Characterization and crystal structures of copper(II), cobalt(II), and nickel(II) complexes with two kinds of piperidine carboxylic acids

Copper(II) complex with -piperidine-3-carboxylic acid ( -Hpipe-3):[Cu( -pipe-3)₂(H₂O)] and cobalt(II) and nickel(II) complexes with piperidine-4-carboxylic acid (Hpipe-4):[M(Hpipe-4)₂(H₂O)₄]Cl₂ (M: Co, Ni) have been prepared and characterized by means of IR and powder diffuse reflection spectra, thermal analysis, and magnetic susceptibility. The crystal structures of these complexes have been determined by X-ray diffraction. The crystal of [Cu( -pipe-3)₂(H₂O)] is orthorhombic with the space group Pbcn. The copper atom is in a square pyramidal geometry, ligated by two carboxylato oxygen atoms, two nitrogen atoms, and a water molecule. One molecule of this complex consists of either -piperidine-3-carboxylic acid or -piperidine-3-carboxylic acid. The crystals of [M(Hpipe-4)₂(H₂O)₄]Cl₂ are monoclinic with space group P2₁/n. In these complexes the metal atom is in an octahedral geometry ligated by two carboxylato oxygen atoms and four water molecules.     

Synthesis, characterization and structure of complexes of o-aminophenol-N,N,O-triacetic acid with cobalt(II), nickel(II), manganese(II) and zinc(II)

The potassium salt of o-aminophenol-N,N,O-triacetic acid (APTA) and KMnL·H₂O, KCoL·3H₂O, KNiL·3H₂O, KZnL·3ZH₂O, Co(CoL)₂·7H₂O and Ni(NiL)₂·8H₂O(L³⁻:anion of APTA) have been synthesized and characterized by elementary analysis, thermogravimetric analysis, molar conductance, IR spectra, magnetic measurements and electronic spectra. The coordination environments of these metal ions have been discussed on the basis of these studies. The single crystal structure of cobalt(II)-APTA has been determined as CoL·0.5Co(H₂O)₆·4H₂O, which contains two types of cobalt(II). One type of cobalt(II) is coordinated with six water molecules to form Co(H₂O)₆²⁺, the other is chelated by APTA to form a distorted octahedron and linked into an infinite chain anion [COC₆H₄(OCH₂COO)N(CH₂COO)₂⁻]_n, in which each cobalt(II) atom is linked with neighbouring cobalt(II) atoms through two carboxylate oxygen atoms of the phenoxyacetate group. Water molecules occupy interstices in the structure.     

Cyano-bridged bimetallic complexes of copper(II) with tetracyanonickelate(II). Crystal structure of [Cu(dpt)Ni(CN)4]

Five new complexes of composition [Cu(dpt)Ni(CN)₄] (1) (dpt=dipropylenetriamine), [Cu(dien)Ni(CN)₄]·2H₂O (2) (dien=diethylenetriamine), [Cu(N,N′-dimeen)Ni(CN)₄]·H₂O (3) (N,N′-dimeen=N,N′-dimethylethylenediamine), [Cu(N,N-dimeen)Ni(CN)₄]·H₂O (4) (N,N-dimeen=N,N-dimethylethylenediamine) and [Cu(trimeen)Ni(CN)₄] (5) (trimeen=N,N,N′-trimethylethylenediamine) have been obtained by the reactions of the mixture of Cu(ClO₄)₂·6H₂O, appropriate amine and K₂[Ni(CN)₄] in water and have been characterized by IR and UV–Vis spectroscopies and magnetic measurements. The crystal structure of [Cu(dpt)Ni(CN)₄] (1) has been determined by single-crystal X-ray analysis. The structure of 1 consists of a one-dimensional polymeric chain ---Cu(dpt)---NC---Ni(CN)₂---CN---Cu(dpt)--- in which the Cu(II) and Ni(II) atoms are linked by CN groups. The nickel atom is four coordinate with four cyanide-carbon atoms (two cyano groups are terminal and two cyano groups (in cis fashion) are bridged) in a square-planar arrangement and the copper atom is five coordinate with two cyanide-nitrogen and three dpt-nitrogen atoms, in a distorted square-pyramidal arrangement. The temperature dependence of magnetic susceptibility (2–300 K) was measured for compound 1. The magnetic investigation showed the presence of a very weak antiferromagnetic interaction (J=−0.16 cm⁻¹) between the copper atoms within each chain through the diamagnetic Ni(CN)₄ ²⁻ ions.     

Neutral pyridylmethylamide ligands and their mononuclear copper(II) complexes

Mononuclear copper(II) complexes of a family of pyridylmethylamide ligands HL, HL^Me, HL^Ph, HL^Me3 and HL^Ph3, [HL = N-(2-pyridylmethyl)acetamide; HL^Me = N-(2-pyridylmethyl)propionamide; HL^Ph = 2-phenyl-N-(2-pyridylmethyl)acetamide; HL^Me3 = 2,2-dimethyl-N-(2-pyridylmethyl)propionamide; HL^Ph3 = 2,2,2-triphenyl-N-(2-pyridylmethyl)acetamide], were synthesized and characterized. The reaction of copper(II) salts with the pyridylmethylamide ligands yields complexes [Cu(HL)₂(OTf)₂] (1), [Cu(HL^Me)₂](ClO₄)₂ (2), [Cu(HL)₂Cl]₂[CuCl₄] (3), [Cu(HL^Me3)₂(THF)](OTf)₂ (4), [Cu(HL^Me3)₂(H₂O)](ClO₄)₂ (5a and 5b), [Cu(HL^Ph3)₂(H₂O)](ClO₄)₂ (6), [Cu(HL)(2,2′-bipy)(H₂O)](ClO₄)₂ (7), and [Cu(HL^Ph)(2,2′-bipy)(H₂O)](ClO₄)₂ (8). All complexes were fully characterized, and the X-ray structures vary from four-coordinate square-planar, to five-coordinate square-pyramidal or trigonal-bipyramidal. The neutral ligands coordinate via the pyridyl N atom and carbonyl O atom in a bidentate fashion. The spectroscopic properties are typical of mononuclear copper(II) species with similar ligand sets, and are consistent their X-ray structures.     

Novel coordination of a hydroxamic acid : Crystal structures of bis(glycinohydroxamoto)nickel(II) and tris(glycinohydroxamoto)cobalt(III)

The structures of two glycinohydroxamoto (GHA) complexes of Ni(II) and Co(III) have been determined by single-crystal X-ray diffraction methods. The crystals of Ni(GHA)₂ are monoclinic with a = 5.360(1), b = 7.315(4), c = 10.194(4) Å, β = 96.57(3), Z = 2, and space group P2₁/c. The crystals of Co(GHA)₃•1/2 H₂O are monoclinic with a = 22.467(19), b = 8.041(4), c = 13.700(11) Å, β = 116.01(7), Z = 8, and space group C2/c. The values of the final residuals R for Ni(GHA)₂ and Co(GHA)₃•1/2 H₂O are 0.0275 and 0.032, respectvely. The molecular structures of Ni(GHA)₂ and Co(GHA)₃ consist of a square planar and an octahedral coordination, respectively, with the glycinohydroxamato (NH₂CH₂CONOH⁻) ligands coordinating to the metal ion via the N (amino) and the N (NOH⁻). These two complexes are the first well-established cases of coordination of the NHO⁻ group of a hydroxamic acid to a transition metal via the nitrogen atom.     

Molecular, supramolecular structure and catalytic activity of transition metal complexes of phenoxy acetic acid derivatives

Six mononuclear complexes [M(L₁)₂(H₂O)₄] (M = Co(II), 1a and M = Mn(II), 1b), [Cu(L₁)₂(H₂O)₂] (1c), [Cu(L₁)₂(H₂O)(Py)₂] (1d), [Cu(L₃)(H₂O)Cl] · H₂O (3a) and [Co(Sal)(H₂O)(Py)₃] · 2ClO₄ · H₂O (3b) of phenoxyacetic acid derivatives and Schiff base were determined by single crystal X-ray diffraction. The Co(II) (1a) and Mn(II) (1b) complexes are isomorphous. X-ray crystal structural analyses reveal that these coordination complexes form polymeric structure via formation of different types of hydrogen bonding and π-stacking interactions in solid. Thermal analysis along with the powder X-ray diffraction data of these complexes shows the importance of the coordinated and/or crystal water molecules in stabilizing the MOF structure. Complexes 1a, 1c, 3a show marginal catalytic activity in the oxidation of olefins to epoxides in the presence of i-butyraldehyde and molecular oxygen.     

Thermal decomposition study on mixed ligand thymine complexes of divalent nickel(II) with dianions of some dicarboxylic acids

Thermal decomposition of mixed ligand thymine (2,4-dihydroxy-5-methylpyrimidine) complexes of divalent Ni(II) with aspartate, glutamate and ADA (N-2-acetamido)iminodiacetate dianions was monitored by TG, DTG and DTA analysis in static atmosphere of air. The decomposition course and steps of complexes [Ni(C₅H₆N₂O₂)(C₄H₅NO₄)²⁻(H₂O)₂]·H₂O, [Ni(C₅H₆N₂O₂)(C₅H₇NO₄)²⁻(H₂O)₂]·H₂O and [Ni(C₅H₆N₂O₂)(C₆H₈N₂O₅)²⁻(H₂O)₂]·1.5H₂O were analyzed. The final decomposition products are found to be the corresponding metal oxides. The kinetic parameters namely, activation energy (E*), enthalpy (ΔH*), entropy (ΔS*) and free energy change of decomposition (ΔG*) are calculated from the TG curves using Coats–Redfern and Horowitz–Metzger equations. The stability order found for these complexes follows the trend aspartate > ADA > glutamate.     

Synthesis, spectral properties, crystal structures and antimicrobial effects of copper(II) pyridinecarboxylate adducts with chelating ligands

The reaction of an ethanolic solution of copper(II) pyridinecarboxylates CuX₂·nH₂O (where X is nicotinate (nic) (n=0) or isonicotinate (isonic) (n=4)) with ethylenediamine (en) in a molar ratio of 1:2 lead to the isolation of solid tetragonally distorted octahedral complexes of the type [Cu(en)₂(H₂O)₂]X₂·nH₂O (n=1 for nic; n=0 for isonic). The analogous reaction of CuX₂·nH₂O with diethylenetriamine (dien) in a molar ratio of 1:1 leads to the formation of square-pyramidal pentacoordinated complexes of the type [CuX(dien)(H₂O)]X. On the other hand, the reaction of equimolar quantities of copper(II) nitrate and dien with nicotinate anions (equimolar quantities of pyridinecarboxylic acid and NaOH) in ethanolic solutions gives a solid monomeric complex [Cu(nic)(NO₃)dien)(H₂O)]·H₂O in which the coordination polyhedron around the Cu(II) atom is a (4+1+1) distorted tetragonal bipyramid. Based on the molecular structure the electronic and IR spectra are discussed. Moreover, the results of the quantitative determination of antimicrobial activity of the isonic complexes [Cu(isonic)₂(H₂O)₄], [Cu(en)₂(H₂O)₂](isonic)₂, [Cu(isonic)(dien)(H₂O)](isonic), as well as isonicotinic acid, ethylenediamine and diethylenetriamine alone are discussed.     

Dinuclear transition metal compounds of a decadentate pyrazole-containing chelating ligand. X-ray crystal structure of Co2(tthd)(ClO4)4(H2O)2(MeOH)1.75

A potentially decadentate ligand, 1,1,4,7,10,10-hexakis(3,5-dimethyl-1-pyrazolylmethyl)-1,4,7,10-tetraazadecane (tthd), has been synthesized from the reaction of tri-ethylenetetramine with six equivalents of N-hydroxymethyl-3,5-dimethylpyrazole. The tthd ligand forms coordination compounds, M₂(tthd)(ClO₄)₄(H₂O)_x, when M is Co, Ni, Cu, Zn and Cd and x = 4–8; and M₂(tthd)(A)₂(ClO₄)₂(H₂O)_x when M is Co and Ni, A is NCS or Cl, and x = 4–8. The cobalt compound, Co₂(tthd)(ClO₄)₂(H₂O)₂(MeOH)_1.75, crystallizes in the triclinic space group P1, a = 1.959(2), b = 1.5657(3), c = 2.1244(3) nm, = 105.5(1), β = 96.9(1), γ = 112.1(1). Due to severe disorder of the anions the structure could only be refined to an R_w, value of 0.099. The ligand acts as a decadentate, dinucleating ligand. The cobalt ions are distorted octahedrally surrounded by five N-atoms of the tthd ligand and an O-atom of water occupying the sixth coordination place. The other perchlorate compounds have very similar structures, as can be concluded from spectroscopic data.

In the thiocyanate and chloride compounds the anions have replaced the coordinated water molecules, resulting in octahedral Ni compounds. With Co thiocyanate, however, tthd acts as an octadentate ligand, resulting only in five-coordinated compounds.     

Thermodynamic, crystallographic and solvent extraction properties of cobalt(II), nickel(II) and copper(II) complexes of ethylenediamine- N,N,N′,N′-tetraacetanilide

Complexes of ethylenediamine-N,N,N′,N′-tetraacetanilide (edtan, C₃₄H₃₆N₆O₁₄) with cobalt(II), nickel(II) and copper(II) in the solid state and in solution are reported for the first time. Thermodynamic data (stability constant, and derived Gibbs energy, enthalpy and entropy changes)for the 1 : 1 complexation of edtan with the metal ions at 298.15 K in water-saturated butan-1-ol gave the selectivity sequence log₁₀K_s; Ni²⁺, 4.56±0.02; Cu²⁺, 4.41±0.01; Co²⁺, 4.18±0.04 as found from microcalorimetric titration studies. The entropies suggested that the structure of the 1 : 1 complex with copper(II) contains fewer chelate rings than those for nickel(II) and cobalt(II) (δ_cS⁰ : Cu-21.4, Co 5.7, Ni 3.9 J mol⁻¹K⁻¹). Solid complexes of the metal ions with edtan and perchlorate as the counter anion were prepared. For each, a complex with a 1 : 1 metal: edtan stoichiometry with non-coordinated perchlorate was isolated. The X-ray structure of [Cu(edtan)(H₂O)][ClO₄]₂·1.5H₂O (1) revealed a six-coordinate Cu centre with edtan acting as pentadentate ligand (2N, 3O) with the coordination sphere completed by an oxygen atom from water. In striking contrast to the Cu complex, the Co centre in [Co(edtan)(H₂O)][ClO₄]₂·H₂O·0.5C₂H₅OH (2) is seven-coordinate with hexadentate edtan (2N, 4O) and one coordinated water molecule. There is thus an excellent confirmation of the results obtained from the microcalometric study in that edtan forms four chelate rings to Cu but five to Co in the solid state. The ability of the ligand to extract metal ions from water to the water-saturated butan-1-ol phase was assessed from distribution data as a function of the aqueous phase hydrogen ion concentration and of the ligand concentration in the organic phase. The data showed that Cu²⁺ is selectively extracted over a wide range of aqeous phase hydrogen ion concentrations.     

Syntheses and structural characterization of transition metal(II) coordination polymers containing 4,4′-dipyridyldisulfide

The reactions of Zn(NO₃)₂ · 6H₂O and FeSO₄ · 7H₂O with 4-PDS (4-PDS = 4,4′-dipyridyldisulfide) and NH₄SCN in CH₃OH afforded the complexes [Zn(NCS)₂(4-PDS)]_n (1) and [Fe(NCS)₂(4-PDS)₂ · 4H₂O]_n (2), respectively, while the reaction of CoCl₂ · 6H₂O with 4-PDS in CH₃OH gave the complex {[Co(4-PDS)₂][Cl]₂ · 2CH₃OH}_n, (3). These complexes have been characterized by spectroscopic methods and their structures determined by X-ray crystallography. The 4-PDS ligands in 1 are coordinated to the metal centers through the nitrogen atoms to form 1-D zigzag-chains, and the distorted tetrahedral coordination geometry at each zinc center is completed by a pair of N-bonded thiocyanate ligands. Compound 2 has a 1-D channel-chain structure and each octahedral Fe(II) metal center is coordinated by four 4-PDS ligands and two trans N-bonded thiocyanate ligands. Weak SS interactions in complex 1 link the 1-D chains into 2-D molecular sheets. In complex 2, the channel chains are interlinked through SS interactions to form molecular sheets, which interpenetrate through the SS interactions to form 3-D structures with large cavities that are occupied by the water molecules. Compound 3 also has a 1-D channel-chain structure with each square-planar Co(II) metal center coordinated by four 4-PDS ligands. Multiple C–HCl hydrogen bonds and SO interactions in 3 link the 1-D chains into 2-D structures.     

Synthesis and magnetism of the first tetranuclear copper(II)–iron(III) complexes of macrocyclic oxamides

Four novel tetranuclear macrocyclic complexes of the formula [(CuLⁱ)₃Fe](ClO₄)₃·3H₂O (i=1–4, Lⁱ are the dianions of the [14]N₄ and [15]N₄ macrocyclic oxamides, namely 2,3-dioxo-5,6:13,14-dibenzo-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene, 2,3-dioxo-5,6:13,14-dibenzo-9-methyl-7,12-bis(ethoxycarbonyl)-1,4,8,11-tetraazacyclotetradeca-7,11-diene and 2,3-dioxo-5,6:14,15-dibenzo-7,13-bis(ethoxycarbonyl)-1,4,8,12-tetraazacyclotetradeca-7,12-diene] have been prepared and characterized. These complexes are the first examples of oxamido-bridged Cu(II)–Fe(III) heterometallic species. Cryomagnetic studies on [(CuL¹)₃Fe](ClO₄)₃·3H₂O (1) and [(CuL³)₃Fe](ClO₄)₃·3H₂O (3) (77–300 K) revealed that the Cu(II) and Fe(III) ions interact antiferromagnetically through the oxamido bridge, with the exchange integral J=−30.8 cm⁻¹ for 1 and J=−28.7 cm⁻¹ for 3 based on . The interaction parameters have been compared with that of the related [Cu₃Mn] compound.     

Synthesis and characterization of two Ni(II) complexes with furfural s-methylthiosemicarbazone

Synthesis of two Ni(II) complexes with furfural S-methylthiosemicarbazone (HL) of the formula [Ni(HL)₂(H₂O)₂](ClO₄)₂ (A) and [Ni(HL)₂(ClO₄)₂] (B) are reported. Compound A was obtained from an ethanolic solution of Ni(ClO₄)₂·6H₂O and HL, whilst compound B was produced by heating compound A to 378 K. An X-ray analysis of the complex A showed that it has a trans(H₂O)-trans(HL) octahedral configuration in which HL behaves as a bidentate (NN) ligand. On the basis of the IR and electronic spectra as well as the magnetism, it was found that the compound B has also an octahedral configuration in which, HL and ClO₄ groups, are coordinated.     

Syntheses, crystal structures and magnetic properties of Ni(II)–2,4-pyridine-dicarboxylates

Two new complexes [Ni(pydc)(H₂O)₂]_n (1) and [Ni₂(pydc)₂(H₂O)₅]_n (2) (H₂pydc = 2,4-pyridinedicarboxylic acid) have been obtained by hydrothermal synthetic method and characterized by single crystal X-ray analysis. In 1 six-coordinate Ni(II) ions are coordinated by pydc ligands to form 2-D layer structures; while in 2 six-coordinate Ni(II) ions are only connected into 1-D zigzag chains constructed by dinuclear nickel units. Although the coordination geometries around Ni(II) centers in both complexes are similar, their structure topologies are greatly tuned by coordination modes of pydc. Variable temperature magnetic susceptibility studies have shown that both compounds 1 and 2 may display antiferromagnetic coupling between paramagnetic metal centers mediated by bridging carboxylate groups.     

Syntheses and X-ray crystal structures of [Co(η-CO3)(NH3)4](NO3)·0.5H2O and [(NH3)3Co(μ-OH)2(μ-CO3)Co(NH3)3][NO3]2·H2O

[Co(η²-CO₃)(NH₃)₄](NO₃)·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O were prepared by prolonged aerial oxidation of a solution of Co(NO₃)₂·6H₂O and ammonium carbonate in aqueous ammonia. The formation of these side products highlights the richness of the chemistry of these systems and the possibility of by products if methods are not strictly adhered to. The X-ray crystal structures of [Co(η²-CO₃)(NH₃)₄][NO₃]·0.5H₂O and [(NH₃)₃Co(μ-OH)₂(μ-CO₃)Co(NH₃)₃][NO₃]₂·H₂O reveal a monomeric octahedral cobalt center with η²-bound CO₃²⁻ in the former, while the latter consists of a dimeric array where the two cobalt centers are bridged by two OH⁻ and one μ₂-CO₃²⁻ groups with three terminal NH₃ ligands for each Co center. In both complexes extensive hydrogen bonding interactions are evident.     

X-ray crystal structure and vibrational spectra of hydrazides and their metal complexes. Part II. Hexaaquacobalt(II)bis(phthalhydrazidato)tetrahydrate

The hexaaquacobalt(II)bis(phthalhydrazidato)tetrahydrate, [Co(H₂O)₆](C₈N₂O₂H₅)₂·4H₂O is examined using single crystal X-ray diffraction analysis. The crystals are triclinic, space group , with a = 9.757(1), b = 10.955(2), c = 11.106(1),  = 100.79(2), β = 90.35(3), γ = 91.54(1) and Z = 2. In [Co(H₂O)₆](C₈N₂O₂H₅)₂·4H₂O, the cobalt(II) is coordinated by six water ligands and the [Co(H₂O)₆]²⁺ is associated with the two O-deprotonated phthalhydrazidato ions only by hydrogen bonds. The infrared and Raman spectra of phthalhydrazide (PH) and infrared spectra of deuterated derivative phthalhydrazide (PD) and of [Co(H₂O)₆](C₈N₂O₂H₅)₂·4H₂O are reported. The theoretical wavenumbers, infrared intensities and Raman scattering activities have been calculated using density functional (B3LYP) method with the 6-311++G(d,p) basis set. The calculated potential energy distribution has proved to be of great help in assigning the spectra PH, its deuterated derivative and [Co(H₂O)₆](C₈N₂O₂H₅)₂·4H₂O. The results from natural bond orbital (NBO) analysis for keto-hydroxy form of PH are presented.     

Infrared study of νOD modes in isotopically dilute (HDO) isostructural compounds M(HCOO)2·2H2O (M=Mn,Fe,Co,Ni,Cu,Zn) with matrix-isolated guest ions (Cu in M(HCOO)2·2H2O and M in Cu(HCOO)2·2H2O)

The infrared spectra of isotopically dilute (matrix-isolated HDO molecules) isostructural compounds M(HCOO)₂·2H₂O (M=Mn,Fe,Co,Ni,Zn,Cu) are presented and discussed in the region of the OD stretching modes. According to the structural data the compounds under study are divided into two groups: in M(HCOO)₂·2H₂O (M=Mn,Ni,Zn) the H₂O(1) molecules form stronger hydrogen bonds as compared to H₂O(2); in M(HCOO)₂·2H₂O (M=Fe,Co,Cu) the H₂O(2) molecules form stronger hydrogen bonds as compared to the H₂O(1) molecules. The influence of the metal–water interactions (synergetic effect) and the unit-cell volumes (repulsion potential of the lattice) on the hydrogen bond strength within the isostructural series is discussed. The wavenumbers of the uncoupled OD stretching modes of the HDO molecules influenced by guest ions (Cu²⁺ ions matrix-isolated in M(HCOO)₂·2H₂O and M²⁺ ions matrix-isolated in Cu(HCOO)₂·2H₂O) are presented and commented. For example, the analysis of the spectra reveals that when Cu²⁺ ions are included in the structure of M(HCOO)₂·2H₂O the hydrogen bonds of the type M–OH₂OCHO–Cu are considerably weaker as compared to those of the same type formed when M²⁺ ions are included in the structure of Cu(HCOO)₂·2H₂O if the cations remain unchanged.     

Solvothermal syntheses and crystal structures of two metal coordination polymers with double-chain structures

Two polymeric complexes, [Cu₂(btec)(phen)₂]_n·(H₂O)_n (1) and [Cd₄(btec)₂(phen)₄(H₂O)₄]_n (2) (H₄btec=1,2,4,5-benzenetetracarboxylic acid; PHEN=1,10-phenanthroline), were synthesized by solvothermal reactions at 140 °C. Both complex 1 and 2 possess infinite double-chain structures, in which each Cu(II) center has a tetrahedral configuration and the Cd(II) centers adopt triangular prismatic and square-based pyramidal configurations simultaneously. The inter-chain face to face π–π interactions among the aromatic rings of phen and the hydrogen bond interactions between aqua molecules and carboxyl O atoms result in 3-D networks in the two complexes. The ESR spectra study of complex 1 shows that there is negligibly small long-range super-exchange interactions between the Cu(II) atoms via benzenecarboxylate bridging.     

Three new polynuclear tetracarboxylato-bridged copper(II) complexes: Syntheses, X-ray structure and magnetic properties

The synthesis, crystal structure and magnetic measurements of three new polynuclear tetracarboxylato-bridged copper(II) complexes, i.e. {[Cu₄(phen)₂(μ-O₂CC₂H₅)₈] · (H₂O)}_n (1), [Cu₂(μ-O₂CC₆H₄OH)₄(C₇H₇NO)₂] · 6H₂O (2) and [Cu₂(μ-O₂CCH₃)₄(C₇H₇NO)₂] (3) (phen = 1,10-phenanthroline, O₂CC₆H₄OH = 3-hydroxy benzoate, C₇H₇NO = 4-acetylpyridine) are reported. All compounds consist of dinuclear units, in which two Cu(II) ions are bridged by four syn,syn-η¹:η¹:μ carboxylates, showing a paddle-wheel cage type with a square-pyramidal geometry, arranged in different ways. The structure of compound 1 consists of an one-dimensional structure generated by an alternating classical dinuclear paddle-wheel unit and an unusual dinuclear Cu₂(μ-OCOC₂H₅)₂(μ-O₂CC₂H₅)₂(phen)₂unit, which are connected to each other via a syn,anti-triatomic propionato bridge in an axial-equatorial configuration. The adjacent chains are connected to generate a 2D structure through the face-to-face π–π interaction between phen rings. Structures of compounds 2 and 3 both consist of a symmetric dinuclear Cu(II) carboxylate paddle-wheel core and pyridyl nitrogen atoms of 4-acetylpyridine ligand at the apical position, and just differ in the substituents of the equatorial ligands.

The magnetic properties have been measured and correlated with the molecular structures. It is found that in the two classical paddle-wheel compounds the Cu(II) ions are strongly antiferromagnetically coupled with J = −278.5 and −287.0 cm⁻¹ for complexes 2 and 3, respectively. In compound 1 the magnetic susceptibility could be fitted with two different, independent Cu(II) units, one strongly coupled and one weakly coupled; the paddle-wheel dinuclear unit has the strongest antiferromagetic coupling with a value for J of −299.5 cm⁻¹, whereas the Cu(II) ions in the propionato-bridged dinuclear unit of 1 display a very weak antiferromagnetic coupling with a value for J = −0.75 cm⁻¹, due to the orthogonality of the magnetic orbitals. Also the exchange within the chain is therefore very weak. The magneto-structural correlations for complexes 1, 2, and 3 are discussed on the basis of the structural parameters and magnetic data for the complexes.     

Large heteropolymetalate complexes formed from lanthanide (Y, Ce, Pr, Nd, Sm, Eu, Gd), nickel cations and cryptate [As4W40O140]: synthesis and structure characterization

A new family of heteropolytungstate complexes (NH₄)₂₁[Ln(H₂O)₅{Ni(H₂O)}₂As₄W₄₀O₁₄₀]·xH₂O(Ln=Y, Ce, Pr, Nd, Sm, Eu, Gd) were prepared by the reaction of Na₂₇[NaAs₄W₄₀O₁₄₀]·60H₂O with NiCl₂·6H₂O and Ln(NO₃)₃·xH₂O at pH≈4.5. The crystal structures of (NH₄)₂₁[Gd(H₂O)₅{Ni(H₂O)}₂As₄W₄₀O₁₄₀]·51H₂O was determined by X-ray diffraction analysis and element analysis. The compound crystallizes in the monoclinic space group P2₁/n with a=19.754(3), b=24.298(4), c=39.350(6) Å, β=100.612(3)°, V=18564(5) ų, Z=2, R1(wR₂)=0.0544(0.0691). The central site S1 and two opposite sites S2 of the big cyclic ligand [As₄W₄₀O₁₄₀]²⁸⁻ are occupied by one Ln³⁺and two Ni²⁺, respectively, each site supply four O_d coordinating to metal ion, another one water molecule and other five water molecules coordinate, respectively, to Ni²⁺and Ln³⁺. Polyanion [Ln(H₂O)₅{Ni(H₂O)}₂As₄W₄₀O₁₄₀]²¹⁻ has C_2v symmetry. IR and UV–vis spectra of [NaAs₄W₄₀O₁₄₀]²⁷⁻ of the title compounds are discussed.