Electrochemical synthesis and crystal structures of nickel(II), copper(II), zinc(II) and cadmium(II) complexes with N,N′-bis[(4-methylphenyl)sulfonyl]ethylenediamine

The electrochemical oxidation of anodic metal (nickel, copper, zinc and cadmium) in acetonitrile solutions containing N,N′-bis[(4-methylphenyl)sulfonyl]ethylenediamine H₂L and an additional nitrogen coligand, such as 1,10-phenanthroline, yielded mixed complexes of general formula [ML(phen)₂] (M=Ni, Cu, Zn and Cd). The compounds have been characterized by microanalysis, IR and UV-Vis (Ni, Cu complexes) spectroscopy, FAB mass spectrometry, ¹H NMR spectroscopic studies (Zn, Cd complexes) and EPR spectroscopy (Cu and Ni complexes). All compounds have also been characterized by single crystal X-ray diffraction. The molecular structures of these compounds consist of individual monomeric molecules in which the metal atom is in an [MN₆] distorted octahedral environment.     

Synthesis and characterisation of copper(II), zinc(II) and cobalt(II) complexes of salicylglycine, a metabolite of aspirin

Copper(II), nickel(II) and cobalt(II) complexes of the aspirin metabolite salicylglycine (H₂L), of stoichiometry M(HL)₂·solvate, have been prepared and characterised. In these complexes salicylglycinate is coordinated to the metal via its carboxylato group and possibly also its amide oxygen in the copper(II) complex. Under basic conditions copper(II) forms the complex Cu(LH₋₁)·2H₂O·MeOH, in which the ligand is coordinated to the metal via its carboxylate and phenolate oxygen atoms and the deprotonated peptide nitrogen atom.     

Synthesis, structural and corrosion inhibition studies on cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 2-acetylthiophene benzoylhydrazone

Cobalt(II), nickel(II), copper(II) and zinc(II) complexes with 2-acetylthiophene benzoylhydrazone have been synthesized and characterized by elemental analyses, magnetic susceptibility measurements, electronic, IR, NMR and ESR spectral techniques. The molecular structures of ligand and its copper(II) complex have been determined by single crystal X-ray diffraction technique. The Cu(II) complex possesses a CuN₂O₂ chromophore with a considerable delocalization of charge. The structure of the complex is stabilized by intermolecular π–π stacking and C–H?π interactions. Hatbh acts as a monobasic bidentate ligand in all the complexes bonding through a deprotonated C–O⁻ and >CN groups. Electronic spectral studies indicate an octahedral geometry for the Ni(II) complex while square planar geometry for the Co(II) and Cu(II) complexes. ESR spectrum of the Cu(II) complex exhibits a square planar geometry in solid and in DMSO solution. The trend g_|| > g_⊥ > 2.0023 indicates the presence of an unpaired electron in the d_x²-y² orbital of Cu(II). The electro-chemical study of Cu(II) complex reveals a metal based reversible redox behavior. The Ni(II) complex shows exothermic multi-step decomposition pattern of the bonded ligand. The ligand and its most of the metal complexes show appreciable corrosion inhibition properties for mild steel in 1 M HCl medium. [Co(atbh)₂] complex exhibited the greatest impact on corrosion inhibition among the other compounds.     

Synthesis and characterization of a series of diphenyldipyrazolylmethane complexes with zinc(II)

The zinc(II) coordination chemistry of a series of diphenyldipyrazolylmethane ligands was explored using ¹H NMR and single crystal X-ray diffraction. Unsubstituted diphenyldipyrazolylmethane (dpdpm), diphenylbis(3-methylpyrazolyl)methane (dpdp′m), and diphenylbis(3,5-dimethylpyrazolyl)methane (dpdp″m) were reacted with Zn(NO₃)₂ to afford Zn(dpdpm)(NO₃)₂, Zn(dpdp′m)(NO₃)₂ and Zn(Pz″)₂(NO₃)₂ where Pz″ = 3,5-dimethylpyrazole, respectively. All attempts to isolate Zn(dpdp″m)(NO₃)₂ with the intact dpdp″m ligand were unsuccessful due to decomposition of the ligand. These bidentate ligands support the formation of 1:1 ligand to metal complexes and structurally model the two histidine coordination mode common in zinc proteins.     

Synthesis,physico-chemical characterization and antimicrobial activity of cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes with some acyldihydrazones

Complexes of the type [M(bssdh)]Cl and [M(dspdh)]Cl, where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); Hbssdh = benzil salicylaldehyde succinic acid dihydrazone, Hdspdh = diacetyl salicylaldehyde phthalic acid dihydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra and X–ray diffraction studies. Magnetic moment values and electronic spectral transitions indicate a spin free octahedral structure for Co(II), Ni(II) and Cu(II) complexes. IR spectral studies suggest that both the ligands behave as monobasic hexadentate ligands coordinating through three > C = O, two > C = N– and a phenolate group to the metal. ESR spectra of Cu(II) complexes are axial type and suggest as the ground state. X–ray powder diffraction parameters for [Co(bssdh)]Cl and [Co(dspdh)]Cl complexes correspond to an orthorhombic crystal lattice. The ligands as well as their metal complexes show a significant antifungal and antibacterial activity against various fungi and bacteria. The metal complexes are more active than the parent ligands.     

Cyanoscorpionates: Co(II), Mn(II), and Ni(II) complexes coordinated only through the cyano group

New complexes have been synthesized of scorpionate ligands with cyano substituents in the 4-positions of the pyrazoles and tert-butyl substituents in the 3-positions of the pyrazoles. Reaction of Co²⁺, Mn²⁺, and Ni(cyclam)²⁺ (cyclam = 1,4,8,11-tetraazacyclotetradecane) with Tp^t-Bu,4CN in a 1:2 ratio produced new octahedral metal complexes of the form (Tp^t-Bu,4CN)₂ML₄ (L₄ = (H₂O)₄, (H₂O)₂(MeOH)₂, or cyclam). Unlike the sandwich complexes previously isolated with Tp^Ph,4CN, the crystal structures showed none of the pyrazole nitrogen atoms coordinated to the metal. Rather, the metal is coordinated to one CN nitrogen atom from each ligand, with two Tp anions coordinated trans to each other around the metal center. This leaves the Tp pyrazole nitrogen atoms open for another metal to coordinate, which could to lead to heterometallic complexes, new coordination polymers, as well as the framework for supramolecular complexes.     

Synthesis and characterization of Co(II), Ni(II), and Cu(II) complexes containing an eight-membered disulfanenitrile chelating ring

New types of λ⁶-sulfanenitrile-transition metal complexes, [MCl₂(ndsdsd)] (1) and [M(ndsdsd)₂]Cl₂ (2) (M = Co(II), Ni(II), Cu(II)), were obtained by reacting MCl₂ with bis[(nitrilo(diphenyl)-λ⁶-sulfanyl)](diphenyl)-λ⁶-sulfanediimide Ph₂S(N-(Ph₂)SN)₂ (ndsdsd). The crystal structures of these complexes have been elucidated by X-ray crystallographic analysis. The results revealed that, in complexes 1 and 2, the two terminal nitrogen atoms chelate to the metal center to form an eight-membered sulfur-nitrogen ring.     

Imidazole-based nickel(II) and cobalt(II) coordination complexes for potential use as models for histidine containing metalloproteins

It has been established that small molecule model complexes have been useful in studying more complex biological systems of metalloproteins. Because many metalloproteins have active sites that contain multiple histidine residues bound to a metal center, a series of imidazole-containing scorpionate ligands and the associated Co and Ni complexes have been developed to investigate the bonding parameters of histidine containing active sites. The tris(2-imidazolyl) carbinol (2-TIC, 6) and tris[2-(N-methylimidazolyl)] carbinol (2-^MeTIC, 7) complexes of Ni²⁺ and Co²⁺, namely [Co(2-^MeTIC)₂]Cl₂ (8), [Co(2-^MeTIC)₂](NO₃)₂ (9), [Ni(2-^MeTIC)₂]Cl₂ (10), [Ni(2-^MeTIC)₂](NO₃)₂ (11), [Co(2-TIC)₂](NO₃)₂ (12), and [Ni(2-TIC)₂](NO₃)₂ (13), have been prepared from the reaction of the appropriate ligand and appropriate metal salt in polar solvent. These complexes have been characterized by single crystal X-ray diffraction, spectroscopic techniques, and magnetic susceptibility. In each solid-state structure the metal center in the cation coordinates to three N atoms from two ligands and adopts a pseudo-octahedral coordination geometry. The X-ray characterization of tris[2-(N-methylimidazolyl)] carbinol is also reported.     

Synthesis,physico-chemical studies of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes with some p-substituted acetophenone benzoylhydrazones and their antimicrobial activity

Complexes of the type [M(pabh)(H₂O)Cl], [M(pcbh)(H₂O)Cl] and [M(Hpabh)(H₂O)₂ (SO₄)] where, M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hpabh = p-amino acetophenone benzoyl hydrazone and Hpcbh = p-chloro acetophenone benzoyl hydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra, thermal (TGA & DTA) and X-ray diffraction studies. Co(II), Ni(II) and Cu(II) chloride complexes are square planar, whereas their sulfate complexes have spin-free octahedral geometry. ESR spectra of Cu(II) complexes with Hpabh are axial and suggest as the ground state. The ligand is bidentate bonding through >C = N ? and deprotonated enolate group in all the chloro complexes, whereas, >C = N and >C = O groups in all the sulfato complexes. Thermal studies (TGA & DTA) on [Cu(Hpabh)(H₂O)₂(SO₄)] indicate a multistep decomposition pattern, which are both exothermic and endothermic in nature. X-ray powder diffraction parameters for [Co(pabh)(H₂O)Cl] and [Ni(Hpabh)(H₂O)₂(SO₄)] correspond to tetragonal and orthorhombic crystal lattices, respectively. The ligands as well as their complexes show a significant antifungal and antibacterial activity. The metal complexes are more active than the ligand.     

Mononuclear nickel(II) and copper(II) complexes with Schiff base ligands derived from 2,6-diformyl-4-methylphenol and S-methylisothiosemicarbazones

Four new square-planar Ni(II) and Cu(II) complexes with [N₂O₂] binding system were synthesized by metal-directed condensation of 2,6-diformyl-4-methylphenol with benzoyl or acetylacetone mono-S-methylisothiosemicarbazone. Only mononuclear “one-armed” complexes were obtained as a consequence of the different reactivity of the two carbonyl groups in the hydroxydialdehyde. The complexes were characterized by elemental analysis, EI MS and UV-Vis spectroscopy. The structural assignment was confirmed by X-ray diffraction analysis and NMR spectroscopy, for the Ni(II) complexes, and by ESR spectroscopy and magnetic measurements, for the Cu(II) complexes.     

D-galactosamine complexes with copper(II), nickel(II), and cobalt(II)

The potentiometric and spectroscopic methods were applied to describe the equilibria for the Cu(II), Ni(II), and Co(II), D-galactosamine solutions. The stability constants, the spectral data, and the results obtained earlier precisely defined the binding ability of the aminosugars.     

Whole cell immobilized amperometric biosensor based on Saccharomyces cerevisiae for selective determination of vitamin B1 (thiamine)

A new amperometric whole cell biosensor based on Saccharomyces cerevisiae immobilized in gelatin was developed for selective determination of vitamin B1 (thiamine). The biosensor was constructed by using gelatin and crosslinking agent glutaraldehyde to immobilize S. cerevisiae cells on the Teflon membrane of dissolved oxygen (DO) probe used as the basic electrode system combined with a digital oxygen meter. The cells were induced by vitamin B1 in the culture medium, and the cells used it as a carbon source in the absence of glucose. So, when the vitamin B1 solution is injected into the whole cell biosensor system, an increase in respiration activity of the cells results from the metabolic activity and causes a decrease in the DO concentration of interval surface of DO probe related to vitamin B1 concentration. The response time of the biosensor is 3 min, and the optimal working conditions of the biosensor were carried out as pH 7.0, 50mM Tris-HCl, and 30 degrees C. A linear relationship was obtained between the DO concentration decrease and vitamin B1 concentration between 5.0 x 10(-3) and 10(-1) microM. In the application studies of the biosensor, sensitive determination of vitamin B1 in the vitamin tablets was investigated.     

Metal complexes of cyclic hydroxamates. Synthesis and crystal structures of 3-hydroxy-2-methyl-3H-quinazolin-4-one (ChaH) and of its Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes

The attempted acetylation of anthranilic hydroxamic acid (2-aminobenzohydroxamic acid) as a possible dual inhibitor of the catalytic sites in prostaglandin-H-synthase (PGHS) gave the cyclic hydroxamic acid 3-hydroxy-2-methyl-3H-quinazolin-4-one (ChaH) which was characterised by spectroscopy and X-ray crystallography. The length of the hydroxamic acid C-N bond, 1.3998(17) Å, in ChaH is longer than normal (∼1.33 Å) indicative of reduced delocalisation of the nitrogen lone pair of electrons into the hydroxamic acid π system. This is confirmed by the appearance of the ν(CO) band at a considerably higher wavenumber in the IR spectrum than normal. The complexes Fe(Cha)₂(Cl)(H₂O)·⁷/₂H₂O, Co(Cha)₂(EtOH)₂, Ni(Cha)₂(EtOH)₂, Cu(Cha)(H₂O)(Cl) and Zn(Cha)₂(H₂O), have been synthesised and their structures determined by X-ray crystallography. The X-ray data confirmed coordination by Cha^- through the carbonyl and deprotonated hydroxamate oxygen in all cases. The M-O (hydroxamate) bonds are shorter than the M-O (carbonyl) bonds by between 0.0930 Å for the Co(II) complex and 0.0448 Å for the Ni(II) complex. The geometries of all complexes conform to the coordination requirements of the particular metal ion involved. Speciation studies for ChaH and its complexes with Ni(II) and Zn(II) were carried out using pH-metric methods. The results show that ChaH is much more acidic than related acyclic hydroxamic acids and that its metal complexes are correspondingly less stable.     

Synthesis, crystal structures and spectroscopy of meclofenamic acid and its metal complexes with manganese(II), copper(II), zinc(II) and cadmium(II). Antiproliferative and superoxide dismutase activity

Some new complexes of meclofenamic acid (N-(2,6-dichloro-m-tolyl)anthranilic acid), Hmeclo (1), with potentially interesting biological activities are described. Complexes [Mn(meclo)₂] (2), [Cu(meclo)₂(H₂O)₂] (3), [Zn(meclo)₂(H₂O)₂] (4) and [Cd(meclo)₂(H₂O)₂] (5) were prepared and structurally characterized by means of vibrational, electronic and ¹H and ¹³C NMR spectroscopies. The crystal structure of complexes [Cu₄(meclo)₆(OH)₂(DMSO)₂]2DMSO (3a) and [Cd(meclo)₂(DMSO)₃] (5a) have been determined by X-ray crystallography. Complex (3a) is a centrosymmetric tetramer built up around the planar cyclic Cu₂(OH)₂ unit. Complex 5a is mononuclear seven-coordinated complex with the meclofenamato ligand behaving as a bidentate deprotonated chelating ligand. Intra and intermolecular hydrogen bonds stabilize these two structures, while the crystal packing is determined by π-π and C−H−-π interactions. Meclofenamic acid and its metal complexes have been evaluated for antiproliferative activity in vitro against the cells of three human cancer cell lines, MCF-7 (breast cancer cell line), T24 (bladder cancer cell line), and A-549 (non-small cell lung carcinoma), and a mouse fibroblast L-929 cell line. Complex 5 exhibits the highest selectivity against MCF-7 and 4 shows the highest selectivity against T-24. Complexes 2-5 were found to be more potent cytotoxic agents against T-24 and complex 5 against MCF-7 cancer cell lines than the prevalent benchmark metallodrug, cis-platin. The superoxide dismutase activity was measured by the Fridovich test which showed that complex [Cu(meclo)₂(H₂O)₂] is a good superoxide scavenger.     

Synthesis, crystal structures, and molecular hyperpolarizabilities of a new Schiff base ligand, and its copper(II), nickel(II), and cobalt(II) metal complexes

A new ligand (HL) obtained from the Schiff base condensation of 4-(diethylamino)salicylaldehyde with 4-nitroaniline is reported, with its nickel(II), copper(II), and cobalt(II) complexes. The crystal structures are reported for the four derivatives. While, Ni^IIL₂ and Cu^IIL₂ are centrosymmetric molecules, Co^IIL₂ exhibits a pseudo-tetrahedral molecular structure. The quadratic hyperpolarizabilities (β) of HL and Co^IIL₂, measured by electric field induced second harmonic (EFISH) technique, are equal to 66 and 110 × 10⁻³⁰ cm⁵ esu⁻¹, respectively. Beside a geometric effect (pseudo-T_d symmetry), the coordination of the metal center provides an intrinsic enhancement of the NLO response. In addition, an enhancement of the thermal stability of about 60° is found upon metal complexation.     

Alternative syntheses and reactivity of platinum(II) terpyridyl acetonitrile complexes

New direct syntheses of [Pt(trpy)(NCCH₃)](CF₃SO₃)₂2 (where trpy = 2,2′:6′,2′′-terpyridine) and [Pt(tBu₃-trpy)(NCCH₃)](CF₃SO₃)₂3 (where tBu₃-trpy = 4,4′,4″-tri-tert-butyl-2,2′:6′,2″-terpyridine) via the displacement of acetonitrile from [Pt(NCCH₃)₄](CF₃SO₃)₂ have been developed. The synthetic utility of 2 was investigated in reactions with triphenylphosphine (PPh₃), 2,6-dimethylphenyl isocyanide (CN-Xyl), 2,5-dimethyl-2,5-diisocyanohexane (TM4), and tert-butyl isocyanide (CN-tBu). Whereas the expected substitution products were observed for reactions with PPh₃, CN-Xyl, and CN-tBu, dealkylation of TM4 occurred to afford [Pt(trpy)(CN)](CF₃SO₃) 6. The structures of [Pt(trpy)L]²⁺ dications show little intermolecular interactions in the solid state, with the exception of the tBu₃-trpy complex 3 which exists as head-to-tail dimers with a Pt-Pt distance of 3.29 Å. The cyano product 6 was found to stack in infinite chains of cations with a Pt-Pt distance of 3.45 Å.     

Preferential azido bridging regulating the structural aspects in cobalt(III) and copper(II)-Schiff base complexes: Syntheses, magnetostructural correlations and catalytic studies

A tridentate NNO donor Schiff base ligand [(1Z,3E)-3-((pyridin-2-yl)methylimino)-1-phenylbut-1-en-1-ol = LH] in presence of azide ions coordinates with cobalt(II) and copper(II) ions giving rise to three new coordination complexes [Co₂(L)₂(μ_1,1-N₃)₂(N₃)₂] (1), [Cu₂(L)₂(μ_1,3-N₃)]·ClO₄ (2) and [(μ_1,1-N₃)₂Cu₅(μ-OL)₂(μ_1,1-N₃)₄(μ_1,1,1-N₃)₂]_n (3). The complexes have been characterized by elemental analysis, FT-IR, UV-Vis spectral studies, and single crystal X-ray diffraction studies. These complexes demonstrate that under different synthetic conditions the azide ions and the Schiff base ligand (LH) show different coordination modes with cobalt(II) and copper(II) ions, giving rise to unusual dinuclear and polynuclear species (1, 2 and 3) whose structural variations are discussed. Magneto-structural correlation for the very rare singly μ_1,3-N₃ bridged Cu^II-Schiff base dinuclear species (2) has been studied. In addition, the catalytic properties of 1 for alkene oxidation and the general catalase-like activity behavior of 2 have been discussed.     

Application of vitamin B(12)-targeting site on Lactobacillus helveticus B-1 to vitamin B(12) assay by chemiluminescence method

Lactobacillus helveticus B-1 is assumed to have a vitamin B(12)-targeting (or B(12)-binding) site on the cells, since the binding reaction of vitamin B(12) with L. helveticus B-1 cells proceeded instantly and quantitatively. This reaction is specific to complete B(12) compounds, cobalamins, and can be used for a vitamin B(12) assay method by chemiluminescence. The calibration graph was linear from 0.1 to 10.0 ng/mL. The B(12) contents in oyster and sardine were 75.9 and 39.4 microg/100g, respectively. These values were very close to those obtained using a chemilumi-ADVIA Centaur immunoassay system with intrinsic factor and to those obtained by microbiological assays.     

Anti-oxidant,in vitro,in vivo anti-inflammatory activity and antiproliferative activity of mefenamic acid and its metal complexes with manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II)

Some new complexes of mefenamic acid with potentially interesting biological activity are described. The complexes of mefenamic acid [Mn(mef)₂(H₂O)₂], 1, [Co(mef)₂(H₂O)₂], 2, [Ni(mef)₂(H₂O)₂], 3, [Cu(mef)₂(H₂O)]₂, 4 and [Zn(mef)₂], 5, were prepared by the reaction of mefenamic acid, a potent anti-inflammatory drug with metal salts. Optical and infrared spectral data of these new complexes are reported. Monomeric six-coordinated species were isolated in the solid state for Mn(II), Ni(II) and Co(II), dimeric five-coordinated for Cu(II) and monomeric four-coordinated for Zn(II). In DMF or CHCl₃ solution the coordination number is retained and the coordinated molecules of water are replaced by solvent molecules. The anti-oxidant properties of the complexes were evaluated using the 1,1-diphenyl-2-picrylhydrazyl, DPPH, free radical scavenging assay. The scavenging activities of the complexes were measured and compared with those of the free drug and vitamin C. We have explored their ability to inhibit soybean lipoxygenase, β-glucuronidase and trypsin- induced proteolysis. The complex [Mn(mef)₂(H₂O)₂] exhibits the highest antioxidant activity and the highest inhibitory effect against the soybean lipogygenase (LOX), properties that are not demonstrated by mefenamic acid. Their inhibitory effects on rat paw edema induced by Carrageenan was studied and compared with those of mefenamic acid. The complex [Zn(mef)₂] exhibited a strong inhibitory effect at 0.1 mmol/Kg B.W. (81.5 ± 1.3% inhibition), superior to the inhibition induced by mefenamic acid at the same dose (61.5 ± 2.3% inhibition). Mefenamic acid and its metal complexes have been evaluated for antiproliferative activity in vitro against the cells of three human cancer cell lines: MCF-7 (human breast cancer cell line), T24 (bladder cancer cell line), A-549 (non-small cell lung carcinoma) and a mouse fibroblast L-929 cell line. The copper(II) complex displays against T24, MCF-7 and L-929 cancer cell lines, IC₅₀ values in a μM range similar to that of the antitumor drug cis-platin and they are considered for further stages of screening in vitro and/or in vivo as agents with potential antitumor activity.     

Anticancer and antifungal activity of copper(II) complexes of quinolin-2(1H)-one-derived Schiff bases

The condensation of substituted aromatic aldehydes with 7-amino-4-methyl-quinolin-2(1H)-one (1) has lead to the isolation of quinolin-2(1H)-one derived Schiff bases (2-14). The copper(II) complexes (2a-14a) of the ligands were also prepared, and together with their corresponding free ligands were fully characterised by elemental analyses, spectral methods (IR, ¹H and ¹³C NMR, AAS, UV-Vis), magnetic and conductance measurements. The bidentate ligands coordinated to the copper(II) ion through the deprotonated phenolic oxygen and the azomethine nitrogen of the ligands in almost all cases. X-ray crystal structures of two of the complexes, 5a and 8a, confirmed the bidentate coordination mode. All of the compounds were investigated for their antimicrobial activities against the fungus, Candida albicans, and against Gram-positive and Gram-negative bacteria. The compounds were found to have excellent anti-Candida activity but were inactive against Staphylococcus aureus and Escherichia coli. Selected compounds (2-8 and 2a-8a) were also screened for their in vitro anticancer potential using the human hepatic carcinoma cell line, Hep-G₂. Several derivatives were shown to be active comparable to that of cisplatin.