Synthesis,characterization, and crystal structure of [Ni(dap(A)<Subscript>2</Subscript>)]<Subscript>2</Subscript> (dap(AH)<Subscript>2</Subscript>: 2,6-diacetylpyridine bis(anthraniloyl hydrazone))—a molecule possessing an infinite double helical chain in the solid state

Anthraniloyl hydrazide (AH) contains two −NH₂ groups, one of them is attached to the aromatic ring and the other is the hydrazinic, −NH₂. It is found that only the later reacts with the carbonyl compounds to form Schiff bases, while the former remains inert. The reasons behind this difference in reactivity are analyzed on the basis of semi-empirical calculations, which show that the lone pair of the ring −NH₂ is considerably delocalized over the ring, resulting in an accumulation of a positive charge on this particular nitrogen. Ni(II) complex of 2,6-diacetylpyridine bis(anthraniloyl hydrazone) has been prepared and characterized by various physico-chemical methods. The structure of the complex was determined by X-ray crystallography. It was found that in the solid state, the compound exist as a dimer, and two coordinated ligand moieties form a double helix around the two metal ions. H-bonding then results in extension of double helix to an infinite chain.     

Models of Molecular Structures of Al<Subscript>2</Subscript>Cr<Subscript>3</Subscript> and Al<Subscript>2</Subscript>Mo<Subscript>3</Subscript> Metal Clusters according to Density Functional Theory Calculations

The geometrical parameters of the molecular structures of aluminum–chromium and aluminum–molybdenum clusters Al₂Cr₃ and Al₂Mo₃ have been calculated by the OPBE/TZVP density functional theory (DFT) method with the Gaussian09 programL package. It has been found that each of these metal clusters can exist in twenty structural modifications, which significantly differ in stability and geometric parameters. Bond lengths and bond and torsion (dihedral) angles are reported for each of these modifications.     

Chemical bonding and electronic structure of LaMnO<Subscript>3</Subscript> and La<Subscript>0.75</Subscript>MnO<Subscript>3</Subscript> orthorhombic crystals

The electronic structure of the LaMnO₃ orthorhombic crystal of a stoichiometric composition and of La_0.75MnO₃ crystals with a La vacancy in the unit cell is calculated in the LSDA+U approximation of density functional theory. The calculations showed that LaMnO₃ is an insulator with a forbidden gap of 0.5 eV and with antiferromagnetic ordering of magnetic moments. The magnetic moment on the manganese ions is 3.78 BM. The La atom has ionic bonds in the lattice, while the bond between oxygen and manganese is covalent. After lanthanum has been removed, geometry optimization of the unit cell leads to La_0.75MnO₃ stable structures. In one of the structures, which is lower in energy, the states of manganese may be attributed to Mn⁴⁺ ions. In both structures with removed lanthanum, the oxygen ions have reduced effective charge, so that one can speak about O^? ions appearing along with O^2? in the structure. The oxygen, as well as lanthanum and manganese, ions are nonequivalent in these structures; their nonequivalence is primarily reflected by the local densities of states. This leads to charge and magnetic nonequivalence of ions. In La_0.75MnO₃ crystals, the degree of bond covalence between manganese and oxygen decreases.     

Models of molecular structures of aluminum–iron clusters AlFe<Subscript>3</Subscript>, Al<Subscript>2</Subscript>Fe<Subscript>3</Subscript>, and Al<Subscript>2</Subscript>Fe<Subscript>4</Subscript> according to quantum-chemical DFT calculations

The geometrical parameters of molecular structures of three types of aluminum–iron clusters containing in total four, five, and six Al and Fe atoms in structural units have been calculated by the OPBE/TZVP density functional theory (DFT) method with the Gaussian09 program package. It has been found that the AlFe₃, Al₂Fe₃, and Al₂Fe₄ clusters can have four, eight, and nine structural modifications, which significantly differ in stability and geometric parameters. Bond lengths and bond and torsion (dihedral) angles are reported for each of these modifications.     

Reassessment of the structural composition of the alkenone distributions in natural environments using an improved method for double bond location based on GC-MS analysis of cyclopropylimines

The usefulness of n-propyl-, iso-propyl-, and cyclopropylamines for the location of double bonds positions in C37-C40 alkenones after formation of imino derivatives has been evaluated. Cyclopropylamine is the best reagent for its high reaction yields, GC retention time difference between derivatives and precursor compounds, and absence of generation of byproducts. The use of this C3 amine involves higher sensitivity and ease of application than previously reported C5 amines. Examination of a large group of alkenones from cultures of Emiliania huxleyi, water particles, and recent and ancient sediments with cyclopropylamine derivatization shows that, in all cases, the double bonds were located at the same carbon atom distance from the carbonyl group, and spaced in intervals of five methylene groups either from the carbonyl or between them, e.g., at sites 7, 14, 21, and 28. This result represents a correction from previous assumptions in which double-bond positions were situated by reference to the methyl end. 4,4-Dimethyloxazoline derivatization of hexatriacontenoates showed that these compounds have also their unsaturations with seven carbon atom spacing and counting by reference to the carboxyl group. The concurrence of both series of isomers in compounds of different oxygen functionalities indicates that the precursor haptophycean algal species have a major biosynthetic pathway leading to the formation of these lipids. The data presented in this work unify the structures of the known alkenones in the present and the recent past under a common metabolic pathway.     

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.     

A novel polyoxometalate chain constructed from sandwich lanthanide-containing polyanions [Pr(PW<Subscript>11</Subscript>O<Subscript>39</Subscript>)<Subscript>2</Subscript>]<Superscript>11−</Superscript> and sodium cation linkers

A novel sandwich-type lanthanide polyoxometalate [(CH₃)₄NH]₄Na₃[Pr(PW₁₁O₃₉)₂] · 12H₂O (1) has been synthesized by conventional method and characterized by cyclic voltammetry, IR spectroscopy and single crystal X-ray diffraction. X-ray diffraction result reveals that the sandwich type polyanions are linked by sodium cations to form a structure of zigzag chains, and the chains are further connected into an extensive two-dimensional (2D) framework depending on hydrogen bond. The emission spectrum result shows weak photoluminescence of compound 1. The magnetic studies of compound 1 demonstrate an antiferromagnetic interaction in 1.     

L-phenyl alanine-attached Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript> nanoparticles as an efficient catalyst for the synthesis of chromenes

In the present paper, L-phenyl alanine has been successfully linked on the surface of magnetic nanoparticles and has been characterized by FT-IR, XRD, SEM, EDS, TGA, and VSM techniques. This new catalyst was employed for one-pot synthesis of chromenes through the reaction of aldehydes, 4-hydroxycoumarin, and 2-hydroxynaphthalene-1,4-dione. Significant features of this method are short reaction time, excellent yields, use of green method, and the use of an effective and novel catalyst that could be recovered and reused several times without loss of its catalytic activity.     

Electron‐induced dissociation (EID) for structure characterization of glycerophosphatidylcholine: determination of double‐bond positions and localization of acyl chains

Glycerophospholipids are a highly abundant and diverse collection of biologically relevant lipids, and distinction between isomeric and isobaric species is a fundamental aspect for confident identification. The ability to confidently assign a unique structure to a glycerophospholipid of interest is dependent on determining the number and location of the points of unsaturation and assignment of acyl chain position. The use of high‐energy electrons (>20 eV) to induce gas‐phase dissociation of intact precursor ions results in diagnostic product ions for localizing double‐bond positions and determining acyl chain assignment. We describe a high‐resolution, tandem mass spectrometry method for structure characterization of glycerophospholipids using electron‐induced dissociation (EID). Furthermore, the inclusion of nomenclature to systematically assign bond cleavage sites with acyl chain position and double‐bond location enables a uniform platform for lipid identification. The EID methodology detailed here combines novel application of an electron‐based dissociation technique with high‐resolution mass spectrometry that facilitates a new experimental approach for lipid biomarker discovery and validation. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis of the mixed oxide catalysts based upon the nickel-copper hydrotalcites of the type Ni<Subscript>x</Subscript>Cu<Subscript>6-x</Subscript>Cr<Subscript>2</Subscript>(OH)<Subscript>16</Subscript>(CO<Subscript>3</Subscript>)×4H<Subscript>2</Subscript>O

Summary High resolution TG coupled to a gas evolution mass spectrometer has been used to study the thermal properties of a chromium based series of Ni/Cu hydrotalcites of formulae Ni_xCu_6-xCr₂(OH)₁₆(CO₃)×4H₂O where x varied from 6 to 0. The effect of increased Cu composition results in the increase of the endotherms and mass loss steps to higher temperatures. Evolved gas mass spectrometry shows that water is lost in a number of steps and that the interlayer carbonate anion is lost simultaneously with hydroxyl units. Differential scanning calorimetry was used to determine the heat flow steps for the thermal decomposition of the synthetic hydrotalcites. Hydrotalcites in which M²⁺ consist of Cu, Ni or Co form important precursors for mixed metal-oxide catalysts. The application of these mixed metal oxides is in the wet catalytic oxidation of low concentrations of retractable organics in water. Therefore, the thermal behaviour of synthetic hydrotalcites, Ni_xCu_6-xCr₂(OH)₁₆CO₃×nH₂O was studied by thermal analysis techniques in order to determine the correct temperatures for the synthesis of the mixed metal oxides.     

Phase equilibria in the Ce<Subscript>2</Subscript>O<Subscript>3</Subscript>-K<Subscript>2</Subscript>O-P<Subscript>2</Subscript>O<Subscript>5</Subscript> system

Ce₂O₃-K₂O-P₂O₅ ternary system has been investigated by thermoanalytical methods (DTA, DSC), powder X-ray diffraction, XPS and IR spectroscopy. The existence of three double potassium-cerium(III) phosphates has been confirmed and a new binary phosphate K₄Ce₂P₄O₁₅ has been found. Phase diagram and isothermal section at room temperature of the system Ce₂O₃-K₂O-P₂O₅ have been presented.     

Photooxidation of Ethylbenzene with TiO<Subscript>2</Subscript> and Metal Coated TiO<Subscript>2</Subscript> and its Kinetics

Summary. Photooxidation of ethylbenzene with oxygen to give ethylbenzene hydroperoxide has been achieved in a stirred photochemical reactor that was cooled by a water system by irradiation with a 400W high-pressure mercury lamp and using TiO₂ powder and metal coated TiO₂. The effects of the amount of copper or silver coated on TiO₂ and of the temperature on the rate of oxidation have been investigated. It is suggested that thermal cleavage of the O–O bond and photochemically generated singlet oxygen should be considered as the initiating step in a radical chain mechanism. An optimum loading of 6% Ag or 4–5% Cu was observed for photooxidation of ethylbenzene.     

A concise synthesis of furo[3,2-c]coumarins catalyzed by nanocrystalline ZnZr<Subscript>4</Subscript>(PO<Subscript>4</Subscript>)<Subscript>6</Subscript> ceramics under microwave irradiation

A simple and concise method catalyzed by nanocrystalline ZnZr₄(PO₄)₆ ceramics has been reported for the synthesis of a series of trans-2-benzoyl-3-(aryl)-2H-furo[3,2-c]chromen-4(3H)-ones using a multicomponent reaction of 2,4′-dibromoacetophenone, benzaldehydes and 4-hydroxycoumarin under microwave irradiation. This method provides several advantages including easy workup, excellent yields, short reaction times, using of microwave as clean method, recoverability of the catalyst and little catalyst loading.     

Electron interactions in the (η<Superscript>2</Superscript>-C<Subscript>60</Subscript>)Pd[P(Ph<Subscript>2</Subscript>)C<Subscript>5</Subscript>H<Subscript>4</Subscript>]<Subscript>2</Subscript>Fe complex

The electronic structure of the (η²-C₆₀)Pd[P(Ph₂)C₅H₄]₂Fe complex was calculated by the “hybrid” B3LYP method. Comparison of the experimental X-ray emission C-Kα spectrum and theoretical spectrum of the compound demonstrated that the electron interactions between the C₆₀ core, palladium atom, and organometallic fragment are described correctly in the framework of the quantum chemical method used. The electronic structure of the organometallic fullerene complex can be presented as a set of blocks of orbitals corresponding to different types of chemical bond. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2640–2644, December, 2005.     

Isomorphism in the KTaWO<Subscript>6</Subscript>-RbTaWO<Subscript>6</Subscript>-CsTaWO<Subscript>6</Subscript> system

Synthetic procedures have been developed and compounds of composition K _x Rb _y Cs _z TaWO₆ (x + y + z = 1) have been obtained. Their structure has been investigated by X-ray diffractometry. It has been shown that a continuous series of solid solutions is formed in the ternary system under study. Thermal decomposition of A^ITaWO₆ compounds (A^I = K, Rb, Cs) has been investigated by high-temperature X-ray diffractometry.     

Theoretical study on the H<Subscript>2</Subscript>S activation by PtCH<Subscript>2</Subscript><Superscript>+</Superscript> in the gas phase

The reaction mechanism of the gas-phase PtCH₂ ⁺ with H₂S has been systematically investigated on the doublet and quartet potential energy surfaces at BPW91/6-311++G(2d, p)∪ SDD level. The Pt in PtCH₂ ⁺ prefers to attack S–H bond in H₂S. For PtCH₂ ⁺ + H₂S reaction, the potential energy surfaces (PESs), including three reaction pathways of hydrogen (including one and two hydrogen elimination) and methane elimination, have been explored and characterized. By contrast with hydrogen elimination, methane elimination reaction channel is energetically favorable, which is in good agreement with the experimental observation. The optimal S–H bond activation is the first step, followed by cleavage of Pt–C and Pt–S bond. About the path a and b, the lowering of activation barrier is mainly caused by the more stabilizing transition state interaction \(\varDelta E_{\text{int}}^{ \ne }\), which is the actual interaction energy between the deformed reactants in the transition state.     

Catalytic hydrochlorination of acetylene on mechanochemically-activated K<Subscript>2</Subscript>PdCl<Subscript>4</Subscript>

We report the catalysis of the hydrochlorination of acetylene on the surface of dry K₂PdCl₄ subjected to prior mechanical activation in an atmosphere of acetylene or propylene. The stereochemistry of the reaction corresponds to trans addition of the halogen and hydrogen atoms to the C-C triple bond. The hydrogen halide is the source of the halogen atom in the reaction product. The mechanical activation of K₂PdCl₄, in contrast to the case of K₂PtCl₄, is also capable of activating the C-C double bond: propylene is hydrochlorinated under similar conditions to isopropyl chloride. Translated from Teoreticheskaya i éksperimental'naya Khimiya, Vol. 44, No. 5, pp. 306–309, September–October, 2008.     

Ruthenium Carbonyl Cluster Complexes with Phenylgermyl Ligands from the Reactions of Ph<Subscript>3</Subscript>GeH with Ru(CO)<Subscript>5</Subscript> and Ru<Subscript>3</Subscript>(CO)<Subscript>12</Subscript>

Four new triphenylgermylruthenium carbonyl compounds HRu(CO)₄GePh₃, 14; Ru(CO)₄(GePh₃)₂, 15; Ru₂(CO)₈(GePh₃)₂, 16; and Ru₃(CO)₉(GePh₃)₃(μ-H)₃, 17 were obtained from the reaction of Ru(CO)₅ with Ph₃GeH in hexane solvent at reflux, 68 °C. The major product 14 was formed by loss of CO from the Ru(CO)₅ and an oxidative addition of the GeH bond of the Ph₃GeH to the metal atom. This six coordinate complex contains one terminal hydrido ligand. Compound 15 is formed from 14 and contains two trans-positioned GePh₃ ligands in the six coordinate complex. Compound 16 contains two Ru(CO)₄(GePh₃) fragments joined by an Ru–Ru single bond. Compound 17 contains a triangular cluster of three ruthenium atoms with three bridging hydrido ligands and one terminal GePh₃ ligand on each metal atom. When heated to 125 °C, 14 was converted to the new triruthenium compound Ru₃(CO)₁₀(μ-GePh₂)₂, 18. Compound 18 consists of a triangular tri-ruthenium cluster with two GePh₂ ligands bridging two different edges of the cluster and one bridging CO ligand. Ru₃(CO)₁₂ was found to react with Ph₃GeH at 97 °C to yield three products: 15, and two new compounds Ru₃(CO)₉(μ-GePh₂)₃, 19 and Ru₂(CO)₆(μ-GePh₂)₂(GePh₃)₂, 20 were obtained. Compound 19 is similar to 18 having a triangular tri-ruthenium cluster but has three bridging GePh₂ ligands, one on each Ru–Ru bond. Compound 20 contains only two ruthenium atoms joined by a single Ru–Ru bond that has two bridging GePh₂ ligands and a terminal GePh₃ ligand on each metal atom. All compounds were characterized by a combination of IR, ¹H NMR, single-crystal X-ray diffraction analyses. This report is dedicated to Professor Dieter Fenske on the occasion of his 65th birthday for his many pioneering contributions to the chemistry of metal chalcogenide cluster complexes.     

Visible-light-driven photocatalytic degradation of microcystin-LR by Bi-doped TiO<Subscript>2</Subscript>

Bi-doped nano-crystalline TiO₂ (Bi–TiO₂) has been synthesized by sonocrystallization at low temperature. The Bi–TiO₂ materials have narrower bandgaps than pristine TiO₂, which endow them with significant visible light absorption. Accordingly, these materials had enhanced photocatalytic activity in the degradation of organic dye pollutants and the cyanotoxin microcystin-LR (MC-LR) under visible irradiation. It was found that degradation of MC-LR is rather efficient. After irradiation with visible light for 12 h the original MC-LR was removed completely, and 78% of the organic carbon was mineralized into CO₂ after irradiation for 20 h. The hydroxyl radical (·OH) is the major active species responsible for the degradation reaction. Identified intermediates primarily originate from attack of ·OH radicals on the double bonds between C4 and C5 (C6 and C7) of Adda and the ethylenic bond of Mdha in MC-LR. Some peptide bonds are also broken with longer irradiation time.     

Theoretical Study of the Solvent Effect on the Electronic and Vibrational Properties of [CpFe(CO)<Subscript>2</Subscript>(NCS)] and [CpFe(CO)<Subscript>2</Subscript>(SCN)] Linkage Isomers

The present study illustrates the stability of [CpFe(CO)₂(NCS)] and [CpFe(CO)₂(SCN)] linkage isomers by the use of MPW1PW91 quantum method in the gas and solution phases. Our results reveal that the [CpFe(CO)₂(NCS)] isomer is more stable than the [CpFe(CO)₂(SCN)] isomer. Based on the polarizable continuum model, the effect of the solvent polarity on the stability, structural parameters, frontier orbital energies, and vibrational modes of carbonyl ligands (ν_CO) of these linkage complexes is explored. The molecular orbital analysis suggests that the major contributions to HOMO and LUMO arise from the ambidentate ligand and Fe in two isomers, respectively. In addition, the bonding interaction between the CpFe(CO)₂ fragment and the ambidentate ligand is studied by means of the energy decomposition analysis. The back-bonding effect in Fe–CO bonds is revealed in the calculation of the quadrupole polarization of the carbon atom by the QTAIM analysis. The character of Fe–N and Fe–S bonds in these complexes is analyzed by the natural bond orbital analysis.