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.
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