Structural investigation of 1-amino-2,4,6-trinitrobenzenes in the solid state and in solution

The crystal structure of 1-pyrrolidino-2,4,6-trinitrobenzene3, 1-morpholino-2,4,6-trinitrobenzene4 and 1-piperidino-2,4,6-trinitrobenzene5 have been determined by single-crystal X-ray diffraction data and the structure in solution was investigated by UV-visible spectrophotometry and¹³C nmr. The three compounds are monoclinic, space groupP2_i/n. Unit cell dimensions area=6.6660(1),b=8.612(1),c=20.696(3) ?, β=90.73(1)^o, andD _c =1.58 g cm⁻³ for compound3;a=7.090(2),b=21.493(9),c=8.298(3) ?, β=101.27(1)^o, andD _c 1.60 g cm⁻³ for compound4 anda=10.426(1),b=10.038(1),c=12.291(1) ?, β=90.04(1)^o withD _c =1.53 g cm⁻³ for compound5 forZ=4. In the solid state, differences regarding the planarity of the aromatic ring in the three substrates were found. Rotation of theortho-nitro groups and of the amino group out of the aromatic plane was observed both in the solid state and in the solution. Greater coplanarity of the two rings was found in3 than in4 and5.     

Structural investigation of 1-amino-2,4,6-trinitrobenzenes in the solid state and in solution

The crystal structure of 1-pyrrolidino-2,4,6-trinitrobenzene3, 1-morpholino-2,4,6-trinitrobenzene4 and 1-piperidino-2,4,6-trinitrobenzene5 have been determined by single-crystal X-ray diffraction data and the structure in solution was investigated by UV-visible spectrophotometry and¹³C nmr. The three compounds are monoclinic, space groupP2_i/n. Unit cell dimensions area=6.6660(1),b=8.612(1),c=20.696(3) Å, β=90.73(1)^o, andD _c =1.58 g cm^?3 for compound3;a=7.090(2),b=21.493(9),c=8.298(3) Å, β=101.27(1)^o, andD _c 1.60 g cm^?3 for compound4 anda=10.426(1),b=10.038(1),c=12.291(1) Å, β=90.04(1)^o withD _c =1.53 g cm^?3 for compound5 forZ=4. In the solid state, differences regarding the planarity of the aromatic ring in the three substrates were found. Rotation of theortho-nitro groups and of the amino group out of the aromatic plane was observed both in the solid state and in the solution. Greater coplanarity of the two rings was found in3 than in4 and5.     

X-ray and spectroscopic investigation of 2-(2-hydroxyphenyl)pyridine-1-oxide

A strong intramolecular hydrogen bond O-HO, found by spectroscopic methods and proved by X-ray analysis, keeps the two planar fragments of the molecule twisted. The angle between the least-squares planes of these fragments is 38.2(1)°. The influence of the conformational rigidity of the molecule on the spectroscopic properties of the title compound is discussed in comparison with its methyl ether and free base.     

Conformational studies of substituted nitroanilines: geometry of 2-methyl-5-nitroaniline

The title compound (C₇H₈N₂O₂), is monoclinic, space group P2₁/n, witha=9.552(2),b=5.677(2),c=13.586(3)Å, =92.68(2)⁰, andD _x=1.374 g-cm^–3 forZ=4. The refinement converged toR=0.043,wR=0.038. The molecule is approximately planar, with dihedral angles of 3.7(2.1)⁰ between the amino group and the aromatic ring, and 3.2(2)⁰ between the nitro group and the ring. According to the UV spectrum in solution, the molecular geometry indicates weak intramolecular charge transfer. The three-dimensional structure is stabilized by three intermolecular H bonds. A bifurcated one induces the formation of chains along , while the other two link molecules that belong to adjacent chains and are related by an inversion center.     

Conversion of 2,4-dihydroxybenzaldehyde to 2-benzoyloxy-4-hydroxybenzaldehyde and structural characterization of both precursor and product

2,4-Dihydroxybenzaldehyde can be acylated at the 2 position if the more reactive 4 position is first protected as the methylmethoxy ether. Deprotection permits isolation of 2-benzoyloxy-4-hydroxybenzaldehyde. 2,4-Dihydroxybenzaldehyde, C₇H₆O₃, crystallizes in P2₁/c, with a = 7.3762(6), b = 11.7455(9), c = 7.3149(6) Å, = 90.533(2)°, Z = 4, and D _X = 1.448 g cm^–3. The individual molecules are characterized by an intramolecular hydrogen bond. The molecules form sheets with additional intermolecular hydrogen bonds. 2-Benzoyloxy-4-hydroxybenzaldehyde, C₁₄H₁₀O₂, crystallizes in Pca2₁, with a = 24.2629(14), b = 3.8445(2), c = 12.3727(8) Å, Z = 4, and D _X = 1.394 g cm^–3. The molecules consist of two planar halves twisted by 51.63(5)° about the ester linkage. Intermolecular hydrogen bonding joins the molecules into ribbons approximately parallel to c.     

X-ray crystal structures of new chiral enaminones from 2,4-pentanedione and their heterocyclic derivatives

New chiral enaminones from 2,4-pentanedione (1, 4) and their 1,4-oxazepinium and 1,4-thiazepinium derivatives (5–7) were synthesized and their crystal structures were determined by single crystal X-ray diffraction studies. The crystallographic data for these compounds are as follows: (R)-(1-Methyl-3-oxo-but-1-enylamino)-phenylacetic acid methyl ester (1): a = 7.574(1) ?, b = 12.530(1) ?, c = 14.245(1) ?, P2₁2₁2₁. (R)-4-(2-hydroxy-1-phenyl-ethylamino)-pent-3-en-2-one (2): a = 5.543(1) ?, b = 9.433(1) ?, c = 12.237(2) ?, β = 100.687(3)°, P2₁. (2S, 3R)-3-hydroxy-2-(1-methyl-3-oxobut-1-enylamine) butyric acid methyl ester (3): a = 5.583(1) ?, b = 8.660(1) ?, c = 12.149(1) ?, α = 92.85(1)°, β = 91.00(1)°, γ = 90.16(1)°, P1. (R)-3-[2-Methoxycarbonyl-2-(1-methyl-3-oxo-butylideneamino)-ethyldisulfanyl]-2-(1-methyl-3-oxo-butylideneamino)-propionic acid methyl ester (4): a = 9.309(1) ?, b = 11.460(1) ?, c = 11.310(1) ?, β = 112.582(2)°,P2_1.(3R)-5,7-dimethyl-3-phenyl-2,3-dihydro-[1,4]oxazepinium trifluoroborate (5): a = 8.958(1) ?, c = 18.085(1) ?, P4₃. (2S, 3R)-3-methoxycarbonyl-2, 5,7-trimethyl-2, 3-dihydro-[1,4] oxazepin-4-ium trifluroborate (6): a = 8.626(1) ?, b = 11.597(1) ?, c = 13.733(19) ?, P2₁2₁2₁. 3-Methoxycarbonyl-5, 7-dimethyl-2, 3-dihydro- [1,4]-thiazepin-4-ium trifluoroborate (7): a = 13.737(1) ?, b = 6.244(1) ?, c = 16.041(1) ?, β = 104.927(2)°, P2₁/n.     

Structural,spectroscopic properties and theoretical studies of (E)-1-(4-Bromophenyl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one as a potential anti-oxidant agent

The new chalcone compound namely (E)-1-(4-Bromophenyl)-3-(2,3,4-trimethoxyphenyl)prop-2-en-1-one (C₁₈H₁₇BrO₄) is crystallized in the monoclinic crystal system of P2₁/c space group. The unit cell dimensions are: a = 8.0753 (10) Å, b = 21.873 (3) Å, c = 9.3362 (12) Å, α = 90°, β = 99.369 (2), γ = 90° and Z = 4. The single crystal was grown using slow evaporation solution growth technique. The newly synthesized compound was characterized by using IR, ¹H- and ¹³C-NMR, UV-Vis and single crystal X-ray diffraction analyses. Quantum chemical method of Density Functional Theory (DFT) with B3LYP/6-311++G(d,p) has been employed to study the structural and spectral properties of the compound. The electronic absorption spectrum was calculated using the time dependent functional theory (TDDFT) method. The most stable conformer of the title chalcone is identified from the computational results. Hirshfeld surface analysis with fingerprint plots has been used as a graphical tool for visualization and understanding of intermolecular interactions. Intermolecular C?H····O interaction observed stabilize the crystal structure, forming an infinite one dimensional column. The effect of this intermolecular interaction in the solid state can be seen in the difference between the experimental and the theoretically optimized geometrical parameters. The crystal is transparent in the entire visible region and absorptive in the UV region. Information about the size, shape, charge density distribution and site of chemical reactivity of the molecule has been obtained by mapping electron potential (MEP). The other molecular properties like charge transfer are explain using Mulliken population analysis. The antioxidant test indicated that the 2,3,4-trimethoxy substitution on the bromide chalcone to be one of the favorable modification to enhance its metal chelating activity.     

Synthesis,spectroscopic and X-ray structural study of 4-p-methoxy-phenylimino-3-hydroxyimino-2-pentanone

4-p-Methoxy-phenylimino-3-hydroxyimino-2-pentanone has been synthesized, characterized by elemental analysis. IR, NMR and mass spectroscopies and its structure determined by single crystal X-ray diffraction. It crystallizes in the orthorhombic space group P2₁2₁2₁, witha=7.2294(7),b=11.540(1),c=14.670(2) Å. Spectroscopic and X-ray data clearly indicate that the oxime tautomer is present. In the solid state, the geometrical isomer is the EZ, which is also the main species in solution according to NMR data. The two C=N bonds are not conjugated to each other.     

Synthesis and crystal structure of 7,9-dideacetyl-1-deoxybaccatinVI

7,9-dideacetyl-1-deoxybaccatinVI was synthesized from 1-deoxybaccatinVI and its crystal structure was determined by X-ray crystallographic techniques. The compound (C₃₃H₄₂O₁₁·2CH₄O) crystallizes into monoclinic space group P2₁ with unit cell parameters: a=8.654(17) ?, b=16.470(5) ?, c=12.671(3) ?, β=97.63(2)°, and Z=2. The X-ray results demonstrated that the reaction of 7,9,10-Trideacetyl-1-deoxy-baccatinVI with Ac₂O in tetrahydrofuran, using CeCl₃ as catalyst, yielded monoacetylated product 7,9-dideacetyl-1-deoxy baccatinVI. In the structure, the six-membered A ring exhibits boat conformation, the eight-membered B ring adopts boat-chair conformation, and the six-membered C ring exhibits sofa conformation.     

Crystal structure of 2-{(R)-1-hydroxy-1-[(2S)-1-tritylaziridin-2-yl] methyl}acrylate and spectroscopic properties of the (R,S) and (S,S) stereoisomers

The crystal and molecular structure of 2-{(R)-1-Hydroxy-1-[(2S)-1-tritylaziridin-2-y1] methy1}acrylate is described. Crystal data: C₂₆H₂₅NO₃, orthorhombic, space group P2₁2₁2₁, a = 9.6954(5), b = 13.1458(5), c = 16.7885(7) Å, V = 2139.8(2) ų, Z = 4. The (R,S) diastereomer shows an intramolecular hydrogen bonding N···H—O under formation of a five-membered ring with N···O distance of 2.664 Å. IR, ¹H NMR and ¹³C NMR data are discussed. The ¹H NMR of the (R,S) diastereomer shows a singlet- whereas the (S,S) diastereomer exhibits a doublet-pattern for the hydroxyl proton.     

Thermal analysis,powder diffraction and spectroscopic investigation of the solid phases of 1‐chloro‐2,2‐dimethylpropane

By the substitution of one methyl group in Neopentane C(CH₃)₄ with a methylchlorid group the globular sphere is expanded in 1‐chloro‐2,2‐dimethylpropane (CH₃)₃C(CH₂Cl). With the aid of DSC measurements, X‐ray powder diffraction, ¹H NMR and ³⁵Cl NQR measurements two orientationally disordered (plastic) phases were established. The low temperature structure was solved and a structural model of phase II is proposed. A mechanism to describe the reorientation in the different phases is given as well as a connectivity scheme between the phases is discussed. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐ray powder diffraction structural characterization of Ba1‐xEuxTiO3 ternary oxides

The single‐phase Ba_1‐xEu_xTiO₃ (0.1≤x≤0.4) samples have been synthesized by solid state reaction under high pressure and ‐temperature. X‐ray powder diffraction data was determined by MS Modeling using Reflex Powder Indexing technique. The Ba_1‐xEu_xTiO₃ series exhibited an interesting orthorhombic‐tetragonal‐cubic structural transformation as Eu composition increases, the distinct change of the X‐ray diffraction peak profile in the vicinity of 45.5º is characteristic of structural transformation. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth, refined structural and spectroscopic characteristics of Tm-doped NaGd(WO4)2 single crystals

The details of Tm³⁺-doped NaGd(WO₄)₂ single-crystal growth are discussed, the results of precise investigations of its structural and spectroscopic characteristics, as well as the analysis of cross-relaxation process of Tm³⁺ ions (³H₄→³F₄, ³H₆→³F₄) in this crystal are presented. Based on the Judd–Ofelt theory, three intensity parameters, spontaneous emission probabilities, fluorescence branching ratios and fluorescence quantum efficiency from ³H₄ and ³F₄ levels were refined.     

X-ray crystal structure and1H-NMR chiral shift reagent study of a crown trimer

3,4,5-Trimethoxybenzyl alcohol was cyclooligomerized with a bentonite clay used as a catalyst. Results of the crystal structure analysis of the racemic (±) nonamethoxy[1,1,1]orthocyclophane trimer, C₃₀H₃₆O₉, are described. The structure was determined by X-ray diffraction at 293 K and shown to belong to the triclinic space group P . The compound possesses a distorted crown conformation with unusual C–H...O intermolecular interactions, and with a crystal packing not observed before in other related derivatives. The racemic mixture was also discriminated in its two enantiomeric isomers, using proton NMR and Eu(III) as a chiral shift reagent.     

AFM investigation of step kinetics and hillock morphology of the {1 0 0} face of KDP

Step velocities and hillock slopes on the {1 0 0} face of KDP were measured over a supersaturation range of 0<σ<0.15, where σ is the supersaturation. The formation of macrosteps and their evolution with distance from the hillock top were also observed. Hillock slope depended linearly on supersaturation and hillock geometry. The two non-equivalent sectors exhibited different slopes and step velocities. AFM shows an elementary step height of 3.7 Å, or half the unit cell height, whereas previous interferometric experiments assumed the elementary step was a unit cell. Values of the step edge energy (), the kinetic coefficients for the slow and fast directions (β_S and β_F), and the activation energies for slow and fast step motion (E_a,S and E_a,F) were calculated to be 24.0 erg/cm², 0.071 cm/s, 0.206 cm/s, 0.26 eV/molecule, and 0.21 eV/molecule, respectively. Analysis of macrostep evolution including the dependence of step height on time and terrace width on distance were performed and compared to predictions of published models. The results do not allow us to distinguish between a shock wave model and a continuous step-doubling model. Analysis within the latter model leads to a characteristic adsorption time for impurities (λ⁻¹) of 0.0716 s.     

The preparation and structural characterization of 1-methylimidazolium and 1,3-dimethylimidazolium tetrachlorobismuthate(III)

In attempting to synthesize complexes of BiCl₃ with 1-methyl-2(3H)-imidazolethione and 1,3-dimethyl-2(3H)-imidazoletellurone, the respective imidazolium salts stabilized by the tetrachlorobismuthate(III) anion were obtained. The two new compounds are characterized via standard methods and X-ray crystallography. One compound, 1,3-dimethylimidazolium tetrachlorobismuthate(III), crystallizes in space group C2/c with a = 14.7000(12), b = 12.7200(8), c = 7.3150(6) Å, and = 117.744(5). The other compound, 1-methylimidazolium tetrachlorobismuthate(III), crystallizes in space group P2₁/c with a = 11.1534(12), b = 12.9635(14), c = 7.2856(8) Å, and = 94.319(2). The large anion is comprised of polymeric zig-zag chains of octahedrally coordinated bismuth sharing alternating edges through cis chlorine bridging. The resulting long linear channels house the planar cations stacked parallel to each other. Differences in anion geometries can be attributed to hydrogen bonding in the 1-methyl imidazolium salt, and there is no strong evidence of lone-pair stereoactivity in either of the compounds.     

Synthesis and structural properties of a 1-D copper(I) coordination polymer

A coordination polymer catena-chloro(4-pyridinecarboxylic acid)copper(I): [Cu(C₆H₅ O₂N)Cl]_n (1) has been prepared directly by reacting Cu^IICl₂ 2H₂O and 4-cyanopyridine in the presence of disodium maleate under hydrothermal conditions at 140°C. Crystal data for 1 are as follows: monoclinic, P2₁/n, a = 16.4623(9) Å, b = 3.7795(2) Å, c = 24.7612(11) Å, = 101.534(1)°, V = 1509.5(1) ų, Z = 4, D _calc. = 1.955 g cm^–3, R1 = 0.0511, wR2 = 0.1060 for all 2666 reflections. In this 1-D stair-polymer, two [Cu–Cl–Cu]_n zigzag chains are held together by weak interchain Cu–Cl bonds. The 4-pyridinecarboxylic acid ligands derived from the 4-CNpy molecules coordinate to the approximately tetrahedral Cu(I) centers through pyridyl-N atoms. The carboxyl ends of 4-pyridinecarboxylic acid participate in interchain hydrogen-bonding interactions to form a 2-D supramolecular network.     

Synthesis and crystal structure of 3,5-di(2-propenyl)-6-phenyl-1,3,5-triazine-2,4-dione and 2-dimethylamino-4-ethoxycarbonylmethoxy-6-phenyl-1,3,5-triazine

The title compound 3,5-di(2-propenyl)-6-phenyl-1,3,5-triazine-2,4-dione has been synthesized by the reaction of 6-phenyl-1,3,5-triazine-2,4-dione with allyl bromide. Its structure was determined by X-ray single crystal diffraction. The crystal belongs to orthorhombic, space group Pbca with the following crystallographic parameters: a = 16.282(4) Å, b = 8.888(2) Å, c = 19.281(5) Å, = 90°, = 90°, = 90°, = 0.088 mm^–1, V = 2790.1(13) ų, z = 8, Dx = 1.282 mg/m³, F(000) = 1136, T = 293(2) K, 2.11° 25.02°, the final R factor: R ₁ = 0.0430, wR₂ = 0.0981. The X-ray results demonstrate that the reaction of 6-phenyl-1,3,5-triazine-2,4-dione with allyl bromide in the presence of N,N-dimethylformamide and potassium carbonate yields the N-alkylated product. The title compound 2-dimethylamino-4-ethoxycarbonylmethoxy-6-phenyl-1,3,5-triazine has been synthesized by a new reaction, in which the solvent N,N-dimethylformamide involves. Its structure was determined by X-ray single crystal diffraction. The crystal belongs to triclinic, space group P-1 with the following crystallographic parameters: a = 7.977(2) Å, b = 10.394(3) Å, c = 10.837(3) Å, = 111.774(5)°, = 104.050(5)°, = 99.446(5)°, = 0.093 mm^–1, V = 776.6(4) ų, z = 2, Dx = 1.293 mg/m³, F(000) = 320, T = 293(2) K, 2.14° 25.03°, the final R factor: R ₁ = 0.0582, wR ₂ = 0.1399. The distance of N(4) C(2) (1.339 Å) is much shorter than the length of normal C N (1.47 Å) and very close to that of C-N (1.33 Å), which is indicative of the significant double bond character.     

N-o-tolyl-2-hydroxy-1-naphthaldimine and its NiII complex. Conformational changes of free ligand by chelatation

The main scope of the paper deals with keto/amine-enol/imine tautomerism in the solid state of an N-aryl substituted naphthaldimine and conformational changes of this ligand after coordinating to the nickel atom. The N-o-tolyl-2-hydroxy-1-naphthaldimine (I) crystallizes in the orthorhombic space group P 2₁2₁2₁ with cell dimensions a = 7.8641(4), b = 12.712(1), c = 13.853(1) Å and corresponding bis-bidentate nickel complex (II) in the monoclinic space group P 2₁/c and unit cell dimensions a = 7.436(3), b = 22.050(5), c = 8.643(4) Å, = 95.05(6)°. In the nonplanar molecule of (I) the presence of the enol tautomer is found. In (II) the metal atom has the characteristic square-planar coordination with Ni^II on crystallographically imposed inversion centers. Two naphthaldimine moieties are not coplanar showing stepped conformation with step height 1.034 Å.     

Chromatographic,spectroscopic, topographic,and X-ray crystallographic studies of the solid solution formed by racemic 3-carboxy-2,2,5,5-tetramethyl-1-pyrrolidinyloxy (3-carboxy-proxyl)

The solid solution formed by the title compound, C₉H₁₆NO₃, has been examined by a variety of techniques and shown to be an equi-molecular mixture of the two enantiomers. Refinement of the disordered structure was based on the orthorhombic space groupPnma witha=8.023(2),b=10.030(3), andc=12.352(2)Å, finalR=0.055. The oxygens of the carboxyl group are disordered and both enantiomers can occupy the same, rather than alternate, crystallographic sites. Results from studies involving IR, GC-MS, and chiral chromatography are also presented. In addition we report on the use of synchrotron X-ray topography to investigate strain in crystals of the solid solution.