Transient Phenomena in the Pulse Radiolysis of Retinyl Polyenes. 4. Environmental Effects on Absorption Maximum of Retinal Radical Anion

Article abstract of DOI:10.1021/j100272a032

The absorption-spectral and kinetic behaviors of radical ions of all-trans-retinal in various solvents have been studied by spectrophotometric pulse radiolysis at room temperature.Upon going from nonpolar and polar-nonprotic solvents to polar-protic ones (alcohols), large hypsochromic shifts occur in the absorption maximum (λ_max) of retinal radical anion.The anion absorption maxima in the alcohols correlate well with solvent dielectric constants.In a number of solvents, parallelism is noted between the energies corresponding to λ_max's of retinal anion and of solvated electron (the latter at 77 K and room temperature).Transient phenomena associated with the radical anion (λ_max's = 448-460 nm) and the retinyl alcohol radical (λ_max = 405 nm) are observed in the course of the pulse radiolysis of retinal in several normal micelles (aqueous).The blue-shifted locations of the anion λ_max's strongly suggest a polar-protic, alcohol-like nature of the micellar region where the polyenal resides.