Macrocyclic effects upon isomeric CuIIMII and MIICuII cores. Formation with unsymmetric phenol-based macrocyclic ligands

This paper discusses coordination-position isomeric M^IICu^II and Cu^IIM^II complexes, using unsymmetric dinucleating macrocycles (L^m;n)²⁻ ((L^2;2)²⁻, (L^2;3)²⁻ and (L^2;4)²⁻) that comprise two 2-(N-methyl)-aminomethyl-6-iminomethyl-4-bromo-phenonate entities, combined through the ethylene chain (m = 2) between the two amine nitrogens and through the ethylene, trimethylene or tetramethylene chain(n = 2, 3 or 4) between the two imine nitrogens. The macrocycles have dissimilar N(amine)₂O₂ and N(imine)₂O₂ metal-binding sites sharing the phenolic oxygens. The reaction of the mononuclear Cu^II precursors, [Cu(L^2;2)], [Cu(L^2;2)] and [Cu(L^2;2)], with a M^II perchlorate and a M^II acetate salt formed (acetato)M^IICu^II complexes: [CoCu(L^2;2)(AcO)]ClO⁴·0.5H₂O] (1), [NiCu(L^2;2) (AcO)]ClO₄ (2), [ZnCu(L^2;2) (AcO)]ClO₄ (3), [CoCu(L^2;3)(AcO)]ClO₄·0.5H₂O (4), [NiCu(L^2;3)(AcO)]ClO₄ (5), [ZnCu(L^2;3)(AcO)]ClO₄·0.5H₂O (6), [CoCu(L^2;4)(AcO)(DMF)]ClO₄ (7), [NiCu(L^2;4) (AcO)]ClO₄·2DMF (8) and [ZnCu(L^2;4)(AcO)]ClO₄ (9) (the formulation [M_aM_b (L^m;n)]²⁺ means that M_a resides in the aminic site and M_b in the iminic site). The site selectivity of the metal ions is demonstrated by X-ray crystallographic studies for 2·MeOH,3,5,7, and9. An (acetato)Cu^IIZn^II complex, [CuZn(L^2;3)(AcO)]ClO₄ (10), was obtained by the reaction of [PbCu(L^2;3)]-(ClO₄)₂ with ZnSO₄·4H₂O, in the presence of sodium acetate. Other complexes of the Cu^IIM^II type were thermodynamically unstable to cause a scrambling of metal ions. The Cu migration from the iminic site to the aminic site in the synthesis of10 is explained by the ‘kinetic macrocyclic effect’. The coordination-position isomers,6 and10, are differentiated by physicochemical properties.     

Thermoanalytical Investigation of Magnesium(II) Complexes with Pyridine as Bio-Active Ligand

TG, DTA and other analytical methods were applied to investigate the thermal behaviour and structures of the compounds Mg(ClAc)₂(Py)₂·2H₂O (I), Mg(Cl₂Ac)₂(Py)·H₂O (II), Mg(Cl₃Ac)₂(Py)·6H₂O (III) and Mg(SCN)₂(Py)₃·2H₂O (IV), where ClAc=ClCH₂COO⁻, Cl₂Ac=Cl₂CHCOO⁻, Cl₃Ac=Cl₃CCOO⁻ and Py=Pyridine. The compositions of the complexes and the solid-state intermediates and products of thermolysis were identified by means of elemental analysis. Possible schemes of destruction of the complexes are suggested. The final products of the thermal decompositions were MgO (I–III) and MgS (IV). The IR data suggest unidentate coordination of the carboxylate ions to Mg(II) in complexes I–III. Py is coordinated to the Mg(II) through the nitrogen atom of its heterocyclic ring. This revised version was published online in August 2006 with corrections to the Cover Date.     

Synthesis and Characterization of Binuclear (μ-Oxalato) Copper(II) Complexes with N,N′-Diethylethylenediamine or N,N,N′-Trimethylethylenediamine

Three new binuclear w -oxalato copper(II) complexes of composition [(Cu(N,N' -dieten) H₂O)₂ox](ClO₄)₂ ·H₂O (1) (N,N'-dieten = N,N'-diethylethylenediamine, H₂ox = oxalic acid), [(Cu(trimeen)H₂O)₂ox](ClO₄)₂·2H₂O (2) (trimeen = N,N,N'-trimethylethylenediamine) and [(Cu(trimeen)H₂O)₂ox](NO₃)₂ ·2H₂O (3) have been isolated from the reactions of Cu(ClO₄)₂ ·6H₂O (or Cu(NO₃)₂ ·3H₂O), the appropriate amine and Na₂ox in water and have been characterized by IR and electronic spectroscopy and magnetic measurements. The crystal structure of [(Cu(N,N' -dieten)H₂O)₂ ox](ClO₄)₂.H₂O (1) has been determined by single-crystal X-ray analysis. The structure of ( 1 ) consists of binuclear cations [(N,N'-dieten)H₂O)Cu(ox)Cu(N,N'-dieten)H₂O)]²⁺, perchlorate anions and water molecules of crystallization. The copper atom is coordinated by two oxygen atoms of the oxalato ligand, two nitrogen atoms belonging to N,N'-dieten and one oxygen atom of water in a distorted square-pyramidal arrangement. The temperature dependence of magnetic susceptibilities (78-293 K) was measured for 1-3 . Magnetochemical measurements show that copper(II) ions in these compounds are antiferromagnetically coupled with J = -172 cm^-1, -172 cm^-1 and -168 cm^-1 (H = -2JS ₁ S ₂, S ₁= S ₂ = 1/2) for 1, 2 and 3, respectively.     

Thermal Behaviour of Some Polyhydrocarboxylic Coordination Compounds with Neodium

New Nd-Co based polynuclear coordination compounds containing as ligand polyhydrocarboxylic acid as tartaric, malic and gluconic acids were prepared, namely: [NdCo(tart)₃]·4H₂O, (NH₄)[NdCo_0.5Cu_0.5(tart)₃]·4H₂O, (NH₄)[NdCo(malic)₃]·4H₂O, (NH₄)[NdCo_0.5Cu_0.5(malic)₃]·4H₂O, [NdCo(gluc)₄]·4H₂O and [Nd₂CoCu(gluc)₇]·5H₂O. A comparison between the thermal behaviour of the studied polynuclear coordination compounds concerning thermal stability and thermal decomposition stoichiometry was inferred. Oxalic and malonic intermediates were identified at about 300°C in the thermal decomposition of tartaric and malic compounds. In all the decomposition processes at about 400°C the presence of oxocarbonate is shown. The residual products are mixed oxides of perovskite type. This revised version was published online in August 2006 with corrections to the Cover Date.     

Partial molar volumes and partial molar adiabatic compressibilities of potassium trioxalato complexes of Al(III), Fe(III), Co(III), and Cr(III) between 15° and 35°C

The apparent and limiting apparent molal volumes of dilute aqueous solutions of K₃[Al(ox)₃] · 3H₂O, K₃[Fe(ox)₃] · 3H₂O, K₃[Co(ox)3] · 3H₂O, and K₃[Cr(ox)₃] · 3H₂O complexes were determined from density data measured at 15°, 25°, and 35°C. The apparent and limiting apparent molal adiabatic compressibilities of these complexes were determined from measured ultrasonic sound velocities at 15°, 25°, and 35° in dilute aqueous solutions. The volume change associated with complex formation is discussed in terms of the nature of the coordinate bond and the overall hydration behavior of these complexes.     

Thermal and spectroscopic properties of light lanthanides (III) and sodium complexes of 2,5-pyridinedicarboxylic acid

Pyridine-2,5-dicarboxylic acid, known as isocinchomeric acid is one of six isomers containing two carboxylic groups. Light lanthanide (III) complexes with pyridine-2,5-dicarboxylic acid with general formula Ln₂L₃·nH₂O, where n = 8, 9, were obtained. Their thermal and spectroscopic properties were studied. Sodium salt was obtained as Na₂L·H₂O. Hydrated complexes of La(III), Ce(III), Pr(III), Nd(III), Sm(III), Eu(III) and Gd(III) are stable to 313–333 K, whereas Na₂L·H₂O is stable to about 333 K. Dehydration process for all compounds runs in one stage, next they decompose into appropriate lanthanide oxalates, oxocarbonates carbonates and finally to metal oxides. Bands of νCOOH vibrations at 1736 and 1728 cm⁻¹ disappear on complex spectra and ν_as and ν_s of COO⁻ groups appear thus indicating that complexation process took place.     

Thermal Studies on Some Lanthanide Complexes

The new mixed ligand complexes with the formulae Zn(2-bipy)(ox), Zn(4-bipy)_1.5 (ox)H₂ O, Zn(2,4'-bipy)₂ (ox)2H₂ O, Cd(2-bipy)(ox)2H₂ O, Cd(4-bipy)₂ (ox) and Cd(2,4'-bipy)(ox)2H₂ O (2-bipy, 4-bipy, 2,4'-bipy=2,2'-, 4,4'- and 2,4'bipyridine, ox=oxalate) were prepared. The thermal decompositions of these compounds were studied by means of TG, DTG and DTA in air. During heating the complexes decompose via different intermediate products to ZnO and CdO. The Zn(II) complexes are thermally more stable than the corresponding Cd(II) complexes. The influence of nitrogen atom position in the bipyridine isomers and nature of central atom on the thermal behaviour of these complexes was discussed. This revised version was published online in August 2006 with corrections to the Cover Date.     

Stabilization of Discrete [Cu(C2O4)2(H2O)2]2— Dianions in the Solid State by an Extensive Hydrogen Bonded Network

The dominant species in aqueous copper(II) solutions containing a high concentration of oxalate (ox) is trans‐[Cu(ox)₂(H₂O)₂]^2—, yet the ability of the oxalate anion to bridge metal ions means that very few examples of this isolated anion are seen in solid state structures. The structure of [pipH₂]²⁺[Cu(ox)₂(H₂O)₂]^2— · 2H₂O (pip = piperazine) ( 1 ) comprises discrete ions held in a complex 3‐dimensional hydrogen bonded network.     

Phase equilibrium system of RbCl-PrCl3-HCl(12.86 mass %)-H2O at 298.15 K and standard molar enthalpy of formation of new solid-phase compound

The equilibrium solubility of the quaternary system RbCl-PrCl₃-HCl-H₂O was determined at 298.15 K and the corresponding equilibrium diagram was constructed in this paper. The quaternary system is complicated with three equilibrium solid phases, RbCl, RbPrCl₄ · 4H₂O (1:1 type) and PrCl₃ · 6H₂O, of which the new compound RbPrCl₄ · 4H₂O was found to be congruently soluble in the system. The new compound obtained was identified and characterized by the methods of X-ray diffraction, thermogravimetry, and differential thermogravimetry. The compound loses its crystal water by one step at 343 K to 453 K. The standard molar enthalpy of solution of RbPrCl₄ · 4H₂O in deionized water was measured to be −24.53 ± 0.22 kJ mol⁻¹ by heat conduction microcalorimetry. Its standard molar enthalpy of formation was calculated to be −2743.20 ± 1.09 kJ mol⁻¹.     

Two New Layered Lanthanide‐Carboxylate Coordination Networks with Unusual Topologies

Two new rare earth coordination polymers, [Sm(HIDC)(ox)_0.5(H₂O)] ( 1 ) and [Pr(HIDC)(ox)_0.5(H₂O)₂] · H₂O ( 2 ) (H₃IDC = 4, 5‐imidazoledicarboxylic acid, ox = oxalate), were synthesized under hydrothermal conditions and characterized by elemental analysis, TGA, and single‐crystal X‐ray diffraction. They exhibit novel (3, 4)‐connected double and single layered architectures with unprecedented (6³)(6⁶) and (4.5²)(4.5³.7²) topologies, respectively. They are, to the best of our knowledge, the first examples constructed by IDC ligand combining with a second carboxylate ligand hitherto.     

The relationship between the structures of Cu(II) complexes and their chemical transformations

The paper reports an attempt to correlate the structures of hydrates of copper(II) sulphate with some characteristic features of the kinetics of their thermal decompositions. Non-isothermal thermogravimetric measurements were employed to obtain values of experimental activation energy and entropy for the dehydration of CuSO₄ · 5 H₂O, CuSO₄ · 3 H₂O and CuSO₄ · H₂O. The values ofE ^* andΔS ^* for the dehydration of CuSO₄ · 3 H₂O were found to be only little affected by the mode of preparation of this compound. On the other hand, the values ofE ^* andΔS ^* for the dehydration of CuSO₄ · ·H₂O are strongly dependent on whether this compound was prepared by thermal decomposition of CuSO₄ · 5 H₂O or CuSO₄ · 3 H₂O, or by crystallization from solution. As regards the crystalline hydrates of copper(II) sulphate, the greatest energetic hindrance for dehydration was observed for CuSO₄ · 3 H₂O. The experimental results are also discussed with respect to the present opinions concerning the possibilities of using thermal analyses to obtain information on the relationship between the structures and reactivities of solids.     

Synthesis,Structure and Property of a Dawson-type Arsenomolybdate with an Appended AsIII Cap

An inorganic–organic hybrid compound, (H₂bpy)₃[As^IIIAs₂ ^VMo₁₅ ^VIMo₃ ^VO₆₂]·3H₂O (bpy: 4,4′-bipyridine) (1) has been synthesized under hydrothermal conditions and characterized by elemental analysis, X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction, IR spectrum, UV–Vis spectrum, thermogravimetric analysis and single-crystal X-ray diffraction. The crystallographic analysis reveals that compound 1 is composed of a Wells–Dawson polyoxoanion [As₂ ^VMo₁₅ ^VIMo₃ ^VO₆₂]^9? with the mixed valence of Mo^V,VI, which acts as a tetradentate ligand coordinating with the As^III cation to form the mixed valence As^III,V containing arsenomolybdate with the single cap structure in a chelate coordination mode. In the solid state, compound 1 shows a 3D supramolecular structure through hydrogen-bonding interactions (C–H···O, N–H···O, N–H···N). In addition, compound 1 exhibits reversible multi-electron redox processes and effective electrocatalytic activities towards the reduction of H₂O₂, NaNO₂ and KBrO₃. Moreover, compound 1 is used as a reducing agent of the graphene oxide to prepare graphene by a green chemistry type one-step synthesis method, which is characterized by XPS, Raman spectroscopy, PXRD, IR, scanning electron microscopy and transmission electron microscopy.     

The structure,stability, and reactivity of oxalato-monoperoxovanadium(V) in solution

In order to understand the solution chemistry of an oxalato-monoperoxovanadium(V) complex (K₃[VO(O₂)(C₂O₄)₂] · ½H₂O, mpVox), the solid and solution-state NMR characteristics, transformation behavior, and exchange phenomena in the solution are described in this article. NMR experimental and theoretical results indicated that the vanadium of mpVox in solid and solution state are seven coordinate. However, some geometric parameters tend to change upon dissolution. The dynamic transformation of mpVox in solution was investigated using NMR, IR, and UV-Vis. The reduction product is oxalato-bisoxovanadate. Concentration, pH, and temperature affect this transformation. ⁵¹V NMR investigation on the system of mpVox with picolinc acid showed that two oxalates are substituted to produce [VO(O₂)(ox)(pic)]^2? and [VO(O₂)(pic)₂]^?.     

Synthesis of micro- and nanosized manganese oxides from hydrated manganese oxalates and products of their chemical modification with ethylene glycol

The reactions of ethylene glycol with manganese oxalates MnC₂O₄ · 2 H₂O and MnC₂O₄ · 3H₂O on heating in air were studied. At temperature below 100°C, ethylene glycol was found to displace water from oxalates to give a new solvate compound according to the reaction MnC₂O₄ · nH₂O + HOCH₂CH₂OH = MnC₂O₄(HOCH₂CH₂OH) + nH₂O↑. The crystals of the solvates retain the morphology of the initial oxalates, which is then inherited by the products of their thermolysis. Thus, thermolysis of MnC₂O₄ · 3H₂O and MnC₂O₄(HOCH₂CH₂OH) having quasi-unidimensional structure gave Mn₃O₄ and Mn₂O₃ nanowhiskers in air and MnO in an inert gas environment. Heating of MnC₂O₄ · nH₂O in ethylene glycol at temperatures above 100°C results in anhydrous manganese oxalate.     

Synthesis,crystal structure,and DNA binding of a new oxalato-bridged binuclear zinc(II) complex

A new binuclear zinc(II) complex bridged by μ-oxalate, and end-capped with 2,2′-bipyridine (bpy), [Zn₂(ox)(bpy)₄](ClO₄)₂ · H₂O, has been synthesized and characterized by elemental analyses, molar conductance, IR, and electronic spectra and single-crystal X-ray diffraction. The single-crystal X-ray analysis reveals that the [Zn₂(ox)(bpy)₄]²⁺ cation has two zinc(II) centers bridged by a planar bis(bidentate) oxalate group with Zn···Zn distance of 5.482(3) Å; each zinc(II) is in a distorted octahedral environment. The crystal structure is stabilized by non-classical C–H···O hydrogen bonds and π–π stacking interactions to form a 3-D supramolecular structure. The interaction of the complex with calf-thymus DNA (CT-DNA) was explored by using electronic and fluorescence spectra and viscosity measurements. The results reveal that the complex intercalates with CT-DNA with intrinsic binding constant of 4.1 × 10⁴ M^?1.     

1–D Framework l-arginine zinc(II) units bridged by oxalate: synthesis,structure, properties,and theoretical studies

We synthesized a l-arginine containing Zn²⁺ complex and oxalate ions. {[Zn₂(l-Arg)₂(ox)₂]·8H₂O}_n (1) (l-Arg =l-arginine, ox = oxalate) crystallize in the monoclinic space group P2₁ with a = 8.979(2), b = 9.840(2) (Å), c = 18.509(3) (Å), β = 95.58(3) (Å), V = 1627.6(6) ų, and Z = 2. The zinc centers are six-coordinate via one l-arginine zwitterion and two bridging oxalates. The binuclear [Zn₂(l-Arg)₂(ox)₂] units are linked via oxalate and form 1-D “stair-like” linear chains. The complex was characterized using FT-IR, FT-Raman, UV–vis spectroscopy, and thermal analysis techniques, as well as DFT methods. Electronic bands above 31,000 cm^?1 originate in ^1,3A_u (n→π*) transitions within oxalate ions. Theoretical studies were performed for the model compound {[Zn(l-Arg)(Hox)₂]·4H₂O} using the fragment of the crystallographic structure of 1. The interaction energy (ΔE) values for l-arginine and two oxalate ions are comparable at -145 kcal mol^?1. Natural bond orbital (NBO) analysis of the electronic structure and bonding is also discussed.     

Syntheses and characterization of three lanthanide(III) complexes containing pyridine-3,5-dicarboxylic acid and oxalic acid ligands

Direct reaction of pyridine-3,5-dicarboxylic acid (H₂PDA) and oxalic acid (H₂ox) with Ln(ClO₄)₃ · nH₂O under hydrothermal conditions gave three 3-D coordination networks, [Ln(PDA)(ox)_0.5(H₂O)₂] · H₂O [Ln = La(1), Nd(2), and Eu(3)]. The complexes were characterized by elemental analysis (EA), X-ray single-crystal diffraction, infrared spectroscopy (IR), and thermogravimetric analysis (TGA). Single crystal X-ray diffractions shows that the compounds are isomorphous and have 3-D framework structures, in which pyridine-3,5-dicarboxylates (PDA^2?) link lanthanides to give 2-D layers, which are further fabricated into a 3-D network via bis-bidentate oxalate bridging. Luminescence of 3 is investigated.     

多孔枝晶镍铜合金的制备及其电催化析氢、肼氧化性能

以镍网(NM)为基体,采用氢气泡模板法合成了独立分相金属Ni、Cu为主晶相、具有四级复合微纳结构的镍铜合金电催化剂(NiCu/NM)。在电催化析氢(HER)及肼氧化(HzOR)反应中,NiCu/NM表现出优良的催化活性,在1.0 mol·L^-1KOH(含0.5 mol·L^-1N2H4·H2O)溶液中,电流密度为10 mA·cm^-2时,其需要的HER及HzOR过电势分别为104和41 mV;在双电极体系中,电流密度为100 mA·cm^-2时,NiCu/NM的分解槽压仅为0.536 V,远低于全水分解过程所需的1.921 V,大大提高了电池的产氢效率。无论三电极体系还是双电极体系,NiCu/NM均表现出优异的催化活性及稳定性。分析认为,镍铜合金薄膜的多级复合结构使其展现出增大了近14倍的电化学活性面积(ECSA),为电催化反应提供了大量催化活性位点,也为电极表面的电荷传输、物质传递提供了充足的通道;Cu的掺入提高了材料的本征HER活性,两者协同促进了电催化活性的提升,其中NiCu/NM的结构优势对其优良的催化性能起主导作用。     

Studies on the magnetic properties of two cobalt(II) complexes bearing 1,4-phenylenediacetate ligands

One reported compound [Co(PDA)(4,4′-bipy)]_n·nH₂O and one new compound [Co(PDA)(Im)₂(H₂O)₂]_n·nH₂O were prepared by the reactions of Co(NO₃)₂·6H₂O or Co(OH)₂ with 1,4-phenylenediacetic acid (H₂PDA) in the presence of the ancillary ligands 4,4′-bipyridine (4,4′-bipy) or imidazole (Im), and their magnetic properties were investigated. The presence of 4,4′-bipy in [Co(PDA)(4,4′-bipy)]_n·nH₂O results in a μ ₃-bridging mode of the PDA²⁻ ligand with one μ ₂-carboxylato group and one chelating carboxylato group and the construction of a 2D framework as reported in the literature. The introduction of Im ligand in [Co(PDA)(Im)₂(H₂O)₂]_n·nH₂O helps to construct a one dimensional chain with the two carboxylato groups of PDA²⁻ ligand in monodentate coordination modes. The magnetic studies reveal the presence of dominant antiferromagnetic interaction in [Co(PDA)(4,4′-bipy)]_n·nH₂O with a field-induced magnetic transition due to spin-flop. Magnetically, [Co(PDA)(Im)₂(H₂O)₂]_n·nH₂O presents a mononuclear structure. This work reveals that the introduction of ancillary ligands in the Co(II)-PDA system adjusts the linking modes of PDA²⁻ and therefore the resulting frameworks and their magnetic properties.     

Novel Co(II) and Cd(II) complexes with non-steroidal anti-inflammatory drugs

New metal(II) complexes with empirical formulae Co(ibup)₂·4H₂O, Cd(ibup)₂·3H₂O, Co(nap)₂·H₂O, Cd(nap)₂·3H₂O (where ibup=(CH₃)₂CHCH₂C₆H₄CH(CH₃COO⁻) and nap=CH₃O(C₁₀H₆)CH(CH₃COO⁻)) were isolated and investigated. The complexes were characterized by elemental analysis, molar conductance, IR spectroscopy and thermal decomposition. The thermal behavior was studied by TG, DTG, DTA methods under non-isothermal conditions in air atmosphere. The hydrated complexes lose water molecules in first step. All complexes decompose via intermediate products to corresponding metal oxides CoO and CdO. A coupled TG-MS system was used to detect the principal volatile products of thermolysis and fragmentation processes of Co(nap)₂·H₂O. The IR spectra of studied complexes revealed also absorption of the carboxylate group. Principal concern with the position of asymmetric, symmetric frequencies. The value of their separation allow to deduce about type of coordination these groups.