A STUDY OF THE PHOTOCHEMICAL PROPERTIES OF SOME CINNAMATE SUNSCREENS BY STEADY STATE AND LASER FLASH PHOTOLYSIS

Abstract The E ⇄ Z photoisomerization of 4′‐methoxycinnamates, used as sunscreens in cosmetics, has been studied by steady state and laser flash photolysis, in aqueous and organic solutions. Photoisomerization quantum yields are found to be fairly high (˜0.5‐1), although no intermediate is detected upon laser flash photolysis. Cinnamates are not photodynamic sensitizers but are able to quench the 8‐methoxy‐psoralen and 5‐methoxypsoralen triplets which produces E → Z isomerization.