Molecular Packing in Unsubstituted Semiconducting Phenylenevinylene Oligomer and Polymer

p-Bis(p-styrylstyryl)benzene, C38H30, a five-ring phenylene−vinylene model compound for unsubstituted PPV, has been obtained in single-crystal form and the crystal structure has been resolved. The arrangement of the molecules is of the herringbone-type, and its characteristic dimensions correspond remarkably well to those of the structure proposed for PPV in 1986. This packing mode is entirely different from what has been found for substituted oligo(phenylenevinylene)s but similar to that observed in other types of conjugated oligomers without lateral substituents. Thin films of the unsubstituted oligomer show electroluminescence at a lower onset voltage and blue-shifted relative to substituted oligo(phenylenevinylene)s.