The fluorescence of diphenyl- and retinol-polyenes

The unusual fluorescence properties of the polyenes are listed. The fluorescence lifetimes and/or quantum yields of the first four all-trans diphenylpolyenes have been determined in seven solvents between ?50 and 50°C. A model is proposed to account for the unusual fluorescence behaviour in terms of a low-lying ¹Ag state, coupled to ¹B_u, and which shifts to lower energies on intramolecular rotation.