ORDER-DISORDER EFFECTS IN CLATHRATES - A CRYSTALLOGRAPHIC AND CL-35 NQR SPECTROSCOPIC STUDY OF CCL(3)X GUEST MOLECULES (X=CL, BR, CH3, CN, NO2, H) IN HEXAKIS(PHENYLTHIO)BENZENE

X-ray crystallography and NQR spectroscopy have been jointly used to s tudy CCl(3)X-hexakis(phenylthio)benzene (HPTB) (X = Cl, Br, CH3, CN, N O2, H) clathrates. The crystal of the non-clathrated HPTB is triclinic , P (1) over bar, a = 9.5614(7), b = 10.2088(13), c = 10.6193(11) Angs trom, alpha = 68.45(1)degrees, beta = 76.98(1)degrees, gamma = 65.62(1 )degrees, Z = 1; crystals of the clathrates with CCl3CH3, CCl3Br, CCl3 NO2, and CCl3CN are isostructural and trigonal, R (3) over bar, a = 14 .18-14.32, c = 20.47-20.62 Angstrom, Z = 3. The trigonal host cavity o f HPTB clathrates contains two CCl(3)X guest molecules, and the X grou p occupies either the axial or one of the equatorial positions and thu s undergoes a molecular order/disorder depending upon its nature. Dipo le-dipole interactions between host and guest molecules are considered here to explain this order/disorder effect quantitatively.