Triplet state behavior of pyrrole-2-carboxyaldehyde and related compounds

Abstract

The triplet state behavior of pyrrole-2-carboxyaldehyde (1) and related compounds was investigated by means of nanosecond laser flash photolysis. Compound 1 did not exhibit fluorescence emission, but underwent intersystem crossing to the triplet state with an efficiency of 0.80 in benzene. The triplet lifetime of 1 depended on its concentration. The self-quenching rate constant was determined to be 1.6 × 10⁸ M⁻¹ s⁻¹ in benzene. Intermolecular hydrogen bonding between the triplet state and the ground state plays an important role in the self-quenching process of 1.