Stability studies on 1:1 or 1:3 stoichiometry complexes of hexaza tripods with zinc(II), copper(II), nickel(II) and cobalt(II)

The coordination properties of two C₃-symmetry hexaza tripods, 1,3,5-tri(2,5-diazahexyl)benzene (L1) and 1,3,5-tri(2,5-diazaheptyl)benzene (L2), towards Zn²⁺, Cu²⁺, Ni²⁺ and Co²⁺ ions, studied by potentiometric techniques, are reported. Both ligands form quite stable complexes either in a 1:1 or 1:3 M:L stoichiometry, presenting a preferential coordination order: Zn²⁺ < Cu²⁺ > Ni²⁺ > Co²⁺. It is observed that the different configurations of metal complexes are achieved due to the fact that tripodal ligands are flexible and not constrained into a rigid geometry.     

Metal-ion directed synthesis of binuclear octaazamacrocyclic complexes of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) and their physico-chemical studies

A novel series of 16-membered binuclear complexes of octaazatetraimine ligand, [M = Mn^II, Co^II, Ni^II, Cu^II and Zn^II; X = Cl or NO₃] have been synthesized by metal template condensation reactions of o-phenylenediamine with N,N′-diacetylhydrazine in 1:1:1 molar ratio in methanol. The proposed stoichiometry and the bonding of the macrocyclic moiety to metal ions along with the overall stereochemistry have been derived from the results of elemental analyses, magnetic susceptibility, conductivity data and the spectral data revealed from FT-IR, , ESI mass, UV–visible studies. An octahedral geometry has been envisaged for Mn^II, Co^II, and Ni^II complexes while a slight distortion in octahedral geometry has been noticed for Cu^II complexes. The low conductivity data of all the complexes suggest their non-ionic nature.     

Co(II), Ni(II), Cu(II) and Zn(II) complexes of aminothiazole‐derived Schiff base ligands: Synthesis,characterization, antibacterial and cytotoxicity evaluation,bovine serum albumin binding and density functional theory studies

Transition metal complexes of type M(L)₂(H₂O)_x were synthesized, where L is deprotonated Schiff base 2,4‐dihalo‐6‐(substituted thiazol‐2‐ylimino)methylphenol derived from the condensation of aminothiazole or its derivatives with 2‐hydroxy‐3‐halobenzaldehyde and M = Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ (x = 0 for Cu²⁺ and Zn²⁺; x = 2 for Co²⁺ and Ni²⁺). The synthesized Schiff bases and their metal complexes were thoroughly characterized using infrared, ¹H NMR, electronic and electron paramagnetic resonance spectroscopies, elemental analysis, molar conductance and magnetic susceptibility measurements, thermogravimetric analysis and scanning electron microscopy. The results reveal that the bidentate ligands form complexes having octahedral geometry around Co²⁺ and Ni²⁺ metal ions while the geometry around Cu²⁺ and Zn²⁺ metal ions is four‐coordinated. The geometries of newly synthesized Schiff bases and their metal complexes were fully optimized in Gaussian 09 using 6–31 + g(d,p) basis set. Fluorescence quenching data reveal that Zn(II) and Cu(II) complexes bind more strongly to bovine serum albumin in comparison to Co(II) and Ni(II) complexes. The ligands and their complexes were evaluated for in vitro antibacterial activity against Escherichia coli ATCC 25922 (Gram negative) and Staphylococcus aureus ATCC 29213 (Gram positive) and cytotoxicity against lever hepatocellular cell line HepG2.     

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.     

Structural studies on cadmium(II), cobalt(II), copper(II), nickel(II) and zinc(II) complexes of 1-malonyl-bis(4-phenylthiosemicarbazide)

Summary Several new complexes of the title ligand (H₂MPTS) with Co^II, Ni^II, Cu^II, and Cd^II have been prepared. Structural assignments of the complexes have been made based on elemental analysis, molar conductivity, magnetic moment and spectral (i.r.,¹H n.m.r., reflectance) studies. The compounds are non-conductors in dimethylsulphoxide. The neutral molecule is coordinated to the metal(II) sulphate as a bidentate ligandvia the two carbonyl groups. The ligand reacts with the metal(II) chlorides with the liberation of two hydrogen ions, behaving as a bianionic quadridentate (NONO) donor. Enolization is confirmed by the pH-titration of H₂ MPTS and its metal(II) complexes against NaOH. A distorted octahedral structure is proposed for the Cu^II complex, while a square planar structure is suggested for both Co^II and Ni^II complexes. The stoichiometry of the complexes formed in EtOH and buffer solutions, their apparent formation constants and the ranges for obedience to Beer's law are reported for Co^II, Ni^II and Cu^II ions. The ligand pK values are calculated. The antimicrobial activity of H₂ MPTS and its Co^II, Ni^II, Cu^II and Mn^II complexes is demonstrated.     

Versatility in the coordination behavior of a hexatopic compartmental Schiff-base ligand in the architecture of binuclear transition metal(II) complexes

Condensation of 1H-pyrazole-3,5-dicarboxylic hydrazide with 1H-indole-2,3-dione (isatin) yield the compartmental ligand, which is capable of encapsulating two transition metal ions namely Co^II, Ni^II, Cu^II, and Zn^II. The ligand is a binuclear hexadentate chelate with N₄O₂ donating sites. The pyrazole core provides the diazine fragment, which serves as an endogenous bridge between the two metal centers. In Co^II and Ni^II complexes, the ligand is in the imidol form and the subsequent coordination through the imidol oxygen. In other complexes, the lactonic oxygen takes part in ligation. All the complexes are non-electrolytes and soluble in DMSO, DMF, and acetonitrile. Spectral and magnetic studies along with analytical data suggest octahedral geometry for the Co^II and Ni^II complexes, whereas the Cu^II and Zn^II complexes are assigned square pyramidal geometry. The Cu^II and Ni^II complexes show one electron redox behavior and the rest are electrochemically inactive.     

Synthesis and structure of transition metal complexes derived from a novel polynucleating oxaza macrocycle having diazine and phenoxo bridging components

Novel Co^II, Ni^II, Cu^II and Zn^II complexes of the polynucleating oxaza macrocyclic ligand (LH₄) derived from the 2:2 condensation of pyrazole-3,5-dicarbohydrazide and 2,6-diformyl-4-methylphenol have been synthesized. Ligand and complexes were characterized on the basis of elemental analysis, IR, ¹HNMR, UV–Visible, magnetic susceptibility, ESR and conductivity measurements, FAB-mass and thermal analysis. Present Zn^II and Cu^II complexes are binuclear in nature with octahedral geometry, where as Co^II and Ni^II complexes are tetranuclear with square-planar geometry. Cu^II and Co^II complexes are paramagnetic whereas Zn^II and Ni^II complexes are diamagnetic. Only the copper complex has shown redox property in the applied potential range while the ligand and other complexes are found to be electrochemically innocent.     

Interactions of the ethanolamino groups of nanofilms with Co(II), Ni(II), Cu(II), Zn(II), and Cr(III) ammoniates at the surface of PVC plates

Interactions of nanofilms containing ethanolamino groups with cobalt(II), nickel(II), copper(II), and zinc(II) ammoniates at the surface of polyvinylchloride plates and with chromium(III) ammoniate in a solution of ammonium chloride were studied. It was found that the groups of the film, together with chloride ions, displace all ammonia molecules from the inner coordination sphere of the metal. The average number of the ethanolamino N atoms of the film participating in formation of the metal ion coordination sphere is 3.35, 3.47, 3.67, 3.42, and 3.37 for Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Cr³⁺ complexes, respectively. The average number of chloride ions is 2 for Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ and 3 for Cr³⁺. The coordination number of the central atoms is 6. The Cr³⁺ ion forms a coordination sphere composed of three N atoms and three chloride ions and a coordination sphere (charged 1+) made up of four N atoms and two chloride ions, with the third chloride ion being in the outer sphere. The Co²⁺, Ni²⁺, and Cu²⁺ ions form uncharged coordination spheres of two types: (1) with four N atoms and two chloride ions and (2) with three N atoms, two chloride ions, and the O atom of the ethanol hydroxyl group.     

Die Chelate von Co(II), Ni(II), Cu(II), Zn(II) und Cd(II) mit Malonsäurehydrazid und dessen Arylidenderivaten

The metal chelates formed by the reaction of Co²⁺, Cu²⁺, Ni²⁺, Zn²⁺, and Cd²⁺ with malonic hydrazide and its arylidene derivatives are investigated. The i.r.-absorption spectra of the solid compounds supported the tetradentate character of these compounds; they also show that the ligand still attained the keto form. The shift of the C=O, C=N bands is utilized in determining the coordination bond length. The stoichiometry of the metal complexes, as studied by spectrophotometric and conductometric methods, is found to be metal ion: ligand =11. The apparent formation constants of the malonic hydrazide complexes are also determined.

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N-Phthaloylglycinate ternary complexes with cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) metal ions and aromatic mono,bi and tridentate amines

Complexes of N-phthaloylglycinate (N-phthgly) and Co^II, Ni^II, Cu^II, Zn^II and Cd^II containing imidazole (imi), N-methylimidazole (mimi), 2,2-bipyridyl (bipy) and 1,10-phenanthroline (phen), and tridentate amines such as 2,2,2-terpyridine (terpy) and 2,4,6-(2-pyridyl)s-triazine (tptz), were prepared and characterized by conventional methods, i.r. spectra and by thermogravimetric analysis. For imi and mimi ternary complexes, the general formula [M(imi/mimi)₂(N-phthgly)₂]·nH₂O, where M = Co^II, Ni^II, Cu^II and Zn^II applies. For Cd^II ternary complexes with imi, [Cd(imi)₃(N-phthgly)₂]·2H₂O applies. For the bi and tridentate ligands, ternary complexes of the formula [M(L)(N-phthgly)₂]·nH₂O were obtained, where M = Co^II, Ni^II, Cu^II and Zn^II; L = bipy, phen, tptz and terpy. In all complexes, N-phthgly acts as a monodentate ligand, coordinating metal ions through the carboxylate oxygen, except for the ternary complexes of Co^II, Ni^II and Cu^II with mimi and Cu^II and Zn^II with imi, where the N-phthgly acts as a bidentate ligand, coordinating the metal ions through both carboxylate oxygen atoms.     

Chelated complexes of cadmium(II), cobalt(II), copper(II), mercury(II), nickel(II), uranyl(II) and zinc(II) with benzil bis(4-phenylthiosemicarbazone)

Summary Complexes of Co^II, Ni^II, Cu^II, Zn^II, Cd^II, Hg^II and UO ₂ ^II with benzil bis(4-phenylthiosemicarbazone), H₂BPT, have been synthesized and their structures assigned based on elemental analysis, molar conductivity, magnetic susceptibility and spectroscopic measurements. The i.r. spectra suggest that the ligand behaves as a binegative quadridentate (NSSN) (Co^II, Cu^II, Hg^II and UO ₂ ^II complexes) or as a binegative quadridentate-neutral bidentate chelating agent (Ni^II, Zn^II and Cd^II complexes). Octahedral structures for the Co^II and Ni^II complexes and square-planar structure for the Cu^II complex are suggested on the basis of magnetic and spectral evidence. The crystal field parameters (Dq, B and _B) for the Co^II complex are calculated and agree fairly well with the values reported for known octahedral complexes. The ligand can be used for the microdetermination of Ni^II ions of concentration in the 0.4–6×10^–4 mol l^–1 range and the apparent formation constant for the species generated in solution has also been calculated.     

Complexes of 4-hydroxyphenylthiocarboxyhydrazide with iron(II), cobalt(II,III), nickel(II), copper(II) and zinc(II)

Summary The 4-hydroxyphenylthiocarboxyhydrazide (Hoth) ligand has been characterized by i.r.,¹H and¹³C spectral studies. Its metal complexes with Fe^II, Co^II,III, Ni^II, Cu^II and Zn^II have been prepared and characterized on the basis of elemental analyses, molar conductance, magnetic susceptibility. Mössbauer, visible, e.s.r., i.r.,¹H and¹³C n.m.r. spectral studies. The bonding and stereochemistry of the complexes are discussed. Hoth and its Cu^II complexes have been screened towards bacteria, viruses and fungi.     

Cobalt(II), nickel(II), copper(II), zinc(II) and uranyl(VI) complexes of acetylacetone bis(4-phenylthiosemicarbazone)

Summary Reaction of one mole of acetylacetone with two moles of 4-phenylthiosemicarbazide yields the unusual Schiff base, MeC(=N-NHCSNHPh)CH₂C(=NNHCSNHPh)Me. APT = H₂L) acetylacetone bis(4-phenylthiosemicarbazone). The complexes of Co^II, Ni^II, Cu^II, Zn^II and U^VIO₂ have been prepared and characterized by analytical, i.r., electronic spectral and magnetic measurements. The Co^II, Ni^II and Cu^II complexes have been assigned square-planar stereochemistry on the basis of magnetic and spectroscopic studies. The ligand is a neutral or dibasic quadridentate SNNS donor as revealed by i.r. spectral studies.     

Syntheses,Characterization, and DNA Binding Studies of a Series of Copper(II), Nickel(II), Platinum(II) and Zinc(II) Complexes Derived from Schiff Base Ligands

Three series of metal salophen complexes derived from Zn²⁺, Cu²⁺, Pt²⁺ and Ni²⁺ have been synthesized and their interaction with quadruplex DNA has been evaluated. The compounds differ on the number of ethyl piperidine substituents. They have been characterized by ¹H NMR, IR and UV-visible spectroscopies and by HR-mass spectrometry. Their luminescent properties have been also evaluated and we can observe that, as expected, Zn²⁺ and Pt²⁺ complexes are those displaying more interesting luminescence with an emission band red-shifted with respect to the corresponding uncoordinated ligand. DNA interactions with G4 and duplex DNA were evaluated by FRET melting assays (for the Zn²⁺, Cu²⁺ and Ni²⁺ complexes) and by emission titrations (for one Pt²⁺ complex) which indicated that the disubstituted compounds 2-Ni and 2-Pt are the only ones that display good affinity for G4 DNA structures.     

Synthesis and chemical characterization of biologically important complexes of vanillin thiosemicarbazone with manganese(II), iron(II), cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), and mercury(II)

Summary Vanillin thiosemicarbazone (VTSC) has been used to isolate the complexes of the types [M(VTSC)₂(H₂O)₂]X₂ (M=Mn^II, Fe^II, Co^II, or Ni^II and X=Cl) and [M(VTSC)X₂]H₂O (M=Cu^II, Zn^II, Cd^II or Hg^II and X=Cl). Probable structures of these complexes are suggested on the basis of elemental analysis, molar conductance, magnetic moment and electronic and i.r. spectral data. The fungicidal activity of VTSC and the isolated complexes has been evaluated on pathogenic fungi,Alternaria (Sp.),Paecilomyces (Sp.) andPestalotia (Sp.).On leave from the University of Myosore.     

N-benzamidosalicylaldimine complexes of copper(II), nickel(II), cobalt(II), iron(II), manganese(II), oxyvanadium(IV) and oxytitanium(IV)

Summary N-benzamidosalicylaldimine (H₂L) complexes of Cu^II, Ni^II, Co^II, Fe^II, Mn^II. VO_IV and TiO_IV have been prepared. The ligand probably coordinates to the metal from the hydroxyl, carbonyl and imino groups.     

Spectral and structural studies of cobalt(II,III), nickel(II), and copper(II) complexes of dehydroacetic acid N4-dialkyl- and 3-azacyclothiosemicarbazones

Co^II,III, Ni^II, and Cu^II complexes of new dehydroacetic acid N4-substituted thiosemicarbazones have been studied. The substituted thiosemicarbazones, N4-dimethyl-(DA4DM), N4-diethyl-(DA4DE), 3-piperidyl-(DApip) and 3-hexamethyleneiminyl-(DAhexim), when reacted with the metal chlorides, produced two Co^II complexes, [Co(DA4DE)Cl₂] and [Co(DAhexim)₂Cl₂]; two Co^III complexes, [Co(DA4DM-H)₂Cl] and [Co(DApip-H)(DApip-2H)]; a paramagnetic Ni^II complex, [Ni(DAhexim)(DAhexim-H)Cl]; three diamagnetic Ni^II complexes, [Ni(DA4DM-H)Cl], [Ni(DA4DE-H)Cl] and [Ni(DApip-H)Cl]; and four Cu^II complexes with the analogous stoichiometry of the latter three Ni^II complexes. These new thiosemicarbazones have been characterized by their melting points, as well as i.r., electronic and ¹H-n.m.r. spectra. The metal complexes have been characterized by i.r. and electronic spectra, and when possible, n.m.r. and e.s.r. spectra, as well as elemental analyses, molar conductivities, and magnetic susceptibilities. The crystal and molecular structure of the four-coordinate Cu^II complex, [Cu(DAhexim-H)Cl] has been determined by single crystal X-ray diffraction and the anionic ligand coordinates via an oxygen of the dehydroacetic acid and the thiosemicarbazone moiety's imine nitrogen and thione sulfur.     

Spectrophotometric determination of the formation constants of some transition metal cations with a new synthetic Schiff base in dichloromethane and chloroform using rank annihilation factor analysis

The complex formation between a new synthesized Schiff base and the cations Ni²⁺, Co²⁺, Cu²⁺, Zn²⁺ in dichloromethane (DCM) and chloroform solutions was investigated spectrophotometrically using rank annihilation factor analysis (RAFA). The results of mole ratio plots and continuous variation data show the stoichiometry of complexation were found to be 1:1, and 2:1 metal ion to ligand. The stoichiometry was obtained as 1:1 metal ion to ligand ratio for Co²⁺, Ni²⁺ and Zn²⁺ in chloroform and 2:1 for Cu²⁺. In DCM the stoichiometry was obtained as 1:1 for Co²⁺ and 2:1 for Ni²⁺ and Zn²⁺ and a consecutive 2:1 metal ion to ligand ratio was obtained for Cu²⁺. Formation constants of these complexes were estimated by application of RAFA on spectrophotometric data. In this process the contribution of ligand was removed from the absorbance data matrix when the complex stability constant acts as an optimizing object and simply combined with the pure spectrum of the ligand, the rank of the original data matrix can be reduced by one by annihilating the information of the ligand from the original data matrix.     

Synthesis,antimicrobial screening,and DNA-binding/cleavage of new pyrazole-based binuclear CoII,NiII, CuII,and ZnII complexes

Pyrazolato endogenous bridged binuclear Co^II, Ni^II, Cu^II, and Zn^II complexes were prepared and characterized by spectro-analytical methods. The hexadentate N₄S₂ donor was synthesized by condensation of 3,5-dichloroformyl-1H-pyrazole with thiosemicarbazide in dry ethanol. All the complexes were binuclear and octahedral in nature. The ligand and complexes are screened for antimicrobial and DNA-binding/cleavage activities. The binding/cleavage activities with Escherichia coli DNA are monitored with absorption, hydrodynamic, thermal denaturation, and electrophoresis studies. The ligand possesses significant activity against microbes which is further enhanced upon complexation. The DNA-binding study reveals classical intercalation. The Ni^II and Cu^II complexes exhibit higher binding ability.     

Synthesis and thermodynamic properties of novel tripod ligands and their cobalt(II), nickel(II), copper(II) and zinc(II) complexes

Three novel compounds, based on the 1,3,5-benzene core with C₃-symmetry, have been prepared and characterized by elemental analysis, i.r. and ¹H-n.m.r. Thermodynamic properties of the ligands and their Co^II, Ni^II, Cu^II, and Zn^II metal complexes have been investigated and the corresponding stability constants obtained at 25.0 ± 0.1 °C and with I = 0.1 mol dm^–3 in KNO₃ by potentiometric titration. A linear free energy relationship exists between the stability constants of complexes and the protonation constants of ligands in the ternary system of the Cu^II-5-substituted phenanthroline-tripod ligand complexes.