A rare case of solution and solid state inter-conversion of two copper(II) dimers and a copper(II) chain

Three Cu(II)-azido complexes of formula [Cu₂L₂(N₃)₂] (1), [Cu₂L₂(N₃)₂]·H₂O (2) and [CuL(N₃)]_n (3) have been synthesized using the same tridentate Schiff base ligand HL (2-[(3-methylaminopropylimino)-methyl]-phenol), the condensation product of N-methyl-1,3-propanediamine and salicyldehyde). Compounds 1 and 2 are basal-apical μ-1,1 double azido bridged dimers. The dimeric structure of 1 is centrosymmetric but that of 2 is non-centrommetric. Compound 3 is a μ-1,1 single azido bridged 1D chain. The three complexes interconvert in solution and can be obtained in pure form by carefully controlling the synthetic conditions. Compound 2 undergoes an irreversible transformation to 1 upon dehydration in the solid state. The magnetic properties of compounds 1 and 2 show the presence of weak antiferromagnetic exchange interactions mediated by the double 1,1-N₃ azido bridges (J = −2.59(4) and −0.10(1) cm−¹, respectively). The single 1,1-N₃ bridge in compound 3 mediates a negligible exchange interaction.     

3D coordination polymer of copper (II)-potassium (I): Crystal structure and thermal decomposition kinetics

A new heterometallacrown coordination polymer [K₂Cu(NPA)₂(H₂O)₄]_n (where H₂NPA = 3-nitro-phthalic acid) has been synthesized and it’s crystal structure has been elucidated. In the complex, the o-phthalate group coordinates to metal atoms behaving as both tetradentate and heptadentate coordination, the modes of which have been found for the first time. The thermal behaviors of this complex and the thermal decomposition kinetics have been studied. Kinetic analysis shows that the decomposition of title complex in the main range acts as two separate transitions with the first one being a double-step following reaction, , and the second being a three-step following reaction of t:f,f, . The kinetic parameters of these processes were also obtained.     

Anticancer activity, structure, and theoretical calculation of N-(1-phenyl-3-methyl-4-propyl-pyrazolone-5)-salicylidene hydrazone and its copper(II) complex

The pyrazolone derivative N-(1-phenyl-3-methyl-4-propyl-pyrazolone-5)-salicylidene hydrazone (H₂L) and its copper(II) complex [Cu₂L₂CH₃OH]·2CH₃OH have been both synthesized and characterized by elemental analyses, IR spectroscopy, X-ray crystallography, theoretical calculation and pharmacological testing. It’s found that the Cu(II) complex possesses more powerful anticancer effectivity than that of the ligand. In order to make its anticancer principium clearly, we investigate their structures. In ligand there are several coordination spots, such as N, O atoms, which are close to biological environment. The crystallographic structural analysis of the complex reveals that the two Cu centers display two different coordination patterns. O1, O2, N3, and N4 from the ligand take part in the coordination with Cu atoms, resulting in the formation of the double-nuclear complex. The pharmacological testing results show that the coordination effect improves the antitumor activity of the ligand. The calculated Fukui function for H₂L and its deprotonated form L²⁻ predicts that the most probable reactive sites for electrophilic attack are oxygen atoms. The result is agreement well with the experimental data of the crystal structure analyses.     

Synthesis, structure and ferromagnetic properties of a copper(II) coordination polymer with azide and 4-pyridylacrylate

A Cu(II) complex with azide and 4-pyridylacrylic acid (4-Hpya), [Cu₂(4-pya)₂(N₃)₂(DMF)₂] (1) has been synthesized and characterized crystallographically and spectroscopically. This compound consists of binuclear units in which Cu(II) ions are connected through two equatorial-equatorial end-on azido bridges. The Cu(II) dimers are interlinked by 4-pya to generate two-dimensional coordination polymers. Magnetic investigations revealed a relatively strong ferromagnetic interaction through the azide bridges with J = 145 cm⁻¹, and a weak ferromagnetic interdimer interaction through the long but π-conjugated 4-pya ligands. The magneto-structural correlations have been discussed in comparison with other Cu(II) dimers with the same bridging motif.     

Supramolecular structures of metronidazole and its copper(II), cobalt(II) and zinc(II) coordination compounds

In this work we present the synthesis and structural and spectroscopic characterization of Cu(II), Co(II) and Zn(II) coordination compounds with the antibiotic metronidazole ([double bond]emni). Coordination to metal ions is through its imidazolic nitrogen, while the hydroxyethyl and nitro groups act as supramolecular synthons. [Co(emni)(2)Br(2)], and [Zn(emni)(2)X(2)] (X(-)=Cl, Br) stabilize zig-zag chains, and a 2D supramolecular structure is formed by inter-chain contacts through inter-molecular hydrogen-bonding. Pleated sheet or layers are formed by [Co(emni)(2)Cl(2)] and [Cu(emni)(2)Cl(H(2)O)](2)Cl(2), respectively. The dinuclear Cu(II) compound [Cu(emni)mu(O(2)CMe)(2)](2) gives a one-dimensional zig-zag arrangement. The contribution of metal ions in metronidazole coordination compounds is shown in the stabilization of the different aggregate structures.     

Spectroscopic,structural and antibacterial properties of copper(II) complexes with bio-relevant 5-methyl-3-formylpyrazole N(4)-benzyl-N(4)-methylthiosemicarbazone

The coordination behaviour of the title ligand, 5-methyl-3-formylpyrazole N(4)-benzyl-N(4)-methylthiosemicarbazone(HMPz4BM), is reported with solid state isolation of copper(II) complexes, [Cu(HMPz4BM)X₂] (X = Cl, Br, NO₃, ClO₄ and BF₄) which have been spectroscopically and structurally characterised. I.r. data for the free ligand and its Cu(II) complexes indicate that HMPz4BM exhibits a neutral NNS tridentate function via the pyrazolyl nitrogen(tertiary), azomethine nitrogen and thione sulphur. Electronic spectral data are suggestive of a square pyramidal environment for the seemingly pentacoordinated Cu(II) species. E.s.r parameters (RT and LNT) of the reported copper(II) complexes are indicative of a dx_x2–y2 ground state for the reported species. Cyclic voltammograms of Cu(II) complexes show a quasireversible Cu^II/Cu^III couple and also an irreversible Cu^II/Cu^I couple. X-ray crystallography of a representative species, [Cu(HMPz4BM)(NO₃)₂] (C2/c, monoclinic ), has unambiguously documented the conjectural findings from i.r. data that coordinating sites of the title ligand are pyrazolyl (tertiary)nitrogen, azomethine nitrogen and the thione sulphur (NNS); and the oxygen of one of the nitrate ions has occupied the basal plane; the fifth coordination position has been occupied by the oxygen of another nitrate ion in a square pyramidal geometry. The antibacterial properties of the ligand and its copper(II) complexes studied on microorganism, Staphylococcus aureus have pointed out that most of the complexes have higher activities than that of the free ligand.     

Preparation and characterisation of copper(II) hyaluronate

Amorphous copper complexes of the general composition Cu(C14H20O11N)2 x xH2O have been prepared with high- and low-molecular-weight hyaluronic acid (HA). Optimal conditions for preparation are obtained at pH values from 5.0 to 5.5, with a molar ratio of HA versus Cu2+ of 1:1, and at a mass concentration of 5 and 10 mg/mL for high- (Mw = 1.8 x 10(6) Da) and low-molecular-weight sodium hyaluronate (Mw = 2 x 10(5) Da), respectively. The coordination polyhedron of the copper ion has been elucidated by EXAFS and XANES spectroscopy. Copper atoms are octahedrally coordinated in both cases with four equatorial Cu-O bond lengths of 1.95 A, and two axial Cu-O bonds of 2.46 A. Visible spectra of acidic aqueous solution suggest that substitution of axial oxygens by NH groups occurs at pH 6.5 or higher. If the pH value of the copper(II) hyaluronate solution increases above 6.5, the coordination of copper(II) changes. It is very likely that the N atom coming from the acetamido group enters into the coordination sphere of the copper(II) ion.     

Orthometallated versus coordination compounds for reactions of platinum(II) and palladium(II) with the ligand benzil bis(4-methyl-3-thiosemicarbazone)

The ligand benzil bis(4-methyl-3-thiosemicarbazone) LH₂ reacts with K₂PtCl₄, both in the presence or in the absence of LiOH·H₂O, to yield simultaneously the cyclometallated mesocate [Pt₂(μ-L)₂] 1 and the coordination monomeric compound [PtL] 2, which can be easily separated by their different solubility. By contrast, reaction of Li₂PdCl₄ without base leads exclusively to the formation of the coordination compound [PdL] 3, while the use of LiOH·H₂O permits the selective synthesis of the cyclometallated mesocate [Pd₂(μ-L)₂] 4. All the complexes have been characterized by the usual techniques, including X-ray single crystal diffraction that show all the metals to be four-coordinate in a square-planar arrangement, but 2 and 3 with a N₂S₂ environment while in 1 and 4 it is CNS₂. The cytotoxic activity has been evaluated against the human lung carcinoma cell line NCI-H460, but the results show that the complexes are not active in this cell line.     

Synthesis, structure and properties of copper(II) and manganese(II) coordination polymers with 1,5-dinitronaphthalene-3,7-dicarboxylate

Two new metal-organic coordination polymers with 1,5-dinitronaphthalene-3,7-dicarboxylate (NNDC), [Cu₂(NNDC)₂(DMF)_1.8(DMSO)_2.2(H₂O)₂]·H₂O (1) and [Mn₃(NNDC)₃(DMSO)₄]·2DMSO (2) have been synthesized under solvothermal conditions and characterized by single crystal X-ray diffraction and Thermogravimetric Analysis (TGA). The structure of compound 1 consists of one-dimensional chains with copper ions being linked by the dicarboxylate ligands. The coordination chains are associated into ladder-like double chains through O-H?O hydrogen bonds and π-π interactions, and the ladders are packed in a cross fashion through further π-π interactions to give the three-dimensional structure. The Mn(II) compound exhibits a 3D framework with the pcu topology, in which [Mn₃(COO)₆] clusters as octahedral secondary building blocks are linked by the naphthalene spacers. Magnetic analyses were carried out based on both temperature- and field-dependent data, consistently suggesting relatively weak antiferromagnetic interactions within the carboxylate bridged [Mn₃(COO)₆] cluster.     

Synthesis, structure and biological activities of cobalt(II) and zinc(II) coordination compounds with 2-benzimidazole derivatives

In this work we present the synthesis, structural and spectroscopic characterisation of a series of cobalt(II) and zinc(II) coordination compounds with benzimidazole (bz) and its 2-benzimidazole derivatives: 2-aminobenzimidazole (2ab), albendazole (abz) and tris(2-benzimidazolylmethyl)amine (ntb). The compounds were evaluated for their in vitro antimicrobial activity against Staphylococcus aureus, Micrococcus luteus, Salmonella typhi, Pseudomonas aeruginosa, Escherichia coli and Proteus vulgaris. Their cytotoxic activity was also evaluated using human cancer lines, HeLa, HCT-15 and SKLU-1. The halide tetrahedral compounds [Co(bz)₂Br₂] 3, [Zn(2ab)₂Cl₂] · 0.5H₂O 11, [Co(abz)Cl₂(H₂O)] · 3H₂O 14, [Co(abz)Br₂(H₂O)] 15, [Zn(abz)Cl₂(H₂O)] · 3H₂O 17 and [Zn(abz)Br₂(H₂O)] · H₂O 18 displayed similar minimal inhibition concentration (MIC) values against Micrococcus luteus and Escherichia coli, comparable to those of amoxicillin and chloramphenicol. Additionally, 11 showed a wide range of activity towards Gram(+) and Gram(−) microorganisms. The tetradentate ntb and its trigonal bipyramidal cobalt(II) and zinc(II) compounds were active, regardless of the anion present in the complex. Compound [Co(abz)Cl₂(H₂O)] · 3H₂O 14 showed promising activity in HeLa cells, while [Co(ntb)Br]Br · H₂O 21 inhibited Hela and HCT-15 cell lines.     

Two new copper(II) polyamine compounds: Synthesis, characterization and crystal structure

Two new compounds of Cu(II) of stoichiometry CuCl₄(polyamineH₂) containing the polyamines (PA): spermidine or spermine were prepared. Their synthesis, spectroscopic and structural characterization are herein described. The obtained complex with spermidine was characterized by elemental and thermogravimetric analysis, electronic and infrared spectroscopy. In the case of the compound with spermine, crystals were obtained. So, beside all other techniques the compound was also characterized by single crystal X-ray diffractometry. In both cases the species [CuCl₄]²⁻ is present and displays a similar polymeric structure. The X-ray, infrared and electronic spectra are herein discussed based on structural peculiarities of the compounds.     

Crystal structure and exchange pathways of the complex l-(trypthophyl-glycinato)copper(II)

The crystal structure and the EPR characterization of the compound Cu [C₁₃H₁₃N₃O₃] is reported. It crystallizes in the P2₁2₁2₁ space group, with a=8.2829(5), b=9.347(2), c=16.499(2) Å and Z=4. The copper ion is in a distorted square planar coordination, bonded to two nitrogen and one oxygen atoms from one dipeptide and to an oxygen atom from a symmetry-related molecule. Thus, neighbor copper atoms at 5.14 Å are connected by equatorial syn–anti carboxylate bridges giving rise to a chain structure along the b-axis. The chains are connected via hydrogen bonds and cation–π interactions, the latter being provided by the ‘sandwich’ structure involving each copper atom and two tryptophan residues from neighbor molecules. The EPR spectra of polycrystalline sample imply an essentially d_x2−y2 ground state orbital for the Cu(II) ions. The g-values reflect a slightly distorted axial symmetry around the Cu(II) ions as expected from the structural results. No hyperfine interaction is observed, which is indicative of the presence of exchange interactions between the copper atoms as suggested by the X-ray results as well.     

Nickel(II)-, cobalt(II)-, copper(II)-, and zinc(II)-phthalate and 1-methylimidazole coordination compounds: synthesis, crystal structures and magnetic properties

Three new coordination polymers [M(Pht)(1-MeIm)₂]_n (where M=Cu (1), Zn (2), Co (3); Pht²⁻=dianion of o-phthalic acid; 1-MeIm=1-methylimidazole) and two compounds [M(1-MeIm)₆](HPht)₂ · 2H₂O (M=Co (4), Ni (5)) have been synthesized and characterized by X-ray crystallography. The structures of 1-3 (2 is isostructural to 3) consist of [M(1-MeIm)₂] building units connected by 1,6-bridging phthalate ions to form infinite chains. In complex 1, each copper(II) center adopts a square coordination mode of N₂O₂ type by two O atoms from different phthalate ions and two N atoms of 1-MeIm, whereas in 3 two independent metal atoms are tetrahedrally (N₂O₂) coordinated to a pair of Pht ligands and a pair of 1-MeIm molecules. There are only van der Waals interactions between the chains in 1, while the three-dimensional network in 3 is assembled by C-H?O contacts. In contrast to polymers 1-3 the structures of 4 and 5 (complexes are also isostructural) are made up of the [M(1-MeIm)₆]²⁺ cation, two hydrogen phthalate anions (HPht⁻) and two H₂O solvate molecules. The coordination around each metal(II) atom is octahedral with six nitrogen atoms of 1-MeIm. Extended hydrogen bonding networks embracing the solvate water molecules and a phthalate residue as well as the weak C-H?O interactions stabilize the three-dimensional structures. Magnetic studies clearly show that the magnetic ions do not interact with each other. Furthermore, in compound 4 we have another example of a highly anisotropic Co²⁺ ion with a rhombic g-tensor and large zero-field-splitting. The complexes were also characterized by IR and ¹H NMR spectroscopy, thermogravimetric analysis, and all data are discussed in the terms of known structures.     

Cytotoxic activity, X-ray crystal structures and spectroscopic characterization of cobalt(II), copper(II) and zinc(II) coordination compounds with 2-substituted benzimidazoles

Herein we present the synthesis, structural and spectroscopic characterization of coordination compounds of cobalt(II), copper(II) and zinc(II) with 2-methylbenzimidazole (2mbz), 2-phenylbenzimidazole (2phbz), 2-chlorobenzimidazole (2cbz), 2-benzimidazolecarbamate (2cmbz) and 2-guanidinobenzimidazole (2gbz). Their cytotoxic activity was evaluated using human cancer cell lines, PC3 (prostate), MCF-7 (breast), HCT-15 (colon), HeLa (cervic-uterine), SKLU-1 (lung) and U373 (glioblastoma), showing that the zinc(II) and copper(II) compounds [Zn(2mbz)₂Cl₂]·0.5H₂O, [Zn(2cmbz)₂Cl₂]·EtOH, [Cu(2cmbz)Br₂]·0.7H₂O and [Cu(2gbz)Br₂] had significant cytotoxic activity. The isostructural cobalt(II) complexes showed not significant activity. The cytotoxic activity is related to the presence of halides in the coordination sphere of the metal ion. Recuperation experiments with HeLa cells, showed that the cells recuperated after removing the copper(II) compounds and, on the contrary, the cells treated with the zinc(II) compounds did not. These results indicate that the mode of action of the coordination compounds is different.     

Crystal structure and magnetic behavior of a copper(II)-(pyrazine 2,3-dicarboxylate) coordination polymer: 3D architecture stabilized by H-bonding

Reaction of Cu(ClO₄)₂ · 6H₂O and pyrazine 2,3-dicarboxylate (pzdc) in aqueous ammonia medium results [Cu(pyrazine 2,3-dicarboxylate)(H₂O)₂] · H₂O (1). The X-ray single crystal structure reveals that the compound is a 1D polymeric sinusoidal infinite chain which through intra- and inter-molecular hydrogen bonding interactions, involving lattice and coordinated water molecules with dicarboxylate oxygens and pyrazine nitrogens, gives rise to a 3D architecture. The variable temperature magnetic measurements show weak antiferromagnetic interactions between the Cu(II) centers. The best fit parameters through the typical equation for a uniform copper (II) chain are: J=−0.25 cm⁻¹, g=2.17, R=1.3×10−6. The EPR spectrum does not alter with temperature (from r.t. to 4 K). The spectra are typical for square-pyramidal geometry of copper(II) ions, g_∥=2.24 and g_⊥=2.10 (average g=2.15, in good agreement to the value obtained by susceptibility fit).     

Hydrogen binding in coordination compounds of 3(5)-(4-methoxyphenyl)pyrazole

The solid state structures of 3(5)-(4-methoxyphenyl)pyrazole and its coordination compounds with a series of two valent transition metals have been investigated. Since pyrazoles provide not only a nitrogen donor site for the coordination to metal ions, but also an additional N–H function, they are ideal ligands for the formation of hydrogen bound coordination polymers or for the implementation of secondary interactions with other ligands bound to the same central ion, resulting in a rigid ligand environment at the central metal. We chose cobalt, nickel, palladium, copper and zinc as twofold positively charged Lewis acids preferring coordination numbers of four and six to prove the capability of pyrazole to undergo intramolecular hydrogen bonds. In the four-coordinate mode, either tetrahedral (Zn²⁺) or square planar coordination geometries (Pd²⁺) are possible, providing different geometric restrictions for hydrogen bonding.     

Crystal structure and properties of the copper(II) complex of sodium monensin A

The preparation and structural characterization of a new copper(II) complex of the polyether ionophorous antibiotic sodium monensin A (MonNa) are described. Sodium monensin A binds Cu(II) to produce a heterometallic complex of composition [Cu(MonNa)₂Cl₂]·H₂O, 1. The crystallographic data of 1 show that the complex crystallizes in monoclinic space group C2 with Cu(II) ion adopting a distorted square-planar geometry. Copper(II) coordinates two anionic sodium monensin ligands and two chloride anions producing a neutral compound. The sodium ion remains in the inner cavity of the ligand retaining its sixfold coordination with oxygen atoms. Replacement of crystallization water by acetonitrile is observed in the crystal structure of the complex 1. Copper(I) salt of the methyl ester of MonNa, 2, was identified by X-ray crystallography as a side product of the reaction of MonNa with Cu(II). Compound 2, [Me-MonNa][H-MonNa][CuCl₂]Cl, crystallizes in monoclinic space group C2 with the same coordination pattern of the sodium cation but contains a chlorocuprate(I) counter [CuCl₂]⁻, which is linear and not coordinated by sodium monensin A. The antibacterial and antioxidant properties as two independent activities of 1 were studied. Compound 1 is effective against aerobic Gram(+)-microorganisms Bacillus subtilis, Bacillus mycoides and Sarcina lutea. Complex 1 shows SOD-like activity comparable with that of the copper(II) ion.