Synthesis and Crystal Structure of a Cyano-Substituted Oligo(<i>p</i>-phenylenevinylene)

Described is the synthesis and the single-crystal structure of an all-trans dicyano-substituted five-ring PPV oligomer having two n-octyloxy side chains attached onto the central phenyl ring. The crystal density (Dcalc = 1.210 g cm-3) appears to be almost 10% higher than that of the crystalline phase of the analogue without cyano substituents. This indicates the presence of considerable packing forces, which is reflected in a remarkable “wavelike” deformation from planarity of the conjugated backbone and the stretching of the n-octyloxy side chains along the backbone. We attribute this dense packing to a large Coulomb interaction between neighbor molecules as a result of cyano substitution. Our results suggest that such intermolecular interactions play an important role with respect to the molecular geometry and packing in the solid state of cyano-substituted PPV-based materials.