Ba(dl-C4H4O5) — An alkaline earth metal-dicarboxylate hybrid crystal with the synergy of multi-bonds

The organic–inorganic hybrid crystal, Ba(dl-C₄H₄O₅), has been firstly prepared by hydrothermal method. It crystallizes in monoclinic crystal system with a centrosymmetric space group of P2₁/c with a = 8.150(2) Å, b = 10.447(3) Å, c = 6.938(2) Å, β = 95.599(3)° and Z = 4. In this compound, the coexistence of organic ligand and the alkaline earth metal cation leads to the diversity of chemical bonds. The synergy of Ba–O ionic bonds and hydrogen bonds strengthens the crystal structure. Characterization of this earth metal-dicarboxylate hybrid crystal is described by using powder X-ray diffraction, infrared spectroscopy, UV–vis–NIR diffuse reflectance spectrum and the TG curve. In addition, Ba(dl-C₄H₄O₅) possesses a short ultraviolet cutoff wavelength lower than 230 nm determined by the electronic transition of C–O group, which signifies the potential use in UV region applications. And the electronic structure and optical properties are studied by first principle calculation method, which obtains a birefringence value of 0.04.     

A Photoluminescent Polymeric 2D Silver(I) Complex Exhibits a Fishbone-like 1D Silver Cluster and New Coordination Mode of the Pyridine-2,3-Dicarboxylate

In this study, a novel organic–inorganic hybrid compound with AgNO₃ and 2,3-pyridinedicarboxylic acid (H₂pydc), [Ag₂(μ₆-pydc)]_n (1) has been synthesized. The molecular structure of complex has been determined by the single crystal X-ray diffraction. The complex has been observed to crystallize in the monoclinic space group P2₁/c. The asymmetric unit of compound consists of two crystallographically different Ag(I) centers and one pydc ligand. The Ag1 and Ag2 adopt tetrahedral and T-shaped geometries, respectively. At the same time, the silver(I) compound consists of a fish bone similar to the 1D silver cluster. Furthermore, novel coordination mode shown by H₂pydc indicates that the crystal exhibits photoluminescence in the solid state at room temperature.     

Two-dimensional square grid of neutral phosphonate ligands and eight-coordinated metal ions

Two dimensional coordination polymer [CdL₂(NO₃)₂]_n (where L = 4,4′-bis(dimethylphosphonomethyl)biphenyl) has been achieved. The crystal structure and molecular composition are measured using elemental analysis and X-ray crystal structure. Two-dimensional square grid was formed by semi-rigid phosphonate ligands bridge metals, in which the metals adopt rare eight-coordinated geometry. Weak C–H⋯O hydrogen bonds which between coordinated nitrate anion and methyl group of phosphonate ligands link two dimensional grids generating three dimensional supramolecular networks without interpenetration.     

Exploration of the transition temperatures and crystal structure of highly crystalline poly(1,3-cyclohexadiene): An experimental and computational investigation

Experimental determination of transition temperatures for highly crystalline polymers such as poly-1,3-cyclohexadiene (PCHD) can be difficult due to reduced solubility and thermalization processes which occur during data acquisition. In order to facilitate further understanding of these processes for PCHD, density functional theory (DFT) and molecular dynamics (MD) were used in conjunction with differential scanning calorimetry (DSC) and powder X-ray diffraction (XRD) to explore the oligomer microstructures, the crystal structure, and the temperature dependence of the specific volume (1/ρ). DFT geometry minimizations on isolated oligomers were used to identify the lowest energy confirmer; revealing that alternating R,R and S,S chiral bonds between monomer units afford the lowest energy structure. MD simulations of crystalline PCHD were constructed so as to replicate the experimental XRD pattern of crystalline PCHD, with the best fit producing a monoclinic crystal structure. The temperature dependence of the specific volume derived from MD simulations provided insight into the glass/vitrification (T_g) and melting (T_m) transition temperatures. Comparison of the simulation transition temperatures with differential scanning calorimetry data of PCHD polymerized with Ni(acac)₂/MAO shows good agreement and solidifies the fidelity of the newly defined PCHD crystalline structure.     

A Novel Insensitive High Explosive 3,4‐Bis (Aminofurazano) Furoxan

A novel insensitive high explosive 3,4‐bis (aminofurazano) furoxan (BAFF) was prepared using 3‐amino‐4‐acylchloroximinofurazan (ACOF) as a precursor. The molecular and crystal structures of BAFF were characterized by IR, MS, ¹H NMR, ¹³C NMR, elemental analysis, and single crystal X‐ray diffraction. The single crystal structure of BAFF recrystallized from water is monoclinic, space group P 21/c, and ρ_c=1.745 g cm⁻³, and that recrystallized from ethanol is triclinic, space group P 1, and ρ_c=1.737 g cm⁻³. BAFF has multiple crystal forms. The calculated detonation velocity by BKW code is 8100 m s⁻¹ (ρ=1.795 g cm⁻³, theoretical density calculated by quantum chemistry) and the experimental value is 7177 m s⁻¹ (ρ=1.530 g cm⁻³, charge density). The tested values of impact, friction, and electrostatic spark sensitivity show that BAFF is insensitive.     

Crystal structure of an aliphatic polyoxamide containing methyl side-groups: Poly(2-methyl-1,8-octamethyleneoxamide)

Poly (2-methyl-1,8-octametyleneoxamide) (nylon-MOMD-2) was prepared from dibutyl oxalate and 2-methyl-1,8-octamethylenediamine. The chemical structure was investigated by ¹³C nuclear magnetic resonance (¹³C NMR). The ¹³C NMR spectrum revealed that the methyl groups distribute among the four β-sites at random. The crystal structure and its temperature dependence were also investigated by molecular mechanics calculations, X-ray diffraction, and differential scanning calorimetry. The structure was determined to be monoclinic and a = 6.26 Å, b = 8.80 Å, c = 14.7 Å, and β = 50.7°. The torsion angle of the NH–CH₂ bonds has a skew conformation and there are the two distinct torsion angles in the crystal structure. The crystal structure of nylon-MOMD-2 has a disordered and statistical structure. The crystal structure shows no phase transition on heating until its melting point, although the unit cell expands in the a and b axis directions.     

Synthesis,crystal structure and photoluminescence of a new Cd(II) coordination polymer with unusual geometry

A new coordination polymer 1 [CdL₂(NO₃)₂]_n (L: 3, 6-di-(1, 2, 4-triazole-1-yl)-N-ethylcarbazole) has been synthesized by self-assembly reaction and characterized by elemental analysis and IR spectroscopy. The single-crystal X-ray diffraction shows that the [CdL₂(NO₃)₂]_n crystallizes in the monoclinic system and C2/m space group and the Cd(II) atom is four-coordinated. The coordination polyhedron can be described as a rectangle which is rather infrequent. The coordination bonds, hydrogen bonds and π–π interactions shaped the 3D network structure. A possible formation mechanism was discussed. The optical property was also studied.     

NMR and MD Analysis of the Bonding Interaction of Vancomycin with Muramyl Pentapeptide

The article describes an NMR spectroscopy study of interactions between vancomycin and a muramyl pentapeptide in two complexes: vancomycin and a native muramyl pentapeptide ended with D-alanine (MPP-D-Ala), and vancomycin and a modified muramyl pentapeptide ended with D-serine (MPP-D-Ser). The measurements were made in a 9:1 mixture of H₂O and D₂O. The obtained results confirmed the presence of hydrogen bonds previously described in the literature. At the same time, thanks to the pentapeptide model used, we were able to prove the presence of two more hydrogen bonds formed by the side chain amino group of L-lysine and oxygen atoms from the vancomycin carboxyl and amide groups. This type of interaction has not been described before. The existence of these hydrogen bonds was confirmed by the ¹H NMR and molecular modeling. The formation of these bonds incurs additional through-space interactions, visible in the NOESY spectrum, between the protons of the L-lysine amino group and a vancomycin-facing hydrogen atom in the benzylic position. The presence of such interactions was also confirmed by molecular dynamics trajectory analysis.     

Microstructure and synthesis mechanism of dysprosia-stabilized zirconia nanocrystals via chemical coprecipitation

In this study, zirconia (ZrO₂) and dysprosia-stabilized zirconia (DySZ) nanocrystals were synthesized using a chemical coprecipitation method. The crystal structure and micromorphology of the as-synthesized powders, as well as the structural evolution from precursors to oxides were investigated, and the synthesis mechanism was also examined. Results show that pure ZrO₂ powders mainly comprise the monoclinic ZrO₂ phase with trace tetragonal ZrO₂, while the DySZ powders exhibit a tetragonal ZrO₂ structure. In addition, the crystal growth rate of DySZ is far slower than that of the pure ZrO₂ under elevated calcination temperature. The addition of Dy could significantly improve the phase stability of DySZ powder and effectively inhibit the crystal growth of DySZ. In the DySZ precursor, the binding energy of chemical bonds is significantly difference than in the ZrO₂ precursor. A composite hydroxide can be formed with -Zr-OH-Dy- and -Zr-OH-Zr- units in the tetramer structure because of the in-situ substitution of Zr by Dy atoms. Both the ZrO₂ and DySZ precursors exhibit analogous dehydration and crystallization behaviours in calcination process. Dy-doping plays a significant role in stabilizing both the intermediate product and the DySZ crystal.     

Preparation and Molecular Structure of {[Ca(CHZ)2(H2O)](NTO)2⋅3.5H2O}n

The title compound {[Ca(CHZ)₂(H₂O)](NTO)₂⋅3.5H₂O}_n was synthesized by using an aqueous solution of calcium 3‐nitro‐1,2,4‐triazol‐5‐onate and carbohydrazide (CHZ, NH₂NHCONHNH₂). Its molecular structure was determined by X‐ray diffraction and its crystals have monoclinic form, with space group C2/c, where a=2.4483(4) nm, b=1.2581(2) nm, c =1.6269(3) nm, β=121.168(12)°, V=4.2879(13) nm³, Z=8, d_c=1.727 g⋅cm⁻³, μ (Mo K_α)=3.9 cm⁻¹, M=557.47, F(000)=2312. The coordination polyhedron is a tricapped trigonal prism in a tetradecahedron with a coordination number of nine. The whole molecule has many long chains formed through the carbohydrazide bridges, and every long chain is unlimited along the c axis. The long chains are linked by hydrogen bonds to form the crystal structure.     

Azo—hydrazone tautomerism in azo dyes. III. The tautomeric structure of 1-(4′-nitrophenylazo)-2-naphthylamine from crystal structure determination

The structure of 1(NO₂)—dioxane 2:1 solvate single crystal has been determined by direct methods and refined by analysis of the three-dimensional Mo Kα intensity data. The unit cell is monoclinic, space group P2₁/c with a = 8·960(3), b = 6·386(2), c = 30·141(11) Å, β = 108·56(2)°. Least-squares refinement of all positional and thermal parameters (hydrogen atoms isotropic) with 1458 independent reflections out of 2817 gave a final R-index of 0·069. The dye molecule is almost planar and of trans configuration. The nitro group, however, is significantly twisted out of the molecular best plane. Six-membered chelate ring structures are formed by intramolecular NH···N bonds while intermolecular NH···O interactions give rise to complex formation involving two dye and one dioxane molecules in a centrosymmetrical arrangement. Two such complexes are accommodated in the unit cell.Based on the observed molecular geometry and quantum chemical (SCF—MO) calculation of bond dimensions a strong predominance of the azo tautomer was concluded for 1(NO₂). This assignment is further supported by empirical correlations, using CN and NN bond distances from a great variety of reported azo and hydrazone structures which are compiled here for the first time. The mobile hydrogen is attached to the amine nitrogen [R(NH) = 1·04(5) Å] thereby excluding a major participation of the hydrazone form. These findings compare well with those for solutions and are in accordance with previous quantum chemical predictions.     

Structures and Properties Prediction of HMX/TATB Co‐Crystal

In this study, a new co‐crystal explosive of 1,3,5,7‐tetranitro‐1,3,5,7‐tetrazocane (HMX)/1,3,5‐triamino‐2,4,6‐trinitrobenzene (TATB) (molar ratio 1 : 1) was designed based on crystal engineering. The crystal structure was predicted using the polymorph predictor (PP) method. The main properties of co‐crystal consisting of mechanical properties, stability, and interaction formats were simulated through molecular dynamics methods. Simulated results indicate that the crystal structure of the HMX/TATB co‐crystal may belong to the P , P2₁2₁2₁ or P2₁/c space group. The calculations of the binding energy and the analysis for radial distribution function show that the two components are connected through electrostatic hydrogen bonding and strong van der Waals interactions. The new co‐crystal has better mechanical properties with the moduli systematically decreased. With the appearance of the new crystal, the trigger bond N NO₂ has little change.     

Preparation of Magnesium‐based Hydrogen Storage Materials and Their Effect on the Thermal Decomposition of Ammonium Perchlorate

Magnesium‐based hydrogen storage materials (MgH₂, Mg₂NiH₄, and Mg₂Cu‐H) were prepared and their structures were determined by XRD and ICP investigations. Mg₂NiH₄ has a monoclinic crystal structure and Mg₂Cu‐H is a mixture of MgCu₂ and MgH₂. The effects of magnesium‐based hydrogen storage materials on the thermal decomposition of ammonium perchlorate (AP) were studied by thermal analysis (DSC). It was found that magnesium‐based hydrogen storage materials show obvious boosting effects on the thermal decomposition of AP. The thermal decomposition peak temperature of AP was decreased, while the heat release of the decomposition of AP was increased. It was revealed that the effects of magnesium‐based hydrogen storage materials on the decomposition of AP become stronger with increasing content. The influence mechanism on the thermal decomposition of AP is suggested as follows: hydrogen released from magnesium‐based hydrogen storage materials and Mg, Ni, or Cu react with the decomposed products of AP.     

The first example of half-sandwich cobalt(III) complex with hydrotris(pyrazolyl)borate ligand

This paper presents the synthesis, crystal structure and spectroscopic properties of a novel half-sandwich mononuclear cobalt(III) complex with hydrotris(3,5-dimethylpyrazolyl)borate ligand and thiocyanate [Tp^*Co(Hpz^*)(NCS)₂]·H₂O·CH₃OH (Tp^*: hydrotris(3,5-dimethyl- pyrazolyl)borate, Hpz^*: 3,5-dimethylpyrazole). The structure was determined by X-ray diffraction. The complex crystallizes in the monoclinic system, space group C_c, a=18.591(6) Å, b=10.536(3) Å, c=17.568(5) Å, β=11.284(5)°, Z=4, R₁=0.0501, wR₂=0.1179. The cobalt(III) ion in the complex is six-coordinated with nitrogen atoms, three from Tp^*, two from pyrazole and two from two thiocyanates, to form octahedral environment. The hydrogen atoms of O(2) of water molecule are connected by hydrogen bonds with S atoms of two adjacent complex molecules to form 1-D chains. The hydrogen atom of N(8) of complex molecule is connected by hydrogen bond with methanol. The spectroscopic results are consistent with the crystallographic study.     

A novel helical chainlike nickel(II) coordination polymer containing 1D trigonal channels with water molecule guests

A novel 1D helical nickel coordination polymer, [Ni(TAU)₂(4,4′-bipy)]_n·2nH₂O (TAU = taurine, 4,4′-bipy = 4,4′-bipyridine), was synthesized and its crystal structure has been determined by X-ray diffraction. Each helix interlinks with six adjacent helices through extensive hydrogen bonds to form 3D supramolecular structure, in which 1D trigonal microporous channels filled with water guest molecules exist within the polymer coils. The framework remains intact on removal of guest water molecules which is proved by XPRD and TGA. Variable temperature magnetic susceptibility indicates weak anti-ferromagnetic interactions between the Ni(II) ions.     

Two Tartrate-Pillared Coordination Polymers: Hydrothermal Preparation, Crystal Structures, Spectroscopic and Thermal Analyses of {[M2(μ-C4H4O6)2(H2O)] · 3H2O}∞ (M = Mn, Cd)

Two novel three-dimensional coordination polymers, formulated as {[M₂(μ-C₄H₄O₆)₂(H₂O)] · 3H₂O}_∞ (M = Mn for 1 and Cd for 2), have been synthesized under hydrothermal reaction condition. Both complexes were characterized by elemental analysis and IR spectroscopy. Their molecular and crystal structures were determined by X-ray crystal structure analysis and their thermal stability by TGA-DTA methods. Compound 1 crystallizes in the monoclinic space group, P2₁, while compound 2 crystallizes the orthorhombic space group, P2₁2₁2₁. The structures are self-assembled from bifunctional tartrate and water molecules. Tartrate ligands in 1 and 2 contribute to both covalent and hydrogen bonds. Polymeric chains of 1 and 2 are composed of M(II) ions bridged by tartrate ions in O,O′ fashion. The asymmetric units of coordination polymers contain two metal centers having different coordination environments.     

Effect of Molecular Symmetry and Intermolecular Halogen-Halogen Interactions on the Crystal Structures of Halogen-Substituted Benzoic Acids. X-ray Crystal Structure of m-Iodobenzoic Acid

The crystal structure of m-iodobenzoic acid is reported. The crystals are monoclinic, P2₁/c, with a = 6.220(3) Å, b = 4.689(2) Å, c = 26.67(1) Å, β = 101.80(3)°, Z = 4, C₇H₅IO₂. The structure has been determined by direct methods and refined to R 0.026 for 1288 reflections recorded with an automatic single crystal diffractometer. The structure is composed of essentially planar hydrogen-bonded dimer units with significant intermolecular iodine-iodine contacts. The configuration of the dimer unit is transoid. Since this is the penultimate member of the family of mono-halogen-substituted benzoic acids its structure is compared with those previously reported. In particular, the effects of differences in molecular geometry of the o-, m-, and p-isomers and the strengths of the intermolecular halogen-halogen interactions are surveyed. The geometry of the carboxyl group of m-iodobenzoic acid in the solid state and the carbonyl absorption in the Ftir spectrum of the crystalline acid at room temperature suggest the presence of dynamic proton isomerism as has been recently found by other investigators in crystalline benzoic acid and some of its derivatives.     

Synthesis,Crystal Structure,Electrochemical and Catalytic Properties of Hybrid Polyoxomolybdate Clusters-Based Terbium Complex

The inorganic–organic compound based on polyoxomolybdate [Tb(C₂H₆SO)₈][PMo₁₂ O₄₀]·2C₂H₆SO·½H₂O (I) has been isolated and structurally characterized by single-crystal X-ray molecular structure, IR spectra, thermogravimetric analysis and cyclic voltammetry measurements. The catalytic activities of (I) were also tested. The title compound crystallizes in monoclinic crystal system with C2/c space group. In the crystal, the polyoxidometalate anions are arranged in chains parallel to the [010] direction. The complex cations are located between these layers and linked to the neighbouring anions via weak C–H?O hydrogen bonding interactions leading to the formation of three dimensional network structure. Their catalytic activity toward organic dye is quite sizeable since the target removal is about 68% in the presence of the system POM-Tb/H₂O₂ after 120 min.     

新型含双水杨醛席夫碱的合成、晶体结构及其抑菌活性研究

利用5,5’-亚甲基-双水杨醛与苯胺缩合反应合成了新型Schiff碱,通过核磁共振技术及红外光谱法进行了表征,并获得了其晶体结构。该晶体属于单斜晶系,空间群为:C2/c,相关晶胞参数为:a=4.3954(12)nm,b=1.0150(2)nm,c=0.9576(2)nm,β=90.822(10)°,V=4.2717(17)nm3。该化合物存在分子内氢键,每相邻的分子之间通过分子间的氢键以及C-H…π作用将化合物连接成为Z字型结构,且该化合物有一定的抑菌活性。     

A 3D Mesomeric Supramolecular Structure of a Cu(II) Coordination Polymer with 1,1′-Biphenyl-2,2′,3,3′-tetracarboxylic Acid and 5,5′-Dimethyl-2,2′-bipyridine Ligands

A novel metal–organic framework {[Cu(H₂bptc)(cbpy)(H₂O)]·(H₂O)} _n (1) has been hydrothermally synthesized through reaction of 1,1′-biphenyl-2,2′,3,3′-tetracarboxylic acid (H₄bptc) with Cu(II) salt in the presence of ancillary nitrogen ligand 5,5′-dimethyl-2,2′-bipyridine (cbpy), and its structure was determined by X-ray diffraction and characterized by elemental analysis, and IR spectrum. The title compound crystallizes in monoclinic space group P2₁/c. Both right- and left-handed helices are detected in the structure. In the ab-plane, adjacent chains are homochiral and parallel to each other, which are connected together by hydrogen bonds to form a 2D supramolecular structure. The supramolecular layers with opposite chirality are arranged alternatively along the c-axis to form a 3D mesomeric supramolecular structure through π···π interactions. The thermal stability of the complex 1 was studied by thermal gravimetric and differential thermal analysis.