Halogenotrinitromethanes: A Combined Study in the Crystalline and Gaseous Phase and Using Quantum Chemical Methods

The halogenotrinitromethanes FC(NO₂)₃ ( 1 ), BrC(NO₂)₃ ( 2 ), and IC(NO₂)₃ ( 3 ) were synthesized and fully characterized. The molecular structures of 1 – 3 were determined in the crystalline state by X‐ray diffraction, and gas‐phase structures of 1 and 2 were determined by electron diffraction. The Hal?C bond lengths in F?, Cl?, and Br?C(NO₂)₃ in the crystalline state are similar to those in the gas phase. The obtained experimental data are interpreted in terms of Natural Bond Orbitals (NBO), Atoms in Molecules (AIM), and Interacting Quantum Atoms (IQA) theories. All halogenotrinitromethanes show various intra‐ and intermolecular non‐bonded interactions. Intramolecular N ??? O and Hal ??? O (Hal=F ( 1 ), Br ( 2 ), I ( 3 )) interactions, both competitors in terms of the orientation of the nitro groups by rotation about the C?N bonds, lead to a propeller‐type twisting of these groups favoring the mentioned interactions. The origin of the unusually short Hal?C bonds is discussed in detail. The results of this study are compared to the molecular structure of ClC(NO₂)₃ and the respective interactions therein.     

Trifluormethylnitrat,CF3ONO2

Trifluoromethyl Nitrate, CF₃ONO₂ From different routes to CF₃ONO₂, the reaction of CF₃OF with NO₂ at room temperature under high pressure is the most favorable to synthesize CF₃ONO₂ in preparative scale. The pure product is isolated for the first time after repeated trap‐to‐trap condensation in vacuo. CF₃ONO₂ is a colourless gas with a boiling point of –18 ± 3 °C (extrapol.) and a melting point of –163 °C. Trifluoromethyl nitrate decays slowly into CF₂O and FNO₂ at room temperature in the gas phase as well as in the liquid state at lower temperatures. Furthermore, CF₃ONO₂ is characterized spectroscopically by NMR, IR, Raman, and UV, and structurally by gas electron diffraction and quantum chemical calculations (B3LYP, MP2). The CF₃–O bond is in the plane of the NO₃ moiety, the central CF₃O–NO₂ bond of 1.493(6) Å is very long. The B3LYP/6‐31G* calculation reproduces best the experimental data.     

Structure determination of a new cocrystal of carbamazepine and dl‐tartaric acid by synchrotron powder X‐ray diffraction

The crystal structure of a new cocrystal of carbamazepine (systematic name: 5H‐dibenzo[b,f]azepine‐5‐carboxamide, C₁₅H₁₂N₂O) and dl ‐tartaric acid (C₄H₆O₆), obtained by liquid‐assisted grinding, was solved by powder X‐ray diffraction (PXRD). The high‐resolution PXRD pattern of this new phase was recorded at room temperature thanks to synchrotron experiments at the European Synchrotron Radiation Facility (Grenoble, France). The starting structural model was generated by a Monte‐Carlo simulated annealing method. The final structure was obtained through Rietveld refinement and an energy minimization simulation was used to estimate the H‐atom positions. The stability of the proposed structure as a function of temperature was also assessed from molecular dynamics simulations. The symmetry is monoclinic (space group P2₁/c) and contains eight molecules per unit cell, namely, four dl ‐tartaric acid and four carbamazepine molecules.     

Synthesis and structural characterization of syndiotactic trans‐1,2 and cis‐1,2 polyhexadienes

The (E) isomer in mixtures of (E) and (Z) 1,3‐hexadiene was polymerized with the system CoCl₂(PⁱPrPh₂)₂‐MAO, a highly active and stereospecific catalyst for the preparation of 1,2 syndiotactic polybutadiene. A new crystalline polymer with a melting point of 109 °C was obtained. The polymer was characterized by IR, NMR (¹³C, ¹H in solution and ¹³C in the solid‐state), X‐ray diffraction, DSC, GPC and it was found to have a trans‐1,2 syndiotactic structure with a 5.18 ± 0.04 Å fiber periodicity. Since only the (E) isomer was polymerized, at the end of the reaction we were able to separate the (Z) isomer, which was ultimately polymerized with CpTiCl₃‐MAO at low temperature, obtaining a low molecular weight, stereoregular polymer that, characterized by IR and NMR methods, was found to exhibit a cis‐1,2 syndiotactic structure, never reported before. Molecular mechanics calculations were carried out on the trans‐1,2 syndiotactic polymer and structural models consistent with the X‐ray diffraction data are proposed. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 5339–5353, 2007     

Crystal structure and magnetic properties of a linear tetranuclear CoII cluster

Polynuclear complexes are an important class of inorganic functional materials and are of interest particularly for their applications in molecular magnets. Multidentate chelating ligands play an important role in the design and syntheses of polynuclear metal clusters. A novel linear tetranuclear Co^II cluster, namely bis{μ₃‐(E)‐2‐[(2‐oxidobenzylidene)amino]phenolato}bis{μ₂‐(E)‐2‐[(2‐oxidobenzylidene)amino]phenolato}bis(1,10‐phenanthroline)tetracobalt(II), [Co₄(C₁₄H₁₁NO₂)₄(C₁₂H₈N₂)₂], was prepared under solvothermal conditions through a mixed‐ligand synthetic strategy. The structure was determined by X‐ray single‐crystal diffraction and bulk purity was confirmed by powder X‐ray diffraction. The complex molecule has a centrosymmetric tetranuclear chain‐like structure and the four Co^II ions are located in two different coordination environments. The Co^II ions at the ends of the chain are in a slightly distorted octahedral geometry, while the two inner Co^II ions are in five‐coordinate distorted trigonal bipyramidal environments. A magnetic study reveals ferromagnetic Co^II…Co^II exchange interactions for the complex.     

Thermal stability of the layered modification of Cu0.5ZrTe2 in the temperature range 25–900 °C

The thermal stability of the layered modification of the Cu_0.5ZrTe₂ polycrystalline intercalation compound, synthesized at room temperature, has been studied in the temperature range 25–900 °C. A change in the occupation of the octahedral and tetrahedral coordinated sites in the interlayer space of the zirconium ditelluride was observed using in‐situ time‐resolved synchrotron X‐ray powder diffraction experiments. The formation of the rhombohedral CuZr₂Te₄ phase, which is stable in the temperature range 300–700 °C, has been observed. The copper intercalation at room temperature leads to the formation of a phase in which the Cu atoms occupy only octahedral sites in the interlayer space. At temperatures above the decay temperature of the rhombohedral CuZr₂Te₄, a layered phase with Cu atoms uniformly distributed between octahedral and tetrahedral sites in the interlayer space is stable. The changes in the crystal structure independent of temperature are in agreement with the previously proposed model, according to which the stability of the layered or the rhombohedral phase is determined by the entropy factor associated with the distribution of the intercalated atoms between the octahedral and tetrahedral sites in the interlayer space.     

Structure and Bonding Nature of the Strained Lewis Acid 3‐Methyl‐1‐boraadamantane: A Case Study Employing a New Data‐Analysis Procedure in Gas Electron Diffraction

Base‐free 3‐methyl‐1‐boraadamantane was synthesized by starting from its known THF adduct, transforming it to a butylate‐complex with n‐butyllithium, cleaving the cage with acetyl chloride to give 3‐n‐butyl‐5‐methyl‐7‐methylene‐3‐borabicyclo[3.3.1]nonane and closing the cage again by reacting the latter with dicyclohexylborane. The identity of 3‐methyl‐1‐boraadamantane was proven by ¹H, ¹¹B and ¹³C NMR spectroscopy and elemental analysis. The experimental equilibrium structure of the free 3‐methyl‐1‐boraadamantane molecules has been determined at 100 °C by using gas‐phase electron diffraction. For this structure determination, an improved method for data analysis has been introduced and tested: the structural refinement versus gas‐phase electron diffraction data (in terms of Cartesian coordinates) with a set of quantum‐chemically derived regularization constraints for the complete structure under optimization of a regularization constant, which maximizes the contribution of experimental data while retaining a stable refinement. The detailed analysis of parameter errors shows that the new approach allows obtaining more reliable results. The most important structural parameters are: r_e(B‐C)_av=1.556(5) Å, ${\angle }$ _e(C‐B‐C)_av=116.5(2)°. The configuration of the boron atom is pyramidal with ${\sum \angle }$ (C‐B‐C)=349.4(4)°. The nature of bonding was analyzed further by applying the natural bond orbital (NBO) and atoms in molecules (AIM) approaches. The experimentally observed shortening of the B? C bonds and elongation of the adjacent C? C bonds can be explained by the σ(C‐C)→p(B) hyperconjugation model. Both NBO and AIM analyses predict that the B? C bonds are significantly bent in the direction out of the cage.     

Solid‐State Form Screen of Cardiosulfa and Its Analogues

Cardiosulfa is a biologically active sulfonamide molecule that was recently shown to induce abnormal heart development in zebrafish embryos through activation of the aryl hydrocarbon receptor (AhR). The present report is a systematic study of solid‐state forms of cardiosulfa and its biologically active analogues that belong to the N‐(9‐ethyl‐9H‐carbazol‐3‐yl)benzene sulfonamide skeleton. Cardiosulfa (molecule 1 ; R¹=NO₂, R²=H, R³=CF₃), molecule 2 (H, H, CF₃), molecule 3 (CF₃, H, H), molecule 4 (NO₂, H, H), molecule 5 (H, CF₃, H), and molecule 6 (H, H, H) were synthesized and subjected to a polymorph search and solid‐state form characterization by X‐ray diffraction, differential scanning calorimetry (DSC), variable‐temperature powder X‐ray diffraction (VT‐PXRD), FTIR, and solid‐state (ss) NMR spectroscopy. Molecule 1 was obtained in a single‐crystalline modification that is sustained by N? H???π and C? H???O interactions but devoid of strong intermolecular N? H???O hydrogen bonds. Molecule 2 displayed a N? H???O catemer C(4) chain in form I, whereas a second polymorph was characterized by PXRD. The dimorphs of molecule 3 contain N? H???π and C? H???O interactions but no N? H???O bonds. Molecule 4 is trimorphic with N? H???O catemer in form I, and N? H???π and C? H???O interactions in form II, and a third polymorph was characterized by PXRD. Both polymorphs of molecule 5 contain the N? H???O catemer C(4) chain, whereas the sulfonamide N? H???O dimer synthon R₂²(8) was observed in polymorphs of 6 . Differences in the strong and weak hydrogen‐bond motifs were correlated with the substituent groups, and the solubility and dissolution rates were correlated with the conformation in the crystal structure of 1 , 2 , 3 , 4 , 5 , 6 . Higher solubility compounds, such as 2 (10.5 mg mL^?1) and 5 (4.4 mg mL^?1), adopt a twisted confirmation, whereas less‐soluble 1 (0.9 mg mL^?1) is nearly planar. This study provides practical guides for functional‐group modification of drug lead compounds for solubility optimization.     

Microwave-assisted sol-gel synthesis of CeO2–NiO nanocomposite based NO2 gas sensor for selective detection at lower operating temperature

The progress in the development of gas sensors has considerably grown using some novel nanomaterials of metal, metal oxide and composite. In the current study, we intended and evaluated the properties of nanomaterials like CeO₂, NiO, and CeO₂–NiO composite and its application as NO₂ gas sensor. Sensing of low concentration of NO₂ gas at optimum functional temperature was succeeded using CeO₂–NiO nanocomposites (NCs) film. The working temperature ranges in between 100 and 225 ?°C. Highly crystalline nanomaterials (CeO₂, NiO and CeO₂–NiO) have been prepared by applying microwave-assisted sol-gel route. The as-prepared nanomaterials are characterized for their structure, size, morphology and constitution by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis. XRD studies of nanoparticles reveal the formation of nanoscale CeO₂ and NiO with crystallite size 26, 23 ?nm, respectively. Both are having a face centered cubic structure. The nanocomposite (NC) Ce:Ni ?= ?60:40 has crystallite size of 13 ?nm. XRD study of NCs shows assimilation of Ni metal into the ceria and proves physical similarities of two phases. It can be observed from SEM that prepared NC has a porous surface which enables more surface active sites for adsorbing oxygen. The optical properties are measured with the help of UV–Vis. Spectroscopy. Optical band gaps of 3.19, 3.41 and 2.9 ?eV were observed for CeO_2, NiO nanoparticles (NPs) and CeO₂–NiO NC, respectively. Gas sensing properties state that the NC material shows a higher gas response % of 67.34% for NO₂ gas (25 ?ppm) at comparatively low operating temperature (125 ?°C). It gives response time as (～28 ?s) and the recovery (～54 ?s). NiO incorporation in CeO₂ results in a decline of operating temperature of NC and improves the sensing features.     

Chlorobis(pentafluoroethyl)phosphane: improved synthesis and molecular structure in the gas phase

(C₂F₅)₂PCl is now accessible through a significantly improved synthesis protocol starting from the technical product (C₂F₅)₃PF₂. (C₂F₅)₃PF₂ was reduced in the first step with NaBH₄ in a solvent‐free reaction at 120 °C. The product, P(C₂F₅)₃, was treated with an excess of an aqueous sodium hydroxide solution to afford the corresponding phosphinite salt Na⁺(C₂F₅)₂PO^? selectively under liberation of pentafluoroethane. Subsequent chlorination with PhPCl₄ resulted in the selective formation of (C₂F₅)₂PCl, which was isolated by fractional condensation in an overall yield of 66 %. The gas electron diffraction (GED) pattern for (C₂F₅)₂PCl was recorded and found to be described by a two‐conformer model. A quantum chemical investigation of the potential‐energy surface revealed the possible existence of many low‐energy conformers, each with a number of low‐frequency vibrational modes and therefore large‐amplitude motions. The conformer calculated to be most stable was also found to be most abundant by GED and comprised 61(5) % of the total. The molecular structure parameters determined by GED were in good agreement with those calculated at the MP2/TZVPP level of theory; the only significant difference was a discrepancy of about 3° in the C‐P‐C angle, which, for the lowest‐energy conformer, was refined to 98.2(4)° and was calculated to be 94.9°.     

A New Chair‐shaped Conformation Containing HgHgOHgHgO: Synthesis and Structure of Hg4(L2)2(NO3)4 (L2 = morpholin‐4‐ylpyridin‐2‐ylmethyleneamine)

. The complex Hg₄(L²)₂(NO₃)₄ ( 1 ) (L² = morpholin‐4‐ylpyridin‐2‐ylmethyleneamine) has been synthesized and characterized by CHN analysis, IR, and UV/Vis spectroscopy. The crystal structure of 1 was determined using single‐crystal X‐ray diffraction. The crystal structure of 1 contains four mercury atoms, four nitrate anions (two terminal and two bridge ones) and two L² ligand molecules. A chair shape, six‐membered ring is formed with the sequence OHgHgOHgHg built from Hg–Hg dumbbells and oxygen atoms from the nitrate co‐ligands. In the crystal structure, the asymmetric unit of the compound is built up by one‐half of the molecule. It contains the Hg₂²⁺ moiety with a mercury–mercury bonded core, in which one diimine ligand is coordinated to one of the mercury atoms. The nitrate anions act as anisobidentate and bidentate ligands.     

Crystal Structure and Formation of TlPd3 and its new Hydride TlPd3H

TlPd₃ was synthesised from the elements in evacuated silica tubes at 600 °C. Alternatively, TlPd₃ was yielded by reduction of TlPd₃O₄ in N₂ gas atmosphere. Reduction of the oxide in H₂ gas atmosphere resulted in the formation of the new hydride TlPd₃H. The structure of tetragonal TlPd₃ (ZrAl₃ type, space group I4/mmm, a = 410.659(9) pm, c = 1530.28(4) pm) was reinvestigated by X‐ray and also by neutron powder diffraction as well as the structure of its previously unknown hydride TlPd₃H (cubic anti‐perovskite type structure, space group Pm\bar{3} m, a = 406.313(1) pm). In situ DSC measurements of TlPd₃ in hydrogen gas atmosphere showed a broad exothermic signal over a wide temperature range with two maxima at 280 °C and at 370 °C, which resulted in the product TlPd₃H. A dependency of lattice parameters of the intermetallic phase on reaction conditions is observed and discussed. Results of hydrogenation experiments at room temperature with gas pressures up to 280 bar hydrogen and at elevated temperatures with very low hydrogen gas pressures (1–2 bar) as well as results of dehydrogenation of the hydrides under vacuum will be discussed.     

Concomitant cocrystal and salt: no interconversion in the solid state

A cocrystal and a molecular salt of β‐alanine and dl ‐tartaric acid, C₃H₈NO₂⁺·C₄H₄O₆^?, of the same chemical composition, were studied over a wide temperature range by single‐crystal and powder X‐ray diffraction. Neither the interconversion between the two phases nor any polymorphic transitions were observed in the temperature range from 100 K to the melting points. This contrasts with the solvent‐mediated phase transition from the salt to the cocrystal in a slurry that has been documented earlier.     

Polynitroethyl‐ and Fluorodinitroethyl Substituted Boron Esters

The reaction of boron oxide with various nitro‐substituted ethanols (2‐nitroethanol, 2‐fluoro‐2,2‐dinitroethanol, 2,2,2‐trinitroethanol) furnished the corresponding nitroethyl borates B(OCH₂CH₂NO₂)₃ ( 1 ), B(OCH₂CF(NO₂)₂)₃ ( 2 ), and B(OCH₂C(NO₂)₃)₃ ( 3 ). Fluorination of the anion [(NO₂)₂CCH₂OH]^? ( 4 ) resulted in 2‐fluoro‐2,2‐dinitroethanol ( 5 ), a precursor for 2 , and was thoroughly characterized. An interesting condensation was observed with the anion 4 to form the unusual dianion [(NO₂)₂CCH₂C(NO₂)₂]^2? ( 6 ). All compounds were fully characterized by multinuclear NMR spectroscopy, vibrational spectroscopy (IR, Raman), mass spectrometry and elemental analysis. The chemical, physical and energetic properties of 1 – 3 and 5 are reported, as well as quantum chemical calculations at the CBS‐4M level of theory to predict the enthalpies and energies of formation. X‐ray diffraction studies were performed, and the crystal structures for compounds 1 – 6 were determined and discussed thoroughly. The boron esters 1 – 3 are of interest as possible candidates for smoke‐free, green colorants in pyrotechnic applications, and in case of 2 and 3 also as promising high energy oxidizers.     

Synthesis and Characterization of Acetone Hydrazones

1‐Isopropylidene‐2‐methylhydrazine ( 1 ), 1‐isopropylidene‐2‐hydroxyethylhydrazine ( 2 ) and 1‐isopropylidene‐2‐formylhydrazine ( 3 ) were synthesized by reaction of the corresponding hydrazine with an excess of acetone in the presence of a drying agent (anhydrous sodium sulfate or barium oxide). All compounds 1 – 3 were characterized by elemental analysis, coupled gas chromatography‐mass spectrometry (GC–MS), multinuclear NMR spectroscopy (¹H, ¹³C and ¹⁵N) and vibrational spectroscopy (infrared and Raman). Compounds 1 and 2 are liquid at room conditions and their density was measured by means of a picnometer, however, (at room conditions) compound 3 is a solid and its crystal density and structure were determined by low temperature X‐ray diffraction techniques (monoclinic, P2₁/n, Z = 4, a = 5.666(1) Å, b = 6.254(1) Å, c = 15.277(4) Å, β = 91.30(2)°, V = 541.2(2) ų). The structure of hydrazone 3 is discussed in detail and compared to that of monoformylhydrazine. Finally, the (gas phase) structure of compound 3 was optimized using DFT calculations (B3LYP/6‐31+G(d, p)) and its NBO charges are reported.     

Reassessment of paracetamol orthorhombic Form III and determination of a novel low‐temperature monoclinic Form III‐m from powder diffraction data

Paracetamol [N‐(4‐hydroxyphenyl)acetamide, C₈H₉NO₂] has several polymorphs, just like many other drugs. The most stable polymorphs, denoted Forms I and II, can be obtained easily and their crystal structures are known. Crystals of the orthorhombic, less stable, room‐temperature Form III are difficult to grow; they need a special recipe to crystallize and suffer from severe preferred orientation. A crystal structure model of Form III has been proposed and solved from a combination of structure prediction and powder X‐ray diffraction (PXRD) [Perrin et al. (2009). Chem. Commun. 22 , 3181–3183]. The final R_wp value of 0.138 and the corresponding considerable residual trace were reasons to check its validity. A new structure determination of Form III using new high‐resolution PXRD data led to a final R_wp value of 0.042 and an improvement of the earlier proposed model. In addition, a reversible phase transition was found at 170–220 K between the orthorhombic Form III and a novel monoclinic Form III‐m. The crystal structure of Form III‐m has been determined and refined from PXRD data to a final R_wp value of 0.059.     

Crystal Structure of the Ordered Double Perovskite,Sr2NiTeO6

The crystal structure of the ordered double perovskite Sr₂MnTeO₆ has been refined at ambient temperature from high resolution neutron and X‐ray powder diffraction data in the monoclinic space group I 1 2/m 1 with a = 5.6166(1) Å, b = 5.5807(1) Å, c = 7.8797(1) Å and β = 90.048(2)°. The structure is the result of out‐of‐phase (–) rotations of virtually undistorted NiO₆ and TeO₆ octahedra in the (0 – –) sense about two of the axes of the ideal cubic perovskite. Electron diffraction measurements have been used to confirm the proposed space group and structure.     

Synthesis, Structure and Biological Activity of Zn（Ⅱ） Complex with Tris（benzimidazol-2-yl-methyl）amine Ligand

A new Zn(II) mononuclear complex with tris(benzimidazol‐2‐yl‐methyl)amine (NTB) was synthesized with stoichiometry of [Zn(NTB)NO₃]NO₃ · DIPY · DMF (DIPY : 4,4′‐dipyridyl). The complex was characterized by elemental analysis, UV and IR spectra. The crystal structure was determined by using X‐ray diffraction analysis. The crystal structure indicates that four N atoms and one O atom coordinate to zinc ion to construct a distorted trigonal‐dipyramid configuration. Three nonprotonated N atoms from imidazole groups are in the equatorial plane, one alkylamino N atom and one O atom from NO₃^?_‐ in the axial directions. The biological activity assay shows that this complex presents certain biological activity by means of pyrogallol autoxidation and it can be called a model compound of superoxide dismutase (SOD).     

Reduction of NO2 in Flue Gas by CO and Propylene over CuO‐CeO2/SiO2 in the Presence of O2

Catalytic reduction of NO₂ with CO and/or propylene in the presence of NO and excess oxygen, a model mixture for flue gas, was studied over a series of CuO‐CeO₂/SiO₂ catalysts between 120–260 °C. The effect of HCl, an impurity in flue gas, on the activity of the catalysts was evaluated. It was found that a binary oxide catalyst, 2% CuO‐8% CeO₂/SiO₂, was active for the reduction of NO₂ by CO and/or propylene. CO was effective for selective reduction of NO₂ in the presence of NO and O₂ in a temperature window between 160–200 °C while propylene was effective at temperature higher than 200 °C. In the presence of HCl, the activity of the catalyst for reduction of NO₂ with CO was irreversibly deactivated. However, the activity for reduction of NO₂ with propylene was not influenced by HCl.     

Crystal structure of a high‐pressure phase of magnesium chloride hexahydrate determined by in‐situ X‐ray and neutron diffraction methods

A high‐pressure phase of magnesium chloride hexahydrate (MgCl₂·6H₂O‐II) and its deuterated counterpart (MgCl₂·6D₂O‐II) have been identified for the first time by in‐situ single‐crystal X‐ray and powder neutron diffraction. The crystal structure was analyzed by the Rietveld method for the neutron diffraction pattern based on the initial structure determined by single‐crystal X‐ray diffraction. This high‐pressure phase has a similar framework to that in the known ambient‐pressure phase, but exhibits some structural changes with symmetry reduction caused by a subtle modification in the hydrogen‐bond network around the Mg(H₂O)₆ octahedra. These structural features reflect the strain in the high‐pressure phases of MgCl₂ hydrates.