Transient phenomena in the pulse radiolysis of retinyl polyenes. 3. Radical cations

Results are presented concerning transient absorption phenomena observed upon pulse radiolysis of several retinyl polyenes at submillimolar concentrations in acetone, n-hexane, and 1,2-dichloroethane under conditions favorable for radical cation formation. Oxygen insensitive, the polyene radical cations are characterized by intense absorption maximum (575-635 nm) with locations that show little or no dependence on functional groups. In acetone, they undergo decay predominantly by first-order kinetics with lifetimes 4 - 11 μs. The biomolecular rate constants for radical cation quenching by water, triethylamine, and bromide ion in acetone are in the ranges (0.8 - 2) x 105, (0.3 - 2) x 108, and (3 - 5) x 1010 M-1 s-1, respectively. 24 references, 10 figures, 2 tables