Synthesis and structural studies of poly(p-phenylenevinylene) analogous model compounds

Described is the synthesis and characterization of three poly(p-phenylenevinylene) (PPV) three-ring model compounds, one unsubstituted at the vinylene moiety (1) and two dicyano-substituted compounds (2, 3), differing in the positions of their cyano groups. Single-crystal analyses of the two cyano-substituted compounds 2 and 3 show that introduction of cyano groups into alkyl-substituted PPV analogous compounds leads to remarkable torsion of the conjugated backbones unlike hexyloxy-substituted compounds. In the case of introducing it into the alpha-position as in 2, the torsion is distributed almost equally over the molecule. Introducing the cyano group into the beta-position as in 3 leads to a one-sided torsion between the inner phenylene ring and the vinylene-CN planes.