An Investigation of Retinal as a Source of Singlet Oxygen

All‐trans retinal is dissolved in alcohols and illuminated at 365 nm in the presence of a singlet oxygen acceptor, 2,5‐dimethylfuran. Illumination produces the photosensitized oxidation of the acceptor which is measured by the disappearance of its 215 nm absorption band. A kinetic study is carried out and βDMF is 1.6 × 10‐‐4M. The quantum yield of 1O2 production from the light‐excited retinal is estimated to 0.096. The retinal sensitized photooxidation of dimethylfuran is inhibited by a 1O2 quencher, 1,4‐diazabicyclo(2,2,2)‐octane, and enhanced by deuteration of the solvent. Deuterated solvents are known to increase 1O2 lifetime. The production of 1O2 from retinal is briefly discussed in relation to the damage which may be induced by light in the visual cells.