Flash photolysis of benzils

Flash photolytic studies on benzils are reported. Two different geometrical conformers, one puckered and the other planar, have been characterized for triplet benzils and benzil anions. They are produced under different conditions. The puckered benzil triplet formed in ethanol galss at 77 K shows an absorption peak at 490 nm accompanied by vibrational bands at 1600 and 1000 cm⁻¹. The planar benzil triplet, which appears at room temperature, absorbs at 470 nm.

Two different conformers of the benzil anion are also found to be present in two different solvents, ethanol and acetonitrile. The planar form absorbs at 540 nm in ethanol and the puckered form absorbs at 620 nm in acetonitrile. Mesitil and α-furil do not undergo a change in conformation under similar conditions.