Vibronic Interactions between nπ* and ππ* States and Radiative and Nonradiative T1 → S Transitions in Aromatic Carbonyl Compounds

Out-of-plane vibrations which may be effective in vibronic coupling between nπ* and ππ* states of aromatic carbonyl compounds are investigated, and the probable importance of these vibrations in radiationless transitions is demonstrated through the dependence of vibrational features, quantum yields, and lifetimes of π* → π phosphorescence upon deuteration of the COR (R is H or an alkyl) group, nature of solvents, and molecular structure (e.g., ketones versus aldehydes).