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

Abstract

Out‐of‐plane vibrations which may be effective in vibronic coupling between $\mathrm{n\pi *}$ and $\mathrm{\pi \pi *}$ 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 $\mathrm{\pi *\hspace{0.17em}\to \hspace{0.17em}\pi }$ phosphorescence upon deuteration of the COR (R is H or an alkyl) group, nature of solvents, and molecular structure (e.g., ketones versus aldehydes).