B. Jaishi, P. Mandal, K. Goubitz
Nov 1, 2003
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Journal
Liquid Crystals
Abstract
The crystal structure of the compound 4-cyanobiphenyl-4′-hexylbiphenyl carboxylate (6CBB), which exhibits both monolayer smectic A and nematic phases, has been determined by direct methods using single crystal X-ray diffraction data. The structure is triclinic with the space group P-1 and Z=2. The unit cell parameters are a=9.3511(7) Å, b=11.2456(7) Å, c=13.1417(6) Å, α=85.872(4)°, β=76.258(5)° and γ=70.697(5)°. The molecule is found to be slightly bow-shaped although the alkyl chain is in all-trans conformation. The phenyl rings in 6CBB are non-coplanar. The packing of the molecules in the crystalline state is found to be a precursor to the smectic A phase structure. Comparison of crystal structures and packing of the four-ring 6CBB with those of the two-ring nCB or nOCB compounds has been made to explain the observed phase behaviour.