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X-ray studies of the crystalline and nematic phases of 4'-(3,4,5-trifluorophenyl)-4-propylbicyclohexyl

Haldar, Sumanta and Mandal, PK and Prathap, SJ and Row, TN Guru and Haase, W (2008) X-ray studies of the crystalline and nematic phases of 4'-(3,4,5-trifluorophenyl)-4-propylbicyclohexyl. In: Liquid Crystals, 35 (11). pp. 1307-1312.

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The crystal and molecular structures of the nematogenic compound 4'-(3,4,5- trifluorophenyl)-4-propylbicyclohexyl (3ccp-fff) were determined by direct methods using single crystal X-ray diffraction data at 293K. The compound (C21H29F3) crystallises in the triclinic system with space group P1 and Z=2. The unit cell dimensions are a=5.3715(14), b=10.559(3), c=16.891(4), =86.331(5), =85.196(6) and =81.938(5). The structure was refined by the least squares method to an R-value of 0.058 for 1398 observed reflections. The fluorine atoms are in the plane of phenyl ring. Both the cyclohexyl groups are found to be in chair conformation and they are coplanar (dihedral angle 0.8). The molecules were found to be in the most extended conformation. Results of the crystal structure analysis were compared with that obtained from molecular modelling and also with that of the related bifluorinated compound (3ccp-ff). An antiparallel imbricated mode of packing of the molecules is found in the crystalline state. Several van der Waals interactions are observed between the neighbouring molecules, suggesting evidence for existence of molecular packings in head-to tail configuration. The average fluctuation length of the molecules within the nematic phase, determined from a small-angle X-ray diffraction study, is found to be about 1.4 times more than molecular length, providing further evidence for the existence of antiparallel associations between neighbouring molecules.

Item Type: Journal Article
Publication: Liquid Crystals
Publisher: Taylor and Francis Group
Additional Information: Copyright of this article belongs to Taylor and Francis Group.
Keywords: nematogen;trifluorophenyl derivative;X-ray study;molecular association;crystal structure;molecular modelling.
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 04 Nov 2009 06:43
Last Modified: 04 Nov 2009 06:43
URI: http://eprints.iisc.ac.in/id/eprint/17821

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