P. Sarkar, P. Sarkar, P. Mandal
Dec 1, 1998
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Journal
Molecular Crystals and Liquid Crystals
Abstract
Abstract Crystal and molecular structure of the compound 4-n-ethyl-4′-cyanobiphenyl (2CB), which exhibits nematic phase monotropically, is determined by direct methods from single crystal X-ray diffraction data. The crystal belongs to monoclinic system with space group P21, cell parameters being a = 8.584(4), b = 5.865(3), c = 11.833(3) (A) and β = 92.30(3)° with 2 molecules per unit cell. Refinement led to R = 0.079 with I > 2[sgrave](I). The molecules are in the most extended conformation. The phenyl rings are highly planar, the dihedral angle between them is 1.46°. Antiparallel pairs of 21 symmetry related molecules are arranged in layers and the layers are stacked along [001]. The thickness of these layers is equal to the length of crystallographic c-axis. van der Waals' type of contact encompasses all the molecules within a layer. Molecular geometry and crystal packing are discussed in the context of geometry and packing of other known nCB and nOCB structures.