Schiff Base Transition Metal Complexes Research Articles

Synthesis, Characterization, Biological Activity and DNA Binding Studies of Metal Complexes with 4‐Aminoantipyrine Schiff Base Ligand

A new series of transition metal complexes of Cu(II),Ni(II),Co(II), Zn(II) and VO(IV) have been synthesized from the Schiff base ligand (L) derived from 4‐amino antipyrine and 5‐ bromo salicylaldehyde. The structural features of Schiff base and metal complexes were determined from their elemental analyses, thermogravimetric studies, magneticsusceptibility, molar conductivity, ESI‐Mass, IR, UV‐VIS, 1H NMR and ESR spectral studies. The data show that the complexes have composition of ML2 type. The UV‐VIS, magnetic susceptibility and ESR spectral data suggest an octahedral geometry around the central metal ion. Biological screening of the complexes reveals that the Schiff base transition metal complexes show significant activity against microorganisms. Binding of Co(II) complex with calf thymus DNA (CT DNA) was studied by spectral methods.

4-Aminoantipyrine-based Schiff-base transition metal complexes as potent anticonvulsant agents

Metal complexes of Co(II), Ni(II), Cu(II), and Zn(II) with ligands (L1H and L2) derived from 4-aminoantipyrine, 2-hydroxy-3-formylquinoline, and isatin were synthesized and characterized by the elemental analysis, conductance measurements, magnetic susceptibility, and spectral analysis. The spectral data revealed that the ligands acted as a neutral tridentate, coordinating to the metal ion through the azomethine nitrogen, phenolic oxygen, and carbonyl oxygen of the 4-aminoantipyrine, 2-hydroxy-3-formylquinoline, and isatin molecule in ligands L1H and L2 only. Both the ligands and their metal complexes were studied for cyclic voltammetry studies. The ligand and the metal complexes were screened for their anticonvulsant activity, and it has been observed that the metal complexes are more potent than the ligands.

Effects of Metal Salophene and Saldach Complexes on Lymphoma and Leukemia Cells

Schiff base transition metal complexes are an important class of compounds with great potential for therapeutic interventions. However, data on antileukemic and antilymphoma effects of these complexes are limited. The activity of N,N'-bis(salicylidene)-1,2-phenylenediamine (salophene, 1), its iron(II/III) and manganese(II/III) complexes as well as rac-trans-N,N'-bis(salicylidene)-1,2-cyclohexanediamine (saldach, 2) and its respective iron(II/III) complexes was evaluated against U-937 non-Hodgkin's lymphoma and the HL-60, SUP-B15, and K-562 leukemia cell lines. The free ligands induced in all cell lines, if at all, only marginal, concentration-dependent growth inhibitory effects, and did not trigger Cu/Zn superoxide dismutase (Cu/Zn SOD) release or induce apoptosis. [Fe(II) (salophene)] (3) and [Fe(III) (salophene)Cl] (4) blocked cellular growth, caused a strong release of Cu/Zn SOD and induced apoptosis. In contrast, the manganese analogs [Mn(II) (salophene)] (5) and [Mn(III) (salophene)OAc] (6) inhibited cell growth, caused the programmed cell death only at higher concentrations and did not provoke release of Cu/Zn SOD in any of the four cell lines. Weaker cell death-promoting effects were observed when the salophene moiety of 3 and 4 was replaced with saldach (complexes 7 and 8), indicating the influence exerted by the ligand structure. In conclusion, Schiff base transition metal complexes induce strong inhibitory effects on human lymphoma and leukemia cells.

Synthesis, molecular docking and biological evaluation of Schiff base transition metal complexes as potential urease inhibitors

Six transition metal compounds of Schiff base ligands were evaluated for the inhibitory activity on jack bean urease, of which compounds 2– 6 were determined by single crystal X-ray analysis. It was found that copper(II) complexes 1 and 4 showed strong inhibitory activity against jack bean urease (IC 50 = 0.52 and 0.46 μM), compared with acetohydroxamic acid (IC 50 = 42.12 μM) as a positive reference. Cobalt(II), nickel(II) and zinc(II) compounds also exhibited potent inhibitory activity (IC 50 = 3.88–25.20 μM). A docking analysis using the AUTODOCK 4.0 program could explain the inhibitory activities of 1 and 4 against urease.

Synthesis, characterization, DNA binding, oxidative damage of DNA strand scission, and antimicrobial activities of β-diketone condensed Schiff-base transition metal complexes

Co(II), Ni(II), Cu(II), Zn(II), and VO(IV) complexes containing a versatile β-diketone Schiff-base ligand (obtained by the condensation of 3-furan-2-ylmethylene-2,4-dione and 2-aminophenol) have been synthesized and characterized. Microanalytical, magnetic, and spectroscopic data reveal that the central metal is coordinated to two oxygens of phenolate and two nitrogens of imine of the ligand. Binding of synthesized complexes with calf thymus DNA has been investigated by spectroscopic and electrochemical methods and viscosity measurements. The complexes are able to form adducts with DNA and to distort the double helix by changing the base stacking. Electrostatic binding of vanadyl complex is observed from the weak hypochromism in electronic absorption spectra and no change in the viscosity with DNA. Oxidative DNA cleavage activities of the complexes are studied with supercoiled pUC19 DNA using gel electrophoresis. The hydroxyl radical (OH•) is likely to be the species responsible for the cleavage of pUC19 DNA by the synthesized complexes. Under our experimental conditions, the vanadyl complex has no significant cleavage of DNA. The compounds have been screened for activity against several bacterial and fungal strains and the results are compared with the activity of standard drugs.

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).

Catalytic epoxidation performance and dioxygen affinities of unsymmetrical Schiff base transition–metal complexes with pendant aza-crown or morpholino groups

Unsymmetrical Schiff base CoII complexes (CoL1–CoL6) and Schiff base MnIII complexes (MnL1Cl–MnL6Cl) with pendant aza-crown or morpholino groups were synthesized according to the literature. The oxygen uptake of Schiff base CoII complexes in MeOCH2CH2OMe solution was determined at different temperatures, and the equilibrium constants (KO2) and thermodynamic parameters (∆H 0, ∆S 0) for oxygenation were calculated. The corresponding MnIII complexes, MnL1Cl–MnL6Cl, were employed to catalyze epoxidation of styrene at ambient temperature and pressures. The effects of crown ether on the modulation of O2-binding capability and the catalytic oxidation of styrene are discussed. The results indicate that the dioxygen affinities of the CoII complexes are much more enhanced by aza-crown pendant group than that by morpholino pendant group, and the O2-binding capabilities of CoL1–CoL3 with aza-crown pendant group can also be enhanced by adding alkali metal cations (Li+, Na+, and K+); similarly, the catalytic activities of the MnIII complexes with aza-crown pendant group, MnL1Cl–MnL3Cl, are higher than those of the MnIII complexes with morpholino pendant group, MnL4Cl–MnL6Cl. Catalytic epoxidation performance and dioxygen affinities of unsymmetrical Schiff base transition–metal complexes with pendant aza-crown or morpholino groups. Jian-zhang Li*, Bin Xu, Wei-dong Jiang Key Laboratory of Green and Technology, Department of Chemistry, Sichuan University of Science & Engineering, Zigong, Sichuan 643000, People’s Republic of China Bo Zhou, Wei Zeng, Sheng-ying Qin Department of Chemistry, Sichuan University, Chengdu, Sichuan 610064, People’s Republic of China The oxygen uptake of Schiff base CoII complexes in MeOCH2CH2OMe solution was determined at different temperatures, and the equilibrium constants (KO2) and thermodynamic parameters (∆H 0, ∆S 0) for oxygenation were calculated. The corresponding MnIII complexes, MnL1Cl-MnL6Cl, were employed to catalyze epoxidation of styrene at ambient temperature and pressures. The effects of crown ether on the modulation of O2-binding capability and the catalytic oxidation of styrene are discussed.

Synthesis, characterization, and biological study of some biologically potent schiff base transition metal complexes

The synthesis and characterization of a Schiff base derived from aniline and salicylaldehyde and its Co(II), Mn(II), and Zn(II) complexes is reported; several physical tools, in particular, elemental analysis, infrared and NMR techniques were used to investigate the chemical structure of the reported complexes. The ligand is found to be bound to the metal atom through the oxygen atom of the hydroxyl group, which is also supported by spectroscopic techniques. The results obtained by FT-IR and NMR showed that the Schiff base-transition metal complexes have octa hedral geometry. Biological screening of the complexes reveals that the Schiff base-transition metal complexes show significant activity against all microorganisms.

Designing, synthesis and 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) and Zn(II) have been designed and synthesized using a Schiff base (L) derived from 4-aminoantipyrine, benzaldehyde and o-phenylenediamine. The structural features were derived from their elemental analyses, magnetic susceptibility and molar conductivity, as well as from mass, IR, UV-Vis, 1H-NMR and ESR spectral studies. The FAB mass spectral data and elemental analyses showed that the complexes had a composition of the ML type. The UV-Vis and ESR spectral data of the complexes suggested a square-planar geometry around the central metal ion. The magnetic susceptibility values of the complexes indicated that they were monomeric in nature. Antimicrobial screening tests were also performed against four bacteria, viz. Salmonella typhi, Staphylococcus aureus, Escherichia coli, and Bacillus subtilis and three fungi, viz. Aspergillus niger, Aspergillus flavus and Rhizoctonia bataicola. These data gave good results in the presence of metal ion in the ligand system. The nuclease activity of the above metal complexes shows that only the copper complex cleaves CT DNA in the presence of an oxidant.

Synthesis and Spectral Characterization of Antifungal Sensitive Schiff Base Transition Metal Complexes

New N2O2 donor type Schiff base has been designed and synthesized by condensing acetoacetanilido-4-aminoantipyrine with 2-aminobenzoic acid in ethanol. Solid metal complexes of the Schiff base with Cu(II), Ni(II), Co(II), Mn(II), Zn(II), VO(IV), Hg(II) and Cd(II) metal ions were synthesized and characterized by elemental analyses, magnetic susceptibility, molar conduction, fast atom bombardment (FAB) mass, IR, UV-Vis, and 1H NMR spectral studies. The data show that the complexes have the composition of ML type. The UV-Vis. and magnetic susceptibility data of the complexes suggest a square-planar geometry around the central metal ion except VO(IV) complex which has square-pyramidal geometry. The in vitro antifungal activities of the compounds were tested against fungi such as Aspergillus niger, Aspergillus flavus, Rhizopus stolonifer, Candida albicans, Rhizoctonia bataicola and Trichoderma harizanum. All the metal complexes showed stronger antifungal activities than the free ligand. The minimum inhibitory concentrations (MIC) of the metal complexes were found in the range of 10~31 μg/ml.

Schiff base transition metal complexes as novel inhibitors of xanthine oxidase

Twenty transition metal complexes with Schiff bases were evaluated for their inhibitory activities on xanthine oxidase (XO), of which 11 were newly synthesized and characterized by X-ray single crystal diffraction. It was found that 9 of the 20 complexes showed potent inhibitory activities against XO near to the standard inhibitor allopurinol. The cadmium(II) complex ( 8) had the most potent inhibitory activity with the IC 50 value of 2.16 μM. Relationships between the structures and the activities showed that the ligands and the metal ions influenced the inhibitory activities. The XO inhibition of the Schiff base metal complexes most probably resulted from their direct interactions with the enzymes “in the whole complex form”. These results demonstrated that the Schiff base transition metal complexes could be potential selective XO inhibitors.

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.

Catalytic Kinetics of the Schiff Base Metal Complexes Bearing Side Chain of Cyclic morpholine in Carboxylic Ester Hydrolysis

AbstractIt has been reported that two Schiff base transition metal complexes bearing the side chain of the morpholine ring were synthesized and characterized, and two complexes with the same base agent but different metal ions were used as a simulant hydrolase in the catalytic hydrolysis of p‐nitrophenyl picolinate in this paper. The mechanism of PNPP catalytic hydrolysis is proposed and supported by the results of the spectral analysis and the kinetic calculation. A kinetic mathematical model, applied to the calculation of the kinetic and thermodynamics parameters of PNPP catalytic hydrolysis, has been established on the foundation of the mechanism proposed. The result of the study shows that the two complexes have a good catalytic activity in PNPP catalytic hydrolysis, and the rate of the PNPP catalytic hydrolysis was increased with the increase of the pH values in the buffer solution and affected by the polarization effect of metal ion of the complexes.

Synthesis and characterization of some Schiff base transition metal complexes derived from vanillin and L(+)alanine

The cobalt(II), nickel(II), copper(II) and zinc(II)-vanillidene-L(+)alanine complexes were synthesized and characterized by elemental analysis, conductivity measurements, magnetic behavior, infrared, electronic spectral measurements, X-ray powder diffraction and biological studies. The conductance measurements indicate that all the complexes are non-electrolytes. The infrared spectra indicate the coordination of imino nitrogen, phenolic oxygen and carboxylato oxygen atoms. The electronic spectral measurements demonstrate that cobalt(II) and nickel(II)-vanillidene-L(+)alanine complexes are tetrahedral, while copper(II)-vanillidene-L(+)alanine complex has square planar geometry. The cobalt(II) complex is found to be ferromagnetic. The powder XRD studies confirm the crystalline nature of the complexes. The ligand and complexes were less active against PN, PA and BC, whereas copper complex shows moderate activity against AN.

Synthesis, spectral characterization, redox and antimicrobial activity of Schiff base transition metal(II) complexes derived from 4-aminoantipyrine and 3-salicylideneacetylacetone

Abstract A novel tetradentate N2O2 type Schiff base, synthesized from 1-phenyl-2,3-dimethyl-4-aminopyrazol-5-one(4-aminoantipyrine) and 3-salicylidene-acetylacetone, forms stable complexes with transition metal ions such as CuII, NiII, CoII and ZnII in ethanol. Microanalytical data, magnetic susceptibility, IR, UV-Vis.,1H-NMR, ESR and Mass spectral techniques were used to confirm the structures. Electronic absorption spectra of the complexes suggest a square-planar geometry around the central metal ion. These complexes show higher conductance values, supporting their electrolytic nature. The monomeric nature of the complexes was confirmed from their magnetic susceptibility values. Cyclic voltammogram of the copper(II) and nickel(II) complexes in DMSO solution at 300 K were recorded and the results are discussed. The X-band ESR spectra of the copper complex were recorded and the molecular orbital coefficient values were calculated from the spectra. The in vitro antimicrobial activities of the investigated compounds were tested against bacteria such as Klebsiella pneumoniae, Staphylococcus aureus, Bacillus subtilis and Escherichia coli and fungi like Aspergillus niger and Rhizoctonia bataicola. Most of the metal chelates show higher antimicrobial activity for the above microorganisms than that of the free ligand.

Preparation, Characterization and Biological Evaluation of Schiff Base Transition Metal Complexes with Cephradine

Preparation, Characterization and Biological Evaluation of Schiff Base Transition Metal Complexes with Cephradine

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 2O and L 2MX 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 aereuguinosa, Klebsiella penumoniae, 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.

Electrocatalytic effects of thionyl chloride reduction by polymeric Schiff base transition metal(II) complexes

Electrocatalytic effects for the reduction of thionyl chloride in LiAlCl 4/SOCl 2 electrolyte solution containing polymeric Schiff base M(II) (M: Ni and Cu) complexes were evaluated by determining kinetic parameters with cyclic voltammetry at a glassy carbon electrode. The charge transfer process during the reduction of thionyl chloride was affected by the concentration of the catalyst. The catalytic effects were demonstrated from both a shift of the reduction potential for the thionyl chloride in a more positive direction and an increase in peak currents. The reduction of thionyl chloride was found to be diffusion-controlled. Catalytic effects are larger in thionyl chloride solutions containing (PVPS)M(II)(SALPR) rather than in those containing (PVPS)M(II)(SALPE). Such results are opposite to those for monomeric Schiff base complexes. Significant improvements in the cell performance were found in terms of both thermodynamics and kinetic parameters for the thionyl chloride reduction. An exchange rate constant, k o, of 1.62×10 −8 cm/s was found at a bare electrode, while larger values of (4.69–8.18)×10 −8 cm/s were observed at the catalyst-supported glassy carbon electrode.