Phenyl Substitution Effects on Triplet-Triplet Absorption Spectra: I. Study of 1,3,6,8-Tetraphenylpyrene

The triplet-triplet (T-T) absorption spectrum of 1,3,6,8-tetraphenylpyrene (TPP) was measured from 400 to 620 nm. The data obtained are compared with theoretical calculations using the Ruedenberg-Scherr FEMO model. A planar triplet state is evidenced by fine vibrational structure. The T-T quenching rate constant measured (1.3 ± 0.1 × 10 9 M − 1 s −1 ) is 20% of the expected diffusion-controlled value.