Photoinduced Electron Transfer from Tetraphenyl-Substituted 1,2-Digermacyclohexa-3,5-dienes and Related Compounds to C60

Article abstract of DOI:10.1246/bcsj.70.2249

The irradiation of benzene-benzonitrile solutions of 3,4,5,6-tetraphenyl-substituted l,2-digermacyclohexa-3,5-dienes and related compounds in the presence of C₆₀ afforded the corresponding ring-contracted products, namely 1-germacyclopenta-2,4-dienes, with the extrusion of germylene and ring-expanded oxadigerma compounds, namely l-oxa-2,7digermacyclohepta-3,5-dienes. The laser flash photolysis of a benzene-benzonitrile solution of 1,2-digermacyclohexa-3,5-dienes in the presence of C₆₀ showed that the transient absorption band of the C₆₀ triplet state (^TC₆₀*) appeared immediately at 730 nm. With the decay of ^TC₆₀*, the absorption bands of the radical anion of C₆₀· ^- appeared at 1060 nm, showing that an electron transfer takes place from 1,2-digermacyclohexa-3,5-dienes to ^TC₆₀*. The formation of cyclic oxadigerma compounds was explained by processes of both the photooxidation of 1,2-digermacyclohexa-3,5-dienes in the absence of C₆₀ with singlet oxygen and oxidation of the cation radical of 1,2-digermacyclohexa-3,5-dienes with triplet oxygen.