Synthesis,characterization, and DNA interaction of mononuclear copper(II) and zinc(II) complexes having a hard–soft NS donor ligand

Knoevenagel condensate-based Schiff base ligands (L) containing N and S donor sites have been designed and synthesized [L = 3-cinnamalideneacetylacetonethiosemicarbazone (CAT)/3-cinnamalideneacetylacetoneethylthiosemicarbazone (CAET)/3-cinnamalideneacetylacetonephenylthiosemicarbazone (CAPT)]. They afford complexes of the type [ML] [M = Cu(II) and Zn(II)]. Both the ligands and their complexes were characterized by analytical and spectral data. Intercalative binding of these complexes with DNA has been investigated by electronic absorption spectroscopy, viscosity measurements, cyclic voltammetry, and differential pulse voltammetry. Electrophoretic study of the complexes indicates that they efficiently cleave supercoiled pUC19 DNA in the presence of hydrogen peroxide.     

Solid–solid synthesis,characterization, thermal decomposition and antibacterial activities of zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base ligand

The zinc(II) and nickel(II) complexes of glycine–vanillin Schiff base were synthesized by one-step solid–solid reaction at room temperature. The composition and structure of the complexes were characterized by elemental analyses, Fourier transform infrared spectra (FTIR), X-ray powder diffraction (XRD), and thermogravimetry and differential scanning calorimetry (TG–DSC). The crystal structure of the complexes belongs to monoclinic system with the lattice parameters: a = 0.6807 nm, b = 1.3818 nm, c = 1.2011 nm, β = 95.80° for [Zn(C₁₀H₉O₄N)(H₂O)₃], and a = 0.7457 nm, b = 1.3331 nm, c = 1.2560 nm, β = 91.89° for [Ni(C₁₀H₉O₄N)(H₂O)₃]·1.5H₂O. The experimental results indicate that the zinc and nickel ions are all six-coordinated by imino nitrogen, carboxylic oxygen, and phenolic oxygen from the Schiff base ligand, and oxygen from three coordinated water molecules, respectively. The possible pyrolysis reactions in the thermal decomposition processes of the complexes and the experimental and calculated percentage mass loss are also given. The two complexes have the most intense antibacterial activities against Escherichia coli.     

Synthesis,spectral, magnetic,electrochemical and kinetic studies of copper(II), nickel(II) and zinc(II) complexes derived from a phenol-based unsymmetrical “end-off” ligand

A new unsymmetrical end-off, aminomethylated N-methylpiperazine and aminomethylated diethanolamine armed binucleating ligand, 2-[bis(2-hydroxyethyl)aminomethyl]-6-[(4-methylpiperazin-1-yl)methyl]-4-formylphenol (HL), was synthesized by following sequential aromatic Mannich reactions. Mononuclear and binuclear Cu(II), Ni(II) and Zn(II) complexes were synthesized and characterized by elemental and spectral analysis. The EPR spectrum of the mononuclear copper complex shows four hyperfine splittings and the binuclear complex shows a broad signal due to anti-ferromagnetic interaction. The room temperature magnetic moment of the mono and binuclear copper complexes are 1.72 and 2.68 BM, respectively. Variable temperature magnetic moment study of the binuclear copper(II) complex shows weak antiferromagnetic coupling (?2J value, 21 cm^?1). The mononuclear Ni(II) complex is square planar and diamagnetic. The six-coordinate binuclear Ni(II) complex shows a magnetic moment of 3.06 BM. Electrochemical studies of the complexes reveal that all mononuclear complexes show a single irreversible one-electron reduction wave and the binuclear complexes show two irreversible one-electron reduction waves in the cathodic region. Catecholase activity of copper(II) complexes using pyrocatechol as a model substrate and the hydrolysis of 4-nitrophenylphosphate using copper(II), nickel(II) and zinc(II) complexes as catalysts showed that binuclear complexes have higher rate constants than corresponding mononuclear complexes.     

Two-photon-excited fluorescence of zinc(II), cadmium(II) complexes containing phenothiazine ligand

Shortly after the experimental verification of two-photon absorption by Kaiser et al.[1] with aCaF2:Eu2+ crystal in 1961, two-photon processes have been used to create a number of chemical or physical processes including optical data storage[2], lithographic fabrication[3], and fluorescence imaging[4]. In fluorescence imaging, two-photon excitation (TPE) has developed as an importantalternative to the traditional one-photon excitation (OPE) in the fluorescence microscopy and spectroscopy[5,…     

Synthesis and magnetic properties of copper(II)-lanthanoid(III)-copper(II) trinuclear complexes with N,N′-bis(2-aminoethyl)-oxamido ligand

Summary Ten novel -oxamido trinuclear complexes, namely Cu₂–(oxae)₂Ln(ClO₄)₃ (Ln = Y, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er and Yb), where oxae donotes the N,N-bis(2-aminoethyl)-oxamido dianion, were prepared and characterized. The magnetic susceptibility of Cu₂(oxae)₂Gd(ClO₄)₃ was measured over the 4–300 K range and the observed data were successfully simulated by an equation based on the spin Hamiltonian operator . The exchange integrals J _(Gd-Cu) and J _Gd-Cu were found to be 2.37 and –0.71cm^-1, respectively, indicating that very weakly ferromagnetic spin-exchange interaction operates between copper(II) and gadolinium(III) ions.Visiting scholar: Qufu Normal University.     

Synthesis,structure and magnetism of a hydrogen-bond-linked three-dimensional network of a novel nickel(II)–cobalt(II)–nickel(II) complex containing a new macrocyclic mononuclear complex ligand

A novel trinuclear complex, [Co(NiL)₂(H₂O)₂](ClO₄)₂ · 2C₂H₅OH, was prepared by self-assembly using [NiL] as a new complex ligand; L is the dianion of dimethyl 5,6,7,8,15,16-hexahydro-6,7-dioxodibenzo[1,4,8,11]tetraazacyclotetradecine-13,18-dicarboxylate. The structure of the trinuclear complex was determined by X-ray crystallography. The Co^II ion is at the center of the trinuclear complex cation and occupies a distorted octahedral O₆ environment, approximating to O _h with a ⁴ T _1g ground state for Co^II that has an unquenched spin–orbit coupling reflected in the magnetic properties. Two Ni^II ions reside in completely same and slightly distorted square-planar N₄ coordination geometries. Co^II and each Ni^II are bridged by an oxamido group from one of the two macrocyclic ligands (L). O—H...O and ... interactions link the trinuclear fragments, perchlorate ions and C₂H₅OH molecules to form a three-dimensional supramolecular architecture.     

Synthesis,characterization and antimicrobial activity studies of N - N ′-tetracarboxydiethyloxamide ligand and its metal(II) complexes

N-N′-tetracarboxydiethyloxamide (hereafter abbreviated as H₆L) was prepared by using L-aspartic acid and diethyl oxalate (DEO). A series of binuclear complexes of divalent metal chlorides viz. Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) with H₆L have been prepared. Spectral studies (IR, UV and NMR) magnetic susceptibility, elemental analysis and molar conductance measurements confirm the formation of binuclear complexes, [M₂H₂L]/[M₂H₂L?·?4H₂O]. Electronic absorption spectra and magnetic susceptibilities suggest square-planar stereochemistry for Cu(II) and tetrahedral for Zn(II) complexes. Mn(II), Co(II), and Ni(II) coordinate two molecules of water and consequently show octahedral geometry. The in vitro antimicrobial activity of the synthesized compounds is discussed against bacterial strains such as S. aureus, S. epididermis, K. pneumonia, S. typhi, P. aerugenosa, and B. subtilis A. brasilense. The metal complexes show higher activity against all the microorganisms than the ligand.     

Synthesis,crystal structure,thermal decomposition,and XPS studies of homo and heterotrinuclear Cu(II)–Cu(II)–Cu(II) and Cu(II)–Ni(II)–Cu(II) complexes obtained from salpn type ligands

In this study, a mononuclear CuL complex was prepared by the use of bis-N,N′-(salicylidene)-1, 3-propanediamine (LH₂) and Cu²⁺ ion. NiCl₂ and NiBr₂ salt were treated with this complex in dioxanewater medium and two new complexes [(CuL)₂NiCl₂(H₂O)₂] and [(CuL)₂NiBr₂(H₂O)₂)] with Cu(II)–Ni(II)–Cu(II) nucleus structure were obtained. In addition to this bis-N,N′-(2-hydroxybenzyl)-1,3-diaminopropane (L^HH₂) was prepared by the reduction of LH₂ with NaBH₄ in MeOH medium. The treatment of this reduced complex with Cu²⁺ ion resulted a complex [(CuL^H)₂CuCl₂] with a structure of Cu(II)–Cu(II)–Cu(II). The complexes prepared were characterized by the use of elemental analysis, IR spectroscopy, thermogravimetric and X-ray diffraction methods. The crystal structures of [(CuL)₂NiBr₂(H₂O)₂] (СIF file CCDC 1448402) and [(CuL^H)₂CuCl₂] (СIF file CCDC 1448401) complexes were elucidated. It was found that halogen ions are coordinated to terminal Cu²⁺ ions which are in a distorted square pyramid coordination sphere. It was determined that the central Cu(II), which joins terminal square pyramidal Cu(II), was coordinated only by the phenolic oxygens of the ligand while the central Ni(II) was coordinated by two phenolic oxygens of the organic ligand and two water molecules. These complexes were investigated by XPS and it was found that the terminal and central Cu²⁺ ions were different in Cu(II)–Cu(II)–Cu(II) complex. Also, the thermal degradation of the CuLH complex unit was observed to exothermic in contrast to the expectations.

     

Synthesis,spectroscopic and biological studies of metal complexes of an ONO donor pyrazolylhydrazone – Crystal structure of ligand and Co(II) complex

A new pyrazolylhydrazone, 2-(2-(1,5-dimethy-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazolyl-4-yl)hydrazono)-5,5-dimethylcyclohexane-1,3-dione (HL) and its Co(II), Ni(II), Cu(II), Zn(II) and Cd(II) complexes were synthesized and structurally characterized by elemental analysis, molar conductance, magnetic measurements and spectral (IR, ¹H NMR, UV–vis, HRMS) measurements. All complexes possess ML₂ stoichiometry with L behaving as monoanionic tridentate ONO donor. Single crystal X-ray diffraction reveals that HL and CoL₂ crystallize in orthorhombic system with Pbcn space group. Hydrogen bonding interactions between molecules of CoL₂ results in the formation of an infinite zig-zag chain extending along the ‘b’ axis. EPR spectrum of Cu(II) complex at 77 K suggests mononuclear and distorted octahedral geometry for [CuL₂]. Antimicrobial activity of HL and its complexes were investigated and minimum inhibitory concentrations identified. Bacterial and fungal organisms used were gram-positive Staphylococcus aureus, gram-negative Escherichia coli, Aspergillus niger and Candida albicans.     

Synthesis,spectral, magnetic,electrochemical and catalytic studies of cyclam-based copper(II) and nickel(II) complexes–effect of N-substitution

New N-substituted cyclam ligands 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-1,4,8,11-tetraazacyclotetradecane, 1,8-[bis(3-formyl-2-hydroxy-5-methyl)benzyl]-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane, 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-1,4,8,11-tetraazacyclotetradecane, and 1,8-[bis(3-formyl-2-hydroxy-5-bromo)benzyl]-4,11-dimethyl-1,4,8,11-tetraazacyclotetradecane (L¹–L⁴) were synthesized and mononuclear copper(II) and nickel(II) complexes prepared. The ligands and complexes were characterized by elemental analysis, electronic, IR, ¹H NMR and ¹³C NMR spectral studies. N-alkylation causes red shifts in the λ_max values of the complexes. Copper(II) complexes show one-electron, quasi-reversible reduction waves in the range ?1.04 to ?1.00 V. The nickel(II) complexes show one-electron, quasi-reversible reduction waves in the range ?1.18 to ?1.30 V and one-electron, quasi-reversible oxidation waves in the range +1.20 to +1.40 V. The reduction potential of the copper(II) and nickel(II) complexes of the ligands L¹ to L² and L³ to L⁴ shift anodically on N-alkylation. The ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry with nuclear hyperfine spin 3/2. All copper(II) complexes show a normal room temperature magnetic moment value μ_eff?=?1.70–1.74 BM which is close to the spin only value of 1.73 BM. Kinetic studies on the oxidation of pyrocatechol to o-quinone using the copper(II) complexes as catalysts and on the hydrolysis of 4-nitrophenylphosphate using the copper(II) and nickel(II) complexes as catalyst were carried out. The tetra-N-substituted complexes have higher rate constants than the corresponding disubstituted complexes.     

p-Nitrophenyl acetate hydrolysis promoted by Zn(II) and Co(II) complexes with the tripodal ligand of N,N′-bis(2-quinolinylmethyl)amantadine

To mimic the function of metallohydrolase, [M(bqad)Cl₂] (M = Zn(II) (1), Co(II) (2), where bqad = N,N′-bis(2-quinolinylmethyl)amantadine), have been synthesized and characterized by elemental analysis, electronic absorption, IR, and single crystal X-ray diffraction. The structural analysis indicated that metal ions in 1 and 2 were coordinated by three nitrogens from bqad and two chlorides, resulting in a distorted trigonal bipyramidal geometry. Kinetic experiments for hydrolytic cleavage of p-nitrophenyl acetate (pNA) catalyzed by 1 and 2 were performed at pH 7.50–10.00 and 298 K. The second-order rate constants (k_obs) increased exponentially with variation of pH values. The Co(II) complex exhibited potent catalytic activity.     

Synthesis,crystal structure and properties of manganese(II) complexes with the tripod ligand tris(2-benzimidazylmethyl)amine and α,β-unsaturated carboxylates

Two new ternary complexes of manganese(II) with tris(2-benzimidazylmethyl)amine (ntb), and two different α,β-unsaturated carboxylates, {[Mn(ntb)(acrylate)](ClO₄)}₂?·?(H₂O)·3(CH₃OH) (1) and {[Mn(ntb)(α-methacrylate)](ClO₄)}₂·(H₂O)·2(CH₃OH) (2), have been synthesized and characterized by means of elemental analyses, thermal analyses, IR, UV and single crystal X-ray diffraction. In the two complexes, ntb functions as a tripodal tetradentate ligand, resulting in trigonal pyramidal geometry. In each complex, an additional ligand, acrylate anion, or α-methacrylate anion, is coordinated at the opened site trans to the apical nitrogen atom of the ntb ligand. The crystal structure of 1 shows two crystallographically independent but chemically identical [Mn(ntb)(acrylate)]⁺ cations. In 2, the crystal structure shows two crystallographically independent and chemically different [Mn(ntb)(a-methacrylate)]⁺ cations. Cyclic voltammograms of the manganese complexes indicate a quasireversible Mn³⁺/Mn²⁺ couple. The X-band EPR spectrum of the complexes exhibits a six-line manganese hyperfine pattern with g?=?2, A?=?97 (1) and 93?G (2). The spectrum confirms that the material is high-spin Mn(II).     

Synthesis,crystal structure and characterization of zinc(II) complexes with the tripod ligand tris(2-benzimidazolylmethyl)amine and α,β-unsaturated carboxylates

Four 5-coordinate zinc complexes containing the tripod ligand, tris(2-benzimidazolylmethyl)amine (ntb), and four different ,-unsaturated carboxylates (L^1–4), with compositions [Zn(ntb)(L^1–4)](NO₃)·nH₂O (L¹ = acrylate; L² = -methacrylate; L³ = trans-cinnamate; L⁴ = 2-hydroxycinnamate; n = 1, 1.5 and 2), were synthesized and characterized by means of elemental analyses, electrical conductivities, thermal analyses, i.r., u.v., and ¹H-n.m.r. spectra. The novel crystal structure of [Zn(ntb)(L³)](NO₃)·H₂O·DMF has been determined by a single-crystal X-ray diffraction method, and shows that each zinc ion is linked to a tris(2-benzimidazolymethyl)amine (ntb) unit and a trans-cinnamate. The zinc ion is 5-coordinate with a N₄O ligand set. The coordination geometries of the zinc ion may be best described as a distorted trigonal bipyramid of site symmetry C₃.     

Solvatochromism and piezochromism of pentacyanoferrates(II) and of mixed valence iron(II)—iron(III) and ruthenium(II)—ruthenium(III) species

Pressure effects on the MLCT bands of the pyrazine- and 4-cyanopyridine-pentacyanoferrate(II) anions have been established. The relation of these piezochromic effects to the solvatochromism of each complex is put into the correlation between these parameters developed for other d⁶ ternary complexes. The conformance of piezochromic and solvatochromic efrects on MMCT bands for diiron and diruthenium mixed valence complexes to this correlation is examined.     

Synthesis, Structure and Properties of Tetrakis (thiourea) mercury (II) Tetrakis (thiocyanato-N) zinc (II)

Introduction In recent years, much attention has been paid to the research of novel, high-quality nonlinear optical (NLO) crystals, especially those metalorganic complex crystals that can generate high efficient second-harmonic blue-violet light using GaAlAs laser diodes. In order to find this type of crystals, much work has been done in our laboratory on the complex crystals of MM'(SCN)4 and MM'(SCN)·nL, where M = Zn, Cd, Mn; M' = Cd, Hg and L = adduct1-6. A 404.5nm blue-violet lig…     

Complexes of Cu(I) and Pd(II) with (+)-camphor and (–)-cavrone thiosemicarbazones: Synthesis,structure, and cytotoxicity of the Pd(II) complex

CuLCl, CuL¹Cl, PdLCl₂, and PdL¹Cl₂ complexes [L and L¹ being (+)-camphor and (–)-carvone thiosemicarbazones, respectively] have been synthesized. The structure of binuclear [Pd₂L²²Cl₄] complex has been determined by means of X-ray diffraction. The L² ligand (dehydrogenated (–)-carvone thiosemicarbazone) is coordinated via the bridging S atom to two Pd atoms. The complexes of Cu(I) and Pd(II) presumably have polynuclear and binuclear structure, respectively. These facts are in good agreement with IR and NMR spectroscopy as well as mass spectrometry data which indicate the coordination of L and L¹ ligands via the S atom. The influence of L¹ and PdL¹Cl₂ on viability of the Hep2 cell line has been studied. The PdL¹Cl₂ complex is more cytotoxic than L¹ ligand.     

Crystal Structures and Characterizations of Bis(pyrrolidinedithiocarbamato) Cu(II) and Zn(II) Complexes

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DNA-binding and photocleavage studies of metallofluorescein–porphyrin complexes of zinc(II) and copper(II)

The DNA-binding behaviors of the fluorescein?Cporphyrinatozinc(II) complex Zn(Fl-PPTPP) (Fl-PPTPP?=?5-(4-fluoresceinpropyloxy)phenyl-10,15,20-triphenylporphyrin) and fluorescein?Cporphyrinatocopper(II) complex Cu(Fl-PPTPP) with calf thymus DNA (CT-DNA) were investigated by UV?CVis absorption titrations, fluorescence spectra, viscosity measurements, thermal denaturation and circular dichroism. The results suggest that both complexes interact with CT-DNA by intercalation. In addition, their photocleavage reactions with pBR322 supercoiled plasmid DNA were investigated. Both complexes exhibit significant DNA cleavage activity, and singlet oxygen may play an important role in these reactions.     

Synthesis, Crystal Structure, Properties and Thermoanalysis of Complexes of Cu(II) and Ni(II) with Taurine-5-chlorosalicylaldelyde Schiff Base

Introduction The complexes of amino acid Schiff base have re-ceived considerable attention because of the interests in the biogical field.1-4 Taurine is a special amino acid in human beings. Recently, the complexes of taurine con-densation salicylaldelyde Schiff base have been re-ported,3-7 but the complexes of taurine condensation derived salicylaldelyde Schiff base have not been re-ported yet. In order to examine its anticancer and antibiosis ac-tivity of the complexes of taurine condensa…