Synthesis and magnetic properties of copper(II)-cobalt(II) complexes ofN,N′-1,2-propanedisalicylamidatocuprate(II)

Summary The binuclear metal complexes [Cu(sampn)Co(L)₂] (L=bipy, phen), have been prepared by the reaction of sodiumN,N-1,2-propanedisalicylamidatocuprate(II) heptahydrate, Na₂[Cu(sampn)] 7H₂O, with a divalent metalion, and 2,2-bipyridine or 1, 10-phenathroline. The complexes were characterized by variable-temperature magnetic susceptibility measurements; the results indicate that a weak antiferromagnetic spin-exchange interaction operates between the metal ions.     

Binuclear complexes of copper(II) with 1′-phthalazinylhydrazones of substituted salicylic aldehydes: Physico-chemical study and quantum-chemical simulation

Binuclear complexes of copper(II) with 1′-phthalazinylhydrazones of substituted salicylic aldehydes have been prepared and studied. Antiferromagnetic exchange interaction between copper(II) ions has been revealed in all the complexes. Taking advantage of quantum-chemical simulation, we have investigated the influence of the complexes structural isomerism on the character of the exchange interaction between the paramagnetic centers. X-ray absorbance spectroscopy afforded the structural parameters of coordination spheres of copper(II) ions; it has been demonstrated that dimerization occurred via the nitrogen atoms of phthalazine fragments.     

Rhenium(IV)–copper(II) heterobimetallic complexes: Synthesis,crystal structure and magnetic properties

Two Re(IV)–Cu(II) heterometallic complexes {(CuL_α)[ReCl₄(ox)]}_n (where L_α = N-meso-5,12-Me₂-7,14-Et₂-[14]-4,11-dieneN₄), 1, and (CuL_β)[ReCl₄(ox)] (L_β = N-rac-5,12-Me₂-7,14-Et₂-[14]-4,11-dieneN₄N-rac-5,12-Me₂-7,14-Et₂-[14]-4,11-dieneN₄), 2, were synthesized. The [CuL²⁺] macrocyclic cation is coordinated from above and below by [ReCl₄(ox)]²⁻ units through the chloro-ligands and creates a chloro-bridged heterometallic Re^IV–Cu^II one-dimensional zig-zag chain. Compound 2 can be viewed as a heterobimetallic dinuclear unit, in which the Re(IV)-Cu(II) centers are linked by an oxalato bridge. The magnetic behavior of 1 and 2 has been investigated over the temperature range 1.8–300 K. Compound 1 behaves like a ferrimagnetic {Re(IV)–Cu(II)} bimetallic, one-dimensional chain with intrachain antiferromagnetic coupling. Compound 2 shows a weak antiferromagnetic interaction within the [Re(IV)–Cu(II)] unit along with a strong single-ion anisotropy, D(Re) = −63 cm⁻¹.     

Synthesis, characterization and magnetic properties of novel μ-isophthalato oxovanadium(IV) binuclear complexes

Four novel oxovanadium(IV) binuclear complexes have been synthesized, namely [(VO)₂(IPHTA) (L)₂SO₄ (L denotes 2,2′-bipyridine (bpy); 1,10-phenanthroline (phen); 4,4′-dimethyl-2,2′-bipyridine (Me₂bpy) and 5-nitro-1,10-phenanthroline (NO₂-phen)), where IPHTA is the isophthalate dianon. Based on elemental analyses, molar conductivity measurements, IR and electronic spectra studies, it is proposed that these complexes have IPHTA-bridged structures and consist of two vanadium(IV) atoms in a square-pyramidal environment. The complexes [(VO)₂(IPHTA)(Me₂bpy)₂]SO₄ (1) and [(VO)₂(IPHTA)(bpy)₂]SO₄ (2) were characterized by variable temperature magnetic susceptibility (4–300 K) and the data could be well fitted by the least-squares method to a susceptibility equation derived from the spin Hamiltonian operator, . The exchange integral, J, was found to be −26.8 cm⁻¹ for (1) and −31.0 cm⁻¹ for (2). These results are commensurate with antifferomagnetic interactions between two oxovanadium(IV) ions within each molecule. The influence of different terminal ligands on magnetic interactions between the metals of this kind of complexes is also discussed.     

Lanthanide complexes with bis(2′-quinolyl)-2,6-pyridine

Complexes of lanthanide (III) nitrates, thiocyanates and perchlorates with the tridendate ligand, bis(2′-quinolyl)-2,6-pyridine are reported. The molar conductivity values in acetonitrile-benzene mixture (80−20) and IR data indicate that the nitrate and thiocyanate complexes are non electrolytes and the perchlorate 1:3 electrolytes. The electronic spectra of the Pr, Nd, Ho, and Er complexes show enhancement of intensities for the hypersensitive bands; moreover, except in the case of the Er^III complexes, where a very slight red shift is observed, other complexes show the expected nephelauxetic effect.     

Synthesis, characterization, and biological properties of N-phenolato-N′-(3-dimethylaminopropyl)oxamide and its binuclear copper(II) complexes

A new asymmetric N,N′-bis(substituent)oxamide ligand, N-phenolato-N′-(3-dimethylaminopropyl)oxamide (H₃pdmapo), and two of its binuclear Cu(II) complexes with different terminal ligands, namely [Cu₂(pdmapo)(phen)(H₂O)](ClO₄) (1) and [Cu₂(pdmapo)(bpy)(CH₃OH)](ClO₄) (2), where phen = 1,10-phenanthroline and bpy = 2,2′-bipyridine, have been synthesized and characterized. The crystal structures of both complexes have been determined by single-crystal X-ray diffraction. Both structures contain binuclear Cu(II) cationic complexes with pdmapo^3? ligands. The asymmetric pdmapo^3? ligands bridge two Cu(II) atoms in the cis conformation and the Cu···Cu separations through the oxamide bridge are 5.2046(18) and 5.207(2) Å for complexes 1 and 2, respectively. The coordination environments of the two Cu(II) atoms in each binuclear complex are different. The copper occupying the inner site of the pdmapo^3? ligand is four-coordinated in a CuN₃O distorted square-planar environment, while the other is five-coordinated in a square pyramid geometry. In complex 1, O–H···O and C–H···O hydrogen bonds link the complex into a one-dimensional chain. In complex 2, O–H···O hydrogen bonds link the molecules to form a dimer, together with two types of strong π–π interactions, giving a two-dimensional network structure. The cytotoxicities and DNA-binding properties of H₃pdmapo and the two complexes were studied. The experimental evidence suggests that the ligand binds to DNA via a groove binding mode, while the binuclear complexes bind intercalatively to DNA.     

Synthesis,electrochemical properties and electro-oxidative polymerization of copper(II) and nickel(II) complexes with N′-benzoylthiourea ligands containing pyrrole groups

The synthesis of four N-benzoylthioureas containing pyrrole groups are described. The electrochemical behaviour of their copper(II) and nickel(II) complexes has been investigated in aprotic solvents by coulometry and by cyclic voltammetry which indicates that the electrochemical oxidation of copper complexes leads to the formation of Cu^II-benzylureate complexes. The oxidative polymerization of nickel complexes on platinum and a glassy carbon electrode, has been carried out in MeCN.The redox properties of the polymeric films formed have been examined by cyclic voltammetry. The films are catalytically active in the electroreduction of oxygen.     

Synthesis,structure and properties of a series of scorpionate oxovanadium(IV)–carboxylate complexes

A series of oxovanadium(IV) complexes: TpVO(pzH)(2,4-Cl–C₆H₃–OCH₂COO) (1), TpVO(pzH)(C₆H₅–OCH₂COO) (2), TpVO(pzH)(p-Cl–C₆H₄–COO) (3), TpVO(pzH)(3,5-NO₂–C₆H₃–COO) (4), Tp∗VO(pzH∗)(p-Cl–C₆H₄–COO) (5) and Tp∗VO(pzH∗)(p-Cl–C₆H₄–COO) · CH₃OH (6) (Tp = hydrotris(pyrazolyl)borate, pzH = pyrazole, Tp∗ = hydrotris(3,5-dimethylpyrazolyl)borate, pzH∗ = 3,5-dimethylpyrazole) were synthesized and their crystal structures were determined by X-ray diffraction. In all the complexes, the vanadium ions are in a distorted-octahedral environment with a N₄O₂ donor set. Hydrogen bonding interaction exists in each complex. Complexes 1 and 2 are hydrogen-bonded dimers. Dimeric units of 2 are connected to one another via weak inter-molecular C–H···O interactions to form a 2D network on the bc-face. In 3–6 there exist intramolecular N–H···O hydrogen bonds between the neutral pyrazole/3,5-dimethylpyrazole and the uncoordinated carboxyl oxygen atom. In addition, the catalytic activity of complex 2 in a bromination reaction in phosphate buffer with phenol red as a trap was evaluated by UV–Vis spectroscopy. Furthermore, the elemental analyses, IR spectra and thermal stabilities were recorded.     

Synthesis,chemical characterization,X-ray crystal structure and magnetic properties of oxalato-bridged copper(II) binuclear complexes with 2,2′-bipyridine and diethylenetriamine as peripheral ligands

Two new μ-oxalato binuclear copper(II) complexes, [{Cu(NO₃)(H₂O)(bipy)}₂(ox)] (1) and [{Cu(dien)}₂(ox)](NO₃)₂ (2), with ox=oxalate, dien=diethylenetriamine and bipy=2,2′-bipyridine, have been synthesized and their crystal and molecular structures have been determined by single-crystal X-ray diffraction methods. The crystal structure of 1 consists of centrosymmetric neutral dimers where the copper atoms lie in a strongly elongated octahedral environment, surrounded by two nitrogen atoms of a bipy molecule and two oxygen atoms of the bridging oxalato group in the equatorial plane and oxygen atoms of water molecules and nitrate ions in the axial positions. Crystal structure of 2 is made up of non-coordinated nitrate anions and asymmetric binuclear cations in which copper atoms are in a distorted square–pyramidal coordination with three atoms of a diethylenetriamine ligand and an oxygen atom of the asymmetrically coordinated oxalato bridge building the basal plane and the other oxygen atom of the oxalato ligand filling the apical position. Both compounds have been also characterized by Fourier transform infrared (FT-IR) and electron spin resonance (ESR) spectroscopies, thermal analysis and variable temperature magnetic susceptibility measurements. The two compounds exhibit antiferromagnetic exchange with a singlet–triplet separation of −382 and −6.5 cm⁻¹ for 1 and 2, respectively. Magnetic and ESR results are discussed with respect to the crystal structure of the compounds.     

Copper(II) and oxovanadium(IV) complexes of α-hydroxymethylserine

Summary Potentiometric and spectroscopic measurements were used to characterize the binding ability of -hydroxy-methylserine (Hms) with copper(II) and oxovanadium(IV) ions. The ligand was found to be generally a more efficient chelating agent than serine. Both of the deprotonated hydroxyl groups of Hms can be involved in coordination to vanadyl ions, whereas copper(II) binds in the same way as with serine.     

2,4′-Bipyridyl complexes with silver(I) and copper(II)

Summary Ag^I and Cu^II complexes with 2,4-bipyridyl (2,4-bipy or L) with the general formulae AgL₂X (where X = NO _inf3 ^sup– or ClO₄ ^-), CuL₂X₂·2H₂O (X = Cl^- or Br^-), CuL₄SO₄·4H₂O, CuL₄(NO₃)₂·2H₂O and CuL₄(ClO₄)₂·H₂O have been isolated pure and characterized by analytical, spectral and magnetic measurements. The thermal decomposition of these complexes was studied under non-isothermal conditions in air.     

Synthesis,characterisation and electrochemical study of 4,4′-bis(salicylideneimino) diphenylethane and its complexes with cobalt(II), copper(II) and cadmium(II)

We have prepared and characterised a new series of metal complexes obtained from 4,4-bis(salicylideneimino)diphenylethane (saldipH₂) and cobalt(II), copper(II) and cadmium(II) chlorides. In every case, the coordinating atoms are N and O. However, each compound has its own structure:[Co(saldip)]·2 H₂O is monomeric and a mononuclear species, [Cu₂(saldip)₂(H₂O)] is a binuclear complex and finally the cadmium complex is formulated as:[(CdCl₂)₂(saldipH₂)]·CdCl₂. An electrochemical study (cyclic voltammetry) indicates that the reduction, as well as the oxidation, of copper in [Cu₂(saldip)₂(H₂O)] proceeds in two steps. For the reduction of the two other complexes, two steps are indicated out: the first is attributed to the reduction of the metal and the second to the reduction of the coordinated ligands.     

Synthesis,characterization and nucleolytic property of bis(N,N′-dimethylglycinato)copper(II)

Aquabis(N,N-dimethylglycinato)copper(II) dihydrate, [Cu(dmg)₂(H₂O)]·2H₂O, has been synthesized and characterized by elemental analysis, FT-IR, magnetic data, thermal analysis, solution UV-visible spectroscopy, X-ray crystal structure analysis and electrospray ionization mass spectroscopy. The square pyramidal copper(II) complex crystallizes in the orthorhombic space group P2₁2₁2₁. The complex cleaves circular plasmid DNA (pBR322) in the presence of H₂O₂. The extent of cleavage varies with the concentration range of the complex, the type of buffer used, pH of buffer and the concentration of H₂O₂. Hydroxyl radical scavenger can inhibit the nucleolytic ability of this complex.     

Synthesis and properties of the copper(Ⅱ) complexes with stable radical

Four novel copper(Ⅱ) complexes have been synthesized,namely Cu(hfac)2NITPhNO2 (1),Cu(hfac)2NITPhCH3 (2),Cu(pfpr)2NITPhNO2,(3) and Cu(Pfpr)2NITPhCH3 (4),where hfac= hexafluoro-acetylacetonate,pfpr=pentafluoropropionate,NITR.=2-R-4,4,5,5-tetraniethyl-4,5-dihydro-1H-imidazolyl-1-oxyl-3-oxide.(R=4-nitrophenyl,4-methylphenyl).These complexes were rharicter-ized by elemental analyses,IR,electronic spectra and molar conductance.The temperature-dependent magnetic susceptibility of complexes 1 and 3 have been studied in the 4 300 K range,giving I he exchange integral J=10.56 cm-1 for complex 1 and J =-30.9 cm-1 for complex 3.     

Synthesis,characterization and photophysical properties of homoleptic platinum(II) complexes with 2,2′-biimidazole-based ligands

Eight pairs of cis–trans isomeric homoleptic platinum(II) complexes based on N-alkyl- or aryl-substituted 2,2′-biimidazole ligands were synthesized, and their photophysical properties were investigated. The cis and trans isomers readily interconvert at slightly elevated temperature, implying that the activation barrier for this process is low. Single crystal X-ray diffraction analysis revealed that the complexes have an ideal square-planar geometry. Their UV–Vis spectra showed lower energy absorption bands in the range of 345–378 nm, which are assigned to the typical MLCT mixed with LC transitions. In frozen glass solution at 77 K and also in the powder state, these complexes exhibit green emission ranging from 440 to 540 nm with photoluminescence quantum yields of 3.3–24.4%. The emitting excited state is dominated by ³ππ* character with some contributions from ³MLCT according to the excitation spectra.     

Synthesis and magnetic properties of heterobinuclear copper(II)–iron(II) complexes with N,N′-bis(2-aminopropyl)oxamidocopper(II)

Six new -oxamido heterobinuclear complexes, namely [Cu(oxap)Fe(L)2]SO4, where oxap denotes the N,N-bis(2-aminopropyl)oxamido dianion and L represents 1,10-phenanthroline (phen); 5-nitro-1,10-phenanthroline (NO2-phen); 5-chloro-1,10-phenanthroline (Cl-phen); 5-methyl-1,10-phenanthroline (Me-phen); 2,2-bipyridine (bpy); and 4,4-dimethyl-2,2-bipyridine (Me2bpy), have been synthesized and characterized by elemental analyses, i.r. spectra, electronic spectra, magnetic moments (at room temperature) and molar conductivity measurements. The temperature dependent magnetic susceptibilities of [Cu(oxap)Fe(bpy)2]SO4 (1) and [Cu(oxap)Fe(phen)2]SO4 (2) have been studied in the 4.2–300K range, giving the exchange integrals J=–20.9cm–1 for (1) and J=–22.5cm–1 for (2). These results are commensurate with antiferromagnetic interactions between adjacent metal ions within each molecule.     

Ruthenium(II)/(III) and oxovanadium(IV) complexes of highly conjugated β-diketones and their macrocyclic Schiff base binuclear copper(II) complexes

Ruthenium(II) complexes of the general formula [Ru(PPh3)2(L)(L)]ClO4 [L=2,2-bipyridine or 1,10-phenanthroline;L=2-hydroxy--4-X-phenylcinnamoylacetophenone] have been prepared by reacting L and L with Ru(PPh3)3Cl2 in CH2Cl2. The complexes are diamagnetic and absorb intensely in the visible region, owing to the MLCT transition. Hexacoordinated ruthenium(III) complexes, [RuCl2(PPh3)2(L)], have also been prepared by reacting Ru(PPh3)3Cl3 with -diketones. Solutions of ruthenium(III) complexes show rhombic e.s.r. spectra at 77 K, and distortion from the octahedral symmetry has been identified from the line spacings. The conjugation in diketones favours reversibility in RuII/III and RuIII/IV and stabilize ruthenium in different oxidation states owing to d–* interaction. Oxovanadyl(IV) complexes of the -diketones with a metal-to-ligand ratio of 1:2 and square pyramidal geometry were also prepared. The e.s.r spectra of these complexes show the presence of an unpaired electron in the dxy orbital and the hyperfine splitting constants are sensitive to solvent change. ¶ A new class of highly conjugated Schiff bases obtained from the above diketones and 2-aminothiophenol behave as dibasic, tridentate ligands in their copper(II) complexes. The subnormal magnetic moments and hyperfine splittings of these complexes are ascribed to an antiferromagnetic exchange interaction arising from dimerization. Cyclic voltammograms show that the electron transfer occurs in two steps corresponding to CuII–CuI and CuI–CuI redox states.     

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.     

Binuclear and mononuclear cobalt(II), nickel(II) and copper(II) complexes of 4,4′-bis(alkylaminoisonitrosoacetyl)diphenyl-methane derivatives

4,4-Bis(chloroacetyl)diphenylmethane has been prepared from ClCH₂COCl and Ph₂CH₂. 4,4-Methylenebis(phenylglyoxylohydroximoyl chloride has also been obtained. Four new substituted 4,4-bis(alkylaminoisonitrosoacetyl)diphenylmethanes (ligands) have been prepared from 4,4-methylenebis(phenylglyoxylohydroximoyl chloride) and the corresponding amines. The Ni^II, Cu^II and Co^II complexes of these ligands were prepared and their structures were identified using AAS, i.r., ¹H-n.m.r. spectral data, elemental analyses and magnetic susceptibility measurements.     

Synthesis, structural characterisation and thermal decomposition studies of some 2,4′-bipyridyl complexes with cobalt(II), nickel(II) and copper(II)

2,4-Bipyridyl (2,4-bipy orL) complexes with cobalt(II), nickel(II) and copper(II) of the formulae M(2,4-bipy)₂(CH₃COO)₂·2H₂O (M(II) = Co, Ni, Cu), Co(2,4-bipy)₂SO₄·3H₂O or Ni(2,4-bipy)₂SO₄·4H₂O have been prepared and their IR and electronic (VIS) spectra are discussed. The thermal behaviour of the obtained compounds has also been studied. The intermediate products of decomposition at different temperatures have been characterized by chemical analysis and X-ray diffraction.We thank dr. A. Malinowska for performing VIS spectra. This work was supported by the KBN project No. PB 0636/P3/93/04.