Synthesis, Properties, and Polymerization of Spiro[(dipyridinogermole)(dithienogermole)]

Compounds with spiro-condensed dithienogermole (DTG) and dipyridinogermole (DPyG) units were synthesized, and their optical and electrochemical properties were investigated. The reaction of tetrachlorogermane and 3,3′-dilithio-5,5′-bis­(trimethylsilyl)­bithiophene, followed by treatment of the resulting mixture containing 1,1-dichlorodithienogermole with 3,3′-dilithio-4,4′-bipyridyl, gave spiro­{(dipyridinogermole) [bis­(trimethylsilyl)­dithienogermole]} (sDPyDTG1). The UV–vis spectrum of sDPyDTG1 showed absorption bands that were due to both electronically isolated DTG and DPyG units. In contrast, the photoluminescence (PL) spectrum showed only the band ascribed to the DTG unit even when the DPyG unit was irradiated, indicating intramolecular photoenergy transfer. It was also suggested that photoinduced electron transfer from DTG to DPyG occurred to suppress the PL quantum yield. Bromination of sDPyDTG1 with NBS provided the dibromide, and the subsequent Stille coupling of the resulting dibromide with distannylbithiophenes produced the corresponding conjugated oligomer and polymer. The oligomer and the polymer also showed different optical properties, suggesting intramolecular photoenergy and electron transfer, depending on the substituent.