Valence Photoisomerization of Aromatic Norbornadiene Derivative

Abstract

Direct and benzophenone (BP)- or 4, 4'-bis (dimethylamino)benzophenone (BAB) -sensitized valence photoisomerizations of 3-phenyl-2, 5-norbornadiene-2-carboxylic acid (PNC) in acetonitrile were found to efficiently proceed affording the corresponding quadricyclane derivative in quantum yields comparable to each other. Kinetic and thermodynamic considerations of the BP, BAB and 4-dimethylaminobenzophenone (DAB) -sensitized photoisomerizations of PNC suggested that the BP-sensitized reaction proceeds by an energy-transfer pathway whereas an electron-transfer pathway also participates in the BAB- and DAB-sensitized reactions.