Synthesis and optical properties of H-shaped silicon-containing molecule with bithiophene units

The H-shaped molecule, 5,5′-bis{[bis(5′-tert-butyldimethylsilyl)-2,2′-(bithiophen-5-yl)]methylsilyl}-2,2′-bithiophene (3) was prepared by the reaction of 5′-(tert-butyldimethylsilyl)-5-lithio-2,2′-bithiophene with 2-bromo-5-(dichloromethylsilyl)thiophene, followed by treatment of the resulting product (5-bromothiophen-2-yl)bis[5′-(tert-butyldimethylsilyl)-2,2′-bithiophen-5-yl](methyl)silane (1) with compound (2), obtained by the reaction of the lithiated derivative of 1 with 2-isopropyl-4,4,5,5-tetramethyl-1,3,2-dioxaborolane, in the presence of dichlorobis(triphenylphosphine)palladium, as light yellow solids. Compound 3 showed absorption maximum (λmax) at 336 nm with a molar absorption coefficient (ε) of 113,000 M−1 cm−1 in dioxane. The fluorescence spectrum of 3 excited at 336 nm in dioxane displayed the emission maxima at 377 and 387 nm, with the fluorescence quantum yield of 48%. We also carried out theoretical treatment of compound 3 to elucidate the geometrical and electronic structure, using the Gaussian 03 program package, with the 6-31G and 6-31G(d) basis sets.