X-ray diffraction study of p-(alkoxybenzylidene)-p′-toluidines: Crystal and molecular structure of C10H21O-C6H4-CH=N-C6H4-CH3

The crystal and molecular structure of p-(decaoxybenzylidene)-p′-toluidine C₁₀H₂₁O-C₆H₄-CH=N-C₆H₄-CH₃ is studied. The molecule is nearly planar. In the crystal packing, loose regions formed by aliphatic fragments of molecules alternate with pseudostacks of aromatic fragments of molecules that are related by the centers of symmetry. The stacks are built of dimers, in which molecules are linked by π-stacking interactions between benzene rings. There are no weak directional interactions between dimers in a stack. The presence of a single structure-forming element in the crystal, namely, the π-stacking interactions in the dimers, along with the similarity of the crystal packing to that of the C₈H₁₇O-homologue, which forms a nematic mesophase on melting, indicate that the crystals under study should exhibit nematic properties.     

Molecular and crystal structure of 4-hexylbenzoic acid: Design of the mesophase

The crystal structure of 4-hexylbenzoic acid C₆H₁₃-C₆H₄-COOH, which forms a nematic mesophase upon melting, is determined. The crystal contains three crystallographically independent molecules. Their molecular skeletons are made up of two almost planar fragments: a benzene ring, π-conjugated with the carboxyl group and a planar zigzag aliphatic fragment. One of the independent molecules forms centrosymmetric dimers via pairs of hydrogen bonds between carboxyl groups, whereas the two others are linked via hydrogen bonds. The dimers in the crystal are packed into pseudostacks with a pronounced nonparallel arrangement of conjugated fragments. There is no good mutual projecting of benzene rings in the stacks, which corresponds to efficient π-stacking interaction. The graph describing the mesophase of this compound contains only one structure-forming element (a hydrogen bond) and corresponds to the nematic mesophase.     

Crystal and molecular structure of 4′-hexyloxyphenyl 4-pentylbenzoate

The molecular and crystal structure of 4??-hexyloxyphenyl 4-pentylbenzoate, C₆H₁₃O-C₆H₄-COO-C₆H₄-C₅H₁₁, which is a liquid-crystal compound, was determined by X-ray diffraction. This compound forms a nematic phase upon melting. The crystal contains three crystallographically independent molecules. In one of them, the alkyl chain is disordered. This is indicative of the looseness of the crystal packing in the aliphatic region. The crystal structure is stabilized by the following two types of weak directional interactions: hydrogen bonds with the participation of the terminal O atom of the ester group and the C-H group of one of the benzene rings and C-H????-system interactions. Only one of the three independent molecules is involved in the latter type of interactions. Hence, the structurization of the mesophase is most likely determined by hydrogen bonding.     

Molecular and crystal structure of 4-alkoxybenzoic acids: Design of the mesogenic phase

The crystal and molecular structures of 4-alkoxybenzoic acids C _n H_{2n + 1}-O-C₆H₄-COOH, n = 4–12, which are nematic (n = 4–6) or smectic-nematic (n = 7–12) mesogenes, are studied. No direct relationship between the molecular geometry and mesogenic properties is found. All the crystal structures contain dimers formed by pairs of O…H-O hydrogen bonds between carboxyl groups. Crystals belonging to the group of smectic-nematic liquid crystals (SNLC) are built of separate regions, namely, loosely packed aliphatic regions and closely packed aromatic regions with significant π-stacking interactions. Loose aliphatic regions occur in crystals belonging to the group of nematic liquid crystals (NLC); however, they are surrounded by dense aromatic regions and do not run throughout the crystal. In NLC, π-stacking interactions are far weaker than in SNLC. At the early stage of melting of SNLC crystals, structurized associates due to both π-stacking interactions and hydrogen bonds are retained in the melt (smectic phase), whereas, upon further heating, only hydrogen-bonded associates are left (nematic phase). In the course of melting of NLC, only hydrogen-bonded dimers are retained in the melt (nematic phase).     

Some properties of aqueous solutions of α-NiSO4 · 6H2O

The concentration dependences of the properties of solutions of ??-NiSO₄ · 6H₂O (mineral retgersite) in H₂O and 20% H₂SO₄ have been measured in a wide range of concentrations (up to ??20 solvent molecules per dissolved-salt molecule). It is shown that the solution density, the light absorption coefficient at a wavelength of 394 nm, and the intensity of the Raman scattering peak characteristic of the sulfate ion depend linearly on the bulk salt concentration in the solutions. No shift of the Raman peak as a result of a change in the concentration was observed. These facts indicate that the type of dissolved particles and the character of interactions between them and with the solvent remain the same with an increase in the salt concentration. The data in the literature on the formation of ion pairs in retgersite solutions are discussed.     

Crystal structure of 4-[benzylideneamino]-3-thiophen-2-yl-methyl-4,5-dihydro-1H-[1,2,4]triazole-5-one

The crystal structure of the title compound C₁₄H₁₂N₄OS was determined by the X-ray diffraction method. The compound crystallizes in the triclinic space group $P\bar 1$ with Z = 2. The molecule is not planar: the dihedral angle between the triazole and thiophene rings is 73.98(2)°, and that between the triazole and benzene rings is 4.05(2)°. The thiophene ring is disordered over two positions, which are approximately parallel and oppositely oriented. The major component refined to a site-occupancy factor of 0.573(3). An intramolecular C-H...O hydrogen bond generates an S(6) ring motif. In the crystal, molecules are linked together by two pairs of N-H...O interactions (to the same O atom as acceptor), forming inversion dimers. The crystal packing is also stabilized by π-π interactions [centroid-centroid distance is 3.978 Å].     

Correlation of mesogenic properties with intermolecular interaction energy for homologous series of HnCBP

Intermolecular interaction energy between a pair of molecules of homologous series 4, 4′-disubstituted biphenyl of the general formula HO?(CH₂)_n?O?C₆H₄?C₆H₄?CN(n = 3 ? 11) (H_nCBP) has been evaluated under various interacting conditions viz. stacking, in-plane and terminal interaction. Molecular geometry of the studied molecules was fully optimized without any constraint and checked for imaginary frequencies using hybrid density functional B3LYP combined with 6–31 g^** basis set. Electronic structure of the molecules obtained through these calculations has been utilized to calculate electrostatic and polarization energies under Rayleigh-Schrodinger perturbation theory modified with multi-centered multi-pole expansion method. Dispersion and repulsion energies have been evaluated using Kitaigorodskii formula. The identified minimum energy complexes have been further utilized to evaluate interaction energy under super molecular approach by employing M06 and DFT-D methods. A comparative analysis of the results has been reported with a view to examine suitability of different methods to study molecular aggregations in moderately large organic systems.     

Molecular and crystal structures of 4-acylphenyl 4′-alkyloxybenzoates

The crystal structures of four liquid-crystal (LC) compounds belonging to 4-acylphenyl 4′-alkyloxybenzoates with the general formula C _n H_{2n + 1}-C(O)-C₆H₄-O-C(O)-C₆H₄-O-C _m H_{2m + 1} numbered as 1/6, 1/7,2/7, and 3/7 (the numbers in the code indicate the ratios of the numbers of alkyl-chain units, n/m) are determined. Compounds 1/6 and 1/7 form smectic and nematic phases, but they are monotropic mesogens, whereas compounds 2/7 and 3/7 form only an enantiotropic smectic phase. Compound 3/7 crystallizes in two crystal modifications—triclinic with Z′ = 2 (3/7 _tr ) and monoclinic with Z′ = 4 (sp. gr. P2, 3/7 _mon ). All crystals consist of alternating aromatic and aliphatic regions and are characterized by the presence of weak directional interactions, such as C-H...O hydrogen bonds and π-stacking interactions. This provides the necessary conditions for the formation of a mesophase, and the existence of two types of structure-forming units is in line with the formation of a smectic phase. An explanation is proposed for the monotropic properties of 1/6 and 1/7.     

Solid-phase synthesis and crystal structure of 5(3-nitrophenyl)-3,7-diphenyl-4H,6H-1,2-diazepine

The title compound, 5-(3-nitrophenyl)-3,7-diphenyl-4H,6H-1,2-diazepine (C₂₃H₁₉N₃O₂), was synthesized, in 76% yield, by one-pot multicomponent solid-phase reaction of 3-nitrobenzylidene phenyl ketone, acetophenone and hydrazine, using the catalyst bismuth nitrate, co-catalyst ZnCl₂, adsorbed on neutral alumina, at 110°C. The compound was characterized by spectral methods and X-ray diffraction studies. The crystals are monoclinic, space group P2₁/c: a = 12.186(2), b = 14.769(3), c = 11.046(2) Å, β = 115.023(3)°, Z = 4; R = 0.0418 for 2576 observed reflections. The diazepine ring assumes a twist chair conformation. The dihedral angles between the mean planes through the diazepine ring and the nitrophenyl rings and two phenyl are: 89.19(5)°, 45.85(5)° and 20.80(6)°, respectively. The crystal structure is stabilized by C-H…N, C-H…O, C-H…π hydrogen bonds and π-π-stacking interactions.     

Synthesis and crystal structure of (1R,2R)-N,N′-bis(4-toluenesulfonyl)-1, 2-di(4-methoxylphenyl)ethylenediamine

The reaction of (1R,2R)-1,2-di(4-methoxylphenyl)ethylenediamine with p-toluene sulfonyl chloride affords the title compound C₃₀H₃₂N₂O₆S₂, the structure of which is ascertained by X-ray diffraction. The title compound contains two chiral centre with each C atom in R configuration. Two adjacent molecules are linked by intermolecular hydrogen bonds through sulfonamide nitrogen and sulfonyl oxygen to form a one-dimensional chain alone a axis.     

Crystal structure of Rb2[GeO2(OH)2]·2H2O

Single crystals of Rb₂[GeO₂(OH)₂] · 2H₂O are studied by X-ray diffraction. The crystals belong to the orthorhombic system, sp. gr. Pna2₁, a = 13.523(6) Å, b = 8.143(4) Å, c = 13.407(6) Å, Z = 8, R ₁ = 0.0506. In [GeO₂(OH)₂]^2? anions, the Ge-O distances (1.71–1.73(1) Å) are shorter than the Ge-OH distances (1.76–1.80(1) Å). Anions are linked to each other by pairs of hydrogen bonds to form infinite chains. The chains are linked by hydrogen bonds involving water molecules to form a 3D structure. The assignment of the bands in the IR spectrum of the compound under study is performed.     

A new nonlinear optical borate, Na0.5Pb2[B5O9](OH)1.5 · 0.5H2O, from the orthorhombic hilgardite family

A new polar representative of the hilgardite structural family, Na_0.5Pb₂[B₅O₉](OH)_1.5 · 0.5H₂O (space group Pnn2), is synthesized under hydrothermal conditions. The crystal structure of the compound synthesized is similar to the structure of the previously studied polar compound Na_0.5Pb₂[B₅O₉]Cl(OH)_0.5 and is intermediate between the latter compound and the centrosymmetric hydrate Pb₂[B₅O₉](OH) · 0.5H₂O. The additional peak revealed in the electron density in the vicinity of the Pb(1) atom is attributed to the stereochemically active lone electron pair of this atom. The lone electron pair is oriented toward the two most distant oxygen atoms involved in the Pb(1) coordination environment, namely, O(7) and O(2), which are located in a boron-oxygen framework layer in the ac plane, not toward the (00_z) channel occupied by water molecules. The nonequivalence in the stereochemical activity of two lead atoms [Pb(1) > Pb(2)] is similar to that observed in the nonlinear optical borate Pb₂[B₄O₅(OH)₄](OH)₂ · H₂O related to BiB₃O₆.     

Molecular and Crystal Structure of 2-{(<Emphasis Type="Italic">E</Emphasis>)-[(5-Chloro-2-methoxyphenyl)imino]methyl}-4-nitrophenol

The molecular structure of the title compound, C₁₄H₁₁ClN₂O₄, was determined by single crystal X-ray diffraction. The compound crystallizes in the monoclinic sp. gr. P2₁/c with Z = 4. The title compound, C₁₄H₁₁ClN₂O₄, is a Schiff base which adopts the phenol-imine tautomeric form in the solid state.The molecule is almost planar and the dihedral angle between the planes of two aromatic ring is 2.2(1)°. The molecular structure is stabilized by intramolecular O–H···N hydrogen bond which generates a six-membered ring. In the crystal structure, the molecules are linked together by intermolecular C–H···O interactions.     

Synthesis,Crystal Structure,and Luminescent Properties of Ag(I) Coordination Polymer with Tricarboxylic Acid and Flexible N-donor Ligand

The reaction of AgNO₃ with combinations of 1,3-bis(4-pyridyl)propane (bpp) and 1,3,5-benzenetricarboxylic acid (H₃btc) in aqueous alcohol/ammonia at room temperature produces crystals of {[Ag₆(H₂O)₂(bpp)₆] · (btc)₂ · 25H₂O} _n (Ι). Single crystal X-ray diffraction analysis reveals that the complex Ι consists of 1D infinite cationic chains of [Ag(bpp)] _n ⁿ⁺ and [Ag(H₂O)(bpp)] _n ⁿ⁺ which are further linked into the cation layer of [Ag(bpp)] _n ⁿ⁺ by Ag···π interactions. The noncoordinated btc^3? serves as template driving surrounding water molecules to aggregate into the anionic water layer. The neighboring anionic water layer and cationic layer were further alternately joined into a 3D sandwich-like framework by hydrogen bonding. In addition, the luminescent properties of Ι were investigated.     

X-ray diffraction study of p -(alkoxybenzylidene)- p ′-toluidines C5H11O-C6H4-CH=N-C6H4-CH3 and C8H17O-C6H4-CH=N-C6H4-CH3

The molecular and crystal structures of two p-(alkoxybenzylidene)-p′-toluidines C₅H₁₁O-C₆H₄-CH=N-C₆H₄-CH₃ (1) and C₈H₁₇O-C₆H₄-CH=N-C₆H₄-CH₃ (2), which form the nematic phase upon melting, is determined by X-ray diffraction. The geometry of the benzylideneaniline fragments in molecules 1 and 2 is actually identical. The crystal packings of 1 and 2 are characterized by the alternation of layers formed by loosely packed aliphatic fragments of molecules and layers of closely packed aromatic fragments. The packing in the aromatic regions of 1 follows the parquet pattern. The crystal packing of 2 has a stacking structure, which is formed by π-stacking dimers superimposed on one another. The formation of the mesogenic phase upon melting of crystals 1 is due to the disturbance of the structurality of loose aliphatic layers with retention of the structure of the aromatic regions, which are stabilized by the cooperative effect of weak directed C-H ··· π-system interactions. The mesogenic phase of crystals 2 is formed upon melting as a consequence of the retention of the structure of π-stacking dimers. Original Russian Text ? L.G. Kuz’mina, N.S. Kucherepa, M.N. Rodnikova, 2008, published in Kristallografiya, 2008, Vol. 53, No. 6, pp. 1079–1085.     

Molecular and crystal structures of p-heptyloxyphenyl p-hexyloxybenzoate and p-butyloxyphenyl p-heptyloxybenzoate: Mesophase design

Two aromatic esters with the formulas C₆H₁₃-O-C₆H₄-C(O)O-C₆H₄-O-C₇H₁₅ (1) and C₇H₁₅-O-C₆H₄-C(O)O-C₆H₄-O-C₄H₉ (2) belonging to nematic liquid-crystal compounds were studied by X-ray diffraction. Compound 1 crystallizes in two modifications: monoclinic (1-m) and triclinic (1-tr). The crystal packing of 1 and 2 is built from alternating loosely packed aliphatic regions and closely packed aromatic regions. In crystal structures 1-m and 2, the aromatic regions are linked into chains by hydrogen bonds with the participation of the carbonyl oxygen atom of the ester group and the C-H fragment of the benzene ring, but these hydrogen bonds in 1-m are much weaker than in 2. In 1-m there are π-stacking interactions between the molecules, resulting in the formation of centrosymmetric dimers with an interplanar distance of 3.45 Å. In 1-tr, the aromatic fragments form a herringbone packing motif favorable for a two-dimensional network of directional C-H...π-system interactions.     

Crystal structure of bis(isothiocyanato)[2,6-diacetylpyridine bis(4-hydroxybenzoylhydrazone)]Fe(III) Chloride bis(dimethylformamide) solvate

The crystal structure of title compound (Fe[(C₂₅H₂₁N₇O₄S₂)] · 4(C₃NOH₇), where C₃NOH₇ is dimethylformamide, DMF) was determined by the X-ray diffraction method. This compound crystallizes in the monoclinic C2/c space group, Z = 4. Unit cell parameters are: a = 13.6080(5), b = 17.6375(7), c = 19.5571(6) Å, β = 108.753(2)°. The N-H...O and O-H...O interactions stabilize the molecules in the lattice. The structure contains also the solvent dimethylformamide molecules, which are connected with intermoleculer hydrogen bond. The O atoms of DMF molecules take place as acceptor atoms.     

Synthesis,spectroscopic characterization and crystal structure of 5-bromo-1-(2-cyano-pyridin-4-yl)-1H-indazole-3-carboxylic acid diethylamide

The title compound 5-bromo-1-(2-cyano-pyridin-4-yl)-1H-indazole-3-carboxylic acid diethylamide, C₁₈H₁₆BrN₅O, is prepared from 5-bromoindazole-3-carboxylic acid methylester. N ¹-arylation is carried out with 4-chloro-2-cyanopyridine and the resulting product is converted to diethylamide by reacting with thionyl chloride and diethylamine. The structure is identified from its FT-IR, ¹H NMR, ¹³C NMR spectroscopy, elemental analysis data and unambiguously confirmed by single crystal X-ray diffraction studies. There are two symmetry independent molecules in the asymmetric unit with no significant differences in bond lengths and angles. The title compound crystallizes in the triclinic system, space group \(P\bar 1\) , with a = 11.2330(2); b = 11.6130(2); c = 15.4710(3) Å, α = 92.515(1)°; β = 109.956(1)°; γ = 107.199(1)°; V = 1788.45(6)ų and z = 4. An intramolecular C-H…N hydrogen bond forms an S(6) ring motif in one of the unique molecules. In the crystal, two molecules are linked about a center of inversion by C-H…O hydrogen bonded dimers generating an R ₂ ² (16) ring motif. The crystal packing is stabilized by C-H…N, C-H…O hydrogen bonds and π…π stacking interactions.     

Crystal structure of disordered diethylammonium oxo(1-hydroxyethane-1,1-diphosphonato)vanadate(IV) hydrate

Crystals of diethylammonium oxo(1-hydroxyethane-1,1-diphosphonato)vanadate(IV) hydrate have been synthesized, and their structure has been determined by X-ray diffraction analysis. In the crystal, three metal atoms of the disordered anionic complex in two orientations (the occupancies are 0.67 and 0.33) are linked in pairs by the tetradentate bis(chelate)-μ₂-bridging ligands H_n L ^{4 ? n} with the formation of the [V₃O₄(H_n L)₃] cyclic trimers. As a first approximation, the coordination polyhedron of the V(1) and V(2) atoms in both orientations can be considered a tetragonal pyramid completed to a strongly distorted octahedron by the O atom of the terminal hydroxo ligand in the case of the V(2) atom or by the μ₃-bridging oxo O atom for the V(1) atom. The diethylammonium cations and crystallization water molecules are disordered. The structural formula of the complex can be most correctly represented as [(C₂H₅)₂NH₂]₂[{V⁴⁺O(μ ₂-H₂ L)}₃ (μ₃-O)]_0.67[{V⁴⁺(OH)(μ₂-HL)} ₃(μ₃-O)]_0.33 · 2H₂O.     

Crystal and molecular structure of di-μ-chlorobis [N-(2-hydroxyethyl)salicylideneiminato-N,0,0′ copper(II)] hemihydrate

The structure of the title compound. [Cu₂Cl₂(C₉H₁₀NO₂)₂]·1/2H₂O. has been determined from single crystal X-ray diffraction data. The structure was solved by direct methods. Full-matrix leastsquares refinement of structural parameters led to a conventionalR factor of 0.056 for 3689 intensities above 3σ(l). There are two independent molecules [A andB] of the title compound in the asymmetric unit. These molecules are linked to one water molecule by a system of four hydrogen bonds. The comlexes contain pairs of deformed square-pyramidal copper(II) centers. A tridetate ligand L forms two condensed chelate rings with mean Cu?O_(C?O)+1.900(6), mean Cu?O_(C?OH)+2.004(6) and mean Cu?N-1.930(6)Å. A chloride ions complete the tetrahedral distorted basal plane of each Cu(II) ion forming a square pyramid with the longer fifth apical Cu?Cl bridging bond. The Cu...Cu nonbonding distances in the complexes are 3.445(1)Å for moleculeA and 3.494(1)Å for moleculeB.