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.     

Schiff碱配合物的研究——Ⅸ.表面Schiff碱配合物对H2O2分解的催化作用

制备了两种表面Schiff碱及其Cu²⁺、Co²⁺、Ni²⁺、Zn²⁺配合物,考察了它们对H₂O₂分解的催化性能,其活性顺序为:Co²⁺>Cu²⁺>Ni²⁺>Zn²⁺,且与金属离子氧化还原电位有关。溶液的pH值增加有利于催化反应,有机配体的加入则对反应有所抑制。     

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,Spectroscopic Characterization and Properties of New Metal Complexes

A new series of the polydentate Schiff base Cu^II, Co^II, Ni^II, Pd^II and Zn^II complexes derived from ethylenediamine (eda), diethylenetriamine (dea) and tris(2-aminoethyl)amine (taa) have been prepared by template condensation in MeOH solution, and characterized by i.r., electronic spectral data, elemental analyses, conductivity and magnetic measurements. The ¹H- and ¹³C-n.m.r. and mass spectral data of the Ni^II, Pd^II and Zn^II complexes have been recorded. In all complexes, some of the chloride ions coordinate to the metal ions. From conductivity measurements, it is shown that the complexes are electrolytes. The Ni^II, Pd^II and Zn^II complexes have diamagnetic character. In this study, the Schiff base Cu^II and Co^II complexes have sub-normal magnetic moments commensurate with their binuclear or tetranuclear nature. Some show antimicrobial activity against bacteria and yeast.     

New Mononuclear and Binuclear Cu(II), Co(II), Ni(II), and Zn(II) Thiosemicarbazone Complexes with Potential Biological Activity: Antimicrobial and Molecular Docking Study

Herein, we report the synthesis of eight new mononuclear and binuclear Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺ methoxy thiosemicarbazone (MTSC) complexes aiming at obtaining thiosemicarbazone complex with potent biological activity. The structure of the MTSC ligand and its metal complexes was fully characterized by elemental analysis, spectroscopic techniques (NMR, FTIR, UV-Vis), molar conductivity, thermogravimetric analysis (TG), and thermal differential analysis (DrTGA). The spectral and analytical data revealed that the obtained thiosemicarbazone-metal complexes have octahedral geometry around the metal center, except for the Zn²⁺-thiosemicarbazone complexes, which showed a tetrahedral geometry. The antibacterial and antifungal activities of the MTSC ligand and its (Co²⁺, Ni²⁺, Cu²⁺, and Zn²⁺) metal complexes were also investigated. Interestingly, the antibacterial activity of MTSC- metal complexes against examined bacteria was higher than that of the MTSC alone, which indicates that metal complexation improved the antibacterial activity of the parent ligand. Among different metal complexes, the MTSC- mono- and binuclear Cu²⁺ complexes showed significant antibacterial activity against Bacillus subtilis and Proteus vulgaris, better than that of the standard gentamycin drug. The in silico molecular docking study has revealed that the MTSC ligand could be a potential inhibitor for the oxidoreductase protein.     

Metal Complexes with Novel Ambidentate Ligands: β-Enaminovinylketones with Annelated 1,2-Benzothiazine-1,1-Dioxide Fragment and Antipyrine Substituent

The data on competitive binding of ligands in metal complexes with ambidentate ligands (Schiff bases and -aminovinylketones) were summarized. Special attention is given to chemical and electrochemical syntheses and structural study of novel chelates of heterocyclic enaminoketones with antipyrine substituent that form tetrahedral (Cu²⁺, Zn²⁺) or octahedral (Co²⁺, Ni²⁺) structures.     

Binuclear transition metal complexes of bicompartmental SNO donor ligands: synthesis,characterization, and electrochemistry

A series of new binucleating Co^II, Ni^II, Cu^II, and Zn^II complexes of bicompartmental ligands with SNO donors was prepared. The Schiff bases were obtained by the condensation of 4,6-diacetylresorcinol and mercapto-substituted 1,2,4-triazoles. The ligands and their complexes were characterized by elemental analysis, infrared, ¹H-NMR, UV-Vis, FAB-mass, and ESR spectral studies, magnetic susceptibility, and conductivity measurements. All the complexes were monomeric and binuclear. Ni^II and Co^II complexes were octahedral, whereas Cu^II and Zn^II complexes were square planar and tetrahedral, respectively. The compounds are investigated for electrochemical activity.     

Study of some metallic silicates as ion-exchangers

The extraction of ammine complexes of Cu²⁺, Cd²⁺, Ni²⁺, Co²⁺ and Zn²⁺ by synthesised manganese, nickel and zinc silicates has been studied at different pH and ionic concentrations in the external solution. It has been found that the uptake of the metal ion Co²⁺, Cu²⁺ and Zn²⁺ increases with increase in pH of the external solution, attains a maximum and then decreases. However, the uptake for Cd²⁺ and Ni²⁺ increases continuously. The q_A values of all the silicates increases with the increase in the concentration of the exchanging ion and its order for the investigated metal ions is Ni²⁺ < Co²⁺ < Cd²⁺ < Zn²⁺ < Cu²⁺.     

Spectroscopic Characterization of <Emphasis Type="Italic">N,N-bis</Emphasis>(2-{[(2,2-Dimethyl-1,3-Dioxolan-4-yl)Methyl]Amino}Ethyl) N′,N′-Dihydroxyethanediimidamide and Its Complexes

A new dioxime ligand, N,N-bis(2-{[(2,2-dimethyl-1,3-dioxolan-4-yl)methyl]amino} ethyl)N′,N′-dihydroxyethanediimidamide (H₂L), and its mononuclear complexes with Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺ and Cd²⁺ are synthesized. H₂L forms transition metal complexes [Co(LH)₂(H₂O)₂] and [M(LH)₂] (M = Ni²⁺, Cu²⁺) with a metal : ligand ratio of 1 : 2. Complexes [M(H₂L)(Cl)₂] (Zn²⁺, Cd²⁺) have a metal : ligand ratio of 1 : 1. The mononuclear Co²⁺, Ni²⁺, and Cu²⁺ complexes indicate that the metal ions coordinate ligand through its two N atoms, as the most of dioximes. In the Co²⁺ complex, two water molecules and in the Zn²⁺ and Cd²⁺ complexes two chloride ions are also coordinated to the metal ion. The structures of these compounds are identified by elemental analyses, IR, ¹H and ¹³C NMR, electronic spectra, magnetic susceptibility measurements, conductivity, and thermogravimetric analysis.__________From Koordinatsionnaya Khimiya, Vol. 31, No. 7, 2005, pp. 540–544.Original English Text Copyright © 2005 by Canpolat, Kaya.The text was submitted by the authors in English.     

Coordination chemistry and biological activity of two tridentate ONS and NNS Schiff bases derived from S-benzyldithiocarbazate

Two tridentate Schiff bases having ONS and NNS donor sequences were prepared by condensing S-benzyldithiocarbazate (NH₂NHCSSCH₂Ph) (SBDTC) with pyridine-2-carboxaldehyde and salicylaldehyde, respectively. Complexes of these ligands with Ni^II, Zn^II, Cr^III, Co^II, Cu^II, and Sn^II were studied and characterized by elemental analyses and various physico-chemical techniques. Ni^II, Cu^II, Zn^II and Sn^II complexes were four-coordinate while the Cr^III, Sr^III and Co^III complexes were six-coordinate. The ONS Schiff base was moderately active against leukemia, while its zinc, antimony and cobalt complexes were strongly active against leukemic cells with DC₅₀ = 0.35–5.00.     

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.     

Vibrational and scanning electron microscopy study of the mordenite modified by Mn, Co, Ni, Cu, Zn and Cd

The mordenite samples loaded with divalent nitrates of Mn, Co, Ni, Cu, Zn and Cd were investigated using FTIR and scanning electron microscopy (SEM) methods. It was found from FTIR spectra that in 3000-4000 cm⁻¹ region of mordenite samples with similar water concentration ions, Mn²⁺, Co²⁺, Cu²⁺, and Zn²⁺ tend to break hydrogen bonds formed between water molecules and zeolite framework, whereas Ni²⁺ and Cd²⁺ accommodate to hydrogen bonds. From SEM results it was concluded, that ions Mn²⁺, Co²⁺, Zn²⁺ form innersphere complexes with oxygens from Brönsted acid sites, whereas Ni²⁺ and Cd²⁺ associate with Brönsted acid sites without exchange of protons.     

Transition metal complexes derived from N′-(4-fluorobenzylidene)-2-(quinolin-2-yloxy) acetohydrazide: Synthesis,structural characterization,and biocidal evaluation

Mononuclear Mn²⁺ and Cu²⁺, - VO²⁺, Co²⁺, Ni²⁺, - and Zn²⁺ complexes of a synthetic novel hydrazone containing a quinoline moiety were prepared. The composition and structure of the prepared compounds were elucidated by spectral and analytical techniques. The results reveal that all complexes were formed in 1:1 mole ratio except Mn²⁺ and Cu²⁺ complexes ( 3 ) and ( 7) , which were formed in 1 M:2 L mole ratio. It was also found that the ligand binds the metal ions via NO donor sites as a monobasic bidentate chelator in all complexes through the enolic carbonyl oxygen and azomethine nitrogen atoms. The electronic absorption spectra and magnetic moment data demonstrated square pyramidal and octahedral geometries for the VO²⁺ and Ni²⁺ complexes, respectively, while the other complexes adopted tetrahedral geometry. The thermal decomposition of the complexes was discussed in relation to structure. The thermal analysis data demonstrated that all complexes were decomposed in one, two, three or four stages starting with the dehydration process, removal of coordination water molecules or elimination of anions and ended with the formation of the metal oxide. The bactericidal activities of the prepared compounds demonstrated that hydrazone ( 1) exerted a highly inhibitory effect against B. subtilis while VO²⁺, Co²⁺, and Cu²⁺ complexes ( 2) , ( 4) , and ( 7) showed an inhibitory effect against E. coli more than the tetracycline. Additionally, the inhibitory effect of the prepared compound against A. niger showed that the Cu²⁺ complex ( 6) is the most active while the Ni²⁺, Cu²⁺, and Zn²⁺ complexes ( 5–8) exhibited an extremely inhibitory effect against C. albicans.     

Preparation and characterization of some transition metal complexes of benzoic acid hydrazones of 2-aminonicotinaldehyde

Summary Cu^II, Ni^II, Co^II, Zn^II and Pd^II complexes of tridentate Schiff base ligands derived from the condensation of benzoic acid hydrazides with 2-aminonicotinaldehyde have been prepared and characterized. For M=Cu, Ni, Co and Zn the complexes were formulated as [M(ligand)(H₂O)X] (X=Cl, Br), with a distorted octahedral geometry and tridentate Schiff base ligands. The Pd complexes were formulated as Pd(ligand)Cl₂, with square planar geometries and bidentate Schiff base ligands. The e.s.r. spectra of the Cu^II complexes are discussed.     

Synthesis,potentiometric and antimicrobial activity studies on 2-pyridinilidene-DL-amino acids and their complexes

To investigate the relationship between antimicrobial activities and the formation constants of Cu^II, Ni^II and Co^II complexes with three Schiff bases, which were obtained by the condensation of 2-pyridinecarboxyaldehyde with DL-alanine, DL-valine and DL-phenylalanine, have been synthesized. Schiff bases and the complexes have been characterized on the basis of elemental analyses, magnetic moments (at ca. 25 °C), molar conductivity, thermal analyses and spectral (i.r., u.v., n.m.r.) studies. The i.r. spectra show that the ligands act in a monovalent bidentate fashion, depending on the metal salt used and the reaction pH = 9, 8 and 7 medium, for Cu^II, Ni^II and Co^II, respectively. Square-planar, tetrahedral and octahedral structures are proposed for Cu^II, Ni^II and Co^II, respectively. The protonation constants of the Schiff bases and stability constants of their ML-type complexes have been calculated potentiometrically in aqueous solution at 25 ± 0.1 °C and at 0.1 M KCl ionic strength. Antimicrobial activities of the Schiff bases and the complexes were evaluated for three bacteria (Bacillus subtillis, Staphylococcus aureus, and Escherichia coli) and a yeast (Candida albicans). The structure–activity correlation in Schiff bases and their metal(II) complexes are discussed, based on the effect of their stability contants.     

Determination of conditional stability constants for some divalent transition metal ion‐EDTA complexes by electrospray ionization mass spectrometry

Conditional stability constants of coordination complexes comprising divalent transition metals, Cu²⁺, Ni²⁺, Zn²⁺, Co²⁺, and ethylenediaminetetraacetic acid (EDTA) were determined utilizing electrospray ionization mass spectrometry. The deviation of signal response of a reference complex was monitored at addition of a second metal ion. The conditional stability constant for the competing metal was then determined through solution equilibria equations. The method showed to be applicable to a system where Co²⁺ and Zn²⁺ competed for EDTA at pH 5. When Cu²⁺ and Ni²⁺ competed for EDTA, the equilibrium changed over time. This change was shown to be affected in rate and size by the type of organic solvent added. In this work, 30% of either methanol or acetonitrile was used. It was found that if calibration curves are prepared for both metal complexes in solution and the measurements are repeated with sufficient time space, any change in equilibrium of sample solutions will be discovered. Copyright © 2014 John Wiley & Sons, Ltd.     

On-line preconcentration and simultaneous determination of heavy metal ions by inductively coupled plasma-atomic emission spectrometry

A flow injection analysis system for on-line preconcentration and simultaneous determination of Bi³⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺, Ni²⁺, Pb²⁺ and Zn²⁺ in aqueous samples by inductively coupled plasma (ICP)-atomic emission spectrometry with a charge coupled detector is described. The preconcentration of analytes is accomplished by retention of their chelates with sodium diethyldithiocarbamate in aqueous solution on a solid phase containing octadecyl silica in a minicolumn. Methanol, as eluent, is introduced into the conventional nebulizer of the ICP instrument. The effects of different parameters, including preconcentration flow rate (equal to sample flow rate (SR)), eluent flow rate (ER), weight of solid phase (W) and eluent loop volume (EV), were optimized by the super-modified simplex method. The optimum conditions were evaluated to be SR 7.2 ml min⁻¹, ER 3.5 ml min⁻¹, W of 100 mg and EV of 0.8 ml. An enrichment factor of 312.5 for each analyte was obtained. The detection limits of the proposed method for Bi³⁺, Cd²⁺, Co²⁺, Cu²⁺, Fe³⁺, Ni²⁺, Pb²⁺ and Zn²⁺ were evaluated as 1.3, 1.0, 0.8, 0.3, 14.7, 0.5, 5.5 and 0.1 ng l⁻¹, respectively. The effect of several metal ions on percent recovery was also studied. The method was applied to the recovery of these heavy metals from real matrices and to the simultaneous determination of these cations in different water samples.     

Cobaltocenium Carboxylate Transition Metal Complexes: Synthesis,Structure, Reactivity,and Cytotoxicity

Cobaltocenium carboxylate is an unusual betaine that functions as a formally neutral carboxylate ligand with late transition metal centers comprising Co²⁺, Ni²⁺, Cu²⁺, Ag⁺, Zn²⁺, Cd²⁺, Hg²⁺, and Rh⁺. Structurally, a rich coordination chemistry is observed – from simple monomeric homoleptic complexes to heteroleptic dimeric, trimeric, and polymeric compounds, as shown by X‐ray diffraction of 11 compounds. Chemically, thermal decarboxylation was investigated aiming at the formation of cobaltocenium‐carbene transition metal complexes, in analogy to such chemistry of imidazolium carboxylate betaines. Cytotoxicity studies of cobaltocenium carboxylate transition metal complexes were performed to evaluate the medicinal bioorganometallic potential of these compounds. While cobaltocenium carboxylate was inactive, its complexes with Ag⁺, Cd²⁺, and Hg²⁺ triggered significant cytotoxic effects.     

Homogeneous electromediated reduction of the 2-cyclohexen-1-one by transition metals

The reduction of the 2-cyclohexen-1-one, mediated by some transition metal ions (Zn²⁺, Cu²⁺, Ni²⁺, Co²⁺ and Fe²⁺) and complexes ([Ni^II(bipy)]Br₂ and [Fe^II(bipy)]Br₂, where bipy = 2,2′-bipyridine), was carried out by using a homogeneous electromediated system: sacrificial anode, nickel cathode, (0.2 M) NaI as supporting electrolyte and undivided cell. A constant current of <100 mA was applied with a maximum cell potential of 2.0 V. Cyclohexanone was the principal product in major cases yielding 98%. Cyclohexanol was also detected in some cases. The selectivity of the process can be controlled by choosing Ni as mediator and Zn or Ni as sacrificial anode. A more reactive system can be reached when Fe sacrificial anode is used, giving cyclohexanol as major product (87%).     

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.