Synthesis and magnetic properties of copper(II)-lanthanoid(III)-copper(II) trinuclear complexes with N,N′-bis(2-aminoethyl)-oxamido ligand

Summary Ten novel -oxamido trinuclear complexes, namely Cu₂–(oxae)₂Ln(ClO₄)₃ (Ln = Y, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb), where oxae donotes the N,N-bis(2-aminoethyl)-oxamido dianion, were prepared and characterized. The magnetic susceptibility of Cu₂(oxae)₂Gd(ClO₄)₃ was measured over the 4–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator . The exchange integrals J _(Gd-Cu) and J _Gd-Cu were found to be 2.37 and –0.71cm^-1, respectively, indicating that very weakly ferromagnetic spin-exchange interaction operates between copper(II) and gadolinium(III) ions.Visiting scholar: Qufu Normal University.     

Synthesis and magneto-structural correlation of a new maleato bridged copper(II) coordination polymer

A one-dimensional (1-D) copper(II) coordination polymer [Cu(maleate)(2,2′-bipyridyl)] _n ·2H₂O has been synthesised. Single crystal X-ray diffraction study reveals that maleate ion bridges two adjacent copper(II) centres along the chain in a syn–anti fashion. A complete cryomagnetic investigation of the title complex correlates well with the distorted square pyramidal geometry of the central copper(II) ion and bridging nature of the maleate. A τ value of 0.26 indicates the distortion towards tbp coordination allowing the magnetic orbital to acquire some character leading to a weak antiferromagnetic interaction having J = −0.26 cm⁻¹. The complex has also been firmly established from several other instrumental techniques like Fourier transform infrared (FT-IR) and EPR spectroscopies.     

Synthesis and Magnetism of Copper(II)-lanthanide(III)-copper(II) Heterotrinuclear Complexes with <Emphasis Type="Italic">N</Emphasis>,<Emphasis Type="Italic">N</Emphasis>′-bis [2-(dimethylamino)ethyl]oxamidocopper(II)

Nine new μ-oxamido-bridged copper(II)-lanthanide(III)-copper(II) heterotrinuclear complexes described by the overall formula Cu₂(dmoxae)₂Ln(NO₃)₃ {Ln = Ce, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er; dmoxae = N,N′-bis[2-(dimethylamino)ethyl]oxamido dianions} have been synthesized by the strategy of ‘complex as ligand’, and characterized by elemental analyses, molar conductivity measurements, i.r. and electronic spectral studies. The variable-temperature susceptibility (2–300 K), e.s.r. measurements, and studies of the Cu₂(dmoxae)₂Gd(NO₃)₃ complex have revealed that the central gadolinium(III) and terminal copper(II) ions are ferromagnetically coupled with the exchange integral J_(Cu-Gd) = +2.1 cm⁻¹, while an antiferromagnetic coupling is detected between the terminal copper(II) ions with J′_(Cu-Cu)=−0.36 cm⁻¹, on the basis of the spin Hamiltonian operator . A plausible mechanism for the ferromagnetic coupling between copper(II) and gadolinium(III) is discussed in terms of spin polarization.     

Synthesis and Magnetism of Ferromagnetically Coupled [Cu 3 II CrIII] Heterotetranuclear Complexes Bridged by Oxalate Groups

Three novel -oxalato-bridged Cu ₃ ^II Cr^III-type heterotetranuclear complexes described by the overall formula [Cu₃Cr(ox)₃L₃](ClO₄)₃, where ox represents the oxalato dianions, L stands for diaminoethane (en), 1,3-diaminopropane (pn), and 1,2-diaminopropane (ap) respectively, have been synthesized and characterized by elemental analyses, molar conductivity and magnetic moment (room-temperature) measurements, i.r., e.s.r. and electronic spectral studies. It is proposed that these complexes have oxalato-bridged structures consisting of three copper(II) ions and a chromium(III) ion, in which the chromium(III) ion has an octahedral environment and the three copper(II) ions have square-planar environments. Variable temperature magnetic susceptibility (4.2–300 K) measurements and studies of complexes [Cu₃Cr(ox)₃(en)₃](ClO₄)₃ (1) and [Cu₃Cr(ox)₃(pn)₃](ClO₄)₃ (2) revealed the occurrence of an intramolecular ferromagnetic interaction between the copper(II) and chromium(III) ions through the oxalato-bridge within each molecule. The magnetic data have been used also to deduce the indicated -oxalato-bridges [Cu ₃ ^II Cr^III] heterotetranuclear structure. On the basis of the spin Hamiltonian operator, , the magnetic analyses were carried out for the two Cu^II—Cr^III heterotetranuclear complexes and the spin-coupling constants (J) were evaluated as +6.36 cm^–1 for (1) and +7.02 cm^–1 for (2). The results indicate that the bridging oxalato entity should be able to transmit ferromagnetic interactions in the strict orthogonality [Cu ₃ ^II Cr^III] system.     

Oxygen non-stoichiometry and diffusion in RBA2CU3O6+x (R=Y, Gd, Ho) investigated by TG method

By means of thermogravimetry (TG) and chemical analysis equilibrium dependencies of oxygen content in GdBa₂Cu₃O_6+x and HoBa₂Cu₃O_6+x on temperature and were studied. It is found that at equal temperature and the oxygen content in RBa₂Cu₃O_6+x increased in order Ho-Y-Gd.On the basis of Fick 2nd law mathematical procedures to determine diffusion coefficients of oxygen from TG data were developed. The oxygen diffusion coefficients in RBa₂Cu₃O_6+x (R=Y, Gd, Ho) were evaluated in a wide temperature (300–900°C) range (at =0.21 bar). The developed model rather satisfactory decribes oxygen diffusion processes in phases under investigation. It is found that for all studied compounds oxygen diffusion in orthorhombic phase happened faster than in tetragonal one. The values of diffusion coefficients increase in order Ho-Y-Gd with increasing of ionic radius of the rare earth element.     

Solubility of Oxygen in Some 1-1, 2-1, 1-2, and 2-2 Electrolytes as a Function of Concentration at 25°C

The solubility of oxygen has been measured in a number of electrolytes [(LiCl, KCl, RbCl, CsCl, NaF, NaBr, NaI, NaNO₃, KBr, KI, KNO₃, CaCl₂, SrCl₂, BaCl₂, Li₂SO₄, K₂SO₄, Mn(NO₃)₃)] as a function of concentration at 25°C. The solubilities, mol (kg-H₂O)^–1, have been fitted to a function of the molality m (standard deviation < 3mol-kg^–1)

A Modified Kinetic Model for the Peroxydisulfate-Iodide Reaction

One kinetic model for the oxidation of iodide ion by peroxydisulfate ion in aqueous solution is proposed. The reaction is regarded as \documentclass{article}\pagestyle{empty}\begin{document} {\rm S}_2 {\rm O}_8^{2 -} + {\rm I}^ - {\rm IS}_2 {\rm O}_8^{3 -} \end{document}, followed by the reaction \documentclass{article}\pagestyle{empty}\begin{document} {\rm IS}_2 {\rm O}_8^{3 -} + {\rm I}l_2 + 2{\rm SO}_4^{2 -} \end{document}. If the initial rates V are obtained from the formation of the iodine molecules, the reaction rate constant k₁ and the ratio k₂/k_-1 can be estimated by plotting the values of [S₂O₈^2?][I^?]/V against that of 1/[I^?]. The extrapolated value for k₁ is 2.20×10^?2 L/mol-sec and k₂/k_-1 is calculated to be 4.25×10² mol/L at 27°C in a solution with an ionic strength of 0.420.     

Structure and electrical properties of oxygen-deficient strontium copper niobate

The transport properties of Sr_5.66 Cu_0.14Nb_2.20 O_11.30 double perovskite, which enters the homogeneity region of (Sr_1-y Cu _y )₆–_2x Nb_2+2x O_11+3x solid solution, are concerned. The total conductivity is differentiated into terms over wide ranges of temperatures and oxygen partial pressures $ p_{O_2 } $ p_{O_2 } in dry and humid atmospheres. When $ p_{O_2 } $ p_{O_2 } is low or high, a test sample has dominant electron transport of n- or p-type, respectively. In air ($ p_{O_2 } $ p_{O_2 } = 0.21 atm), the p-type electron conductivity term increases with temperature elevation. In a humid atmosphere ($ p_{H_2 O} $ p_{H_2 O} = 0.02 atm), a sample is capable of a reversible incorporation of water occlusion from the gas phase; as a result, some proton conductivity term appears and ion transference numbers increase over a wide range of $ p_{O_2 } $ p_{O_2 } values.     

Kinetics and mechanism of dissociation of copper(II) complexes of biguanide and someN 1-substituted biguanides in aqueous acetate buffer media

The kinetics fo dissociation of thebis complexes [Cu(LH)₂]²⁺ formed by Cu^II with biguanide andN ¹-substituted methyl, phenyl, dimethyl and diethyl biguanides into the mono biguanide complexes in aqueous NaOAc-HOAc buffer media have been studied by stopped-flow spectrophotometry. The results, under pseudo-first-order conditions, indicate k_obs=k_o+k_H[H⁺]. For the different complexes k_o values are comparable, but k_H values differ appreciably; log k_H versus log K _d ^H is linear withca. unit slope K _d ^H being the equilibrium constant for the process:

Molecular magnets based on chain polymer complexes of copper(II) bis(hexafluoroacetylacetonate) with isoxazolyl-substituted nitronyl nitroxides

First isoxazolyl-substituted nitronyl nitroxides (L and $L^{Me_2 }$ ) were synthesized and characterized. Their reactions with Cu(hfac)₂ and Mn(hfac)₂ (hfac is hexafluoroacetylacetonate) afford the heterospin complexes [Cu(hfac)₂L] _n , [Cu₂(hfac)₄L] _n , $\left[ {Cu_2 (hfac)_4 L^{Me_2 } } \right]_n$ , $\left[ {Cu(hfac)_2 L^{Me_2 } } \right]_n$ , $\left[ {Cu(hfac)_2 L^{Me_2 } _2 } \right]$ , $\left[ {Cu(hfac)_2 L^{Me_2 } (MeCN)} \right]$ , [Mn(hfac)₂]₃L₄, and $\left[ {Me(hfac)_2 L^{Me_2 } } \right]_2$ . In the ligand L, the N atom of the isoxazole ring (NIz) has weak electron-donating properties. For example, the paramagnetic ligand in the chain polymer complex [Cu(hfac)₂L] _n acts as a bidentate bridging ligand coordinated through both O atoms of the nitronyl nitroxide group (O_N-O); the N_Iz and O_Iz atoms are not involved in the coordination. The introduction of Me groups into the isoxazole substituent results in an increase in the electron density on the N_Iz atom and enables the synthesis of the chain polymer complex $\left[ {Cu(hfac)_2 L^{Me_2 } } \right]_n$ , in which the bidentate bridging ligand $L^{Me_2 }$ is coordinated through the O_N-O and N_Iz atoms. In the mononuclear complexes $\left[ {Cu(hfac)_2 L^{Me_2 } _2 } \right]$ and $\left[ {Cu(hfac)_2 L^{Me_2 } (MeCN)} \right]$ , the paramagnetic ligand is coordinated only through the N_Iz atom. The solid heterospin Mn complexes [Mn(hfac)₂]₃L₄ and $\left[ {Mn(hfac)_2 L^{Me_2 } } \right]_2$ have a molecular structure. In these complexes, strong antiferromagnetic intracluster exchange interactions arise. The residual magnetic moments of the exchange clusters in the complex [Mn(hfac)₂]₃L₄ are ferromagnetically coupled, resulting in the increase in the effective magnetic moment (??_eff) of the complex with decreasing temperature in the range of 300??30 K. The thermomagnetic study of the complexes [Cu(hfac)₂L] _n , [Cu₂(hfac)₄L] _n , and $\left[ {Cu_2 (hfac)_4 L^{Me_2 } } \right]_n$ in the range of 2?C300 K revealed the ferromagnetic ordering at temperatures below 5 K. The ESR study of the solid complex $\left[ {Cu(hfac)_2 L^{Me_2 } } \right]_n$ showed that the decrease in its ??_eff in the temperature range of 30?C300 K is associated with the direct exchange interaction between the unpaired electrons of the nitronyl nitroxides of adjacent chains, whereas at temperatures below 30 K, only Cu²⁺ ions contribute to the magnetic susceptibility of the complex.     

Mixed-Valence 24-Vanadophosphate Decorated with Six RuII(dmso)3 Groups: [{RuII3(dmso)9PVV11VIVRuIIIO37(OH)3}2]8?

The mixed-valence 24-vanadophosphate (1) has been synthesized and characterized in the solid state by IR, magnetism, EPR, XPS, and elemental analysis. Single-crystal X-ray analysis was carried out on (Na-1), which crystallizes in the triclinic system, space group , with a = 17.168(3) ?, b = 18.1971(14) ?, c = 20.1422(13) ?, α = 114.753(3)°, β = 99.390(4)°, γ = 95.124(4)°, and Z = 2. Polyanion 1 has an unusual, open structure composed of 2 Ru^IIIO₆ octahedra, 2 V^IVO₆ octahedra, 14 V^VO₅ square-pyramids, 8 V^VO₄ tetrahedra, and 2 PO₄ tetrahedra which are all directly linked via edges and corners. The outer surface of 1 is decorated with six Ru^II(dmso)₃ groups. XPS studies on Na-1 confirm the presence of 2 Ru^III and 6 Ru^II as well as 22 V^V and 2 V^IV centers. Magnetic susceptibility data on Na-1 show that the V^IV–Ru^III pairs are coupled antiferromagnetically, with J ₁ = −13 K and J ₂ ∼ −3 K. We did not detect any peak in our EPR measurements on Na-1, thus supporting the conclusion that Na-1 is diamagnetic in its ground state. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. In Memoriam Prof. F. A. Cotton     

Synthesis, characterization and redox properties of macrocyclic Schiff base by reaction of 2,6-diaminopyridine and 1,3- bis (2-carboxyaldehyde phenoxy)propane and its CuII, NiII, PbII, CoIII and LaIII complexes

A new macrocyclic ligand, 1,3,5-triaza-2,4:7,8:,14,15-tribenzo-9,13-dioxacyclohexadeca-1,5-diene (L) was synthesized by reaction of 2,6-diaminopyridine and 1,3-bis(2-carboxyaldehyde phenoxy)propane. Then, its Cu^II, Ni^II, Pb^II, Co^III and La^III complexes were synthesized by a template effect by reaction of 2,6-diaminopyridine and 1,3-bis (2-carboxyaldehyde phenoxy)propane and Cu O, Ni O, Co O, La O, respectively. The ligand and its metal complexes have been characterized by elemental analysis, IR, ¹H- and ¹³C-NMR-, UV-vis spectra, magnetic susceptibility, conductivity measurements, mass spectra and cyclic voltammetry. All complexes are diamagnetic and the Cu^II complex is binuclear. The diamagnetic behaviour of the binuclear complex may be explained by a very strong anti-ferromagnetic interaction in the Cu–Cu pair. The Co^II was oxidised to Co^III.     

The Formation and Stability of the [FePy3Cl3]· Py Clathrate in the Pyridine–Iron(III) Chloride System: Phase Diagram and Solid–Gas Equilibria Study

The phase diagram of the pyridine–iron(III) chloride system has been studied for the 223–423 K temperature and 0–56 mass-% concentration ranges using differential thermal analysis (DTA) and solubility techniques. A solid with the highest pyridine content formed in the system was found to be an already known clathrate compound, [FePy₃Cl₃]·Py. The clathrate melts incongruently at 346.9 ± 0.3 K with the destruction of the host complex: [FePy₃Cl₃]·Py_(solid)=[FePy₂Cl₃]_(solid) + liquor. The thermal dissociation of the clathrate with the release of pyridine into the gaseous phase (TGA) occurs in a similar way: [FePy₃Cl₃]·Py_(solid)=[FePy2Cl₃]_(solid) + 2 Py_(gas). Thermodynamic parameters of the clathrate dissociation have been determined from the dependence of the pyridine vapour pressure over the clathrate samples versus temperature (tensimetric method). The dependence experiences a change at 327 K indicating a polymorphous transformation occurring at this temperature. For the process in the range 292–327 K, ΔH =70.8 ± 0.8 kJ/mol, ΔS =197 ± 3 J/(mol K), ΔG =12.2 ± 0.1 kJ/mol; in the range 327–368 K, ΔH =44.4 ± 1.3 kJ/mol, ΔS =116 ± 4 J/(mol K), ΔG =9.9 ± 0.3 kJ/mol.     

High-pressure defect phase Ce x Cu3V4O12

Nonstoichiometric perovskite oxide Ce _x Cu₃V₄O₁₂ (space group Im $ \bar 3 Nonstoichiometric perovskite oxide Ce _x Cu₃V₄O₁₂ (space group Im Z = 2, a = 7.264–7.328 ?) with cationic vacancies was prepared barothermally. This compound has metal-type conductivity, paramagnetic properties, and a phase transition. Original Russian Text ? N.I. Kadyrova, Yu.G. Zainulin, V.L. Volkov, G.S. Zakharova, A.V. Korolev, 2008, published in Zhurnal Neorganicheskoi Khimii, 2008, Vol. 53, No. 10, pp. 1650–1654.     

Mixed-conducting dense ceramic membranes for air separation and natural gas conversion

Non-perovskite SrFeCo_0.5O _x (SFC2) was found to have high electronic and ionic conductivities as well as structural stability. At 800°C in air, total and ionic conductivities of 17 and 7 S·cm⁻¹ were measured, respectively; the ionic transference number was calculated to be ≈0.4. This material is unique because of its high electronic conductivity and comparable electronic and ionic transference numbers. X-ray diffraction analysis showed that air-sintered SFC2 consists of three phase components, ≈75 wt% , ≈20 wt% perovskite , and ≈5 wt% rock salt CoO. Argon-annealed SFC2 contains brownmillerite Sr₂(Fe_1−x Co _x )₂O₅ and rock salt CoO. Dense SFC2 membranes were able to withstand large pO₂ gradients and retain mechanical strength. A 2.9-mm-thick disk membrane was tested in a gas-tight electrochemical cell at 900°C; an oxygen permeation flux rate ≈2.5 cm³(STP)·cm⁻²·min⁻¹ was measured. A dense thin-wall tubular membrane of 0.75-mm thickness was tested in a methane conversion reactor for over 1,000 h. At 950°C, the oxygen permeation flux rate was ≈10 cm³(STP)·cm⁻²·min⁻¹ when the SFC2 thin-wall membrane was exposed with one side to air and the other side to 80% methane balanced with inert gas. Results from these two independent experiments agreed well. The SFC2 material is a good candidate as dense ceramic membranes for oxygen separation from air or for use in methane conversion reactors.     

Metal-ion directed synthesis of binuclear octaazamacrocyclic complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) and their physico-chemical studies

A novel series of 16-membered binuclear complexes of octaazatetraimine ligand, [M = Mn^II, Co^II, Ni^II, Cu^II and Zn^II; X = Cl or NO₃] have been synthesized by metal template condensation reactions of o-phenylenediamine with N,N′-diacetylhydrazine in 1:1:1 molar ratio in methanol. The proposed stoichiometry and the bonding of the macrocyclic moiety to metal ions along with the overall stereochemistry have been derived from the results of elemental analyses, magnetic susceptibility, conductivity data and the spectral data revealed from FT-IR, , ESI mass, UV–visible studies. An octahedral geometry has been envisaged for Mn^II, Co^II, and Ni^II complexes while a slight distortion in octahedral geometry has been noticed for Cu^II complexes. The low conductivity data of all the complexes suggest their non-ionic nature.     

An <Emphasis Type="Italic">ab initio </Emphasis> Quantum-Chemical Study of C<Subscript>6</Subscript>H<Subscript>5</Subscript>S(O)CH<Subscript>3</Subscript> and C<Subscript>6</Subscript>H<Subscript>5</Subscript>S(O)CF<Subscript>3</Subscript>

The potential functions of internal rotation around the C -S bond in the C₆H₅S(O)CH₃ and C₆H₅S(O)CF₃ molecules were obtained by ab initio MP2(full)/6-31+G* calculations. The stationary points were identified by solving the vibrational problems. The structures in which the plane of the C -S-C bonds is approximately perpendicular to the benzene ring plane correspond to the energy minimum. The barriers to rotation around the C -S bond, corrected for the zero-point vibration energy, are 21.29 [C₆H₅S(O)CH₃] and 28.98 [C₆H₅S(O)CF₃] kJ mol⁻¹. The bond angles (deg) are as follows: 95.7 (CSC), 107.1 (C SO), 106.3 (C SO) in C₆H₅S(O)CH₃; 93.5 (CSC), 108.2 (C SO), 105.2 (C SO) in C₆H₅S(O)CF₃. The bond lengths are as follows (Å): 1.520 (S=O), 1.804 (C -S), 1.810 (C -S) in C₆H₅S(O)CH₃; 1.507 (S=O), 1.799 (C -S), 1.870 (C -S) in C₆H₅S(O)CF₃. According to the results of NBO calculations, the formally double S=O bond consists of a strongly polarized covalent σ bond (S→O) and an almost ionic bond. An increase in the S=O bond multiplicity relative to a single bond is mainly due to hyperconjugation by the mechanism n(O)→σ*(C -S) and n(O)→σ*(C -S) and, to a lesser extent, by interaction of the oxygen lone electron pairs with the Rydberg orbitals of the S atoms, characterized by a large contribution of the d component.__________Translated from Zhurnal Obshchei Khimii, Vol. 75, No. 1, 2005, pp. 96–104.Original Russian Text Copyright © 2005 by Bzhezovskii, Il’chenko, Chura, Gorb, Yagupol’skii.     

The First Structurally Characterized Mn(III) Substituted Sandwich-type Polyoxotungstates

The new polyoxotungstates H₂O (1), · 28H₂O (2) and H₂O (3) were synthesized in aqueous solution and characterized by IR and Raman spectroscopy, energy dispersive X-ray fluorescence and single-crystal X-ray analysis. The anions in 1 and 2 are the first structurally characterized sandwich-type polyoxoanions which contain trivalent manganese atoms. The manganese atoms are coordinated by four oxygen atoms of two Keggin fragments and one water molecule, forming a square pyramid. The manganese(II) containing anions in 3 are linked via Mn–O–W-bonds, forming a two-dimensional network.Dedicated to Prof. M.T. Pope on the occasion of his retirement.     

Solubility of Siderite (FeCO3) in NaCl Solutions

The solubility of siderite (FeCO₃) at 25°C under constant CO₂ partial pressure [p(CO₂)] was determined in NaCl solutions as a function of ionic strength. The dissolution of FeCO₃(s) for the reaction