Synthesis, Optical Properties, and Crystal Structures of Dithienostannoles

Reactions of dichlorodiphenylstannane
with 3,3′-dilithio-5,5′-bis­(trimethylsilyl)-2,2′-bithiophene
and 3,3′-dilithio-2,2′-di­(benzo­[b]­thiophene)
gave 1,1-diphenyl-3,6-bis­(trimethylsilyl)­dithienostannole (DTSn1) and di­(benzo­[b]­thieno)-1,1-diphenylstannole (DTSn2), respectively. Optical properties of the dithienostannoles
and the results of DFT calculations on a model suggested an in-phase
interaction between Sn σ* and bithiophene π* orbitals,
stabilizing the LUMO. Interestingly, DTSn1 showed crystallization-enhanced
emission and the photoluminescence (PL) quantum yield of the crystals
was determined to be higher by about 20 times than that in the amorphous
and solution phase, while DTSn2 exhibited moderate PL
efficiency both as crystals and in solution. Crystal structures of
the dithienostannoles were determined by X-ray diffraction studies,
which showed the differences in the molecular packing between DTSn1 and DTSn2, being responsible for their
different PL properties in the crystal state.