Synthesis of Pyridinothienogermoles as Unsymmetrically Condensed Germoles

Pyridinothienogermoles (PyTGs) were prepared by the reaction of dilithiopyridylthiophene with dichlorodi­(n-octyl)­germane and dichlorodiphenylgermane, and their electronic states were investigated by optical measurements and density functional theory (DFT) calculations. Bromination of trimethylsilyl-substituted PyTG with N-bromosuccinimide gave PyTG bromide, and palladium-catalyzed Stille coupling reactions of bromide with diphenyl­[(trimethylstannyl)­phenyl]­amine and N-[(trimethylstannyl)­phenyl]­carbazole provided donor–acceptor compounds with pyridine as the acceptor and triphenylamine or phenylcarbazole as the donor. These compounds showed clear solvatochromic properties in the photoluminescence (PL) spectra. Bi­(pyridinothienogermole) was prepared by the Stille coupling of DPyG bromide and trimethylstannyl-substituted DPyG. The Lewis basicity of the pyridine ring made it possible to use these DPyG derivatives as ligands for complex formation. Protonation and complex formation of the PyTG pyridine unit with tris­(pentafluorophenyl)­borane enhanced the donor–acceptor interaction, shifting the UV absorption and PL bands to lower energies.