Crystal structure and packing analysis of the liquid crystal dimer alpha,omega-bis(4-cyanobiphenyl-4 '-yloxy)octane

The crystal structure of the liquid crystal dimer alpha,omega -bis(4-cyanob iphenyl-4'-yloxy)octane has been determined from diffraction data obtained with synchrotron radiation. The structure is triclinic, with the space grou p P-1 with Z = 2 and the unit cell parameters are a = 7.135(5) Angstrom, b = 12.811(5) Angstrom, c = 15.639(5) Angstrom, alpha = 75.800(5)degrees, bet a = 84.690(5)degrees, gamma = 77.930(5)degrees. The flexible spacer linking the mesogenic groups is in the all-trans-conformation. Although the molecu le has a potential centre of symmetry, it occupies a general position in th e cell; this unusual behaviour has been investigated with the aid of a theo retical evaluation of the packing energy.