Novel Conjugated Donor-π-Acceptor Molecules Based on 1,3-Diselenol-2-ylidene Units.

Abstract The synthesis is described of a series of conjugated donor-π-acceptor molecules where 1,3-diselenoles are the electron donor moieties and dicyanomethylene or N-cyanoimine groups function as the acceptor moieties. Alkenes and aryl groups act as the conjugated spacers. The UV-VIS absorption spectra of these molecules in solution possess a low energy band resulting from intramolecular charge transfer; the wavelength of this band varies significantly with the structure of the spacer group. The solution redox properties, studied by cyclic voltammetry, reveal a reversible one-electron oxidation wave, attributed to the formation of the radical cation of the 1,3-diselenol-2-ylidene moiety, and an irreversible one-electron reduction to form the radical anion located on the dicyanomethylene or N-cyanoimine groups. The X-ray crystal structure of 9 9-(1,1-dicyanomethylene)-10-(4,5-dimethyl-1,3-diselenol-2-ylidene)-9,10-dihydroanthracene 14 is reported. The molecule is strained and adopts a “butterfly conformation” in the ground state due to unfavourable peri-interactions between the 1,3-diselenole selenium atoms and the peri hydrogens.