Absorption and Emission Studies of Electronic States of N‐arylbenzamides

Absorption and emission spectra of several N‐arylbenzamides have been measured. The quantum yields for their fluorescence were found to be dependent on matrix viscosity and temperature. Singlet‐triplet splittings for these compounds were determined from their emission spectra and found to be abnormally small for π. π* states (˜ 1500 cm ‐1 ). Indeed, the phosphorescence maxima of N‐arylbenzamides occur slightly to the blue relative to their fluorescence maxima. Intersystem crossing efficiencies were determined for several of these compounds and are consistent with S 1 → S 0 radiationless decay.