Crystal structure of a polar nematogen 4-(trans-4-undecylcyclohexyl) isothiocyanatobenzene

Crystal and molecular structures of a nematogenic compound 4-(trans-4-undecylcyclohexyl) isothiocyanatobenzene (11CHBT) have been determined by direct methods using single crystal X-ray diffraction data. The compound (C24H37N1S1) crystallizes in the monoclinic system with the space group P2(1)/c and Z=4. The unit cell parameters are a=5.5539(11) angstrom, b=8.1341 (10) angstrom, c=51.494(5) angstrom, and beta=91.127(14)(0). The structure was refined to R-w=0.051. The molecule is found to be slightly bow-shaped though the alkyl chain is in all-trans conformation. The phenyl ring and the alkyl chain are planar and the cyclohexyl group is in chair conformation. The isothiocyanato groups are almost linear. Parallel imbricated mode of packing of the molecules is found in the crystalline state which is precursor to the nematic phase structure. There are many van der Waals' interactions particularly in the isothiocyanato benzene part of the molecule. Of the various associated pairs of molecules the one having anti-parallel configuration with overlaps in the isothiocyanato phenyl group probably exists in both the crystalline and the nematic phases. (C) 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.