The crystal structure of dibiphenyleneethylene

Dibiphenylene-ethylene crystallizes in the space group Pcan. The data for the unit cell are: a = 17.2, b = 36.9, c = 8.23 A., Z = 12. The strong negative birefringence and marked pleochroism indicate a layer crystal structure, and the morphology suggests an arrangement of molecules compatible with optical data and supported by Fourier syntheses. Satisfactory agreement of calculated with observed structure amplitudes is obtained with a centrosymmetric, planar molecular model constructed on customary C-C distances and angles. The anomalous reactivity and color of dibiphenylene-ethylene are discussed as steric effects of molecular planarity.