Preparation,Thermal Behaviour,and Crystal Structure of MgAl<Subscript>2</Subscript>F<Subscript>8</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>

Summary.  Single crystals of MgAl₂F₈(H₂O)₂ have been obtained under hydrothermal conditions (250°C, 14 d) from a starting mixture of AlF₃ and MgAlF₅(H₂O)₂ in a 5% (w/w) HF solution. The crystal structure has been determined and refined from single crystal data (Fmmm (#69), Z = 4, a = 7.2691(7), b = 7.0954(16), c = 12.452(2) ?, 281 structure factors, 27 parameters, R(F ² > 2σ (F ²)) = 0.0282, wR(F ² all) = 0.0885). The obtained crystals were systematically twinned according to (010/100/001) as twinning matrix, reflecting the pseudo-tetragonal metric. The crystal structure is composed of perowskite-type layers built of corner sharing AlF₆ octahedra with an overall composition of AlF₄ ⁻ which are connected via common fluorine atoms of [MgF_4/2(H₂O)_2/1] octahedra. Group-subgroup relations of MgAl₂F₈(H₂O)₂ to WO₃(H₂O)_0.33 and to other M(II)M(III)₂ F₈(H₂O)₂ structures are briefly discussed. Above 570°C, MgAl₂F₈(H₂O)₂ decomposes under elimination of water into α-AlF₃, β-AlF₃, and MgF₂. Received October 29, 2001. Accepted (revised) December 6, 2001     

Synthesis and structure of the pyrazolate-bridged cobalt(II) benzoate Co<Subscript>2</Subscript>(μ-dmpz)<Subscript>2</Subscript>(Hdmpz)<Subscript>2</Subscript>(OOCPh)<Subscript>2</Subscript>

The reaction between Co(Hdmpz)₂(OOCPh)₂ and cobalt acetate hydrate leads to the deprotonation of coordinated pyrazole and formation of pyrazolate-bridged Co₂(μ-dmpz)₂(Hdmpz)₂(OOCPh)₂ binuclear complex. The structure of the complex was determined by X-ray crystallography.     

Synthesis,molecular, crystal and electronic structure of [RuCl<Subscript>2</Subscript>(PPh<Subscript>3</Subscript>)<Subscript>2</Subscript>(3,5-Me<Subscript>2</Subscript>HPz)<Subscript>2</Subscript>]

The reaction of [RuCl₂(PPh₃)₃] complex with dimethylpyrazole has been examined. A new ruthenium complex—[RuCl₂(PPh₃)₂(3,5-Me₂HPz)₂] has been obtained and characterized by IR, ¹H NMR and UV-VIS measurements. Crystal and molecular structure of the complex has been determined. The electronic structure of the complex has been calculated by TDDFT method.     

Synthesis and alkylation of n<Subscript>(3)</Subscript>-aryl-n<Subscript>(5)</Subscript>-phenyl-6-amino-4-aryl(2-furyl)-2-thioxo-1,2,3,4-tetrahydropyridine-3,5-dicarboxamide

N₍₃₎-Aryl-N₍₅₎-phenyl-6-amino-4-aryl(2-furyl)-2-thioxo-1,2,3,4-tetrahydropyridine-3,5-dicarboxamides have been obtained by the interaction of N-phenyl-3-aryl(2-furyl)-2-cyanoacrylamides with 3-amino-3-thioxopropananilides under the conditions of the Michael reaction. N₍₃₎-Aryl-N₍₅₎-phenyl-2-alkylthio-6-amino-4-aryl(2-furyl)-3,4-dihydropyridine-3,5-dicarboxamides and N₍₃₎, N₍₅₎-diphenyl-6-benzylthio-4-(2-furyl)-2-oxo-1,2,3,4-tetrahydropyridine-3,5-dicarboxamides were synthesized by alkylation of the products. __________ Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 7, pp. 1018–1023, July, 2008.     

Thermochemistry of the solid complex Gd(Et<Subscript>2</Subscript>dtc)<Subscript>3</Subscript>(phen)

Summary A ternary solid complex Gd(Et₂dtc)₃(phen) has been obtained from reactions of sodium diethyldithiocarbamate (NaEt₂dtc), 1,10-phenanthroline (phen) and hydrated gadolinium chloride in absolute ethanol. The title complex was described by chemical and elemental analyses, TG-DTG and IR spectrum. The enthalpy change of liquid-phase reaction of formation of the complex, Δ_rH^Θ_m(l), was determined as (-11.628±0.0204) kJ mol^-1 at 298.15 K by a RD-496 III heat conduction microcalorimeter. The enthalpy change of the solid-phase reaction of formation of the complex, Δ_rH^Θ_m(s), was calculated as (145.306±0.519) kJ mol^-1 on the basis of a designed thermochemical cycle. The thermodynamics of reaction of formation of the complex was investigated by changing the temperature of liquid-phase reaction. Fundamental parameters, the apparent reaction rate constant (k), the apparent activation energy (E), the pre-exponential constant (A), the reaction order (n), the activation enthalpy (Δ_rH^Θ_≠), the activation entropy (Δ_rS^Θ_≠), the activation free energy (Δ_rG^Θ_≠) and the enthalpy (Δ_rH^Θ_≠), were obtained by combination of the thermodynamic and kinetic equations for the reaction with the data of thermokinetic experiments. The constant-volume combustion energy of the complex, Δ_cU, was determined as (-18673.71±8.15) kJ mol^-1 by a RBC-II rotating-bomb calorimeter at 298.15 K. Its standard enthalpy of combustion, Δ_cH^Θ_m, and standard enthalpy of formation, Δ_fH^Θ_m, were calculated to be (-18692.92±8.15) kJ mol^-1 and (-51.28±9.17) kJ mol^-1, respectively.     

Synthesis and characterization of two new coordination supramolecular structures from a versatile unsymmetric 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) ligand

Two new inorganic–organic coordination networks based on a versatile and unsymmetric building block 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and inorganic Co^II and Cd^II salts have been synthesized in mixed solvent media and structurally characterized by single-crystal X-ray diffraction analysis. Crystal Hpot (1) was obtained from methanol solution. Reaction of Co(NO₃)₂ · 6H₂O with Hpot afforded a neutral two-dimensional (2-D) porous coordination polymer {[Co(pot)₂] · 6H₂O}_n (2) with a (4,4) network, which shows a 3-D supramolecular network through O–H?O weak interactions. While substituting the transition metal ions used in 2 with Cd(NO₃)₂ · 6H₂O, a neutral 2-D coordination polymer [Cd₂(pot)₄]_n (3) with a (6,3) network which further extended to a 3-D supramolecular structure through versatile hydrogen bonds C–H?X (X = O, N and S) was obtained. It is remarkable that the building block “pot” anion exhibits versatile coordination modes in complexes 2 and 3. These results indicate that the versatile nature of this rigid unsymmetric ligand, together with the coordination preferences of the metal centers, plays a critical role in construction of novel coordination polymers. The properties of gas absorption, magnetism and luminescence of 2 and 3 have been investigated and discussed in detail.     

Experimental Studies on Isonicotinato Cadmium(II) Complex [Cd(C<Subscript>6</Subscript>H<Subscript>4</Subscript>NO<Subscript>2</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>4</Subscript>] and Density Functional Calculations

Isonicotinato cadmium(II) complex [Cd(C₆H₄NO₂)₂(H₂O)₄] has been synthesized by hydrothermal method and characterized by elemental analysis, electronic-spectra and thermogravimetric analysis. Density functional theory (DFT) method calculations of the structure, atomic charges distribution, electronic spectra, natural population analysis and the thermodynamic properties at different temperatures have been performed. The calculated results show the electronic transitions are mainly derived from the contribution of bands π → π^* and the decomposition of the title compound should first occur at the bond of Cd—O, then at the bond of Cd—N, which agrees very well with the experimental data.     

Hydrothermal synthesis and crystal structure of [Ni(Bptc)<Subscript>2</Subscript>(Bimb)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>]

In the compound [Ni(Bptc)₂(Bimb)₂(H₂O)₂] (I), where H₄Bptc is 3,3′,4,4′-biphenyltetracarboxylic acid; Bimb is 4,4′-bis(1-imidazolyl)biphenyl), Ni(II) has a distorted octahedral coordination geometry, which was bonded with two N atoms from two Bimb ligands, two O atoms from two H₂Bptc²⁻ ligands and two water O atoms. The crystal structure of compound I is stabilized by the π-π-stacking and hydrogen bonds interaction.     

Antiferromagnetic coupling in [Mn<Subscript>12</Subscript>O<Subscript>12</Subscript>(O<Subscript>2</Subscript>CMe)<Subscript>6</Subscript>(<Emphasis Type="Italic">p</Emphasis>-CO<Subscript>2</Subscript>-phenyl nitronyl

The synthesis of [Mn₁₂O₁₂(O₂CMe)₆(p-CO₂-phenyl nitronyl nitroxide)₁₀(H₂O)₄]· 4H₂O, (1), by direct replacement of some of the acetate groups in [Mn₁₂O₁₂(O₂CMe)₁₆(H₂O)₄] · 4H₂O · 2MeCO₂H, (2), with the organic radical p-HO₂C-phenyl nitronyl nitroxide, (3), is reported. E.p.r. spectra show exchange narrowing in (1) due to coupling between the manganese ions and radicals. The isotropic hyperfine splitting constant from the manganese ions is a = 96 Oe at 5.5K. The magnetic susceptibility indicates antiferromagnetic exchange interactions between the manganese ions and the radicals with the Weiss constant = -25 K. The spin was determined to be S = 6 from magnetization data in the 2--30 K temperature range at 50 kOe, suggesting a mixture of ground state with excited states.     

Synthesis and study of sodium triuranate Na<Subscript>2</Subscript>(UO<Subscript>2</Subscript>)<Subscript>3</Subscript>O<Subscript>3</Subscript>(OH)<Subscript>2</Subscript>

Sodium triuranate Na₂(UO₂)₃O₃(OH)₂ was synthesized by the reaction between aqueous uranyl acetate solution and aqueous sodium nitrate solution under hydrothermal conditions at 200°C. The composition and structure of the synthesized compound were determined, and its dehydration and thermal decomposition were studied, by chemical analysis, X-ray diffraction, IR spectroscopy, and thermal analysis.     

Calorimetric and volumetric data of nucleating bovine albumin solutions at various NaCl,Li<Subscript>2</Subscript>SO<Subscript>4</Subscript> and (NH4)<Subscript>2</Subscript>SO<Subscript>4</Subscript> concentrations

Summary Heat effects and densities of bovine albumin solutions in Na-acetate buffer pH 4.2 at various NaCl, Li₂SO₄ and (NH₄)₂SO₄ concentrations were determined by a LKB 10700-2 microcalorimeter and an Anton Paar 60/602 densimeter (25&deg;C). The density measurements were made after 1 and 48 h of the dissolution of bovine albumin in the buffer. The correlations between the changes of the enthalpy of salting and apparent molar volumes vs. concentrations of salts were determined.     

Thermal study of cyclopalladated complexes of the type [Pd<Subscript>2</Subscript>(dmba)<Subscript>2</Subscript>X<Subscript>2</Subscript>(bpe)]

The synthesis, characterization and thermal analysis of the novel cyclometallated compounds [Pd₂(dmba)₂Cl₂(μ-bpe)] (1), [Pd₂(dmba)₂(N₃)₂(μ-bpe)] (2), [Pd₂(dmba)₂(NCO)₂(μ-bpe)] (3), [Pd₂(dmba)₂(SCN)₂(μ-bpe)] (4), [Pd₂(dmba)₂(NO₃)₂(μ-bpe)] (5) (bpe=trans-1,2-bis(4-pyridyl)ethylene; dmba=N,N-dimethylbenzylamine) are described. The thermal stability of [Pd₂(dmba)₂X₂(μ-bpe)] complexes varies in the sequence 1>4>3>2>5. The final residues of the thermal decompositions were characterized as metallic palladium by X-ray powder diffraction.     

Phase equilibria in the liquid ternary system [Th(NO<Subscript>3</Subscript>)<Subscript>4</Subscript>(TBP)<Subscript>2</Subscript>]-[Gd(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>(TBP)<Subscript>3</Subscript>]-TBP-isooctane at different temperatures

The phase diagrams of the ternary system [Th(NO₃)₄(TBP)₂]-[Gd(NO₃)₃(TBP)₃]-TBP-isooctane in the temperature range 298.15–333.15 K were constructed.     

Two novel four-coordinated zinc(II) complexes [Zn(dmatrz)<Subscript>2</Subscript>Cl<Subscript>2</Subscript>] and [Zn(dmatrz)<Subscript>2</Subscript>(SCN)<Subscript>2</Subscript>] exhibiting strong blue fluorescent properties

Two novel complexes, [Zn(dmatrz)₂]Cl₂ (1) and [Zn(dmatrz)₂(SCN)₂] (2), have been prepared and characterized by X-ray crystallography, absorption and luminescence spectrometries (dmatrz=3,5-dimethy-4-amino-1,2,4-triazole). The coordination environment of the zinc(II) ions in (1) and (2) has a distorted tetrahedral geometry completed via two independent nitrogen atoms of two triazole ligands and two anions, respectively. Both (1) and (2) show strong blue luminescence properties. Furthermore, (1) displays stronger blue photoluminescence than (2) as the result of different anions (Cl^- and SCN^-) coordinated to the zinc(II) ions.     

Crystal structure of <Emphasis Type="Italic">cis</Emphasis>-[PdCl<Subscript>2</Subscript>(CNMes)<Subscript>2</Subscript>]

The interaction between PdCl₂(CH₃CN)₂ and 2,4,6-Me₃C₆H₂NC (MesNC) proceeds with the substitution of acetonitrile ligands and leads to the synthesis of a cis-[PdCl₂(MesNC)₂] complex. The structure of this compound is determined by single crystal X-ray diffraction (XRD). The complex has a slightly distorted square-planar structure of the metal center with two cis-positioned isocyanide ligands. In both CN isocyanide moieties the triple bonds have lengths similar to the lengths of the respective bonds in other isocyanide complexes. In the structure, the cis-[PdCl₂(MesNC)₂] complexes are bound by weak С–H???Cl hydrogen bonds and π-stacking interactions.     

Quantum-chemical modeling of endohedral derivatives of buckminsterfullerenes Gd@C<Subscript>60</Subscript>(CHR)<Subscript>2</Subscript> and Gd@C<Subscript>80</Subscript>(CHR)<Subscript>2</Subscript>

The structural energies of the endohedral derivatives of buckminsterfullerenes Gd@C₆₀(CHR)₂ and Gd@C₈₀(CHR)₂ were calculated by quantum-chemical methods – semiempirical PM3 and nonempirical RHF SCF MO LCAO with the S. Huzinaga MINI minimum basis set and GAMESS software.     

Synthesis,crystal structure,and biological properties of the complex [Co(DmgH)<Subscript>2</Subscript>(Seu)<Subscript>1.4</Subscript>(Se-Seu)<Subscript>0.5</Subscript>(Se<Subscript>2</Subscript>)<Subscript>0.1</Subscript>][BF<Subscript>4</Subscript>]

A new Co(III) dioxime complex with selenocarbamide was obtained by the reaction of Co(BF₄)₂ ? 6H₂O, DmgH₂, and Seu (DmgH2 = dimethylglyoxime, Seu = selenocarbamide). According to X-ray diffraction (CIF file CCDC no. 1485732), the product was an ionic coordination compound with unusual composition, [Co(DmgH)₂(Seu)_1.4(Se-Seu)_0.5(Se₂)_0.1][BF₄] (I). Apart from two monodeprotonated DmgH￣ molecules, the central atom coordinates neutral Seu, Se-Seu, and Se₂ molecules. Thus, the crystal contains the complex cations [Co(DmgH)₂(Seu)₂]⁺, [Co(DmgH)₂(Seu)(Se-Seu)]⁺, and [Co(DmgH)₂(Seu)(Se₂)]⁺. Each [BF₄]￣ anion is linked to the cations not only by electrostatic forces but also by intermolecular N–H···F hydrogen bonds (H-bonds). The complex cations are combined by intermolecular N–H···O H-bonds. The new coordination compound was found to possess biological activity. Treatment of the garlic (Allium sativum L.) foliage with an aqueous solution of I optimizes the content of selenium in the leaves and cloves and enhances the growth and plant productivity. The organs of treated plants are characterized by enhanced antioxidant protection owing to increasing activity of antioxidant enzymes and contents of proline and assimilation pigments, and decreasing lipid peroxidation.     

Radius-dependent assembly of complexes with the rigid unsymmetric ligand 5-(2-pyridyl)-1,3,4-oxadiazole-2-thione: Syntheses,structures and luminescence properties

The free ligand, 5-(2-pyridyl)-1,3,4-oxadiazole-2-thione (1, HL5), has been synthesized and characterized; its three new functional d¹⁰ transition-metal complexes, [Zn(L5)₂(H₂O)₂] (2), [Cd(L5)₂]_n (3) and [Hg₂(L5)₄] (4), have been successfully obtained by a diffusion synthetic method and characterized by single-crystal X-ray diffraction, infrared spectroscopy, elemental analysis, thermogravimetric analysis, and photoluminescence. On the basis of the X-ray analyses, the radii of the metal ions are found to play an important role in determining the structures. The radii and nature of the metal ions can impart their influence on the coordination geometry of the d¹⁰ transition-metal atoms, which seems to be the main factor controlling the structures and luminescent properties of the reaction products in this system.     

Synthesis,structures and characterization of two new supramolecular coordination complexes with the ambidentate ligand 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot)

Two new coordination supramolecular complexes based on a versatile and unsymmetrical 5-(4-pyridyl)-1,3,4-oxadiazole-2-thione (Hpot) and Mn^II and Ni^II have been synthesized and structurally characterized by single-crystal X-ray diffraction analysis. Reaction of MnCl₂?· 4H₂O with Hpot afforded a neutral mononuclear complex [Mn(pot)₂(H₂O)₄]?·?2H₂O (1), which exhibits a three-dimensional (3-D) supramolecule through versatile intermolecular O–H?···?X (X=O, N and S) hydrogen bond interactions. When using NiCl₂?·?6H₂O instead of MnCl₂?· 4H₂O under similar reaction conditions, a neutral mononuclear complex [Ni(pot)₂(H₂O)₄] (2) is also obtained, which does not exhibit intermolecular hydrogen bonds and π–π stacking interactions. It is very interesting that the pot anion exhibits different coordination modes in complexes 1 and 2. The IR spectra and the TGA for 1 and 2 have been investigated and discussed in detail.     

Spectroscopic,thermal and structural studies of a new mercury(II) one-dimensional coordination polymer, [Hg(3-bpo)2(SCN)2], 3-bpo = 2,5- bis (3-pyridyl)-1,3,4-oxadiazole

A new mercury(II)-organic polymeric complex generated from 2,5-bis(3-pyridyl)-1,3,4-oxadiazole (3-bpo) as an angular dipyridyl derivative ligand, [Hg(3-bpo)₂(SCN)₂], was prepared from reactions of ligand 3-bpo with mercury(II) thiocyanate. The compound was characterized by elemental analysis, IR-, ¹H NMR-, ¹³C NMR-spectroscopy and structurally determined by X-ray single crystal diffraction. The thermal stability of [Hg(3-bpo)₂(SCN)₂] was studied by thermal gravimetric (TG) and differential thermal analyses (DTA).