Photochemical isomerizations of 2-phenyl-1,3-indanedione to E- and Z-benzalphthalide and of E-benzalphthalide to Z-benzalphthalide

The photochemical isomerizations have been studied of 2-phenyl-1,3-indanedione to mixture of E- and Z-benzalphthalide and of E-benzalphthalide to Z-benzalphthalide depending on the solvent used, concentration, and the light wavelength. The attempts at the reverse photochemical isomerization of E-benzalphthalide to 2-phenyl-1,3-indanedione have failed. Quantum yields of the isomerization of 2-phenyl-1,3-indanedione decrease in the following solvent series: cyclohexane acetonitrile benzene tetrachlormethane methanol. The isomerization quantum yield of 2-phenyl01,3-indanedione is inversely proportional to concentration of the starting substance, but the dependence of 1/φ on the concentration is not linear.