Influence of the counter anion and solvent in the structure of copper derivatives with the 2,3-bis(2-pyridyl)pyrazine ligand

Several compounds have been isolated from the reaction between different copper bis(acetylacetonato) derivatives and the potentially bridging ligand 2,3-bis(2-pyridyl)pyrazine (bppz). A compound of formula [Cu(tfacac)₂(bppz)] (1) is obtained when the substituted trifluoromethylacetylacetonato is used. The use of different anions and the unsubstituted acetylacetonato give rise to new derivatives of general formula [{Cu(acac)}₂(μ-bppz)₂]X₂ (X⁻ = BF₄⁻, 2; PF₆⁻, 3; BPh₄⁻, 4). In these compounds the bppz ligand is acting as a bridge by chelating one copper atom and bonding monodentate a second copper atom. The presence of anions with different coordination abilities introduces variations in the copper environment and geometry. When the non-coordinating tetraphenylborate is used different compounds depending on the nature of the solvent are obtained. The dimer 4 was isolated from a methanol/chloroform mixture, while in the absence of chloroform the monomeric compound of formula [Cu(acac)(bppz)(ROH)](BPh₄)·ROH (ROH = MeOH, 5) was obtained. When ethanol was used instead of methanol the analogous derivative 6 (R = EtOH) was isolated. Both species show a mononuclear structure with the copper atom five-coordinated by the chelating acac and bppz ligands and one hydroxo group occupying the apical position. A similar environment for the copper appears in [Cu(tfacac)(bppz)(MeOH)](BPh₄), 7, which shows a dimeric structure through hydrogen bonds interactions. The magnetic susceptibility data of the dimeric compounds show very weak antiferromagnetic interactions between the copper atoms, an expected fact since the bridging bppz ligand is not planar but the monodentate pyridine is more or less perpendicular to the other two aromatic rings, precluding the spin exchange via the π ligand electrons.     

Chemistry at the apical position of square-pyramidal copper(II) complexes: Synthesis, crystal structures, and magnetic properties of homopolynuclear complexes with azido bridges containing [Cu(AA)(BB)] moieties (AA = acetylacetonate; BB = 1,10-phenanthroline, bipy = 2,2′-bipyridine)

Three new homopolynuclear complexes with azido bridges have been obtained by using [Cu(AA)(BB)]⁺ building-blocks (AA = acetylacetonate; BB = 1,10-phenanthroline or 2,2′-bipyridine). The reaction between [Cu(acac)(phen)(H₂O)](ClO₄) and NaN₃ leads to a mixture of two compounds: a binuclear complex, [{Cu(acac)(phen)}₂(μ_1,3-N₃)](ClO₄) · 2H₂O (1), and a linear tetranuclear one, [{Cu(acac)(phen)(ClO₄)}₂{Cu(phen)(μ_1,1-N₃)₂}₂] (2). The reaction between [Cu(acac)(bipy)(H₂O)](ClO₄) and NaN₃ affords also a mixture of two compounds: [{Cu(acac)(bipy)}₂(μ_1,3-N₃)]₃(ClO₄)₃ · 3.75H₂O (3) and [Cu(acac)(bipy)(N₃)][Cu(acac)(bipy)(H₂O)](ClO₄) (4). The X-ray crystal structures of compounds 1-4 have been solved (for compound 4 the crystal structure was previously reported). In compounds 1 and 3, two {Cu(AA)(BB)} fragments are bridged by the azido anion in an end-to-end fashion. Two isomers, cis and trans with respect to azido bridge, were found in crystal 3. The structure of compound 2 consists of two Cu(II) central cations bridged by two μ_1,1-azido ligands, each of them being also connected to a {Cu(acac)(phen)} fragment through another μ_1,1-azido ligand. The cryomagnetic properties of the compounds 1 and 2 have been investigated and discussed. The magnetic behaviour of compound 1 shows the absence of any interactions between the metallic ions. In the tetranuclear complex 2, the magnetic interactions between the external and central copper(II) ions(J₁), and between the central metallic ions (J₂) were found ferromagnetic (J₁ = 0.36 cm⁻¹, J₂ = 7.20 cm⁻¹).     

Synthesis of novel mononuclear and dinuclear ruthenium(II) complexes with terpyridine and acetylacetonate ancillary ligands and cyanamide derivative ligands

Several new mononuclear and dinuclear ruthenium(II) complexes - incorporating 2,2′:6′,2″-terpyridine and acetylacetonate as ancillary ligands and phenylcyanamide derivative ligands - of the type [Ru(tpy)(acac)(L)] and [{Ru(tpy)(acac)}₂(μ-L′)] (where tpy = 2,2′:6′,2″-terpyridine, acac = acetylacetonate, L = hmbpcyd = 4-(3-hydroxy-3-methylbutynyl)phenylcyanamide anion (2) and epcyd = 4-ethynylphenylcyanamide anion (3) and L′ = bcpda = bis(4-cyanamidophenyl)diacetylene dianion (4) and bcpea = 9,10-bis(4-cyanamidophenylethynyl)anthracene dianion (5)) were synthesized in a stepwise manner starting from [Ru(tpy)(acac)(Ipcyd)] (1), where Ipcyd = 4-iodophenylcyanamide anion. Tetraphenylarsonium salts of the phenylcyanamide derivative ligands were also prepared. The four complexes have been characterized by UV-Vis, IR, ES-MS, electrochemistry and ¹H NMR. Mononuclear complexes 2 and 3 were further characterized by ¹³C NMR. The single crystal X-ray structure of 2 was determined, it crystallized with one molecule of water with empirical formula of C₃₂H₃₁N₅O₅Ru, in a monoclinic crystal system and space group of P2₁/n with a = 17.642(5) Å, b = 9.634(2) Å, c = 20.063(7) Å, β = 92.65(3)°, V = 3406(2) Å³ and Z = 4. The structure was refined to a final R factor of 0.040. The Ru(III/II) couple of 1-3 appeared around 0.34 V versus the saturated calomel electrode in dimethylformamide and at a slightly higher potential, around 0.36-0.37 V for 4 and 5. Spectroelectrochemical studies were also performed for 4 and 5, no intervalence transition was observed despite all attempts.     

Structures and magnetic properties of one-dimensional polymers constructed with copper(II) salts and pyridinecarboxamide-type ligands

Three complexes of the composition {[Cu(μ_1,5-dca)₂(mppca)₂] · H₂O}_n (1), [Cu(μ_1,5-dca)₂(nppca)₂]_n (2) and [Cu(μ-Cl)₂(mppca)₂]_n (3) (dca = dicyanamide, ; mppca = N-(4′-methylphenyl)-4-pyridinecarboxamide; nppca = N-(4′-nitrophenyl)-4-pyridinecarboxamide) have been synthesized and characterized by single crystal X-ray crystallography and magnetic susceptibility studies. Different supramolecular structures of the complexes have been constructed by different non-covalent motifs in the crystalline solids. In complex 1, adjacent copper(II) atoms are connected by double μ_1,5-dca(end-to-end) bridges to form a chain-like structure. The chains are linked by π-π interactions and hydrogen bonds between the ligands and water molecules to form a 3D network. In complex 2, copper(II) atom has a coordination environment similar to 1, but water molecules have not been found. Weak C-H?N hydrogen bonding and π-π interaction yield a 3D supramolecular network which is different from that of complex 1. Complex 3 is a 1D polymeric chain in which Cu(II) ions are bridged by Cl⁻, and only CH/π interactions had been found. Magnetic measurements revealed antiferromagnetic properties of 1, 3 and ferromagnetic behavior of 2.     

3D supramolecular network assembly and thermal decomposition of new copper(II) complexes with pyrazine-2,6-dicarboxylic acid

Four new Cu(II) complexes [Cu(pzda)(2,2′-bpy)(H₂O)] · 2.5H₂O (1), [Cu(pzda)(phen)(H₂O)] · H₂O (2), [Cu(pzda)(4,4′-bpy)] · H₂O (3) and [Cu(pzda)(bpe)_0.5(H₂O)] (4) were synthesized by hydrothermal reactions of copper salt (acetate or sulphate) with pyrazine-2,6-dicarboxylic acid (H₂pzda), and 2,2′-bipyridine (2,2′-bpy), 1,10-phenanthroline (phen), 4,4′-bipyridine (4,4′-bpy) or 1,2-bis(4-pyridyl)-ethane (bpe), respectively. For 1 and 2, they are both monomeric entities which are further assembled into 3D supramolecular networks by hydrogen bonds and π-π stacking interactions. Complex 3 has a 2D metal-organic framework which is connected into 3D supramolecular network by hydrogen bonds. However, for 4, the bpe ligand bridges two Cu(II) ions into binuclear unit, and then the binuclear molecules are assembled into 3D supramolecular network by hydrogen bonds between the coordination water molecule and the carboxylate oxygen atoms. The thermal decomposition mechanism of complexes 1 and 2 cooperated with powder XRD at different temperatures is discussed. The results reveal that once liberation of water molecules takes place the supramolecular network of 1 and 2 collapses.     

X-ray structure and magnetic properties of dinuclear and polymer iron(II) complexes

Five new octahedral iron(II) complexes [FeL2(4-dpa)]_n(EtOH) (1), [FeL2(bipy)]_n(DMF) (2), [FeL1(bpee)]_n (3), [Fe₂L3(1-meim)₄](1-meim)₄ (4) and [FeL1(DMAP)₂] (5), with L1 and L2 being tetradentate coordinating Schiff base like ligands (L1 = (E,E)-[{diethyl-2,2′-[1,2-phenylenebis(iminomethylidyne)]bis[3-oxobutanato](2-)-N,N′,O³,O³′}, L2 = (3,3′)-[{1,2-phenylenebis(iminomethylidyne)]bis(2,4-pentane-dionato)(2-)-N,N′,O²,O²′}) and L3 being a octadentate dinucleating coordinating Schiff base like ligand ({tetraethyl-(E,E,E,E)-2,2′,2′′,2′′′-[1,2,4,5-phenylentetra(iminomethylidine)]tetra[3-oxobutanoato](2-)-N,N′,N′′,N′′′,O³,O³′,O³′′,O³′′′}); 4-dpa = di(4-picolyl)-amine, bipy = 4,4′-bipyridine, bpee = trans-1,2-bis(4-pyridyl)ethylene, 1-meim = 1-methylimidazole and DMAP = 4-dimethylaminopyridine, have been synthesized and characterised using X-ray structure analysis and T-dependent susceptibility measurements. Both methods indicate that all iron(II) centres are in the paramagnetic high-spin state over the whole temperature range investigated. The O-Fe-O angle, the so called bit of the equatorial ligand, is with an average of 111° in the region typical for high-spin iron(II) complexes of this ligand type. In the case of compound 1 an infinite two-dimensional hydrogen bond network can be found, for the compounds 2-4 no hydrogen bond interactions are observed between the complex molecules. A comparison of the curve progression obtained from the magnetic measurements of the mononuclear complex 5 and the polymeric complexes 1-3 leads to the conclusion that no magnetic interactions are mediated over the bridging axial ligands. For the dinuclear complex 4 weak antiferromagnetic interactions between the two iron centres are found.     

New examples of μ-η:η-disulfido dicopper(II,II) complexes with bis(tetramethylguanidine) ligands

The new ligand N,N′-(2-methyl-2-(2-pyridyl)propan-1,3-diyl)bis(tetramethylguanidine) (L) and its four-coordinate, distorted square-planar copper(II) complex [CuLCl₂] (1) were synthesized and structurally characterized. Similarly, bis(μ-OH)dicopper(II,II) complex [Cu₂L₂(OH)₂](OTf)₂ (2) was synthesized and structurally characterized. The pyridyl group in L does not coordinate in either 1 or 2. New examples of μ-η²:η²-disulfido dicopper(II,II) complexes were synthesized by treating a copper(I) complex of either L or L′ [L′ = 2′,2′-(propane-1,3-diyl)bis(1,1,3,3-tetramethylguanidine)] with elemental sulfur. [Cu₂L₂(S₂)](PF₆)₂ (3) and [Cu₂(S₂)](PF₆)₂ (4) were both structurally characterized, and both structures have two copper(II) ions bridged by a disulfido ligand in a μ-η²:η²-manner. The ligands L and L′ coordinate in a bidentate fashion (like 1 and 2, the pyridyl ring does not coordinate in 3), and the geometry around the copper ions in 3 and 4 is distorted square planar. The metrical parameters of 3 and 4 were found to be similar to other μ-η²:η²-disulfido dicopper(II,II) complexes, and the Cu-S and Cu···Cu distances are among the shortest reported for this class of copper disulfide dimers.     

Synthesis and structural characterization of three hydrogen-bonding connected supramolecular complexes of nickel, zinc and copper with 1,3-diphenyl-4-(salicylidene hydrazide)-acetyl-pyrazolone-5 and 2,2′-bipyridine

A new set of supramolecular complexes, [Ni(DPAP-SHZ)(2,2′-bipy)CH₃OH] (1), [Zn(DPAP-SHZ)(2,2′-bipy)CH₃OH] (2) and [Cu(DPAP-SHZ)(2,2′-bipy)] · 2CH₂Cl₂ (3) (DPAP-SHZ = 1,3-diphenyl-4-(salicylidene hydrazide)-acetyl-pyrazolone-5, 2,2′-bipy = 2,2′-bipyridine) have been synthesized and characterized by elemental analysis, TG-DTA, IR spectroscopy and X-ray crystallography. The X-ray diffraction analyses of the complexes show that the Ni(II) ion and Zn(II) ion centers are six-coordinated while the Cu(II) ion center is five-coordinated. The three supramolecular complexes contain the same ligands, namely DPAP-SHZ and 2,2′-bipy. However, their hydrogen bonds are significantly different, and this variation apparently is responsible for the dissimilar structures of the three supramolecular complexes.     

Dicopper(II) complexes showing DNA hydrolase activity and monomeric adduct formation with bis(4-nitrophenyl)phosphate

Ferromagnetic dicopper(II) complexes [Cu₂(μ-O₂CCH₃)(μ-OH)(L)₂(μ-L¹)](PF₆)₂, where L = 1,10-phenanthroline (phen), L¹ = H₂O in 1 and L = dipyrido[3,2-d:2′,3′-f]quinoxaline (dpq), L¹ = CH₃CN in 2, are prepared and structurally characterized. Crystals of 1 and 2 belong to the monoclinic space group of P2₁/n and P2₁/m, respectively. The copper(II) centers display distorted square-pyramidal geometry having a phenanthroline base and two oxygen atoms of the bridging hydroxo and acetate group in the basal plane. The fifth coordination site has weak axially bound bridging solvent molecule H₂O in 1 and CH₃CN in 2. The Cu···Cu distances are 3.034 and 3.046 Å in 1 and 2, respectively. The complexes show efficient hydrolytic cleavage of supercoiled pUC19 DNA as evidenced from the mechanistic studies that include T4 DNA ligase experiments. The binuclear complexes form monomeric copper(II) adducts [Cu(L)₂(BNPP)](PF₆) (L = phen, 3; dpq, 4) with bis(4-nitrophenyl)phosphate (BNPP) as a model phosphodiester. The crystal structures of 3 and 4 reveal distorted trigonal bipyramidal geometry in which BNPP binds through the oxygen atom of the phosphate. The kinetic data of the DNA cleavage reactions of the binuclear complexes under pseudo- and true-Michaelis-Menten conditions indicate remarkable enhancement in the DNA hydrolysis rate in comparison to the control data.     

Dinuclear fumarato- and terephthalato-bridged copper(II) complexes: Structural characterization and magnetic properties

The dinuclear dicarboxylato-bridged copper(II) complexes [Cu₂(TPA)₂(μ-tp)](ClO₄)₂ · H₂O (1), [Cu₂(TPA)₂(μ-fum)](ClO₄)₂ · 2H₂O (2) and [Cu₂(pmedien)₂(μ-fum)(H₂O)₂](ClO₄)₂ (3) (tp = terephthalate dianion, fum = fumarate dianion, TPA = tris(2-pyridylmethyl)amine and pmedien = N,N,N′,N″,N″-pentamethyldiethylenetriamine) were synthesized and structurally characterized by X-ray crystallography. The structures of the TPA complexes 1 and 2 consist of μ-tp or μ-fum bridging two Cu(II) centers in a bis(monodentate) bonding fashion. The coordination geometry around the Cu(II) ions in these compounds has a distorted trigonal bipyamidal geometry, TBP with four nitrogen atoms from the TPA ligand and a coordinated oxygen atom supplied by the carboxylate group of the bridged dicarboxylato ligand. Complex 3 has a distorted square pyramidal geometry achieved by the three N-atoms of the pmedien, one fum-carboxylate-oxygen and by an oxygen atom from a coordinated water molecule. The intradimer Cu…Cu distances in these complexes are 11.078(3), 8.663(4) and 9.520(3) Å for 1, 2 and 3, respectively. The electronic spectra of the complexes in aqueous solutions are in complete agreement with the assigned X-ray geometry around the Cu(II) centers. Also, analysis of the infrared spectral data for the ν(COO⁻) stretching frequencies of the tp-carboxalato groups reveals the existence of the bis(mondentate) coordination mode for the bridged dicarboxylato ligands in compounds 1 and 2. The susceptibility measurements at variable temperature over the 2-300 K range are reported. For 1-3, it has been observed slight antiferromagnetic coupling with J values of −0.8, −3.0 and −2.9 cm⁻¹, respectively.     

1,10-Phenanthroline-5,6-dione complexes of middle transition elements: Mono- and dinuclear derivatives

The synthesis and the characterization of several mono- and dinuclear middle transition metal derivatives of 1,10-phenanthroline-5,6-dione, 1, are presented. The reaction of 1 with CrCl₂(THF)₂ gives CrCl₂(O,O′-C₁₂H₆N₂O₂)(THF)₂, 2, while the halides of iron(II), cobalt(II) and nickel(II) afford adducts of general formula MX₂(N,N′-C₁₂H₆N₂O₂), M = Fe, 4, Co, 5, X = Cl; M = Ni, 6, X = Br. DFT calculations on CrCl₂(L)(THF)₂ with L = O,O′-C₁₂H₆N₂O₂ or O,O′-C₁₄H₈O₂ allowed a direct comparison of the coordination properties of 9,10-phenanthrenequinone and 1,10-phenanthroline-5,6-dione to be made. Dinuclear compounds of general formula CrCl₂(THF)₂(O,O′-C₁₂H₆N₂O₂-N,N′)MX_nL_m, M = Zr, 7, X = Cl, n = 4, m = 0; M = Cr, 8, X = Cl, n = 2, L = THF, m = 2; M = Fe, 9, Co, 10, X = Cl, n = 2, m = 0; M = Ni, 11, X = Br, n = 2, m = 0, are prepared from 2 and the corresponding metal halide, while VCp₂(O,O′-C₁₂H₆N₂O₂-N,N′)FeCl₂, 12, is synthesized by reacting 4 with VCp₂. The electronic properties of the different complexes are investigated by magnetic moment measurements and EPR spectroscopy.     

Dinuclear triply bridged copper(II)-carboxylato compounds with different bischelating ligands: Synthesis, crystal structure, spectroscopic and magnetic properties

Three new triply bridged dinuclear copper(II) compounds containing carboxylato bridges, [Cu₂(μ-CH₃COO-κ-O¹,O²)₂(μ-CH₃COO-κ-O¹)(dpyam)₂](BF₄) (1), [Cu₂(μ-CH₂CH₃COO-κ-O¹,O²)(μ-OH)(μ-OH₂)(bpy)₂](ClO₄)₂ (2) and [Cu₂(μ-CH₃COO-κ-O¹,O²)(μ-OH)(μ-OH₂)(phen)₂](ClO₄)₂ (3) (in which dpyam = di-2-pyridylamine, bpy = 2,2-bipyridine, phen = phenanthroline), have been synthesized in order to investigate the magnetic super-exchange pathway between coupled copper(II) centres. All three compounds display a distorted square-pyramidal arrangement around each copper(II) ion with a CuN₂O₃ chromophore. Compound 1 has three acetato bridges, two of which connect each square pyramid at two equatorial sites in a triatomic bridging mode and the third acetato bridge acts at the apical site in the monoatomic bridging mode. The structures of compounds 2 and 3 are mutually similar. In each dinuclear unit, both copper(II) ions are linked at two equatorial positions through a hydroxo bridge and a triatomic carboxylato bridge and at the axial position through a water molecule.The magnetic susceptibility measurements, measured from 5 to 300 K, revealed an antiferromagnetic interaction between the Cu(II) ions in compound 1 and a ferromagnetic interaction for compounds 2 and 3 with singlet-triplet energy gaps (J) of −56, 149 and 120 cm⁻¹, for compounds 1, 2 and 3, respectively.     

The coordination chemistry of mono(di-2-pyridylamine) copper(II) complexes with monovalent and divalent oxoanions: crystal structure, spectroscopic and magnetic properties of dinuclear [Cu(L)(μ-H2PO4)(H2PO4)]2 and polynuclear [Cu(L)(μ3-HPO4)]n

The crystal structures of two copper(II) complexes containing the ligand di-2-pyridylamine (dpyam) with monovalent H₂PO₄ ⁻ and divalent HPO₄ ²⁻ oxoanions, [Cu(dpyam)(μ-H₂PO₄-O,O^′)(H₂PO₄)]₂ (1) and [Cu(dpyam)(μ₃-HPO₄-O,O^′,O″)]_n (2), are reported and determined by X-ray crystallography. The dinuclear Cu(II) complex 1 was obtained by the reaction of dpyam with Cu(NO₃)₂ · 3H₂O and KH₂PO₄ in a water-ethanol (45/55) mixture. The molecules are linked into dinuclear units by two bridging didentate dihydrogenphosphate groups (endo/exo) in an equatorial-equatorial configuration giving a slightly distorted square pyramidal stereochemistry. The Cu-Cu contact distance of 5.136(2) Å is unusually large due to the exo/endo binding of the phosphate bridges. Complex 2 is a polymeric copper(II) derivative with helical [Cu(HPO₄)]₃ units surrounded by dpyam ligands and stabilized by intermolecular hydrogen bonds. Two nearest Cu(II) ions are bridged by a tridentate hydrogenphosphate group which is didentately coordinated to one copper(II) ion, and monodentately coordinated to another in an equatorial-equatorial configuration in an unusual bridging coordination mode. Each copper(II) ion in 2 exhibits a tetrahedrally distorted square-based geometry with the third oxygen atom (Cu-O=2.719(3) Å), from the hydrogenphosphate group weakly bound in an approximately axial position giving an extremely tetrahedrally distorted square-based pyramidal CuN₂O₂O^′ chromophore. The magnetic susceptibility measurements (5-300 K) reveals an antiferromagnetic interaction with J values of −2.85(1) and −26.20(2) cm⁻¹ for complexes 1 and 2, respectively. Some magneto-structural trends are discussed, along with their EPR and electronic reflectance spectra and compared with those of related complexes.     

Two new end-to-end single dicyanamide bridged Cu(II) complexes with Schiff base ligands: Structural, electrochemical and magnetic properties

The synthesis, crystal structures and magnetic properties of two different copper(II) complexes of formula [Cu(L¹)(dca)]_n · nClO₄ (1) and [Cu(L²)]₂(dca)(ClO₄) (2) [L¹ = N,N-dimethylethylene-N′-(pyridine-2-carbaldiiminato), HL² = N,N-dimethylethylene-N′-salicylaldiiminato, dca = dicyanamide anion] are described. Spectroscopic and electrochemical properties have also been discussed. A one-dimensional chain structure with single, symmetrical, μ_1,5-dca bridges is found in compound 1. The copper atom in 1 has a square pyramidal geometry. A tridentate Schiff base ligand, having NNN donor sites, and one nitrogen atom from dca occupy the basal plane. N(18) of a neighbouring unit occupies the apical site. The Schiff base used in compound 2 is a tridentate anion with NNO donor sites, which changes the structure in a dinuclear unit of copper atoms bridged by single end-to-end dicyanamide ion. The environment around copper in 2 is square planar. Magnetic susceptibility measurements for 1 and 2 reveal the occurrence of weak antiferromagnetic interaction through the dca ligand.     

Synthesis, crystal structure, antibacterial assay and DNA binding activity of new binuclear Cu(II) complexes with bridging oxamidate

Two new binuclear copper complexes, [Cu₂(oxpn)(bpy)(pic)(H₂O)](pic) (1) and [Cu₂(oxpn)(Me₂bpy)(pic)](pic) (2) [H₂oxpn = N,N′-bis(3-aminopropyl)oxamide; Hpic = 2,4,6-trinitrophenol; bpy = 2,2′-bipyridine; Me₂bpy = 4,4′-dimethyl-2,2′-bipyridine], have been synthesized and characterized by elemental analyses, conductivity measurements, IR, UV-visible spectroscopy and single crystal X-ray analyses. Both complexes have similar molecular structures. In complex 1, the central two Cu(II) atoms are bridged by cis-oxpn²⁻ with the Cu1-Cu2 separation of 5.221 Å and the polyhedron of each copper atom is a square-pyramid. Similarly, complex 2 is a cis-oxpn²⁻-bridged binuclear complex with the Cu1-Cu2 separation of 5.196 Å. Cu1(II) central atom situated in a tetrahedral geometry is four-coordinated and Cu(II) atom situated in a square-pyramidal geometry is five-coordinated. Hydrogen bonding interactions and π-π stacking interactions link the binuclear copper complex 1 or 2 into a 2D infinite network. The antibacterial assays indicate that the two complexes showed better activities than their ligands. The interactions of the two binuclear complexes with herring sperm DNA (HS-DNA) have been studied by UV absorption titration, fluorescence titration and viscosity measurements. The results suggest that the two binuclear complexes bind to HS-DNA via an intercalative mode.     

Organic-inorganic hybrid materials: Ligand influences on the structural chemistry of copper-vanadates

Hydrothermal reactions were used in the preparation of a series of bimetallic organic-inorganic hybrid materials of the M(II)/V_xO_y/organonitrogen ligand class. Compound 1, [{Cu₂(bpa)₂(C₂O₄)}₂V₄O₁₂]·H₂O, is molecular, while [{Cu(terpy)}₂V₆O₁₇] (2), [Cu₂(bpyrm)V₄O₁₂] (4) and [{Cu(phen)(H₂O)₂}VOF₄(H₂O)]·2H₂O (5) are two-dimensional, three-dimensional and one-dimensional, respectively (bpa = 2,2′-bipyridylamine; terpy = 2,2′:6,2″-terpyridine; bpyrm = 2,2′-bipyrimidine; phen = 1,10-phenanthroline). In contrast to the 2-D structure of 2, the Ni(II) analogue [{Ni(terpy)}₂V₄O₁₂]·2H₂O (3) is one-dimensional. The {V₄O₁₂}⁴⁻ cluster is a building block of structures 1, 3, and 4 while 2 is constructed from {V₆O₁₇}⁴⁻ rings.     

Structural and magnetic characterization of a novel series of dinuclear Cu(II) complexes bridging by 2,5-pyrazine dicarboxylate

A new series of dinuclear 2,5-pyrazine dicarboxylato-bridged copper(II) complexes were synthesized and characterized by spectroscopic techniques. The complexes have the general structural formula [Cu₂(L)₂(μ-pyzdc)](ClO₄)₂·nH₂O where L = TPA, n = 2 (1); L = pmedien, n = 2 (2); L = aepn, n = 3 (3); L = dpt, n = 2 (4); L = Medpt, n = 0 (5); L = dien, n = 0 (6) and L = MeDPA, n = 2 (7) with TPA = tris(2-pyridylmethyl)amine, pmdien = N,N,N′,N′′,N′′-pentamethyldiethylenetriamine, aepn = N-(2-aminoethyl)-1,3-diaminopropane, dpt = dipropylene-triamine, Medpt = 3,3′-diamino-N-methyldipropylamine, dien = diethylenetriamine, MeDPA = N,N-di(2-pyridylmethyl)methylamine. In these complexes, the bridging nature of the 2,5-pyrazine dicarboxylato ligand (pyzdc) was confirmed by single-crystal X-ray crystallography. The structure of the TPA complex 1 consists of μ-pyzdc bridging two Cu(II) centers in a bis(monodentate) bonding fashion through a single oxygen atom supplied by each carboxylate group of the bridged pyzdc in a distorted trigonal bipyramidal geometry achieved by the four nitrogen atoms from the TPA ligand. In the complexes 2-5 derived from tridentate amines, the bridged pyzdc acts as a bis(bidentate) ligand in a distorted square pyramidal geometry achieved by one nitrogen and one carboxylate-oxygen of pyzdc, and by the three N-atoms of the amine coligands. The intradimer Cu?Cu distances in the complexes 2-5 are in the range 6.97-7.45 ? and in it is 10.96 ? in 1. The corresponding intermolecular distances are even shorter (5.34-7.99 ?). The susceptibility measurements at variable temperatures over the 5-300 K range reveal weak antiferromagnetic coupling with J values ranging from −0.61 to −4.78 cm⁻¹.     

Spectral properties and bio-activity of copper(II) clofibriates, part III: crystal structure of Cu(clofibriate)2(2-pyridylmethanol)2, Cu(clofibriate)2(4-pyridylmethanol)2(H2O) dihydrate, and Cu2(clofibriate)4(N,N-diethylnicotinamide)2

New copper(II) clofibriates (clof, {2-(4-chlorophenoxy)-2-methylpropionic or 2-(4-chlorophenoxy)isobutyric acid}) of composition Cu(clof)₂L₂ (where L=2-pyridylmethanol (2-pymeth) (1), N-methylnicotinamide (Menia) (4), N,N-diethylnicotinamide (Et₂nia) (5), isonicotinamide (isonia) (7) or methyl-3-pyridylcarbamate (mpc) (8)), [Cu(clof)₂(4-pymeth)₂(H₂O)] · 2H₂O (4-pymeth=4-pyridylmethanol) (2 · 2H₂O) and Cu(clof)₂L (where L=4-pymeth (3) or Et₂nia (6)) have been prepared and spectroscopically characterized. All the Cu(clof)₂L₂ compounds seem to possess distorted octahedral copper(II) stereochemistry with differing tetragonal distortions. An X-ray analysis of 1 was carried out and it featured a tetragonal-bipyramidal geometry around the copper(II) atom. X-ray analysis of 2 · 2H₂O featured a square-pyramidal geometry around copper(II) atom. Both the Cu(clof)₂L compounds seem to consist of a binuclear unit of tetracarboxylate type bridging. An X-ray analysis of 6 revealed typical binuclear paddle-wheel type structure, consisting of two copper(II) atoms in square-pyramidal geometry bridged by four carboxylate anions in the xy-plane. All complexes under study were characterized by EPR and electronic spectroscopy. The antimicrobial effects have been tested on various strains of bacteria, yeasts and filamentous fungi.     

Different coordination modes of 5,5-diethylbarbiturate in the copper(II) complexes with some aliphatic amines: Synthesis, spectroscopic, thermal and structural studies

Three new copper(II) complexes of 5,5-diethlybarbiturate (barb), [Cu(barb)₂(dmen)]·0.5H₂O (dmen = N,N-dimethylethylenediamine) 1, [Cu(barb)₂(bapa)] (bapa = bis(3-aminopropyl)amine) 2, and [Cu(barb)(apen)](barb)·2H₂O (apen = N,N′-bis(3-aminopropyl)ethylenediamine) 3, have been synthesized and characterized by chemical, spectroscopic and thermal methods. Single crystal X-ray diffraction studies revealed that all complexes are mononuclear. The copper(II) ion exhibits a square-pyramidal coordination geometry in 1 and 3, but a trigonal-bipyramidal geometry in 2. The barb ligand shows different coordination modes. 1 presents the unequal coordination of the barb ligands: one is monodentate (N) and the other one is bidentate (N, O). In 2, both barb ligands are N-coordinated, whereas in 3, one barb ligand is N-coordinated, while the second barb ligand behaves as a counter-ion. The dmen, bapa and apen ligands act as bi-, tri- and tetradentate ligands, respectively. All complexes display a hydrogen-bonded network structure. The IR spectroscopic analysis shows that the ν(CO) stretching frequencies do not correlate predictably with the coordination mode of the barb ligand in 1. Thermal analysis data for 1-3 are in agreement with the crystal structures.     

Synthesis, structure and magnetic studies of two-dimensional network of Cu(II) polymer using malonate and 4,4′-azobispyridine ligands

The malonato-bridged copper(II) complex [Cu(mal)(H₂O)(azpy)_1/2] · H₂O (1) (mal = malonate, azpy = 4,4′-azobispyridine) has been synthesized and characterized by X-ray diffraction. The structure of 1 consists of malonato-bridged uniform copper(II) chains which are covalent connected through azpy to form two-dimensional wavelike network. The magnetic pathway of complex 1 is through a single syn-anti carboxylate bridge connecting equatorial and equatorial positions of adjacent copper(II) atoms, and have the value of the intrachain ferromagnetic coupling (J = 8.73(3) cm⁻¹) and interchain antiferromagnetic coupling (zJ′ = − 1.31(1) cm⁻¹) through a numerical expression for a ferromagnetic uniform chain.