The Preparation of Dithieno[3,2-<i>b</i>:4,5-<i>c</i>’]germole, and Its Application as a Donor Unit in Conjugated D–A Compounds

Group 14 metalloles have attracted much attention as core structures of conjugated functional materials. In this work, we prepared dithieno[3,2-<i>b</i>:4,5-<i>c</i>’]germole as a new unsymmetrically condensed dithienogermole and benzo[4,5]thieno[2,3-c]germole as the benzene-condensed analog. The electronic states and properties of these unsymmetrically condensed germoles are discussed on the basis of the results of optical and electrochemical measurements with the help of quantum chemistry calculations on the simplified model compounds. The Stille cross-coupling reactions of bromodithieno[3,2-<i>b</i>:4,5-<i>c</i>’]germole with di(stannylthienyl)- and di(stannylthiazolyl)benzothiadiazole provided conjugated donor–acceptor compounds that exhibited clear solvatochromic behavior in the photoluminescence spectra, indicating the potential application of the dithieno[3,2-<i>b</i>:4,5-<i>c</i>’]germole unit as an electron donor in donor–acceptor systems.