Influence of the solvent of crystallization on the orientational disorder of (trans)-4-chloro-4′-nitrostilbene

The polar molecule (trans)-4-chloro-4'-nitrostilbene, which shows significant second harmonic generation in the solid state, has been crystallized from 12 different solvents. Careful X-ray diffraction studies on 18 different crystals revealed varying deviations from an exact 50 : 50 head-to-tail orientational disorder and thus from the centrosymmetric average structure reported previously. The degree of disorder varies somewhat with the solvents used for crystallization. A weak correlation is found between the deviations from a centrosymmetric structure and the polarity of the solvent. No polymorphs were observed.