Studies on the EPR parameters and local angular distortion for the tetragonal Cu2+ center in CaWO4 crystal

The electron paramagnetic resonance (EPR) parameters—g factors g_i (i = || and ⊥) and hyperfine structure constants A_i (M) and A_i(N), with M and N belonging to isotopes ⁶³Cu²⁺ and ⁶⁵Cu²⁺—and local structure of Cu²⁺ ion occupying W⁶⁺ site in CaWO₄ crystal are theoretically studied based on the perturbation formulas of these parameters for a 3d⁹ ion under tetragonally elongated tetrahedra. In these formulas, the ligand orbital (LO) and spin–orbit coupling (SOC) contributions are included due to the shorter impurity-ligand distance R (≈1.83 Å) and hence the strong covalency of the studied [CuO₄]⁶⁻ cluster, and the related molecular orbital coefficients are quantitatively determined from the cluster approach in a uniform way; meanwhile, the required crystal field (CF) parameters for the tetragonally distorted tetrahedron (TDT) are estimated from the superposition model and the local structure of the impurity Cu²⁺ center. According to the calculation, the bond angle θ between the four equivalent Cu²⁺-O²⁻ bonds and the C₄ axis in the CaWO₄:Cu²⁺ is found to be about 2.1° smaller than that (θ₀ ≈ 54.74°) for an ideal tetrahedron due to the Jahn–Teller (JT) effect and the size mismatch. The fitted results agree well with the observed values, and the validity of the present assignment for the local structure of the Cu²⁺ center is also discussed.     

Studies on the local structures for the trigonal Ni3+ centers in cathode materials LiAlyCo1–yO2 (y = 0, 0.1, 0.5, and 0.8)

The local angular distortions Δθ are theoretically studied for the various Ni³⁺ centers in LiAl_yCo_1–yO₂ at different Al concentrations (y = 0, 0.1, 0.5, and 0.8) based on the perturbation calculations of electron paramagnetic resonance g factors for a trigonally distorted octahedral 3d⁷ cluster with low spin (S = 1/2). Due to the Jahn–Teller effect, the [NiO₆]^9– clusters are found to experience the local angular distortions (Δθ ≈ 5°–9°) along the C₃ axis. The variation trend of Δθ with y is in accordance with that of anisotropy (Δg = g_|| − g_⊥). As the substitutions can weaken bond strengths between transition metal and oxygen and the structural stability plays an important role in cathode performances, detailed investigations on the structural properties of the cathode materials LiAl_yCo_1–yO₂ can be practically helpful to understand the performances of these materials. The oxy‐redox properties of LiAl_yCo_1–yO₂ systems are comprehensible in the framework of Ni³⁺/Ni⁴⁺ couples, and the trigonally compressed octahedral [NiO₆]^9– clusters are applicable to the clarification of the electrochemical properties of lithium nickel oxide batteries. It appears that LiAl_0.8Co_0.2O₂ with the largest Al concentration may correspond to the smallest distortion among the mixing systems.     

Theoretical investigations on the defect structures and g factors for V4+ in 30PbO-5Bi2O3-(65-x)SiO2 glasses at different concentrations

For 3d¹ (V⁴⁺) impurity in 30PbO-5Bi₂O₃-(65-x)SiO₂ glass systems with different concentrations x of V2O5, the defect structures and gyromagnetic factors are theoretically investigated by using the perturbation formulas of g factors for a tetragonally compressed octahedral 3d¹ group. The concentration dependences of d-d transition band and g factors are suitably explained from the Fourier type concentration functions of the cubic crystal field parameter Dq, covalency factor N and relative tetragonal compression ratio ρ. The above concentration dependences of these quantities are suitably illustrated by the modifications of the local crystal field strength and electron cloud distribution with increasing x. The concentration variations of the electrical conductivity and dielectric relaxation are further analyzed from the stability of the systems in view of two competitive factors (increasing network polymerization and bulk stability at low concentrations and decreasing former SiO₂ and stability at high concentrations).     

Theoretical studies of the EPR parameters and local structures for the two Cu2+ centers in Cd(HCOO)2·2H2O

Based on the studies of the electron paramagnetic resonance parameters for two types of the Cu²⁺ centers in Cd(HCOO)₂·2H₂O by using the high‐order perturbation formulas for a 3d⁹ ion in a rhombically elongated octahedron, local structure of the doped copper ion is determined. Research suggests that the impurity Cu²⁺ replaces the host Cd²⁺ and undergoes the local rhombic elongation distortion, characterized by the axial elongation ratios of 4.1%, and 3.8% along the z‐axis and the planar bond length variation ratios of 3.8%, and 3.1% along the x‐axis and y‐axis, for Cu²⁺ Centers, I and II, respectively. The above slightly different axial elongation ratios and planar bond length variation ratios may suitably account for the slightly dissimilar axial g anisotropies Δg (≈0.351 and 0.339) and perpendicular g anisotropies δg (≈0.028 and 0.022) of the two centers, respectively.     

Cu(II) immobilized on guanidinated epibromohydrin‐functionalized γ‐Fe2O3@TiO2 (γ‐Fe2O3@TiO2‐EG‐Cu(II)): A highly efficient magnetically separable heterogeneous nanocatalyst for one‐pot synthesis of highly substituted imidazoles

A simple, efficient and eco‐friendly procedure has been developed using Cu(II) immobilized on guanidinated epibromohydrin‐functionalized γ‐Fe₂O₃@TiO₂ (γ‐Fe₂O₃@TiO₂‐EG‐Cu(II)) for the synthesis of 2,4,5‐trisubstituted and 1,2,4,5‐tetrasubstituted imidazoles, via the condensation reactions of various aldehydes with benzil and ammonium acetate or ammonium acetate and amines, under solvent‐free conditions. High‐resolution transmission electron microscopy analysis of this catalyst clearly affirmed the formation of a γ‐Fe₂O₃ core and a TiO₂ shell, with mean sizes of about 10–20 and 5–10 nm, respectively. These data were in very good agreement with X‐ray crystallographic measurements (13 and 7 nm). Moreover, magnetization measurements revealed that both γ‐Fe₂O₃@TiO₂ and γ‐Fe₂O₃@TiO₂‐EG‐Cu(II) had superparamagnetic behaviour with saturation magnetization of 23.79 and 22.12 emu g^?1, respectively. γ‐Fe₂O₃@TiO₂‐EG‐Cu(II) was found to be a green and highly efficient nanocatalyst, which could be easily handled, recovered and reused several times without significant loss of its activity. The scope of the presented methodology is quite broad; a variety of aldehydes as well as amines have been shown to be viable substrates. A mechanism for the cyclocondensation reaction has also been proposed.     

Thermal degradation of poly(acrylic acid) containing metal nitrates and the formation of YBa2Cu3O7−x

The use of polymers containing metal salts as ceramic high‐temperature superconductor (HTSC) precursors may provide a relatively simple and rapid method for producing materials that can take advantage of advanced polymer processing and then be pyrolyzed to HTSCs. The mechanisms of thermal degradation in these precursors, which have not been characterized, can be used to optimize the pyrolysis conditions for HTSC production. This article describes the degradation of a precursor based on poly(acrylic acid) (PAAc) containing yttrium, barium, and copper nitrates in the proportions needed for the formation of the HTSC YBa₂Cu₃O_7?x (YBCO). This article also describes the effects of the pyrolysis process on the resulting materials. The degradation of the precursor is a complex, multistage process. The presence of the metal ions and HNO₃ reduces the thermal stability of PAAc and increases the degradation rate. The results indicate that the initial stages of the pyrolysis should be conducted in argon or nitrogen to inhibit BaCO₃ formation and that the final stages should be conducted in air/oxygen to enhance oxidation. Optimization of the pyrolysis conditions produces a YBCO film with minimal contamination. © 2005 Wiley Periodicals, Inc. J PolymSci Part B: Polym Phys 43: 1168–1176, 2005     

Effect of metal cations [Li+, Na+, K+, Be2+, Mg2+, and Ca2+] on the structure of 2‐(3′‐hydroxy‐2′‐pyridyl)benzoxazole: A theoretical investigation

Density functional theory calculations were performed at the B3LYP/6‐311++G(d,p) level to systematically explore the geometrical multiplicity and binding strength for the complexes formed by alkaline and alkaline earth metal cations, viz. Li⁺, Na⁺, K⁺, Be²⁺, Mg²⁺, and Ca²⁺ (Mⁿ⁺, hereinafter), with 2‐(3′‐hydroxy‐2′‐pyridyl)benzoxazole. A total of 60 initial structures were designed and optimized, of which 51 optimized structures were found, which could be divided into two different types: monodentate complexes and bidentate complexes. In the cation‐heteroatom complex, bidentate binding is generally stronger than monodentate binding, and of which the bidentate binding with five‐membered ring structure has the strongest interaction. Energy decomposition revealed that the total binding energies mainly come from electrostatic interaction for alkaline metal ion complexes and orbital interaction energy for alkaline earth metal ion complex. In addition, the electron localization function analysis show that only the Be? O and Be? N bond are covalent character, and others are ionic character. © 2012 Wiley Periodicals, Inc.     

Nonisothermal crystallization and melting behavior of poly(β‐hydroxybutyrate)–Poly(vinyl‐acetate) blends

Nonisothermal crystallization and melting behavior of poly(β‐hydroxybutyrate) (PHB)–poly(vinyl acetate) (PVAc) blends from the melt were investigated by differential scanning calorimetry using various cooling rates. The results show that crystallization of PHB from the melt in the PHB–PVAc blends depends greatly upon cooling rates and blend compositions. For a given composition, the crystallization process begins at higher temperatures when slower scanning rates are used. At a given cooling rate, the presence of PVAc reduces the overall PHB crystallization rate. The Avrami analysis modified by Jeziorny and a new method were used to describe the nonisothermal crystallization process of PHB–PVAc blends very well. The double‐melting phenomenon is found to be caused by crystallization during heating in DSC. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 443–450, 1999     

3Mg(OH)2·MgSO4·8H2O: A Metastable Phase in the System Mg(OH)2‐MgSO4‐H2O

In the course of investigations relating to magnesia oxysulfate cement the basic magnesium salt hydrate 3Mg(OH)₂ · MgSO₄ · 8H₂O (3–1–8 phase) was found as a metastable phase in the system Mg(OH)₂‐MgSO₄‐H₂O at room temperature (the 5–1–2 phase is the stable phase) and was characterized by thermal analysis, Raman spectroscopy, and X‐ray powder diffraction. The complex crystal structure of the 3–1–8 phase was determined from high resolution laboratory X‐ray powder diffraction data [space group C2/c, Z = 4, a = 7.8956(1) Å, b = 9.8302(2) Å, c = 20.1769(2) Å, β = 96.2147(16)°, and V = 1556.84(4) ų]. In the crystal structure of the 3–1–8 phase, parallel double chains of edge‐linked distorted Mg(OH₂)₂(OH)₄ octahedra run along [–110] and [110] direction forming a pattern of crossed rods. Isolated SO₄ tetrahedra and interstitial water molecules separate the stacks of parallel double chains.     

Gas phase isomeric differentiation of oleanolic and ursolic acids associated with heptakis‐(2,6‐di‐O‐methyl)‐β‐cyclodextrin by electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry

Oleanolic acid (OA) and ursolic acid (UA) are isomeric triterpenoid compounds with similar pharmaceutical properties. Usually, modern chromatographic and electrophoretic methods are widely utilized to differentiate these two compounds. Compared with mass spectrometric (MS) methods, these modern separation methods are both time‐ and sample‐consuming. Herein, we present a new method for structural differentiation of OA and UA by Fourier transform ion cyclotron resonance mass spectrometry (FT‐ICR MS) with the association of heptakis‐(2,6‐di‐O‐methyl)‐β‐cyclodextrin (DM‐β‐CD). Exact MS and tandem MS (MS/MS) data showed that there is no perceptible difference between OA and UA, as well as their β‐cyclodextrin and γ‐cyclodextrin complexes. However, there is a remarkable difference in MS/MS spectra of DM‐β‐CD complexes of OA and UA. The peak corresponding to the neutral loss of a formic acid and a water molecule could only be observed in the MS/MS spectrum of the complex of DM‐β‐CD : OA. Molecular modeling calculations were also employed to further investigate the structural differences of DM‐β‐CD : OA and DM‐β‐CD : UA complexes. Therefore, by employing DM‐β‐CD as a reference reagent, OA and UA could be differentiated with purely MS method. Copyright © 2010 John Wiley & Sons, Ltd.     

Zinc(II) and Cadmium(II) Complexes of the 3‐(2‐Pyridyl)‐5,6‐diphenyl‐1,2,4‐triazine (PDPT) Ligand,Structural Studies of [Zn(PDPT)2Cl(ClO4)] and [Cd(PDPT)2(NO3)(ClO4)]

Two new mixed‐anion zinc(II) and cadmium(II) complexes of 3‐(2‐pyridyl)‐5,6‐diphenyl‐1,2,4‐triazine (PDPT) ligand, [Zn(PDPT)₂Cl(ClO₄)] and [Cd(PDPT)₂(NO₃)(ClO₄)], have been synthesized and characterized by elemental analysis, IR‐ and ¹H NMR spectroscopy. The single crystal X‐ray analyses show that the coordination number in these complexes is six with four N‐donor atoms from two “PDPT” ligand and two of the anionic ligands, ZnN₄ClO_perchlorate, CdN₄O_nitrateO_perchlorate. Self‐assembly of these compounds in the solid state via π–π‐stacking interactions is discussed.     

Cu(II) immobilized on Fe3O4–diethylenetriamine: A new magnetically recoverable catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H)‐ones and oxidative coupling of thiols

Cu(II) immobilized on Fe₃O₄–diethylenetriamine was designed as a new, inexpensive and efficient heterogeneous catalyst for the synthesis of 2,3‐dihydroquinazolin‐4(1H )‐ones and the oxidative coupling of thiols. The structure of the nanomagnetic catalyst was comprehensively characterized using Fourier transform infrared spectroscopy, scanning electron microscopy, energy‐dispersive X‐ray spectroscopy, vibrating sample magnetometry, thermogravimetric analysis, X‐ray diffraction and atomic absorption spectroscopy. Simple preparation of the catalyst from commercially available materials, high catalytic activity, simple operation, high yields, use of green solvents, easy magnetic separation and reusability of the catalyst with unaltered activity make our protocol a green and feasible synthetic strategy.     

IrIn7GeO8 = [IrIn6](GeO4)(InO4) und Verbindungen der Mischkristallreihe [IrIn6](Ge1+xIn1−4x/3O8) (0 ≤ x ≤ 0.75) – erste Oxide mit [IrIn6]‐Oktaedern

IrIn₇GeO₈ = [IrIn₆](GeO₄)(InO₄) and Compounds of the Solid Solution Series [IrIn₆](Ge_1+xIn_1?4x/3O₈) (0 ≤ x ≤ 0.75): First Oxides containing [IrIn₆] Octahedra The low valent indiumoxides IrIn₇GeO₈ = [IrIn₆](GeO₄)(InO₄) and [IrIn₆](Ge_1+xIn_1?4x/3O₈) (0 x ≤ 0.75) are formed by heating intimate mixtures of Ir, In, In₂O₃ and GeO₂ in corundum crucibles under an atmosphere of argon (1420 K, 70 h). The compounds are black and semiconducting. X‐ray powder diffraction patterns can be indexed on the basis of a face centered cubic unit cell with lattice parameters ranging from a = 1012.3(1) pm (x = 0) to a = 1007.3(1) pm (x = 0.75). Characteristic building units in [IrIn₆](Ge_1+xIn_1?4x/3O₈) are isolated [IrIn₆]⁹⁺ octahedra with short Ir‐In distances of 253.5 pm, which are linked via [GeO₄]^4? and [InO₄]^5? tetrahedra to a three dimensional framework. Starting from IrIn₇GeO₈ = [IrIn₆](GeO₄)(InO₄), the isoelectronic substitution of 4 In³⁺ ions by 3 Ge⁴⁺ ions and one Ge‐vacancy leads to the formation of a solid solution series [IrIn₆](GeO₄)_1+x(O₄)_x/3(InO₄)_1?4x/3, which shows a slight decrease in the cubic lattice parameter with increasing x. According to Rietveld refinements the structure of [IrIn₆](GeO₄)(InO₄) exhibits a statistical distribution of the tetrahedrally coordinated Ge and In atoms ( , R(prof.) = 4.4 %, R(int.) = 2.5 %). The crystal and electronic structures of [IrIn₆](GeO₄)(InO₄) are discussed on the basis of first principles electronic structure calculations.     

Tris[3‐hydroxy‐2(1 H)‐pyridinonato]‐Komplexe von Al3+, Cr3+ und Fe3+ – Kristall‐ und Molekülstrukturen von 3‐Hydroxy‐2(1 H)‐pyridinon und Tris[3‐hydroxy‐2(1 H)‐pyridinonato]chrom(III)

Tris[3‐hydroxy‐2(1 H)‐pyridinonato] Complexes of Al³⁺, Cr³⁺, and Fe³⁺ – Crystal and Molecular Structures of 3‐Hydroxy‐2(1 H)‐pyridinone and Tris[3‐hydroxy‐2(1 H)‐pyridinonato]chromium(III) Tris[3‐hydroxy‐2(1 H)‐pyridinonato] complexes of Al³⁺, Cr³⁺ and Fe³⁺ are obtained by reactions of 3‐hydroxy‐2(1 H)pyridinone with the hydrates of AlCl₃, CrCl₃ or Fe(NO₃) in aqueous alkaline solutions as polycrystalline precipitates. The compounds are isotypic. X‐ray structure determinations were performed on single crystals of the uncoordinated 3‐hydroxy‐2(1 H)‐pyridinone ( 1 ) (orthorhombic, space group P2₁2₁2₁, a = 405.4(1), b = 683.0(1), c = 1770.3(3) pm, Z = 4) and of the chromium compound 3 (rhombohedral with hexagonal setting, space group R3c, a = 978.1(1), c = 2954.0(1) pm, Z = 6).     

Poly(ε‐caprolactone)–poly(isobutylene): A crystallizing,hydrogen‐bonded pseudo‐block copolymer

The crystallization of block copolymers (BCPs) under homogeneous and heterogeneous nucleation is currently well understood revealing the strong interplay of crystallization in competition to microphase separation. This article reports investigations on synthesis and crystallization processes in weakly interacting supramolecular pseudo‐BCPs, composed of poly(ε‐caprolactone) (PCL) and poly(isobutylene) (PIB) blocks, connected by a specifically interacting hydrogen bond (thymine/2,6‐diaminotriazine). Starting from ring opening polymerization of ε‐caprolactone, the use of “click”‐chemistry enabled the introduction of thymine endgroups onto PCL polymer, thus generating the fully thymine‐substituted pure PCLs ( 1a , 1b ) as judged via NMR and MALDI analysis. Physical mixing of 1a , 1b with a bivalent, bis(2,6‐diaminotriazine)‐containing molecule ( 2 ) generated the bivalent polymers BC1 and BC2 , whereas mixing of 1a or 1b with the 2,6‐diaminotriazine‐substituted PIB ( 3 ) generated the supramolecular pseudo‐BCPs BC3 and BC4 . Thermal investigations (DSC, Avrami analysis) revealed only minor changes in the crystallization behavior of BC1 – BC4 with Avrami exponents close to three, indicative of a confluence of the growing crystals during the crystallization process. © 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011     

Magnetized inorganic–bioorganic nanohybrid [nano Fe3O4‐SiO2@Glu‐Cu (II)]: A novel nanostructure for the efficient solvent‐free synthesis of thiazolidin‐2‐imines

In this research, a solvent‐free four‐component one‐pot reaction of phenyl isothiocyanate, phenylacetylene, various kinds of aldehydes, and amines was interpreted to obtain the desired five‐membered heterocycles named thiazolidin‐2‐imines. The promotor of this transformation is a novel magnetite‐based multilayered inorganic–bioorganic nanohybrid prepared via embedding glutamic acid on the magnetized silica followed by anchoring Cu (II) [nano Fe₃O₄‐SiO₂@Glu‐Cu (II)]. The newly synthesized nanostructure is characterized through Fourier‐transform infrared (FT‐IR), field‐emission scanning electron microscopy (FESEM), energy dispersive X‐ray analysis (EDAX), transmission electron microscopy (TEM), X‐ray fluorescence (XRF), thermogravimetric analysis or derivative thermogravimetric (TGA/DTG), vibrating sample magnetometer (VSM), X‐ray photoelectron spectroscopy (XPS), and Brunauer–Emmett–Teller (BET) techniques. This protocol is a straightforward one‐step procedure to obtain thiazolidin‐2‐imines without requirement to propargylamines or imines as substrates. In addition, easy work‐up procedure, high yields of products, absence of organic solvents in the reaction media, recovery and reusability of nano Fe₃O₄‐SiO₂@Glu‐Cu ( II) to promote the reaction at least for three runs without activity lost, simple separation of the catalyst from reaction mixture via an external magnet, and regioselectivity of the method are some highlighted aspects of the approach.     

Tl4Pd3Cl10 – eine Verbindung mit neuartiger [(PdCl2Cl2/2)4]4–‐Baugruppe

Tl₄Pd₃Cl₁₀ – A Compound with a New [(PdCl₂Cl_2/2)₄]^4– Group Single crystals of Tl₄Pd₃Cl₁₀ can be obtained by hydrothermal synthesis. They show tetragonal symmetry with lattice parameters a = 15.956(1) Å and c = 14.146(1) Å, Z = 8 and space group I42d (No. 122). The atomic arrangement of Tl₄Pd₃Cl₁₀ is explored by X‐ray crystal structure analysis. Tl₄Pd₃Cl₁₀ is the first example of a new structural type with a hitherto not isolated tetramer [(PdCl₂Cl_2/2)₄]^4– group.     

1‐(α‐Aminobenzyl)‐2‐naphthol as phosphine‐free ligand for Pd‐catalyzed Suzuki and one‐pot Wittig‐Suzuki reaction

Air stable and easily accessible, 1‐(α‐aminobenzyl)‐2‐naphthols are used as efficient phosphine‐free ligands in palladium‐catalyzed Suzuki reaction for a variety of substrates under conventional heating as well as ultrasonic conditions. Multi‐brominated aromatic substrates were successfully converted to corresponding arylated moieties with good conversion and selectivity. A novel one‐pot two‐step cascade reaction strategy involving Wittig and Suzuki reactions is developed for efficient synthesis of 4‐styryl biphenyls (C₆‐C₂‐C₆‐C₆ unit). Copyright © 2012 John Wiley & Sons, Ltd.     

Structure of tetra[β‐(1,2,4‐triazole‐l‐yl) propiophenone] dichloro nickel(II) solvate hexahydrate complex: [NiCl2(C2H2N3CH2CH2‐COPh)4]·6H2O

The mononuclear complex, [NiCl₂ (trzCH₂CH₂COPh)₄]·6H₂O (trz =1,2,4‐triazole), was synthesized and its structure was determined by single crystal X‐ray determination. It crystallizes in the monoclinic system, space group P2₁/c, with lattice parameters: a = 0.80391(2) nm, b = 1.08215(2) tun, c = 2.90133(2) nm, β = 94.792 (1)° and Z = 2. Each nickel atom is coordinated by four N atoms of triazole from four β‐(1,2,4‐triazole‐1‐yl)propiophenone ligands and two chloride anions in trans arrangement with octahedral coordination geometry. In addition to the coordinating nickel complex, there are six uncoordinated water molecules. The Ni‐Cl distance is 0.24865(8) nm and the Ni‐N distances are in the range of 0.2072(2) to 0.2099(2) nm, respectively. In the solid state, the title compound forms three dimensional network structure through hydrogen bonds. The intermolecular hydrogen bonds connect the [NiCl₂(C₂H₂N₃CH₂CH₂COPh)₄] and H₂O moieties. The deep green crystals were also examined by elemental analysis, FT‐IR and UV spectra, which are in agreement with the structural data.