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.