Photophysics of 5,10,14c,15-tetra-azabenzo[a]naphth[1,2,3-de]anthracene (tricycloquinazoline, TCQ) and some of its derivatives

Abstract

The photophysical properties of tricycloquinazoline (TCQ) and its 2-methyl (2-Me-TCQ) and 2-bromo (2-Br-TCQ) derivatives in various solvents at different temperatures have been investigated and found to be similar except for those of the triplet states. Absorption spectra, fluorescence and phosphorescence spectra, polarization properties, fluorescence and phosphorescence yields and their corresponding lifetimes have been measured and characterized.

Both the S₁ and S₂ states are π, π^* in nature. The S₁↔S₀ transition is symmetry forbidden whereas the S₀↔S₂ transition is symmetry allowed. The presence of an S_0–0 peak in absorption and fluorescence arises from a solvent-dependent perturbation. A “hot band” arising from an S_0V0â†�S_2V0 transition is detected in fluorescence emission. The total rate of radiationless deactivation from S₁ involves temperature-dependent processes. The T₁-state is π, π^* in nature and phosphorescence from T₁ is symmetry allowed.