, the triplet was found to disappear in a first order process with a half lifetime of 230 μs.—The triplet state of 3‐nitropyrene abstracts a hydrogen atom from diphenylamine with k = 2.9 · 10 9 M −1 s −1 . Electron abstraction from Fe 2+ and CO 3 2‐ , which should be possible from the point of energetics, could not be observed.