Crystal and molecular structures of the 1 : 2 "host-guest" complex betweencis-anti-cis Isomer of dicyclohexano-18-crown-6 and 2-thiouracil

The molecular and crystal structures of the 1 : 2 "host-guest" complex betw een cis-and-cis isomer of dicyclohexano-18-crown-6 (host, H) and 2-thiourac il (guest, G; complex I) have been determined by X-ray diffraction analysis . The crystals are monoclinic; a = 10.638(2), b = 13.755(3), and c = 11.283 (2) Angstrom; beta = 105.83(3)degrees; space group P2(1)/n; Z = 4, and the final R factor is 0.064. A crown ether molecule and two 2-thiouracil molecu les are joined together into a centrosymmetric associate via hydrogen bonds of two types: N-H ... O [N ... O = 2.842(8) Angstrom] and C-H .. O [C ... O 3.217(11) Angstrom]. In turn, die guest molecules also form centrosymmetr ic dimers via the hydrogen bonds N-H ... S=C [N ... S 3.462(7) Angstrom]. T he dimerization leads to the formation of linear chains in the crystal. The molecular skeleton of the crown ether is described by the D-3d symmetry.