Solid-state photodecarboxylation induced by exciting the CT bands of the complexes of arylacetic acids and 1,2,4,5-tetracyanobenzene

Crystalline charge transfer complexes (3a, 3b, and 3c) of 1- and 2-naphthylacetic and 3-indoleacetic acid (la, Ib, and Ic) with 1,2,4,5-tetracyanobenzene (2) were prepared by crystallization from the acetonitrile solutions. Irradiation of 3a and 3b gave methylnaphthalenes by decarboxylation and naphthyl(2,4,5-tricyanophenyl)methanes by subsequent dehydrocyanating condensation in the solid state. On the other hand, the photoreactivity of the crystal 3c was low; similar photoreaction occurred only at high temperature. These solid-state reactions are induced by exciting the CT bands of 3a and 3b. The product selectivities were different from those of the solution photoreaction. The relationships between the photoreactivities and the crystal structures of 3a and 3c are discussed.