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 sigma* and bithiophene pi* 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.