Synthesis,spectral and antimicrobial studies of rare earth metal complexes with Schiff-base hydrazone containing quinoline moiety

The synthesis and characterization of lanthanide(III) complexes with the Schiff-base hydrazone, o-hydroxyacetophenone-7-chloro-4-quinoline, (HL) are reported. The complexes were characterized by different physicochemical methods: mass spectrometry, ¹H NMR, ¹³C NMR, and IR, UV-visible, molar conductance and magnetic studies. They have the stoichiometry [Ln(L)₂(NO₃)]·nH₂O where Ln = La(III), Pr(III), Nd(II), Sm(III), Eu(III) and n = 1–3. The spectra of the complexes were interpreted by comparison with the spectrum of the free ligand. The Schiff-base ligand and its metal complexes were tested against one stain Gram +ve bacteria (Staphylococcus aureus), Gram ?ve bacteria (Escherichia coli), and Fungi (Candida albicans). The tested compounds exhibited high antimicrobial activities     

Conventional and microwave synthesis,spectral, thermal and antimicrobial studies of some transition metal complexes containing 2-amino-5-methylthiazole moiety

Schiff base metal complexes of Cr(III), Co(II), Ni(II) and Cu(II) derived from 5-chlorosalicylidene-2-amino-5-methylthiazole (HL¹) and 2-hydroxy-1-naphthylidene-2-amino-5-methylthiazole (HL²) have been synthesized by conventional as well as microwave methods. These compounds have been characterized by elemental analysis, FT-IR, FAB-mass, molar conductance, electronic spectra, ¹H-NMR, ESR, magnetic susceptibility, thermal, electrical conductivity and XRD analyses. The complexes exhibit coordination number 4 or 6. The complexes are coloured and stable in air. Analytical data reveal that all the complexes exhibit 1:2 (metal:ligand) ratio. IR data show that the ligand coordinates with the metal ions in a bidentate manner through the phenolic oxygen and azomethine nitrogen. FAB-mass and thermal data show degradation pattern of the complexes. The thermal behaviour of metal complexes shows that the hydrated complexes lose water molecules of hydration in the first step; followed by decomposition of ligand molecules in the subsequent steps. XRD patterns indicate crystalline nature for the complexes. The Schiff bases and metal complexes show good activity against the Gram-positive bacteria; Staphylococcus aureus and Gram-negative bacteria; Escherichia coli and fungi Aspergillus niger and Candida albicans. The antimicrobial results also indicate that the metal complexes are better antimicrobial agents as compared to the Schiff bases.     

Synthesis, spectral characterization of Schiff base transition metal complexes: DNA cleavage and antimicrobial activity studies

A new series of transition metal complexes of Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) have been synthesized from the Schiff base (L) derived from 4-aminoantipyrine, 3-hydroxy-4-nitrobenzaldehyde and o-phenylenediamine. Structural features were obtained from their elemental analyses, magnetic susceptibility, molar conductance, mass, IR, UV-Vis, ¹H NMR and ESR spectral studies. The data show that these complexes have composition of ML type. The UV-Vis, magnetic susceptibility and ESR spectral data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The redox behaviour of copper and vanadyl complexes was studied by cyclic voltammetry. Antimicrobial screening tests gave good results in the presence of metal ion in the ligand system. The nuclease activity of the above metal complexes shows that Cu, Ni and Co complexes cleave DNA through redox chemistry whereas other complexes are not effective.     

Physicochemical characterization,thermal, and electrical conductivity studies of some transition metal complexes of bis-chelating Schiff base

Polychelates of Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and VO(IV) with a new bis-chelating Schiff base derived from 5-acetyl-2,4-dihydroxyacetophenone and isonicotinic acidhydrazide have been synthesized. The resulting polychelates have been characterized by elemental analyses, IR and electronic spectral data, magnetic susceptibility measurements and thermogravimetric analysis. All the polychelates are dark coloured solids and insoluble in water and common organic solvents. Thermogravimetric analyses confirm coordination of water in complexes. Various kinetic and thermodynamic parameters have been evaluated from thermal data. The ligand acts as a bis-tridentate molecule coordinating through deprotonated phenolic/enolic oxygen atoms and azomethine nitrogen atoms. The solid-state conductivity of ligand and its polychelates have been measured in their compressed pellet form and all compounds were found to be semiconducting in nature.     

Synthesis,characterization and thermal study of some tetradentate Schiff base transition metal complexes

Several mononuclear Co(II), Ni(II), Cu(II), and Fe(II) complexes of tetradentate salpren-type diimine, obtained from 3,5-di-tert-butyl-2-hydroxybenzaldehyde and 1,3-diaminopropane have been prepared and characterized by analytical, spectroscopic (FT-IR, UV–VIS) techniques, magnetic susceptibility measurements and thermogravimetric analyses (TG). The thermodynamic and thermal properties of complexes have been investigated. For further characterization Direct Insertion Probe-Mass Spectrometry (DIP-MS) was used and the fragmentation pattern and also stability of the ions were evaluated. The characterization of the end products of the decomposition was achieved by X-ray diffraction. The thermal stabilities of metal complexes of N,N′-bis(3,5-di-t-butylsalicylidene)-1,3-propanediamine ligand (L) were found as Ni(II) > Cu(II) > Co(II) > Fe(II).     

Synthesis, structural, thermal studies and biological activity of a tridentate Schiff base ligand and their transition metal complexes

Schiff base (L) ligand is prepared via condensation of pyridine-2,6-dicarboxaldehyde with -2-aminopyridine. The ligand and its metal complexes are characterized based on elemental analysis, mass, IR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG and DTA). The molar conductance reveals that all the metal chelates are non-electrolytes. IR spectra shows that L ligand behaves as neutral tridentate ligand and bind to the metal ions via the two azomethine N and pyridine N. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II), Cu(II), and Th(IV)) and tetrahedral (Mn(II), Cd(II), Zn(II), and UO2(II)). The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, ΔH*, ΔS* and ΔG* are calculated from the DTG curves using Coats-Redfern method. The synthesized ligand, in comparison to their metal complexes also was screened for its antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data shows that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species.     

Redox, thermodynamic and spectroscopic of some transition metal complexes containing heterocyclic Schiff base ligands

Complexes of two series of Schiff base ligands, H₂L_a and H₂L_bderived from the reaction of 2,6-diacetyl pyridine with semicarbazide, H₂L_a and thiosemicarbazide, H₂L_b, with the metal ions, Co(II), Ni(II), Cu(II), VO(IV) and UO₂(VI) have been prepared. The ligands are characterized by elemental analysis, IR, UV–vis and ¹H NMR. The structures of the complexes are investigated with the IR, UV–vis, X-band ESR spectra, ¹H NMR and thermal gravimetric analysis as well as conductivity and magnetic moment measurements. The IR-spectra reveal the presence of variable modes of chelation for the investigated ligands. A variety of binuclear or mononuclear complexes were obtained with the two ligands in tri-, tetra or pentadentate forms. The bonding sites are the pyridine nitrogen, two azomethine nitrogen atoms and ketonic oxygen in case of H₂L_a or sulphur atoms in case of H₂L_b. The Coats–Redfern equation has been used to calculate the kinetic and thermodynamic parameters for the different thermal decomposition steps of some complexes. Cyclic voltammograms of Co(II) and Ni(II) show quasi-reversible peaks. The redox properties and the nature of the electro-active species of the complexes have been characterized.     

Synthesis, characterization and thermal analysis of some new transition metal complexes of a polydentate Schiff base

A new polydentate Schiff base (H3L) was synthesized from the condensation of 2,6-diformyl-4-methylphenol and S-methylhydrazine-carbodithionate. The 1:1 metal complexes were obtained from the interaction of H3L and the metal ions Cr(III), Co(II), Ni(II), Cu(II), Cd(II) and Hg(II). The complexes were characterized by elemental analysis and IR spectroscopy. Detailed studies of the thermal properties of the complexes were investigated by thermogravimetry techniques.     

Derivatives of phosphate Schiff base transition metal complexes: synthesis, studies and biological activity

We report the synthesis and structural characterization of series of tetra- and hexacoordinate metal chelate complexes of phosphate Schiff base ligands having the general composition LMX(n).H(2)O and L(2)MX(n) (L=phosphate Schiff base ligand; M=Ag(+), Mn(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+), or Fe(3+) and X=NO(3)(-), Br(-) or Cl(-)). The structure of the prepared compounds was investigated using elemental analysis, IR, 1H and 31P NMR, UV-vis, mass spectra, solid reflectance, magnetic susceptibility and conductance measurements as well as conductometric titration. In all the complexes studied, the ligands act as a chelate ligand with coordination involving the phosphate-O-atom and the azomethine-N-atom. IR, solid reflectance spectra and magnetic moment measurement are used to infer the structure and to illustrate the coordination capacity of ligand. IR spectra show the presence of coordinated nitrate and water molecule, the magnetic moments of all complexes show normal magnetic behavior and the electronic spectra of the metal complexes indicate a tetra- and octahedral structure for Mn(2+), octahedral structure of Fe(3+) and both square-planar and distorted octahedral structure for Cu(2+) complexes. Antimicrobial activity of the ligands and their complexes were tested using the disc diffusion method and the chosen strains include Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, Escherichia coli, Microsporum canis, Trichophyton mentagrophyte and Trichophyton rubrum. Some known antibiotics are included for the sake of comparison and the chosen antibiotic are Amikacin, Doxycllin, Augmantin, Sulperazon, Unasyn, Septrin, Cefobid, Ampicillin, Nitrofurantion, Traivid and Erythromycin.     

Spectroscopic, and thermal studies of some new binuclear transition metal(II) complexes with hydrazone ligands containing acetoacetanilide and isoxazole

A new chelating ligand, 2-(2-(5-tert-butylisoxazol-3-yl)hydrazono)-N-(2,4-dimethylphenyl)-3-oxobutanamide (HL), and its four binuclear transition metal complexes, M(2)(L)(2) (micro-OCH(3))(2) [M=Ni(II), Co(II), Cu(II), Zn(II)], were synthesized using the procedure of diazotization, coupling and metallization. Their structures were postulated based on elemental analysis, (1)H NMR, MALDI-MS, FT-IR spectra and UV-vis electronic absorption spectra. Smooth films of these complexes on K9 glass substrates were prepared using the spin-coating method and their absorption properties were evaluated. The thermal properties of the metal(II) complexes were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). Different thermodynamic and kinetic parameters namely activation energy (E*), enthalpy of activation (DeltaH*), entropy of activation (DeltaS*) and free energy change of activation (DeltaG*) are calculated using Coats-Redfern (CR) equation.     

Antimicrobial activity studies of the binuclear metal complexes derived from tridentate Schiff base ligands

Three novel tridentate Schiff base ligands derived fromthe 3-hydroxysalicylaldehyde (H₂L¹), 4-hydroxysalicylaldehyde (H₂L²) and 5-bromosalicylaldehyde (H₂L³) with a new amine N-(pyridyl)-2-hydroxy-3-methoxy-5-aminobenzylamine (2) have been prepared. The ligands and their metal complexes have been characterized by elemental analyses, conductivity and magnetic susceptibility measurements, i.r., electronic absorption and ¹H and ¹³C n.m.r. spectroscopy. All complexes are binuclear and, in some, the H₂O molecules are coordinated to the metal ion. Antimicrobial activities of the ligands and their complexes have been tested against to the Bacillus subtilis IMG 22 (bacteria), Micrococcus luteus LA 2971 (bacteria) Saccharamyces cerevisiae WET 136 (yeast), and Candida albicans CCM 314 (yeast). Thermal properties of all complexes have been studied by t.g. and d.t.a techniques.     

Synthesis,characterization, anticancer activity,thermal and electrochemical studies of some novel uranyl Schiff base complexes

Some tetradentate N₂O₂ Schiff base ligands, such as N,N′-bis(naphtalidene)-1,2-phenylenediamine, N,N′-bis(naphtalidene)-4-methyl-1,2-phenylenediamine, N,N′-bis(naphtalidene)-4-chloro-1,2-phenylenediamine, N,N′-bis(naphtalidene)-4-nitro-1,2-phenylenediamine, N,N′-bis(naphtalidene)-4-carboxyl-1,2-phenylenediamine, and their uranyl complexes were synthesized and characterized by ¹H NMR, IR, UV–Vis spectroscopy, TG (thermogravimetry), and elemental analysis (C.H.N.). Thermogravimetric analysis shows that uranyl complexes have very different thermal stabilities. This method is used also to establish that only one solvent molecule is coordinated to the central uranium ion and this solvent molecule does not coordinate strongly and is removed easier than the tetradentate ligand and also trans oxides. The electrochemical properties of the uranyl complexes were investigated by cyclic voltammetry. Electrochemistry of these complexes showed a quasireversible redox reaction without any successive reactions. Also, the kinetic parameters of thermal decomposition were calculated using Coats–Redfern equation. According to Coats–Redfern plots the kinetics of thermal decomposition of the studied complexes is first-order in all stages. Anticancer activity of the uranyl Schiff base complexes against cancer cell lines (Jurkat) was studied and determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazoliumbromide) assay.     

Antimicrobial activity studies of the metal complexes derived from substituted cyclobutane substituted thiazole Schiff base ligands

Two novel bidentate Schiff base ligands derived from 4-(1-methyl-1-mesitylcyclobutane-3-yl)-2-aminothiazole (LH) have been prepared and characterized by elemental analyses, i.r., ¹³C- and ¹H-n.m.r. spectra, u.v.–vis. and magnetic susceptibility measurements. The complexes are mononuclear. Antimicrobial activities of the ligands and their complexes have been tested: Bacillus megaterium DSM 32, Candida albicans FMC 17, Enterobacter aeroginosa CCM 2531, Escherichia coli ATCC 25922, Listeria monocytogenes SCOTTA, Micrococcus luteus LA 2971, Proteus vulgaris FMC 11, Pseudomonas aeruginosa DSM 50071, Saccharomyces cerevisiae FMC 16 and Staphylococcus aureus COWAN I. The thermal properties of the ligands and their complexes have been studied by t.g.a.     

Synthesis, spectral and thermal studies of some transition metal mixed ligand complexes: modeling of equilibrium composition and biological activity

Several mixed ligand Ni(II), Cu(II) and Zn(II) complexes of 2-amino-3-hydroxypyridine (AHP) and imidazoles viz., imidazole (him), benzimidazole (bim), histamine (hist) and L-histidine (his) have been synthesized and characterized by elemental and spectral (vibrational, electronic, 1H NMR and EPR) data as well as by magnetic moment values. On the basis of elemental analysis and molar conductance values, all the complexes can be formulated as [MAB]Cl except histidine complexes as MAB. Thermogravimetric studies reveal the presence of coordinated water molecules in most of the complexes. From the magnetic measurements and electronic spectral data, octahedral structure was proposed for Ni(II) and Cu(II)-AHP-his, tetrahedral for Cu(II)-AHP-him/bim/hist, but square planar for the Cu(II)-AHP complex. The g∥/A∥ calculated supports tetrahedral environment around the Cu(II) in Cu(II)-AHP-him/bim/hist and distorted octahedral for Cu(II)-AHP-his complexes. The morphology of the reported metal complexes was investigated by scanning electron micrographs (SEM). The potentiometric study has been performed in aqueous solution at 37 °C and I=0.15 mol dm(-3) NaClO4. MABH, MAB and MAB2 species has been identified in the present systems. Proton dissociation constants of AHP and stability constants of metal complexes were determined using MINIQUAD-75. The most probable structure of the mixed ligand species is discussed based upon their stability constants. The in vitro biological activity of the complexes was tested against the Gram positive and Gram negative bacteria, fungus and yeast. The oxidative DNA cleavage studies of the complexes were performed using gel electrophoresis method. Cu(II) complexes have been found to promote DNA cleavage in presence of biological reductant such as ascorbate and oxidant like hydrogen peroxide.     

Synthetic,spectroscopic and thermal studies of some complexes of unsymmetrical Schiff base ligand

New unsymmetrical Schiff base ligand (H₂L) is prepared via condensation of 2-hydroxy-5-methyl acetophenone, 2-hydroxy-5-chloro-3-nitro acetophenone and carbohydrazide in 1:1:1 ratio. Metal complexes of VO(IV), Cr(III), Mn(III), Fe(III), Zr(IV), MoO₂(VI), WO₂(VI) and UO₂(VI) have been prepared. These complexes were characterized by elemental analysis, UV–Vis and IR spectroscopy and magnetic moment and thermogravimetric analysis. The purity of the ligand and the metal complexes is confirmed by microanalyses, while unsymmetrical nature of ligand was further corroborated by ¹H NMR. All the complexes are air stable and insoluble in water and common organic solvents but fairly soluble in DMSO. The elemental analysis shows 1:1 metal to ligand stoichiometry for all the complexes. Thermal behaviour of the complexes was studied, the complexes were found to be quite stable and their thermal decomposition was generally via partially loss of the organic moiety and ended with respective metal oxide as a final product. Comparison of the IR spectrum of ligand and its metal complexes confirm that Schiff base behave as a dibasic tetradentate ligand towards the central metal ion with an ONNO donor sequence. The dc electrical conductivity is studied and data obtained obeyed the relation σ = σ ₀ exp(−E _a/kT) over the temperature range 40–130 °C. X-ray diffraction study of VO(IV) complex shows its crystalline nature with triclinic crystal system.     

Synthesis,characterization and cytotoxic activity of ferrocenyl hydrazone complexes containing a furan moiety

A ferrocenyl ligand 1 was prepared from condensation of 5-methyl-2-furaldehyde with l,l′-diacetylferrocene dihydrazone. This ligand forms 1:1 complexes with cobalt(II), nickel(II), copper(II) and zinc(II) 2–5 in good yield. Characterization of the ligand and complexes was carried out using infrared, nuclear magnetic resonance, mass spectra, electronic absorption, magnetic susceptibility, molar conductivity, and elemental analysis. Cytotoxic activity of the prepared ligand and its complexes were tested against different human cancer cell lines. The results suggested that the synthesized compounds were more potent than the comparative standards drugs used in most cases, whereas they had less activity in the others.     

Antimicrobial agents: synthesis,spectral, thermal,and biological aspects of a polymeric Schiff base and its polymer metal(II) complexes

Some new coordination polymers of Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) obtained by the interaction of metal acetates with polymeric Schiff base containing formaldehyde and piperazine have been investigated. Structural and spectroscopic properties have been studied by elemental, spectral (FT-IR, ¹H-NMR, and UV-Vis), and thermogravimetric analysis. UV-Vis spectra and magnetic moments indicate that Mn(II), Co(II), and Ni(II) polymer metal complexes are octahedral, while Cu(II) and Zn(II) polymer metal complexes are square planar and tetrahedral, respectively. All compounds were screened for their antimicrobial activities against Escherichia coli, Bacillus subtillis, Staphylococcus aureus, Pseudomonas aeruginosa, Salmonella typhi, Candida albicans, Agelastes niger, and Microsporum canis using the Agar well diffusion method with 100?µg?mL^?1 of each compound.     

Synthesis,characterization and antimicrobial studies of novel ONO donor hydrazone Schiff base complexes with some divalent metal (II) ions

Metal complexes of two general formulae [M(L)(Cl)(H₂O)₂] [M = Mn(II), Co(II), Ni(II) and Cu(II)] and [M(L)(H₂O)] [M = Zn(II) and Cd(II)] with pyrazine-2-carbohydrazone of 2-hydroxy-5-methylacetophenone (H₂L) are synthesized and characterized by microanalytical, thermal, magnetic susceptibility measurement, spectroscopic (IR, ¹H NMR, ¹³C NMR), mass, molar conductance, X-ray powder diffraction, ESR and SEM studies. While the molar conductance measurements in DMSO indicated their non-electrolytic nature, the spectroscopic studies confirmed a tridentate ONO donor behaviour of the ligand towards the central metal ion. Based on the physico-chemical studies monomeric octahedral geometry around Mn(II), Co(II), Ni(II) and Cu(II) ions (i.e. for the first series of complexes) whereas tetrahedral to Zn(II) and Cd(II) ions (i.e. for the second series of complexes) are suggested. Based on the thermal behavior of the complexes, various kinetic and thermodynamic parameters were evaluated using Coats-Redfern method. The ligand and its metal complexes were screened for in vitro antibacterial and antifungal activity against Gram +ve S. aureus, B. subtilis and Gram –ve E. coli and S. typhi. and fungal strains, C. albicans and A. niger. The observed data infer promising biological activity of some of these complexes compared the parent ligand against all bacterial and fungal species.     

Synthesis and genotoxicity of Schiff base transition metal complexes

A new ONNO‐type azomethine ligand, 2,2′‐(ethane‐1,2‐diylidenedinitrilo)dibenzoic acid, (YLH₂) ( 1 ) has been prepared by the condensation of 2‐aminobenzoic acid and glyoxal. The coordination compounds [Ni(YL)] ( 2 ), [Co(YL)] ( 3 ), [Cu(YL)(H₂O)] ( 4 ), [Zn(YL)] ( 5 ), and [Cd(YL)] ( 6 ) of the YLH₂ ligand with five transition metal ions, Ni(II) Co(II), Cu(II), Zn(II), and Cd(II) have been prepared. The structures of these new azomethine compounds are proposed on the basis of the elemental analyses, proton nuclear magnetic resonance, infrared, ultraviolet–visible spectroscopy, and X‐ray powder diffraction patterns. Elemental analyses indicate a ligand metal ratio of 1:1 in the coordination compounds. X‐ray powder diffraction parameters for [Cu(YL)(H₂O)] and [Cd(YL)] compounds correspond to orthorhombic and monoclinic structures, respectively. The ligand acts as a tetradentate ligand bending through oxygen atoms of the hydroxyl groups of benzoic acid and nitrogen atoms of the azomethine groups. In addition, the ligand and its metal complexes have been studied for their possible genotoxic potential. © 2011 Wiley Periodicals, Inc. Heteroatom Chem 22:119–130, 2011; View this article online at wileyonlinelibrary.com . DOI 10.1002/hc.20665