(C9H7INO • C12H4N4) triclinic PT, a = 7.161(5) A, b = 8.639(5) Ä, c = 17.392(6) A, a 64.96(4)°, ß = 80.64(3)°, y = 76.99(3)°, V = 1075.6 A3, Z = 2, dc = 1.47 Mgm-3. The structure was refined to R — 0.114 for 2022 reflections. It consists of segregated diadic stacks of TCNQ and 4-oxo-iodoquinolinium ions. Interplanar distances in the TCNQ stack are 3.09( 1) A and 3.32(1) A ; 3.37(1) A and 3.55(1...

The mol-ecule of the title compound, C(26)H(28)O(5), is chiral with five stereogenic centres; however, the centrosymmetric triclinic group gives a racemic crystal. The fused ring system adopta boat conformation in which the cyclo-propane ring plane is roughly perpendicular to the styryl group plane, forming a dihedral angle of 74.78 (19)°. The dihedral angle between the two benzene rings is 77....

The sample of the title compound, C12H15N3S, chosen for study consisted of triclinic crystals twinned by a 180° rotation about the a axis. The five-membered ring adopts a twisted conformation. The dihedral angle between the phenyl ring and the mean plane of the thio-urea unit is 78.22 (8)°. In the crystal, molecules are linked via pairs of N-H⋯S hydrogen bonds forming inversion dimers.

The structure of the title compound, pentoxifylline, C(13)H(18)N(4)O(3), has been previously characterized as a triclinic polymorph [Pavelčík et al. (1989 ▶). Acta Cryst. C45, 836-837]. We have discovered the monoclinic form. There are no strong hydrogen bonds in the crystal structure, rather, moderate C-H⋯O hydrogen bonds are present, which serve to stabilize the three-dimensional architecture.

Octakis(m-tolyloxymethyl)naphthalene, the first Type I spider host produced, crystallises from tetraglyme forming a novel channel structure with the host molecule attaining exact D(2) symmetry. The (flexible) channel structure is retained for guest CS(2), the host now only having exact C(2) symmetry. The octa-sulfone octakis(m-tolylsulfonylmethyl)naphthalene is also of Type I in its triclinic D...

The title compound, [Fe(C(5)H(5))(C(15)H(14)NO(2))], is a monoclinic polymorph of the previously reported triclinic form [Shi et al. (2006 ▶). Acta Cryst. C62, m407-m410]. The polymorphs feature the same strong intra-molecular N-H⋯O=C hydrogen bonds, but show different packing modes. The mol-ecules in the monoclinic form associate into double chains via O-H⋯O=C and (Cp)C-H⋯O-H inter-actions.

Tetartohedral crystal twinning is discussed as a particular case of (pseudo)merohedral twinning when the number of twinned domains is four. Tetartohedrally twinned crystals often possess pseudosymmetry, with the rotational part of the pseudosymmetry operators coinciding with the twinning operators. Tetartohedrally twinned structures from the literature are reviewed and the recent structure dete...