Synthesis and properties of bis(methylthio)dithienosilole and its oxides

A dithienosilole (DTS) possessing methylthio (SMe) groups at the alpha,alpha'-positions of the thiophene rings was prepared. The electronic states were tunable by oxidation of the sulfur atoms of DTS(SMe)2 with the corresponding amount of mCPBA, giving DTS(SOMe)(2) or DTS(SOMe)(2), and the UV absorption and fluorescence maxima shifted to higher energy regions by oxidation. DTS(SMe)(2) and the oxides were also examined with cyclic voltammetry, which showed a reversible two-step oxidation for DTS(SMe)(2). A polymer having DTS and sulfide as repeating units was prepared, and its properties were examined. We found that DTS(SMe)2 and poly(DTS sulfide) are potentially useful as hole-transporting materials in electroluminescence (EL) devices. The structure of DTS(SMe)2 was identified by X-ray crystallography.