Bithiophene-fusedbenzo[c]phospholes were successfully prepared by a TiII-mediated cyclization of dialkynylated bithiophene derivatives. It was revealed that the optical and electrochemical properties of the bithiophene-fusedbenzo[c]phospholes are deeply related to the π-conjugation modes at the fused bithiophene subunits. Both experimental and theoretical results demonstrate that the appropriately