Molecular Structure and Packing Analysis of Two Nematogenic Fluoro-Phenyl Compounds in the Crystalline Phase

Abstract

The crystal and molecular structures of two nematogenic compounds 4′-(3, 4-difluoro-phenyl)-4-propyl-bicyclohexyl(3ccp-ff) and 4′-(3,4,5-trifluoro-phenyl)-4-propyl-bicyclohexyl(3ccp-fff) have been determined by direct methods using single crystal X-ray diffraction data. The compounds (C₂₁ H₃₀ F₂) and (C₂₁H₂₉F₃) crystallize in the monoclinic system with the space group P2₁/n and Z = 4 and in the triclinic system with the space group ${\text{P}}\overline{1}$ and Z = 2 respectively. The fluorine atoms are in the plane of phenyl ring. Both the cyclohexyl groups are found to be in chair conformation. Parallel imbricated mode of packing of the molecules are found in the crystalline state which is precursor to the nematic phase. Several van der Waals interactions are observed between the neighbouring molecules. Results of crystal structure have been compared with that obtained from molecular modelling.