Hydrogen and fluorine in crystal engineering: systematics from crystallographic studies of hydrogen bonded tartrate-amine complexes and fluoro-substituted coumarins, styrylcoumarins and butadienes

Three aspects of crystal engineering in molecular crystals are presented to emphasize the role of intermolecular interactions and factors influencing crystal packing. Hydrogen bonded tartrate-amine complexes have been analyzed with the propensity for formation of multidirectional hydrogen bonding as a key design element in the generation of materials for second harmonic generation (SHG). The invariance of the framework in DBT and its possible implications on SHG is outlined. The role of Fluorine in orienting molecules of coumarins, styrylcoumarins and butadienes for photodimerization is described with particular emphasis on its steering capability. Usage of coumarin as an design element for the generation of polymorphs of substituted styrylcoumarins is examined with specific examples

Phase transitions in A<SUB>4</SUB>Li(HSO<SUB>4</SUB>)<SUB>3</SUB>(SO<SUB>4</SUB>); A = Rb, K: single crystal X-ray diffraction studies

The crystal structure of ferroelastic Rb4Li(HSO4)3(SO4) has been determined at two temperatures, which indicates a structural phase transition, tetragonal P43 with a = 7.629(1) &#197;,c = 29.497(2) &#197; at 293 K and monoclinic P21 witha = 7.583(3) &#197;,b = 29.230(19) &#197;,c = 7.536(5) &#197;,&#946; = 90.14(1)&#176; at 90 K. The crystal structure of K4Li(HSO4)3(SO4)4 has also been determined at two temperatures, tetragonalP41 witha = 7.405(1) &#197;,c = 28.712(6) &#197; at 293 K and tetragonalP41 with a = 7.371(5) &#197;,c = 28.522(5) &#197; at 100 K. The overall coordination features in both the structures have been analysed in terms of bond valence sum calculations

Crystal structure and ionic conductivity of a new bismuth tungstate, Bi<SUB>3</SUB>W<SUB>2</SUB>O<SUB>10.5</SUB>

The compound Bi3W2O10.5 was synthesized by the solid-state technique from Bi2O3 and WO3 in stoichiometric quantities. Single crystals were grown by the melt-cooling technique and the crystal structure was solved in the tetragonalI4/m space group with a = 3.839 (1) &#197;,c = 16.382 (5) &#197;,V = 241.4 (1) &#197;3,Z = 4 and was refined to anR index of 0.0672. The structure represents a modification of the Aurivillius phase and consists of [Bi2O2]2+ units separated by WO8 polyhedra. a.c. impedance studies indicate oxide ion conductivity of 2.91 10-5 Scm-1 at 600&#176;C

Ab initio structure determination via powder X-ray diffraction

Structure determination by powder X-ray diffraction data has gone through a recent surge since it has become important to get to the structural information of materials which do not yield good quality single crystals. Although the method of structure completion when once the starting model is provided is facile through the Rietveld refinement technique, the structure solutionab initio is still not push-button technology. In this article a survey of the recent development in this area is provided with an illustration of the structure determination of &#945;-NaBi3V2O10

1-(4-Chlorophenyl)-2,6,6-trimethyl-1,5,6,7-tetrahydro-4H-indol-4-one

In the title compound, C17H18ClNO, the tetrahydroindole ring system is nearly planar, except for the dimethyl-substituted C atom. Molecules are linked via C-H...O and C-H...π interactions, forming chains along the b axis

Structural studies of `push–pull' butadienes

Compound (I), ethyl 2-cyano-5-dimethylamino-3- methyl-2,4-pentadienoate, C11H16N2O2, Mr = 208.26, monoclinic, P21/n, a = 7.679(2), b = 13.368 (2), c = 11.756 (2) Å, β = 92.62 (2)°, V = 1205.5 (4) Å3, Z = 4, Dx = 1.15 g cm-3, λ(Cu Kα) = 1.5418Å, μ = 6.15cm-1, F(000)=448, T=293K, R=0.062 for 1721 unique reflections. Compound (II), 4,4-bis(methylthio)-2-phenyl- 1,3-butadiene- 1,1- dicarbonitrile, C14H12N2S2, Mr=272.38, triclinic, P1&#773;, a = 8.833 (1), b = 9.419 (2), c = 9.520 (1) Å, α = 106.77 (1), β = 93.14 (1), ᵞ = 109.61(1)°, V= 704.2 (2) Å3, Z = 2, Dx = 1.28 g cm-3, λ(Cu Kα) = 1.5418 Å, μ = 32.29 cm-1, F(000) = 284, T = 293 K, R = 0.062 for 2059 unique reflections. Compound (III), ethyl 2-cyano-5-dimethylamino-3-phenyl-2,4- pentadienoate, C16H18N2O2, Mr=270.33, mono- clinic, C2/c, a = 17.468 (1), b= 13.753 (4), c= 15.218 (1) Å, β = 125.49 (1)°, V = 2976.7 (9) Å3, Z = 8, Dx = 1.21 g cm-3, λ(Cu Kα)= 1.5418Å, μ = 6.12 cm-1, F(000)=1152, T = 293 K, R = 0.055 for 2211 unique reflections. Compound (IV), 4-dimethylamino-4-methylthio-3-phenyl-l,3- butadiene-1,1-dicarbonitrile, C15H15N3S, Mr = 269.36, monoclinic, P21/n, a = 9.951 (1), b – 10.040 (1), c = 14.764 (2) Å, β = 98.67 (1)°, V = 1458.9 (2) Å3 Z = 4, Dx = 1.23 g cm-3, λ(Cu Kα) = 1.5418 Å, μ = 18.37 cm -1, F(000) = 568, T = 293 K, R = 0.052 for 2479 unique reflections. The influence of different electron donor-acceptor pairings on the molecular geometry is discussed

N-[(9E)-2-Chloro-9-thia-9H-xanthen-9-ylidene]-N-(4-fluorophenyl)amine

In the title compound, C19H11ClFNS, the central 4H-thiapyran ring of the 9H-thiaxanthene moiety shows a roof-shaped structure, with a dihedral angle of 34.3 (2)°. The molecules pack in the crystal structure via aromatic π-π interactions