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The crystal structure of bis(cholesteryl)4,4'-(1,2-phenylenebis(oxy))dibutanoate (C68H106O6) has been determined by direct methods using single-crystal X-ray diffraction data. It crystallises in the monoclinic system with space group P21 and Z = 2. The unit cell parameters are a = 10.7917(9) Å, b = 10.4719(7) Å, c = 27.172(2) Å, β = 97.754(3)°. The final reliability factor is R = 0.0448 for 4862 observed reflections and the goodness of fit is equal to 1.016. The bond distances and angles are in good agreement with the corresponding values for compounds containing phenyl and cholesterol moieties. The phenyl ring is planar and makes dihedral angles of 52.1(1)° and 85.6(1)° with the cholesterol segments. The cholesterol segments have the usual structure: rings A, C, E, G have chair conformation, and rings B, D, F, H adopt half-chair conformation. The molecules in the unit cell are arranged in layers. The crystal structure is stabilised by inter-molecular C-H...O and C-H ... π interactions. [ABSTRACT FROM AUTHOR]

The crystal structure of cholesteryl 5-[4-(4-n-heptylphenylethynyl)phenoxy]- pentanoate (C53H76O3) was determined by direct methods using single crystal X-ray diffraction data. It crystallises in the triclinic system with space group P1 and Z = 2. The unit cell parameters are: a = 10.6791(5), b = 13.0903(7), c = 18.6430(9)Å, α = 94.413(3), β = 98.222(3), γ = 112.987(3)°. The final reliability factor was R = 0.0510 for 7284 observed reflections and the goodness of fit was equal to 1.062. The asymmetric unit cell of the compound was found to contain two symmetry-independent molecules, A and B. In both molecules, the six-membered rings of the cholesterol moiety are conformationally very similar. However, pronounced differences were observed in the conformation of the five-membered ring, which is a half-chair in molecule A and assumes an envelope conformation in molecule B. In both molecules, the phenyl rings are planar. The dihedral angle between the two phenyl rings is 43.4(2) and 42.7(2)° for molecules A and B, respectively. The packing of molecules in the crystalline state was found to be a precursor to the smectic A phase structure. The crystal structure is stabilised by inter-molecular C-H...O and C-H...π interactions. [ABSTRACT FROM AUTHOR]

The crystal structure of cholesteryl 4-[4-(4- n -butylphenylethynyl)phenoxy]butanoate [phase sequence: Cr 155°C (46.1?J?g -1 ) SmA 186.8°C (1.5?J?g -1 ) TGB-N* 204.7 (6?J?g -1 ) I] has been solved from single crystal X-ray diffraction data. The compound crystallizes in the monoclinic space group P 21 with unit cell parameters: a ?=?13.129(2), b ?=?9.3904(10), c ?=?17.4121(8)?Å, ß?=?92.790(7)°, Z ?=?2. The structure has been solved by direct methods and refined to R ?=?0.0606 for 3?250 observed reflections. The bond distances and angles are in good agreement with the corresponding values for compounds containing phenyl and cholesterol moieties. The phenyl rings A and B are planar. The dihedral angle between the least-squares planes of the two phenyl rings is 28°. The cholesterol moiety has the usual structure: the C and E rings have chair conformations, and the D and F rings adopt half-chair conformations. The molecules in the unit cell are arranged in an antiparallel manner. The crystal structure is stabilized by an intermolecular C–H...O contact of 2.989(10)?Å. [ABSTRACT FROM AUTHOR]