Synthesis and optical properties of spirobi(dithienometallole)s and spirobi(dithienothiametalline)s

Spiro-condensed dithienometalloles (metal = Si, Ge) and dithienothiametallines (metal = Si, Ge, Sn) were prepared by the ring closure reactions of dilithiated bithiophene and dithienyl sulfide with metal tetrachlorides, and their optical properties were studied with respect to the UV absorption and emission spectra. The absorption and emission maxima of them moved to higher energies by increasing the size of the center metal from Si to Ge and Sn, and stepwise oxidation of the ring sulfur atom in the dithienothiasiline system forming sulfoxide and sulfone linkages, making the fine tuning of the electronic states possible.