Silyl-Substituted Dithioles as Candidates for New Electron Donors

Abstract

Abstract Molecular orbital calculations revealed that the introduction of a silyl group onto the 2-position of 1,3-dithiole caused significant decrease of the ionization potential and that 2-silyl-1,3-dithioles served as a pseudo π-electron system. The silyl group could also be utilized as a bridge for linking π-electron systems to achieve artificial stacking. These concepts led us to the design and synthesis of silyl-substituted 1,3-benzodithioles as candidates for new electron donors. The oxidation potential of monosilyl-substituted 1,3-benzodithiole was found to be significantly less positive than that of the parent 1,3-benzodithiole. The introduction of the second silyl group caused further decrease of the oxidation potential. Compounds composed of two 1,3-benzodithiole units linked by a silyl group were also synthesized. These showed comparable oxidation potentials to those of the corresponding monomeric compounds. The effect of stannyl-substitution onto the 2-position of 1,3-dithiole was found to be larger than that of silyl-substitution. The effects of silyl- and stannyl-substitution for related systems such as thioanisole and 1,3-dithiane were also studied.