The crystal structure and low temperature magnetic susceptibility of square-planar bis(1,5-diazacyclooctane)nickel(II) perchlorate dihydrate

Summary We have carried out low temperature magnetic susceptibility measurements and a redetermination of the crystal and molecular structure of bis(1,5-diazacyclooctane)nickel(II) perchlorate dihydrate from three-dimensional intensity data collected on a CAD4 diffractometer. The structure was refined by full-matrix least-squares to the R value of 6.3% for 1501 observed reflections. The positions of the hydrogen atoms were obtained from the diffraction data. Contrary to our earlier conclusions drawn by inspection of molecular models of bis(diazacyclooctane) complexes, the axial sites in the actual crystal structure are open for ligation. The Ni-N bonds are, however, sterically protected by the coplanar N-H bonds, allowing maximum ligand-field stabilization for the squareplanar geometry around the nickel atom. The observed magnetic transition from a diamagnetic state at room temperature to a paramagnetic state at 78 K is explained on the basis of long-range exchange interactions along sterically unshieldedz axis. The crystal structure is compared with other similar structures.     

Similarity in structures of racemic and enantiomeric ibuprofen sodium dihydrates

The crystal structures of two ibuprofen sodium dihydrates, racemic sodium (RS)‐2‐(4‐isobutylphenyl)propanoate dihydrate or (RS)‐NaIBDH, Na⁺·C₁₃H₁₇O₂⁻·2H₂O, and enantiomeric sodium (S)‐2‐(4‐isobutylphenyl)propanoate dihydrate or (S)‐NaIBDH, Na⁺·C₁₃H₁₇O₂⁻·2H₂O, have been determined in the space groups P and P1, respectively. The unit cells of the two triclinic structures have similar lattice parameters and cell volumes. The constituent ions have similar coordination environments, but differ slightly in their hydrogen‐bonding inter­actions. The dominance of the inter­actions between the O atoms and the Na⁺ cations explains the structural similarity of these two structures, despite the fact that one is heterochiral while the other is homochiral.     

Enthalpies of solution and standard enthalpy of formation of crystalline NaVO3 · 2H2O

The enthalpies of solution of sodium metavanadate dihydrate in aqueous solutions of sodium perchlorate at ionic strength I = 0.3, 0.5, and 1.0 mol/L were calorimetrically measured at 298.15 K. The resulting experimental data were used to calculate the standard enthalpy of formation of crystalline NaVO₃ · 2H₂O.     

Physical characterization of the polymorphic variations of magnesium stearate and magnesium palmitate hydrate species

The anhydrate, dihydrate, and trihydrate phases of chemically pure magnesium stearate and magnesium palmitate have been prepared and characterized as to their structural characteristics. The magnesium palmitate materials were obtained as significantly larger crystals than were the magnesium stearate materials, and the crystals of the dihydrate phase of either material were found to be the most fully developed. The crystal structures of all materials were judged to be very similar to each other, differing primarily in the magnitude of the long (001) crystal spacing. Thermal analysis studies revealed that the water of hydration contained within the dihydrate phases of either magnesium stearate or magnesium palmitate was more tightly bound than was the water of hydration within the corresponding trihydrate phases. These findings provide further support for the structural picture where the water contained in these lattice structures is present between the intermolecular planes.     

Enthalpies of dissolution of NaVO3 · 2H2O in aqueous chloric acid and the standard formation enthalpy of the VO 2 + ion

The enthalpies of dissolution of sodium metavanadate dihydrate in aqueous solutions of chloric acid and sodium perchlorate were measured by calorimetry at 298.15 K at ionic strengths of I = 0.3, 0.4, 0.5, 0.6, and 1.0 M. The standard formation enthalpy of the VO ₂ ⁺ ion in aqueous solution was calculated from the resulting experimental data.     

Reactions of p-hydroxyphenyl- and p-phenolatothianium compounds

p-Hydroxyphenylthianium perchlorate reacts with OH^– to give bis(p-phenolatothianium) dihydrate, in which the oxygen atoms of the zwitter ions are tied up in an eight-membered ring by hydrogen bonds with the H₂O molecules, The unit cell of the perchlorate consists of two cations and two anions bonded by linear and forked hydrogen bonds. p-Hydroxyphenylthianium perchlorate reacts with a concentrated solution of KOH in methanol to give 1-(p-hydroxyphenyl)-1-(p-phenolato)bisthianium perchlorate, which is also obtained by the reaction of p-hydroxyphenylthianium perchlorate with bis(p-phenolatothianium) dihydrate and of the latter with HClO₄. 1-(p-Hydroxyphenyl)-1'-(p-phenolato)bisthianium chloride hydrate and 1-(p-phenolato)thianiumbisphenol, respectively, were obtained by the reaction of bis (p-phenolatothianium) dihydrate with p-hydroxyphenylthianium chloride or with C₆H₅OH. Under the influence of picric or perchloric acid, 1-(p-h droxyphenyl)-1'-(p-phenolato)bisthianium perchlorate is converted to p-hydroxyphenylthianium picrate or its perchlorate, respectively, while reaction with OH^– gives bis(p-phenolatothianium) dihydrate, and heating with piperidine gives p-hhdroxyphenyl -piperidinoamyl sulfide. When bis(p-phenolatothianium) dihydrate is heated, it undergoes dehydration and polymerization to [-OC₆H₄S(CH₂)₅-]_n; depending on the conditions, n = 2, 3, 14, or 25. p-Hydroxyphenyl -piperidinoamyl sulfide is formed when II is heated with piperidine.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 8, pp. 1050–1055, August, 1980.     

The coordination properties of aminobenzoate ligands in complexes with alkali metals

The crystal structures of sodium 4-amino-2-hydroxybenzoate dihydrate [NaL·2H₂O, L?= C₆H₃(NH₂)(OH)COO] and potassium 2-aminobenzoate monohydrate [KL*·H₂O, L*?=?C₆H₄(NH₂)COO] were determined by X-ray diffraction methods. The compound NaL·2H₂O crystallizes in the monoclinic system, space group P2₁/c with a?=?8.820(2), b?=?14.632(3), c?=?6.948(2)?Å, β?=?97.88(3)°. The structure consists of sodium ion pairs joined together by tridentate 4-amino-2-hydroxybenzoate moieties creating a polymeric chain. In the metal centres, two water molecules bridge the sodium atoms. Five oxygen atoms and one nitrogen atom form a distorted octahedral environment. The compound KL*·H₂O crystallizes in the monoclinic system, space group P2₁/c with a?=?14.684(3), b?=?7.618(2), c?=?7.512(2)?Å, β?=?96.95(3)°. The structure consists of octacoordinated potassium atoms bonded with three water molecules and five carboxylate oxygen atoms. Water molecules appear as bridging ligands. The 2-aminobenzoate ligand acts as a pentadentate ligand with the molecular network stabilized by hydrogen bonds. Among the polymeric chains in both structures appear noncovalent interactions of type N?H···X.     

Hydrogen-bonded networks of 2,2′-substituted 4,4′-biimidazoles: New ligands for the assembled metal complexes

4,4′-Biimidazole derivatives having alkyl-substituents at 2- and 2′-positions were synthesized as new component molecules of supramolecular assemblies based on hydrogen-bonding interaction. The crystal structure analyses of methyl and ethyl derivatives revealed intriguing three-dimensional structures constructed by hydrogen-bonded networks. Furthermore, the methyl derivative formed a six-membered cyclic motif of hydrogen-bonded network to build up a channel structure. The ethyl derivative gave the two polymorphous, anhydrate and dihydrate, depending on conditions of the crystallization. The anhydrate constructed three-dimensional hydrogen-bonded networks by direct N–H⋯N hydrogen-bondings. In the crystal structure of the dihydrate of ethyl derivative, three-dimensional hydrogen-bonding interaction through water molecules formed a channel structure.     

Interactions in Calcium Oxalate Hydrate/Surfactant Systems

Phase transformation of calcium oxalate dihydrate (COD) into the thermodynamically stable monohydrate (COM) in anionic (sodium dodecyl sulfate (SDS)) and cationic (dodecylammonium chloride) surfactant solutions has been studied. Both surfactants inhibit, but do not stop transformation from COD to COM due to their preferential adsorption at different crystal faces. SDS acts as a stronger transformation inhibitor. The general shape of adsorption isotherms of both surfactants at the solid/liquid interface is of two-plateau-type, but differences in the adsorption behavior exist. They originate from different ionic and molecular structures of crystal surfaces and interactions between surfactant headgroups and solid surface. Copyright 1999 Academic Press.     

Insights into the Crystallisation Process from Anhydrous,Hydrated and Solvated Crystal Forms of Diatrizoic Acid

Diatrizoic acid (DTA), a clinically used X‐ray contrast agent, crystallises in two hydrated, three anhydrous and nine solvated solid forms, all of which have been characterised by X‐ray crystallography. Single‐crystal neutron structures of DTA dihydrate and monosodium DTA tetrahydrate have been determined. All of the solid‐state structures have been analysed using partial atomic charges and hardness algorithm (PACHA) calculations. Even though in general all DTA crystal forms reveal similar intermolecular interactions, the overall crystal packing differs considerably from form to form. The water of the dihydrate is encapsulated between a pair of host molecules, which calculations reveal to be an extraordinarily stable motif. DTA presents functionalities that enable hydrogen and halogen bonding, and whilst an extended hydrogen‐bonding network is realised in all crystal forms, halogen bonding is not present in the hydrated crystal forms. This is due to the formation of a hydrogen‐bonding network based on individual enclosed water squares, which is not amenable to the concomitant formation of halogen bonds. The main interaction in the solvates involves the carboxylic acid, which corroborates the hypothesis that this strong interaction is the last one to be broken during the crystal desolvation and nucleation process.     

Strong Attraction of Caffeine to the Mercurous Dumbbell in the Salt [Hg2(Caf)2](ClO4)2(H2O)2

Colourless single crystals of the caffeine adduct of mercurous perchlorate dihydrate, [Hg₂(Caf)₂](ClO₄)₂(H₂O)₂, were grown from aqueous solutions of mercurous perchlorate and caffeine by isothermal evaporation at ambient temperature. The crystal structure (monoclinic, P2₁/n, Z = 4, a = 1628.0(2), b = 780.4(1), c = 2229.6(3) pm, β = 99.84(1)°, R₁(all data) = 0.0894) contains [trans‐Caf‐Hg‐Hg‐Caf]²⁺ cations with a Hg‐Hg distance of 250.88(6) pm, Hg‐N (bond) distances of 214.4(6) and 215.1(6) pm and Hg‐Hg‐N angles of 176.9(2) and 165.1(2)°, respectively. These cations are attached via weak Hg‐O contacts to dimers which are further arranged to leave large channels into which one crystal water molecule is included. The second water molecule and the two perchlorate anions are weakly attracted to one Hg atom.     

Crystal and molecular structures of pentazoline hydrochloride dihydrate

The crystal structure of pentazoline hydrochloride dihydrate has been established by x-ray structural analysis. A comparative analysis has been made of the crystal structures of the dihydrates of the hydrochlorides of pentazoline and of deoxypeganine.     

2H NMR和DSC法研究十二烷基磺酸钠-正戊醇-水三元体系的溶致液晶

测定了十二烷基磺酸钠/正戊醇/水体系的相平衡,在相图中的液晶区选取样品点,采用²H NMR和差示扫描量热方法,并结合其液晶纹理,研究了该体系液晶相的结构特点。结果表明,在一定温度下,整个液晶区均为层状液晶,其相结构不随水含量和醇含量的变化而变化。在组成固定的情况下,该体系液晶的相结构随温度的升高而发生变化。     

Synergistic effects of CdS in sodium titanate based nanostructures for hydrogen evolution

Synergistic effect of CdS decorated sodium titanate nanostructures showed enhanced H₂ production abilities. The confinement effect and synergistic effect of decorated CdS inside the sodium titanate nanotubes are investigated.     

Silica Sulfuric Acid/Sodium Dichromate Dihydrate as an Efficient Heterogeneous Method for the Oxidation of Alcohols Under Mild Conditions

A combination of silica sulfuric acid and sodium dichromate dihydrate in the presence of wet SiO 2 were used as an effective oxidizing agent for the oxidation of alcohols to their corresponding aldehyde or ketone derivatives in dichloromethane or toluene with excellent yields.     

Infrared and laser Raman studies of L-phenylalanine L-phenylalaninium perchlorate and bis(DL-phenylalaninium) sulphate monohydrate

Both crystals under study have two phenylalanine groups in the cationic part of the complex. In the L-phenylalanine L-phenylalaninium perchlorate crystal, two phenylalanine groups share one proton and become monoprotonated. In the bis(DL-phenylalaninium) sulphate monohydrate crystal, on the other hand, both the phenylalanine groups are protonated. This leads to several differences in the infrared and Raman spectra of these two crystals. The presence of both the carbonyl and the ionized carboxylic groups has been identified in the perchlorate crystal, while the sulphate crystal has only the carbonyl group. Extensive hydrogen bonding further leads to the shifting of bands due to several stretching and bending modes. It also reduces the Td symmetry of the anions to C2v symmetry causing the degeneracies of several modes to be removed.     

Crystal Structure and Magnetic Property of 2-(Imidazo[1,2-a]pyri-din-2-yl)-2-oxoacetic Acid and Its Perchlorate

We herein report two crystals based on 2-(imidazo[1,2-a]pyridin-2-yl)-2-oxoacetic acid radical and its perchlorate, and investigate the relationship between magnetic properties and crystal stacking structures or supramolecular interactions. 2-(Imidazo[1,2-a]pyridin-2-yl)-2-oxoacetic acid radical in two crystals mainly exist as diamagnetic dimer formed via short atomic contacts or supramolecular interactions (hydrogen bonds, anion-π or lonepair-π interactions), leading to low magnetic susceptibilities. 2-(Imidazo[1,2-a]pyridin-2-yl)-2-oxoacetic acid radical crystal exhibits quasi-one-dimensional columnar stacking chain and weak antiferromagnetism. However, its perchlorate crystal possesses one-dimensional doublestranded chain structure assembled through double hydrogen bonds and anion-π interactions, and reveals weak ferromagnetism.     

Crystallographic Studies of Synthetic Corrinoids. III. Structural similarities and differences between A/D-seco-corrinoid complexes of divalent nickel,palladium and platinum

X-ray crystal structure investigations of the isomorphous perchlorate salts of complexes of an A/D-seco-corrinoid ligand (I) with divalent nickel, palladium and platinum are reported. The structures determined for the Pd- and Pt-complexes are virtually superposable, that of the Ni-complex, although similar to the other two, shows significant differences with respect to metal coordination and to the spatial relationship of the A and D rings and their substituents. These similarities and differences are discussed in relation to the photochemical A/D cyclization leading to corrin complexes (II).     

Structural microheterogeneites in strontium perchlorate solutions of posteutectic concentrations

Aqueous solutions of strontium perchlorate were studied in a wide range of concentrations at room temperature by X-ray diffraction, thermogravimetry, and calorimetry. The features of the solubility polytherm of strontium perchlorate, that distinguish it from those of other Group II metal perchlorates, were explained in terms of two coexisting interconverting crystal hydrates.     

Metal–Organic Frameworks (MOFs) as Safer,Structurally Reinforced Energetics

Second‐generation cobalt and zinc coordination architectures were obtained through efforts to stabilize extremely sensitive and energetic transition‐metal hydrazine perchlorate ionic polymers. Partial ligand substitution by the tridentate hydrazinecarboxylate anion afforded polymeric 2D‐sheet structures never before observed for energetic materials. Carefully balanced reaction conditions allowed the retention of the noncoordinating perchlorate anion in the presence of a strongly chelating hydrazinecarboxylate ligand. High‐quality X‐ray single‐crystal structure determination revealed that the metal coordination preferences lead to different structural motifs and energetic properties, despite the nearly isoformulaic nature of the two compounds. Energetic tests indicate highly decreased sensitivity and DFT calculations suggest a high explosive performance for these remarkable structures.