Synthesis and structure of a Schiff base and its bivalent transition metal complexes

A Schiff base (HCSmz) was synthesized via (E)-cinnamaldehyde with S-methyl dithiocarbazate and six bivalent transition metal complexes [M(CSmz)₂] (M=Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺, and Hg²⁺) were prepared. The complexes were characterized by elemental analyses, IR, ¹H NMR, and UV-Vis spectra, and the Ni(II) and Zn(II) complexes were also characterized by single crystal X-ray diffraction. After tautomerism of thiotone to thioenol and deprotonization of the thioenol, two ligands chelate the metal by two nitrogens of azomethine and two sulfurs of thioenol. Ni(CSmz)₂ crystallizes in the centrosymmetric space group P2₁ /n with a perfectly square planar trans-configuration with Ni located at the center of the square; crystal packing is stabilized by intra- and intermolecular C–H···S hydrogen bonds. Zn(CSmz)₂ is in the mirror-symmetric space group I4₁ /a in a distorted tetrahedral geometry with two equivalent Zn–N and Zn–S bonds; crystal packing is stabilized by intermolecular C–H···π hydrogen bonds.     

Quinoxaline-based Schiff base transition metal complexes: review

The literature survey highlights spectra and biological activity of transition metal complexes derived from Schiff bases of quinoxaline. The extensive studies of synthesis, spectral, structural characterization, and biological activities of the metal complexes with heterocyclic Schiff bases of quinoxaline are reviewed.     

Synthesis and characterization of Schiff base metal complexes: their antimicrobial,genotoxicity and electrochemical properties

We have synthesized the three Schiff-base ligands H₂L¹–H₂L³ and their Co^II, Fe^III and Ru^III metal complexes. All compounds have been characterized by analytical and spectroscopic methods. Oxidation of cyclohexane has been done by the metal complexes in CH₃CN using H₂O₂ and/or t-butylhydroperoxide (TBHP) as a co-catalyst. The keto-enol tautomeric forms of the ligands have been studied in polar and non-polar organic solvents. Electrochemical properties of the complexes have been studied at different scan rates. Thermal studies were carried out for the compounds. The ligands H₂L¹–H₂L³ were mutagenic on Salmonella Typhimurium TA 98 strain in the presence and/or absence of S9 mix. While the ligands H₂L¹ and H₂L² showed mutagenic activity on the strain TA 100 with and without S9 mix, the ligand H₂L³ was not mutagenic for TA 100. Antimicrobial activity studies of the compounds have also been carried out.     

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).     

Electrochemistry of transition metal complexes of Schiff base compartmental ligands

Summary The electrochemical behaviour of a series of mononuclear and dinuclear complexes of dioxouranium(VI), nickel(II) and copper(II) ions with the Schiff base, H₄fsalacen, derived from the condensation of 3-formylsalicylic acid and 1,2-diaminoethane, is reported.The potentially hexadentate compartmental ligand H₄fsalacen has an outer O₂O₂ and an inner N₂O₂ coordination site. The redox properties of the metal ions in these two different and adjacent chambers have been investigated and compared with those of the analogous complexes with the ligand H₄ aapen, obtained by reaction ofo-acetoacetylphenol and 1,2-diaminoethane.A preliminary report was presented at the 1st International Conference on the Chemistry and Technology of the Lanthanides and Actinides, Venice, 5 September, 1983, Italy.     

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,characterization and antifungal activity of glycylglycine Schiff base complexes of 3d transition metal ions

Summary Two new Schiff bases, N-4-hydroxysalicylidene-glycylglycine (K·GGRS·H₂O), N-O-vanillal-glycylglycine (K· GGVS·3H₂O) and their manganese(II), cobalt(II), nickel(II) and copper(II) complexes have been synthesized and characterized by elemental analysis, t.g.a., molar conductance, i.r. and u.v. spectral studies. The ¹³Cn.m.r. spectrum of one of the Schiff base ligands has been recorded. The results show that the ligand is coordinated to the central metal ion via amide nitrogen, imino nitrogen, phenolic oxygen and carboxyl oxygen to form a quadridentate complexes. Some of the complexes exhibit strong inhibitory action towards Candida albicans and Cryptococcus neoformans.     

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.     

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.     

Synthesis and physicochemical studies of metal complexes of ferrocene Schiff base derivatives

Two new Schiff bases were prepared by condensing acetylferrocene and 1,1′-diacetylferrocene with S-methyl- dithiocarbazate. Complexes of the two ligands acetylferrocene-1-hydrazono-S-methyldithiocarbazate HmaL and diacetylferrocene-1,1′-dihydrazono-S-methyldithio-carbazate H2daL, with copper(II), nickel(II) and cobalt(II) ions were isolated. The ligands coordinate to the metal ions through either their thioketone or thioenol forms. Both mono- and bis-ligand metal complexes as well as bis-metal complexes of the general formulae: [(H2daL)M]2+, [(daL)M], [(HmaL)2M]2+, [(maL)2M], [(HmaL)2MX2], [(H2daL)M2X4] and [(daL)M2X2] were prepared. All compounds under investigation were characterized and some of their physicochemical properties are reported. This revised version was published online in June 2006 with corrections to the Cover Date.     

Synthesis,characterization of Schiff base metal complexes and their biological investigation

A new Schiff base ligand named (E)‐2‐(((3‐aminophenyl)imino)methyl)phenol (HL) was prepared through condensation reaction of m‐phenylenediamine and 2‐hydroxybenzaldehyde in 1:1 molar ratio. The new ligand was characterized by elemental analysis and spectral techniques. The coordination behavior of a series of transition metal ions named Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) with the newly prepared Schiff base ligand (HL) is reported. The nature of bonding and the stereochemistry of the complexes have been deduced from elemental analyses, IR, UV–Vis, ¹H NMR, mass, electronic spectra, magnetic susceptibility and conductivity measurements and further their thermal stability was confirmed by thermogravimetric analysis (TG). From IR spectra, it was observed that the ligand is a neutral tridentate ligand coordinates to the metal ions through protonated phenolic oxygen, azomethine nitrogen and nitrogen atom of NH₂ group. The existence, the number and the position of the water molecules was studied by thermal analysis. The molecular structures of the Schiff base ligand (HL) and its metal complexes were optimized theoretically and the quantum chemical parameters were calculated. The synthesized ligand and its complexes were screened for antimicrobial activities against bacterial species (Staphylococcus aureus and Bacillis subtilis, (gram positive bacteria)), (Salmonella SP., Escherichia coli and Pseudomonas aeruginosa, (gram negative bacteria)) and fungi (Aspergillus fumigatus and Candida albicans). The complexes were found to possess high biological activities against different organisms. Molecular docking was used to predict the efficiency of binding between Schiff base ligand (HL) and both receptors of Escherichia coli (3 T88) and Staphylococcus aureus (3Q8U). The receptor of Escherichia coli (3 T88) showed best interaction with Schiff base ligand (HL) compared to receptor of Staphylococcus aureu (3Q8U).     

Schiff碱金属配合物的研究进展

简要介绍了Schiff碱金属配合物的发展历程、缩合反应机理、合成方法及其在材料、医药、催化等领域的研究、应用概况,并展望了其发展、应用前景.     

Transition metal complexes of heterocyclic Schiff base

Metal complexes of Schiff base derived from 2-furancarboxaldehyde and 2-aminobenzoic acid (HL) are reported and characterized based on elemental analyses, IR, ¹H NMR, UV-Vis, solid reflectance, magnetic moment, molar conductance and thermal analysis. The ligand dissociation as well as the metal-ligand stability constants have been calculated pH-metrically at 25°C and ionic strength μ=0.1 (1 M NaCl). The complexes are found to have the formulae [M(HL)₂](X)_n·yH₂O (where M=Fe(III) (X=Cl, n=3, y=4), Co(II) (X=Cl, n=y=2), Ni(II) (X=Cl, n=y=2), Cu(II) (X=Cl, n=y=2) and Zn(II) (X=AcO, n=y=2)) and [UO₂(L)₂]·2H₂O. The thermal behaviour of these chelates is studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. The ligand and its metal complexes show a biological activity against some bacterial species.     

Synthesis,characterization, and thermal analysis of transition metal complexes of polydentate ONO donor Schiff base ligand

Mn(II), Co(II), Ni(II), Cu(II), Cd(II), and Hg(II) metal complexes with Schiff bases derived from 3-formyl-4-hydroxycoumarin and semicarbazone are synthesized and characterized on the basis of elemental analysis, molar conductance, magnetic moment, IR, electronic, ¹H NMR spectrum, and ESR spectrum, TGA, and X-ray diffraction powder methods. Molar conductance values indicate that the complexes are nonelectrolytic in nature. Magnetic moment and spectral studies suggest either tetrahedral or square-planar geometry around the central metal ions. The analytical data indicate that metal-to-ligand stoichiometry in all complexes is 1: 1. The article was submitted by the authors in English.     

Antibacterial activity of transition metal complexes with a tridentate NNO amoxicillin derived Schiff base. Synthesis and characterization

From the reaction of amoxicillin ( 1 ) antibiotic with 2,6?diaminopyridine ( 2 ) an amoxicillin?based Schiff base (HL) ( 3 ) was obtained and its transition metal Schiff base complexes were synthesized. Spectroscopic and physicochemical techniques, namely, UV?Vis, FT?IR, ¹H?NMR, EPR, mass spectrometry, molar conductance, magnetic susceptibility, molecular modelling, together with elemental and thermal analyses, were used to characterize the synthesized compounds. Spectral and magnetic data suggested an octahedral geometry for all the complexes and the general formulae [ML(H₂O)₃][PF₆] (M(II) = Mn²⁺ ( 4 ), Co²⁺ ( 5 ), Ni²⁺ ( 6 ), Cu²⁺ ( 7 ), Zn²⁺ ( 8 ), was proposed for them, where L represents deprotonated tridentate NNO amoxycillin?derived Schiff base. All compounds were screened for antibacterial activity by using agar disc diffusion method. The zinc(II) complex exhibited promising bactericidal activity against E. coli and S. aureus.     

Redox and antimicrobial studies of transition metal(II) tetradentate Schiff base complexes

Neutral tetradentate chelate complexes of Cu^II, Ni^II, Co^II, Mn^II, Zn^II and VO^II have been prepared in EtOH using Schiff bases derived from acetoacetanilido-4-aminoantipyrine and 2-aminophenol/2-aminothiophenol. Microanalytical data, magnetic susceptibility, i.r., u.v.–vis., ¹H-n.m.r. and e.s.r. spectral techniques were used to confirm the structures of the chelates. Electronic absorption and i.r. spectra of the complexes suggest a square-planar geometry around the central metal ion, except for VO^II and Mn^II complexes which have square-pyramidal and octahedral geometry respectively. The cyclic voltammetric data for the Cu^II complexes in MeCN show two waves for copper(II) copper(III) and copper(II) copper(I) couples, whereas the VO^II complexes in MeCN show two waves for vanadium(IV) vanadium(V) and vanadium(IV) vanadium(III) couples. The e.s.r. spectra of the Cu^II, VO^II and Mn^II complexes were recorded in DMSO solution and their salient features reported. The in vitro antimicrobial activity of the investigated compounds was tested against the microorganisms such as Salmonella typhi, Staphylococcus aureus, Klebsiella pneumoniae, Bacillus subtilis, Shigella flexneri, Pseudomonas aeruginosa, Aspergillus niger and Rhizoctonia bataicola. Most of the metal chelates have higher antimicrobial activity than the free ligands.     

Synthesis of pyrimidine Schiff base transition metal complexes: characterization,spectral and electrochemical analyses,and photoluminescence properties

Research on Chemical Intermediates - This study includes the synthesis, characterization, electrochemical analysis and photoluminescence properties of a Schiff base ligand bearing a pyrimidine ring...     

Synthesis,physico-chemical and DNA interactive studies of l-tryptophan based mononuclear Schiff base complexes of first transition metal series

l-Tryptophan derived Schiff base ligand and its complexes of the type, [ML(H₂O)₂]·H₂O [M?=?Co(II), Ni(II), Zn(II)] and [CuL] have been synthesized and characterized on the basis of results obtained from elemental analysis, conductivity measurements, ESI-Mass spectral studies, FT-IR, ¹H and ¹³C NMR, UV–Vis spectroscopy and magnetic moment data. The synthesized complexes were subjected to thermogravimetric analysis to study their decomposition pattern and stability. The fluorescence and viscosity measurements reveal that complexes have significant CT-DNA binding. However, upon comparing the DNA binding analyses, Cu(II) complex exhibited significant binding affinity.     

Synthesis of transition metal complexes containing a Schiff base ligand derived from 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-aminobenzenethiol

The synthesis of a new Schiff base containing 1,10-phenanthroline-2,9-dicarboxaldehyde and 2-aminobenzenethiol subunits is described. The reaction of 1,10-phenanthroline-2,9-dicarboxaldehyde with 2-aminobenzenethiol leads to the isolation of 2,9-bis(2-benzothiazolinyl)-1,10-phenanthroline (I) which undergoes rearrangement when reacted with cobalt, nickel, copper or zinc ions to produce complexes of the tautomeric Schiff base 2,9-bis[2-(2-mercaptophenyl)-2-azaethene]-1,10-phenanthroline (L). The [Cu(L)ClO₄][ClO₄] and [M(L)X₂] complexes (where M = Co(II), Ni(II) and Zn(II) and X = Br) were characterized by physical and spectroscopic measurements which indicated that the ligand is acting probably as a tetradentate N₄ chelating agent.