Composition and stability of copper(II), nickel(II), and cobalt(II) complexes with mono- and bis(2-carboxy)-2-pycolylamine

Complexation of N-(2-pyridyl)methyl-3-aminopropionic (HL¹) and N-(2-pyridyl)methyliminodipropionic (H₂L²) acids with copper(II), nickel(II), and cobalt(II) ions is studied. The composition of complexes is determined using the Starik–Barbanel relative yield method. The acid dissociation constants of HL¹ and H₂L² are determined potentiometrically; the stability constants of HL¹ and H₂L² complexes with metal ions are calculated.     

Complexation en solution aqueuse des ions magnesium(II), manganese(II), nickel(II), cuivre(II) et plomb(II) avec la s-carboxymethyl-l-cysteine: Complex formation of magnesium(II), manganese(II), nickel(II), copper(II) and lead(II) with S-carboxymethyl-L-cysteine in aqueous solution

Complex formation of magnesium(II), manganese(II), nickel(II), copper(II) and lead(II) with S-carboxymethyl-L-cysteine in aqueous solution.The complex formation between Mg(II), Mn(II), Ni(II). Cu(II), Pb(II) ions and S-carboxy-methyl-l-cysteine (H₂A) has been studied by measurement of pH at 25°C and constant ionic strength (1 M NaClO₄). Although no interaction occurs with Mg(II), this work provides evidence for a variety of complexes: MnA; CuHA⁺; CuA; CuA₂^2-; NiHA⁺; NiA; NiA₂^2-; PbHA⁺; PbA et PbA(OH)^-. The overall formation constants of all these species are computed and refined. The results allow the determination of the distribution of the complexes as a function of pH; some structural features of the metal complexes in solution are indicated.     

Copper(II), nickel(II) and cobalt(II) complexes of 5,5-dimethylcyclohexane-1,2,3-trione-2-arylhydrazones

Summary Copper(II), nickel(II) and cobalt(II) perchlorate complexes of 5,5-dimethylcyclohexane-1,2,3-trione-2-(p-nitrophenyl-hydrazone) (HL¹), 5,5-dimethyl-cyclohexane-1,2,3-trione-2-(p-chlorophenylhydrazone) (HL²), 5,5-dimethylcyclohexane-1,2,3-trione-2-(o-chlorophenylhydrazone) (HL⁴), 5,5-dimethylcyclohexane-1,2,3-trione-2-(o-methylphenyl-hydrazone) (HL⁵) and 5,5-dimethylcyclohexane-1,2,3-trione-2-(m-methylphenylhydrazone) (HL⁶) have been prepared, and characterized using analytical, spectral and magnetic measurements. The data reveal that the reaction of Cu(ClO₄)₂ (1 mol) in EtOH, with all ligands, produces complexes of the type CuL(ClO₄)(H₂O).nH₂O. Nickel(II) and cobalt(II) perchlorates react only with HL¹ and HL² to produce the complexes ML(ClO₄)(H₂O)₃ (where M = Ni^II, L = L^– and L², M = Co^II, L = L¹) and Co(HL₂)₂-(ClO₄)₂.2H₂O. The spectral data show that the ligands behave as monobasic bidentate in their azo forms, except HL² which reacts with cobalt(II) as a neutral bidentate ligand in its hydrazone form.     

N-acetyl-DL-leucinate cobalt(II), nickel(II) and zinc(II) complexes

Summary Complexes of the type M(AcLeu)₂ · B₂ (M = Co^II, Ni^II or Zn^II; B = H₂O, py, 3-pic, 4-pic; AcLeu =N-acetyl-DL-leucinate ion) and M(AcLeu)₂ B (M = Co^II or Zn^II and B = o-phen) were prepared and investigated by means of magnetic and spectroscopic measurements. The i.r. spectra of all the complexes are consistent with bidentate coordination of the amino acid to the metal ion. The room temperature solid state electronic spectra indicate that the symmetry of this species is closer toD _4h and that MO₆ and MO₄N₂ chromophores are present in the M(AcLeu)₂ · 2 H₂O and M(AcLeu)₂B_n · x H₂O (B = py, 3-pic, 4-pic, n=2 and x=0 for M = Ni^II; B = o-phen, n=1 and x=0 for M = Co^II; B = py, 3-pic, 4-pic, n=1 and x=1 for M = Co^II) complexes, respectively. By comparing the Dq values of the amino acid and those of other N-substituted amino acids previously studied, a spectrochemical series of the the cobalt(II) and nickel(II) complexes is proposed. The¹ H n.m.r. spectra of the zinc(II) complexes confirm the proposed stereochemistry.     

Copper(II), nickel(II) and cobalt(II) complexes of oxaldihydrazide and succindihydrazide Schiff bases with salicylaldehyde ando-hydroxyacetophenone

Summary Polymeric copper(II), nickel(II) and cobalt(II) complexes of the type M₂L where M = Cu^II, Ni^II or Co^II and H₄L = disalicylaldimine oxamide (H₄A), di(o-hydroxyacetophenoneimine)oxamide (H₄B), disalicylaldimine succinamide (H₄C) or di(o-hydroxyacetophenoneimine)succinamide (H₄D), have been synthesized and characterized by analysis, i.r. and electronic spectra and magnetic moment data. Copper(II) complexes and some of the nickel(II) and cobalt(II) complexes are planar while other nickel(II) complexes are distorted octahedral and other cobalt(H) complexes are square pyramidal. Anomalously low magnetic moments of some complexes have been related to M-M interactionsvia oxo-bridge structures.     

Stability constants of phthalate complexes of copper (II), nickel (II), zinc (II), cobalt (II), uranyl (II) and throium (IV) by paper electrophoresis

Summary Stoichiometric stability constants of Cu(II), Ni(II), Zn(II), Co(II), UO₂(II) and Th(VI) phthalate have been determined by paper electrophoresis. Phthalic acid (0.005 mol dm⁻³) was added to the background electrolyte: 0.1 mol dm⁻³ HClO₄. The proportions of C₆H₅C₂O ₄ ⁻ and C₆H₄C₂O ₄ ⁼ were varied by changing the pH of the electrolyte. These anions yielded the complexes, Cu C₆H₅C₂O ₄ ⁺ , Cu C₆H₄C₂O₄, Zn C₆H₅C₂O ₄ ⁺ , Co C₆H₅C₂O ₄ ⁺ , Ni C₆H₅C₂O ₄ ⁺ , UO₂ C₆H₅C₂O ₄ ⁺ , UO₂ (C₆H₄C₂O₄) ₂ ⁼ and Th (C₆H₄C₂O₄)₂ whose stability constants are found to be 10^3.0, 10^4.7, 10^2.6, 10^2.5, 10^2.3, 10^3.5, 10^12.6 and 10^13.4 respectively (μ=0.1, temp 40°C).     

Solution state and complexing ability of 1,4-bis(amidomethylsulfinyl)butane toward iron(III), copper(II), cobalt(II), nickel(II), and manganese(II)

The solution state and thermodynamic stability of complexes of the new antituberculosis agent 1,4-bis(amidomethylsulfinyl)butane (L) with iron(III), copper(II), cobalt(II), nickel(II), and manganese(II) in an aqueous solution in the presence and in the absence of the nonionic surfactant Brij 35 were studied by spectrophotometry, pH potentiometry, NMR relaxation technique (T = 25 °C; variable ionic strength), and mathematical simulation. The geometry optimization of all structures was carried out by the molecular mechanics method MM2 in order to obtain data on coordination modes. In addition, the structure of 1,4-bis(amidomethylsulfinyl)butane was refined by the DFT/B3LYP/6-311++G(d,p) quantum chemical method using the IEFPCM model to take into account solvent effects. In an aqueous solution (in the concentration range of 1.3?10^–5—1?10^–3 mol L–1) and in the presence of Brij 35, 1,4-bis(amidomethylsulfinyl)butane exists as a neutral monomer. The Beer—Lambert—Bouguer law is obeyed in a wide concentration range for compound L in an aqueous solution, as well as in the presence of the surfactant, which can be used for the quantification of compound L. Iron(III), cobalt(II), and nickel(II) were shown to form 1: 1 mononuclear complexes with L; and copper(II) forms, 1: 1 and 2: 2 complexes. The presence of Brij 35 in the Cu²⁺—L system at a micellar concentration promotes the formation of a dinuclear complex.     

Synthesis and characterization of cobalt(II), nickel(II), copper(II) and zinc(II) complexes with acetylacetone bis-benzoylhydrazone and acetylacetone bis-isonicotinoylhydrazone

Summary Acetylacetone bis-benzoylhydrazone (PhCONHN=CMe)₂ CH₂(LH₂) and acetylacetone bis-isonicotinoylhydrazone (NC₅H₄CONHN=CMe)₂CH₂(LH₂) complexes of the types [ML] and [ML] (M = Co^II, Ni^II, Cu^II or Zn^II) have been prepared and characterized. All the complexes are non-electrolytes and the cobalt(II) complexes are lowspin, the nickel(II) complexes are diamagnetic and the copper(II) complexes are paramagnetic. The ligands chelate via two C=N groups and two deprotonated enolate groups. The e.s.r. spectra of the copper(II) complexes indicate a tetragonally distorted dimeric structure. The X-ray diffraction parameters for [CoL] and [NiL] correspond to a tetragonal crystal lattice.     

Synthesis and characterization of nickel(II), cobalt(II), copper(II), manganese(II), zinc(II), zirconium(IV), dioxouranium(VI) and dioxomolybdenum(VI) complexes of a new Schiff base derived from salicylaldehyde and 5-methylpyrazole-3-carbohydrazide

Summary Synthesis of a new Schiff base derived from salicylaldehyde and 5-methylpyrazole-3-carbohydrazide, and its coordination compounds with nickel(II), cobalt(II), copper(II), manganese(II), zinc(II), zirconium(IV), dioxouranium(VI) and dioxomolybdenum(VI) are described. The ligand and the complexes have been characterized on the basis of analytical, conductance, molecular weight, i.r., electronic and n.m.r. spectra and magnetic susceptibility measurements. The stoichiometries of the complexes are represented as NiL · 3H₂O, CoL · 2H₂O, CuL, MnL · 2H₂O, ZnL · H₂O, Zr(OH)₂(LH)₂, Zr(OH)₂L · 2MeOH, UO₂L · MeOH and MoO₂L · MeOH (where LH₂ = Schiff base). The copper(II) complex shows a subnormal magnetic moment due to antiferromagnetic exchange interaction while the nickel(II), cobalt(II) and manganese (II) complexes show normal magnetic moments at room temperature. The i.r. and n.m.r. spectral studies show that the Schiff base behaves as a dibasic and tridentate ligand coordinating through the deprotonated phenolic.oxygen, enolic oxygen and azomethine nitrogen.     

Metal complexes of sulphur-nitrogen chelating agents. Part 14. Nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) complexes of the tetradentate schiff bases having ONNS donor sites

Summary Complexes of nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) with methyl-2-(-salicylaldiminoethyl)-cyclopent-1-en-dithiocarboxylate (H₂L¹) and methyl-2-(-salicylaldiminoisopropyl)cyclopent-1-en-dithiocarboxylate (H₂L²) have been prepared. They contain the donor sites ONNS. The metal(II) ions from neutral, monomeric square planar chelate complexes. The cobalt(III) complexes [CoL¹-(H₂O)₂]X (X=Cl or ClO₄) appear to betrans-diaqua-species. All compounds have been characterized by a number of physico-chemical methods.     

Synthesis and characterization of 2,3-bis(hydroxyimino)-1,2,3,4-tetrahydro-pyrido[2,3-b]pyrazine and its nickel(II), cobalt(II), copper(II), palladium(II), cadmium(II) and cobalt(III) complexes

Summary 2,3-Bis(hydroxyimino)-1,2,3,4-tetrahydro-pyrido[2,3-b]pyrazine (H₂L), prepared from 2,3-diaminopyridine and cyanogen-di-N-oxide has been converted into nickel(II), palladium(II), copper(II), cobalt(II), and cobalt(III) complexes (H₂L) with a 12 metal:ligand ratio. The ligands coordinate through the two N atoms, as do most vicinal dioximes. [(LH)Cl(H₂O)Cd], contains a six-membered chelate ring. [Co(HL)₂(L)Cl] has also been prepared using triphenylphosphine, triphenylarsine, thiophene and chloride as axial ligands. The structure of thevic-dioxime and its complexes are proposed on the basis of elemental analysis, i.r.,¹H-n.m.r. and uv-visible measurements.     

The relaxation spectra of nickel(II) and cobalt(II) arginine complexes

The temperature-jump method has been used to determine the nickel(II)- and cobalt(II)-arginine complexation kinetics. In the pH range studied, the neutral form of the ligand, HL, is the attacking, as well as the complexed, ligand species. The reactions reported on are of the type where n = 1, 2, 3 and M is Ni or Co. At 25° and ionic strength 0.1M the association rate constants are: for nickel(II) k₁ = 2.3 × 10³(±20%), k₂ = 2.4 × 10⁴(±20%), k₃ = 3.5 × 10⁴(±40%) M^?1 sec^?1; for cobalt(II) k₁ = 1.5 × 10⁵(±20%), k₂ = 8.7 × 10⁵(±20%), k₃ = 2.0 × 10⁵(±40%) M^?1 sec^?1. Arginine binds to metal ions less well than homologous chelating agents due to the electrostatic repulsion arising from the positively charged terminus of the zwitterion. Kinetically, the effect appears in the association rate constants with nickel reactions more strongly influenced than cobalt.     

Synthesis,characterization, and biological properties of Ni(II), Co(II), and Cu(II) complexes of Schiff bases derived from 4-aminobenzylamine

New Schiff bases, N,N′-bis(salicylidene)-4-aminobenzylamine (H₂L¹), N,N′-bis(3-methoxysalicylidene)-4-aminobenzylamine (H₂L²), and N,N′-bis(4-hydroxysalicylidene)-4-aminobenzylamine (H₂L³), with their nickel(II), cobalt(II), and copper(II) complexes have been synthesized and characterized by elemental analyses, electronic absorption, FT-IR, magnetic susceptibility, and conductance measurements. For the ligands, ¹H and ¹³C NMR and mass spectra were obtained. The tetradentate ligands coordinate to the metal ions through the phenolic oxygen and azomethine nitrogens. The keto-enol tautomeric forms of the Schiff bases H₂L¹, H₂L², and H₂L³ have been investigated in polar and apolar solvents. All compounds were non-electrolytes in DMSO (～10^?3 M) according to the conductance measurements. Antimicrobial activities of the Schiff bases and their complexes have been tested against Acinobacter baumannii, Pseudomonas aeruginosa, Micrococcus luteus, Bacillus megaterium, Corynebacterium xerosis, Staphylococcus aureus, Escherichia coli, Candida albicans, Rhodotorula rubra, and Kluyveromyces marxianus by the disc diffusion method; biological activity increases on complexation.     

Heteroleptic cobalt(II) and nickel(II) complexes with iminodiacetic and dicarboxylic acids in aqueous solution

Equilibria in binary and ternary systems containing cobalt(II) and nickel(II) salts, iminodiacetic acid, and dicarboxylates were studied by spectrophotometry at I = 0.1 (NaClO₄) and T = 20 ± 2°C. The molar and proton compositions of the resulting complexes and the pH ranges of their existence were determined. The stability constants of the homo- and heteroleptic complexes were calculated. The pH-distribution of the detected complexes was obtained. The experimental data were analyzed using the mathematical models that predict the existence of a wide spectrum of complex species in solution and allow ignoring those species that are negligible for accurate reproduction of the observed pattern.     

Synthesis and characterisation of nickel(II), cobalt(II), manganese(II), copper(II), zinc(II), dioxouranium(VI) and dioxomolybdenum(VI) complexes of tridentate dibasic ONO donor Schiff bases derived from 2-benzothiazolecarbohydrazide and salicylaldehyde/2-hydroxy-1-naphthaldehyde

Summary The syntheses of several new coordination complexes of nickel(II), cobalt(II), manganese(II), copper(II), zinc(II), dioxouranium(VI) and dioxomolybdenum(VI) with new Schiff bases derived from 2-benzothiazolecarbohydrazide and salicylaldehyde or 2-hydroxy-1-naphthaldehyde are described. These complexes have been characterised by elemental analyses, electrical conductance, magnetic susceptibility, molecular weight, i.r. and electronic spectra. The Schiff bases behave as dibasic and tridentate ligands coordinating through the ONO donor system and form complexes of the types NiL · 3H₂O, MnL · 2H₂O, CoL · 2H₂O, CuL, ZnL · H₂O, UO₂L · MeOH and MoO₂L · MeOH (where LH₂ = Schiff base). The copper(II) complexes exhibit subnormal magnetic moments indicating the presence of an antiferromagnetic exchange interaction, whereas the nickel(II), cobalt(II) and manganese(II) complexes behave normally at room temperature. Zinc(II), dioxouranium(VI) and dioxomolybdenum(VI) complexes are diamagnetic; the zinc (II) complexes are tetrahedral, the copper(II) complexes are square planar, all the other complexes are octahedral. Thev(C=N),v(C-O),v(N-N) andv(C-S) shifts have been measured in order to locate the Schiff base coordination sites.     

Synthesis,characterization and catalytic studies of iron(III), cobalt(II), nickel(II) and copper(II) complexes containing triphenylphosphine and β-diketones

A series of new β-diketonato complexes have been synthesized from the reactions of iron(III), cobalt(II), nickel(II) and copper(II) Ph₃P complexes with β-diketones (acetylacetone, benzoylacetone and dibenzoylmethane). All the complexes have been characterized by elemental analyses, spectral studies (i.r., electronic., magnetic., e.p.r., ¹H-n.m.r.) and cyclic voltammetry. The new complexes have been used as catalysts for aromatic coupling and oxidation reactions. Higher catalytic activity has been observed for the nickel(II) complexes compared to the other complexes.     

Potentiometric determination of stability constants of cyanoacetato complexes of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II) and lead(II)

Stability constants of cyanoacetato complexes of cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II) and lead(II) were determined potentiometrically at 25.0 +/- 0.1 degrees and ionic strength 2M (sodium perchlorate). The stability constants were evaluated by a weighted least-squares method.     

Synthesis,structures, and urease inhibition of nickel(II), zinc(II), and cobalt(II) complexes with similar hydroxy-rich Schiff bases

Four new nickel(II), zinc(II), and cobalt(II) complexes, [Zn(L¹)₂]?·?H₂O (1), [Ni(L¹)₂]?·?H₂O (2), [Ni(L²)₂] (3), and [Co(L³)₂]?·?H₂O (4), derived from hydroxy-rich Schiff bases 2-{[1-(5-chloro-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol (HL¹), 2-{[1-(2-hydroxy-3-methoxyphenyl)methylidene]amino}-2-ethylpropane-1,3-diol (HL²), and 2-{[1-(5-bromo-2-hydroxyphenyl)methylidene]amino}-2-methylpropane-1,3-diol (HL³) have been synthesized and characterized by elemental analyses, infrared spectroscopy, and single-crystal X-ray determination. Each metal in the complexes is six-coordinate in a distorted octahedral coordination. The Schiff bases coordinate to the metal atoms through the imino N, phenolate O, and one hydroxyl O. In the crystal structures of HL¹ and the complexes, molecules are linked through intermolecular O–H···O hydrogen bonds, forming 1-D chains. The urease inhibitory activities of the compounds were evaluated and molecular docking study of the compounds with the Helicobacter pylori urease was performed.     

Iron(II), cobalt(III), nickel(II) and copper(II) chelates of furan and thiophene azo-oximes

Summary Complexes of furan and thiophene azo-oximes with iron(II), cobalt(III), nickel(II) and copper(II) have been prepared and characterised. Iron(II), cobalt(III) and copper(II) complexes are diamagnetic in the solid state. The diamagnetism of the copper(II) chelates is suggestive of antiferromagnetic interaction between two copper centres.¹H n.m.r. spectral data suggest atrans-octahedral geometry for the tris-chelates of cobalt(III). Nickel(II) complexes are paramagnetic, in contrast to the diamagnetism of the analogous complexes of arylazooximes. The electronic spectra are suggestive of octahedral geometry for the iron(II), cobalt(III) and nickel(II) complexes, andD _4h -symmetry for copper(II). Infrared data indicate N-bonding of the oximino-group to the metal ions.     

Synthesis,structure, and solvent-extraction properties of tridentate oxime ligands and their cobalt(II), nickel(II), copper(II), zinc(II) complexes

Synthesis of four different types of ligands Ar[COC(NOH)R] _n (Ar = biphenyl, n = 1, HL¹; Ar = biphenyl, n = 2, H₂L²; Ar = diphenylmethane, n = 1, HL³; Ar = diphenylmethane, n = 2, H₂L⁴; R = furfurylamine in all ligands) and their dinuclear Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ complexes is reported herein. These compounds were characterized by elemental analysis, ICP-OES, FT-IR spectra, and magnetic susceptibility measurements. The ligands were further characterized by ¹H NMR. The results suggest that dinuclear complexes of HL¹ and HL³ have a metal to ligand mole ratio of 2: 2 and dinuclear complexes H₂L² and H₂L⁴ have a metal to ligand mole ratio of 2: 1. Square pyramidal or octahedral structures are proposed for complexes of oxime ligands. Furthermore, extraction abilities of the four ligands were also evaluated in chloroform using selected transition metal picrates such as Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, Hg²⁺, Pb²⁺. The ligands show strong binding ability towards Hg²⁺ and Cu²⁺ ions.