Synthesis, physico-chemical characterization and antimicrobial activity of cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes with some acyldihydrazones

Complexes of the type [M(bssdh)]Cl and [M(dspdh)]Cl, where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); Hbssdh = benzil salicylaldehyde succinic acid dihydrazone, Hdspdh = diacetyl salicylaldehyde phthalic acid dihydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra and X-ray diffraction studies. Magnetic moment values and electronic spectral transitions indicate a spin free octahedral structure for Co(II), Ni(II) and Cu(II) complexes. IR spectral studies suggest that both the ligands behave as monobasic hexadentate ligands coordinating through three > C = O, two > C = N- and a phenolate group to the metal. ESR spectra of Cu(II) complexes are axial type and suggest d(x(2)-y(2)) as the ground state. X-ray powder diffraction parameters for [Co(bssdh)]Cl and [Co(dspdh)]Cl complexes correspond to an orthorhombic crystal lattice. The ligands as well as their metal complexes show a significant antifungal and antibacterial activity against various fungi and bacteria. The metal complexes are more active than the parent ligands.     

Synthesis,physico-chemical characterization and antimicrobial activity of cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes with some acyldihydrazones

Complexes of the type [M(bssdh)]Cl and [M(dspdh)]Cl, where M = Co(II), Ni(II), Cu(II), Zn(II) and Cd(II); Hbssdh = benzil salicylaldehyde succinic acid dihydrazone, Hdspdh = diacetyl salicylaldehyde phthalic acid dihydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra and X–ray diffraction studies. Magnetic moment values and electronic spectral transitions indicate a spin free octahedral structure for Co(II), Ni(II) and Cu(II) complexes. IR spectral studies suggest that both the ligands behave as monobasic hexadentate ligands coordinating through three > C = O, two > C = N– and a phenolate group to the metal. ESR spectra of Cu(II) complexes are axial type and suggest as the ground state. X–ray powder diffraction parameters for [Co(bssdh)]Cl and [Co(dspdh)]Cl complexes correspond to an orthorhombic crystal lattice. The ligands as well as their metal complexes show a significant antifungal and antibacterial activity against various fungi and bacteria. The metal complexes are more active than the parent ligands.     

Synthesis, physico-chemical studies of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes with some p-substituted acetophenone benzoylhydrazones and their antimicrobial activity

Complexes of the type [M(pabh)(H2O)Cl], [M(pcbh)(H2O)Cl] and [M(Hpabh)(H2O)2 (SO4)] where, M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hpabh = p-amino acetophenone benzoyl hydrazone and Hpcbh = p-chloro acetophenone benzoyl hydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra, thermal (TGA & DTA) and X-ray diffraction studies. Co(II), Ni(II) and Cu(II) chloride complexes are square planar, whereas their sulfate complexes have spin-free octahedral geometry. ESR spectra of Cu(II) complexes with Hpabh are axial and suggest d(x(2)-y(2) as the ground state. The ligand is bidentate bonding through > C = N--and deprotonated enolate group in all the chloro complexes, whereas, >C = N and >C = O groups in all the sulfato complexes. Thermal studies (TGA & DTA) on [Cu(Hpabh)(H2O)2(SO4)] indicate a multistep decomposition pattern, which are both exothermic and endothermic in nature. X-ray powder diffraction parameters for [Co(pabh)(H2O)Cl] and [Ni(Hpabh)(H2O)2(SO4)] correspond to tetragonal and orthorhombic crystal lattices, respectively. The ligands as well as their complexes show a significant antifungal and antibacterial activity. The metal complexes are more active than the ligand.     

Synthesis, characterization and biocidal activity of some transition metal(II) complexes with isatin salicylaldehyde acyldihydrazones

Cobalt(II), nickel(II), copper(II), zinc(II) and cadmium(II) complexes with two new unsymmetrical ligands, isatin salicylaldehyde oxalic acid dihydrazide (isodh) and isatin salicylaldehyde malonic acid dihydrazide (ismdh) were synthesized and characterized by elemental analyses, electrical conductance, magnetic moments, electronic, NMR, ESR and IR spectral studies. The isodh acts as a dibasic tetra dentate ligand bonding through two >C=N-, a deprotonated phenolate and deprotonated indole enolate groups to the metal. The ismdh ligand shows monobasic tetra dentate behaviour in bonding with metal ion through two >C=N-, indole >C=O and a deprotonated phenolate group. The electronic spectral data suggest 4-coordinate square planar geometry for Co(II), Ni(II) and Cu(II) complexes of isodh, whereas, 6-coordinate octahedral structure for the ismdh complexes. The ESR studies also indicate a square planar and distorted octahedral environment around Cu(II) for isodh and ismdh complexes, respectively. Most of the metal complexes show better antifungal activity than the standard and a significant antibacterial activity against various fungi and bacteria.     

Metal complexes of salicylhydroxamic acid (H2Sha), anthranilic hydroxamic acid and benzohydroxamic acid. Crystal and molecular structure of [Cu(phen)2(Cl)]Cl x H2Sha, a model for a peroxidase-inhibitor complex

Stability constants of iron(III), copper(II), nickel(II) and zinc(II) complexes of salicylhydroxamic acid (H2Sha), anthranilic hydroxamic acid (HAha) and benzohydroxamic acid (HBha) have been determined at 25.0 degrees C, I=0.2 mol dm(-3) KCl in aqueous solution. The complex stability order, iron(III) > copper(II) > nickel(II) approximately = zinc(II) was observed whilst complexes of H2Sha were found to be more stable than those of the other two ligands. In the preparation of ternary metal ion complexes of these ligands and 1,10-phenanthroline (phen) the crystalline complex [Cu(phen)2(Cl)]Cl x H2Sha was obtained and its crystal structure determined. This complex is a model for hydroxamate-peroxidase inhibitor interactions.     

Self-assembly and cytotoxicity study of waterwheel-like dinuclear metal complexes: the first metal complexes appended with multiple free hydroxamic acid groups

Two waterwheel-like dinuclear complexes [M(2)(PHA)(4)(H(2)O)(2)] (M = Cu(II) (1), Zn(II) (2); HPHA = phthal-hydroxamic acid) appended with four free hydroxamic acid groups, namely, free hydroxamic acid metal complexes (FHAMCs) have been synthesized and characterized. The crystal structure of complex 1 was determined by single crystal X-ray diffraction, which adopts the paddlewheel motif with four bidentate carboxylate ligands joining two Cu(II) ions. The relative cytotoxicities of compounds 1 and 2 against SMMC-7721 and HO-8910 cell lines are similar and more predominant than HPHA (IC(50): Cu(II)>Zn(II)>HPHA). The synergic effect of the bound water molecules, multiple free hydroxamic acid groups and dimetal active sites with bridging carboxylate may have significant impacts on their pharmacological activity. As the prototype for a new class of hydroxamic acid derivatives, the self-assembly of FHAMCs presents a promising new strategy in designing multiple hydroxamic acids with remarkable bioactivities.     

Solution and solid-state studies of complexation of transition-metal cations and Al(III) by aroylhydrazones derived from nicotinic acid hydrazide

Reactions of first series transition-metal cations, Cd(II) and Al(III) with two aroylhydrazones derived from nicotinic acid hydrazide and salicylaldehyde or o-vanillin were studied at 25 °C in buffered dioxane/water 1/1 mixture (pH 5.8) by means of spectrophotometric and spectrofluorimetric titrations. The addition of Mn(II) or Cd(II) ions in hydrazone solutions had no effect on their absorption spectra whereas the addition of Ni(II) and Cr(III) immediately caused precipitation. The reaction of Zn(II) with salicylaldehyde derivative was found to be photosensitive. Relatively high conditional stability constants of 1:1 complexes of Cu(II), Zn(II) and Al(III) with both ligands were determined. Solid complexes of Cu(II), Ni(II) and Zn(II) with aroylhydrazones studied were isolated and characterized by elemental and thermogravimetric analyses, magnetic susceptibility measurements (in the case of Cu(II) and Ni(II)) and IR spectrometry.     

Antibacterial dimeric copper(II) complexes with chromone-derived compounds

A new series of six chromone-derived compounds and their Cu(II) complexes have been synthesized and characterized by their physical, spectral and analytical data. The ligands and their Cu(II) complexes were screened for their in vitro antibacterial activity against four Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri) and two Gram-positive (Bacillus subtilis, Staphylococcus aureus) bacterial strains by agar-well diffusion method. The ligands were found to exhibit either no or low-to-moderate activities against one or more bacterial species whereas, the Cu(II) complexes exhibited moderate-to-high activity. The ligands which were inactive before complexation became active upon complexation with the Cu(II) metal ion and less active became more active.     

Antibacterial dimeric copper(II) complexes with chromone-derived compounds

A new series of six chromone-derived compounds and their Cu(II) complexes have been synthesized and characterized by their physical, spectral and analytical data. The ligands and their Cu(II) complexes were screened for their in vitro antibacterial activity against four Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, Shigella flexneri) and two Gram-positive (Bacillus subtilis, Staphylococcus aureus) bacterial strains by agar-well diffusion method. The ligands were found to exhibit either no or low-to-moderate activities against one or more bacterial species whereas, the Cu(II) complexes exhibited moderate-to-high activity. The ligands which were inactive before complexation became active upon complexation with the Cu(II) metal ion and less active became more active.     

Synthesis of novel chiral metal complexes derived from chiral thiosemicarbazide ligands as potential antioxidant agents

Two new chiral thiosemicarbazide ligands and their Cu (II), Ni (II), Pd (II), and Zn (II) complexes were synthesized and characterized by nuclear magnetic resonance (NMR) (only for ligand), Fourier transform infrared (FT‐IR), ultraviolet visible (UV‐Vis), mass, and elemental analysis. The antioxidant activity of ligands and their metal complexes was examined. It was found that the antioxidant activity of metal complexes was better than their ligands. In addition, the antioxidant activity, as reflected by free radical scavenging, was evaluated. Besides, Pd (II) complexes exhibited better antioxidant activity than Ni (II), Cu (II), and Zn (II) complexes. Therefore, complexes (3a‐Pd and 3b‐Pd) can be used as an antioxidant agent or antioxidant test standard.     

Metal based drugs: design,synthesis and in-vitro antimicrobial screening of Co(II), Ni(II), Cu(II) and Zn(II) complexes with some new carboxamide derived compounds: crystal structures of N-[ethyl(propan-2-yl)carbamothioyl]thiophene-2-carboxamide and its copper(II) complex

A new series of compounds derived from thiophene-2-carboxamide were synthesized and characterized by IR, ¹H-NMR and ¹³C-NMR, mass spectrometry and elemental analysis. These compounds were further used to prepare their Co(II), Ni(II), Cu(II) and Zn(II) metal complexes. All metal(II) complexes were air and moisture stable. Physical, spectral and analytical data have shown the Ni(II) and Cu(II) complexes to exhibit distorted square-planar and Co(II) and Zn(II) complexes tetrahedral geometries. The ligand (L¹) and its Cu(II) complex were characterized by the single-crystal X-ray diffraction method. All the ligands and their metal(II) complexes were screened for their in-vitro antimicrobial activity. The antibacterial and antifungal bioactivity data showed that the metal(II) complexes were found to be more potent than the parent ligands against one or more bacterial and fungal strains.     

Synthesis,physico-chemical studies of manganese(II), cobalt(II), nickel(II), copper(II) and zinc(II) complexes with some p-substituted acetophenone benzoylhydrazones and their antimicrobial activity

Complexes of the type [M(pabh)(H₂O)Cl], [M(pcbh)(H₂O)Cl] and [M(Hpabh)(H₂O)₂ (SO₄)] where, M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hpabh = p-amino acetophenone benzoyl hydrazone and Hpcbh = p-chloro acetophenone benzoyl hydrazone have been synthesized and characterized with the help of elemental analyses, electrical conductance, magnetic susceptibility measurements, electronic, ESR and IR spectra, thermal (TGA & DTA) and X-ray diffraction studies. Co(II), Ni(II) and Cu(II) chloride complexes are square planar, whereas their sulfate complexes have spin-free octahedral geometry. ESR spectra of Cu(II) complexes with Hpabh are axial and suggest as the ground state. The ligand is bidentate bonding through >C = N ? and deprotonated enolate group in all the chloro complexes, whereas, >C = N and >C = O groups in all the sulfato complexes. Thermal studies (TGA & DTA) on [Cu(Hpabh)(H₂O)₂(SO₄)] indicate a multistep decomposition pattern, which are both exothermic and endothermic in nature. X-ray powder diffraction parameters for [Co(pabh)(H₂O)Cl] and [Ni(Hpabh)(H₂O)₂(SO₄)] correspond to tetragonal and orthorhombic crystal lattices, respectively. The ligands as well as their complexes show a significant antifungal and antibacterial activity. The metal complexes are more active than the ligand.     

2-methyl- and 2-ethylamino-3-pieoline N-oxide complexes formed from various copper(II) salts

Copper(II) complexes with 2-methylamino-3-picoline N-oxide (3MMH) and 2-ethylamino-3-picoline N- oxide (3MEH) have been prepared from the following salts: tetrafluoroborate, nitrate, chloride, bromide and acetate. Solids of the general formula [Cu(LH)₄]- (X₂) (where LH = either ligand when X = BF₄^tau; and LH = 3MMH when X = NO₃^tau; ); [Cu(3MEH)₂- (ONO₂)₂]; [Cu(LH)X₂] (where LH = either ligand and X = Cl^tau; , Br^tau; ) and CuL₂ (where L = either ligand's conjugate base) were characterized using spectral methods (i.e., IR, UV-Vis and ESR). Both coordinate as monodentate ligands via their N-oxide oxygen in their complexes with salts having polyatomic anions. They bond as neutral bidentate ligands in their halide complexes, but as anionic bidentate ligands in the complexes formed from copper(II) acetate. The bonding to Cu(II) ccnters via the N-oxide oxygen is the strongest tor these two ligands based on spectral data than any of the 2-aminopyridine N-oxides or 2- aminopicoline N-oxides studied to date.     

Metal complexes of a new class of polydentate Mannich bases: Synthesis and spectroscopic characterisation

A new class of polydentate Mannich bases featuring an N₂S₂ donor system, bis((2-mercapto-N-phenylacetamido)methyl)phosphinic acid H₃L¹ and bis((2-mercapto-N-propylacetamido)methyl)phosphinic acid H₃L², has been synthesised from condensation of phosphinic acid and paraformaldehyde with 2-mercaptophenylacetamide W1 and 2-mercaptopropylacetamide W2, respectively. Monomeric complexes of these ligands, of general formula K₂[Cr^III(Lⁿ)Cl₂], K₃[M′^II(Lⁿ)Cl₂] and K[M(Lⁿ)] (M′ = Mn(II) or Fe(II); M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) or Hg(II); n = 1, 2) are reported. The structures of new ligands, mode of bonding and overall geometry of the complexes were determined through IR, UV–Vis, NMR, and mass spectral studies, magnetic moment measurements, elemental analysis, metal content, and conductance. These studies revealed octahedral geometries for the Cr(III), Mn(II) and Fe(II) complexes, square planar for Ni(II) and Cu(II) complexes and tetrahedral for the Co(II), Zn(II), Cd(II) and Hg(II) complexes. Complex formation studies via molar ratio in DMF solution were consistent to those found in the solid complexes with a ratio of (M:L) as (1:1).     

Synthesis,characterization of some transition metal(II) complexes of acetone <Emphasis Type="Italic">p-</Emphasis>amino acetophenone salicyloyl hydrazone and their anti microbial activity

Complexes of the type [M(apash)Cl] and [M(Hapash)(H2O)SO4], where M = Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hapash = acetone p-amino acetophenone salicyloyl hydrazone have been synthesized and characterized by elemental analyses, molar conductance, magnetic moments, electronic, ESR and IR spectra, thermal studies (TGA & DTA) and X-ray diffraction studies. The ligand coordinates through two >C=N and a deprotonated enolate group in all the chloro complexes, whereas through two >C=N- and a >C=O group in all the sulfato complexes. The electronic spectra suggest a square planar geometry for Co(II), Ni(II) and Cu(II) chloride complexes and an octahedral geometry for the sulfate complexes. ESR data show an isotropic symmetry for [Cu(apash)Cl] and [Cu(Hapash)(H2O)SO4] in solid state. However, ESR spectra of both Cu(II) complexes indicate the presence of unpaired electron in d x2-y2. The X-ray diffraction parameters for [Co(apash)Cl] and [Cu(Hapash)(H2O)SO4] complexes correspond to a tetragonal and an orthorhombic crystal lattices, respectively. Thermal studies of [Co(apash)Cl] complex shows a multi-step decomposition pattern. Most of the complexes show better antifungal activity than the standard miconazole against a number of pathogenic fungi. The antibacterial activity of these complexes has been evaluated against E. coli and Clostridium sp. which shows a moderate activity.     

Synthesis, crystal structure, spectral and magnetic studies and catecholase activity of copper(II) complexes with di- and tri-podal ligands

Five complexes of copper(II) acetate with Schiff base ligands based on salicylaldehyde and N,N-dimethylamino)ethyl/propyl amine and their reduced products, have been synthesized and characterized by various spectroscopic methods. The solid state structures of 1, 2 and 3 have been determined using single crystal X-ray diffraction method. The structures of the other two compounds have been proposed on the basis of spectroscopic and physical methods. The compounds 1, 3 and 4 are dinuclear complexes of the tridentate ligands, where the two Cu(II) centers have square pyramidal geometry with bridging acetate or phenoxo groups. Each arm of the tripodand ligand forms a mononuclear, magnetically dilute complex 5 having five coordinated Cu(II) ions. Complex 2 is mononuclear with a square pyramidal stereochemistry. The catalytic performance of the oxidation of 3,5-di-tert-butylcatechol to quinone was studied using UV-Vis absorption spectral methods. Complex 4 exhibits the highest activity with a turnover number of 41 h⁻¹ while other showed lower rates of oxidation. A kinetic treatment on the basis of Michaelis-Menten model was applied. Ease of removal of the exogenous acetate ligands and easy access to the Cu(II) ions have been seen to affect the activity in the complexes. At the same time presence of two endogenous phenoxo bridges in the dinuclear complexes reduces the activity.     

Chiral bimetallic complexes from chiral salen metal complexes and mercury (II) halides and acetates: the anionic groups interact with Cu(II) in apical position

A series of chiral bimetallic complexes have been prepared containing both Cu(II) and Hg(II) metal centers. The complexes possess chiral salen ligands which host Cu(II) in the center of the cis-N₂O₂ chromophore and Hg(II) via two oxygen atoms of the chromophore. Halogen and acetate groups from mercury salts interact with the Cu(II) center. The X-ray crystallographic data of 11 reveals a short distance of Cl?Cu (3.22-3.26 Å). EPR study also discloses a strong interaction, in particular, of acetate group with Cu.     

Synthesis,spectral characterization and in vitro biological studies of Co(II), Ni(II) and Cu(II) complexes with 1,2,4-triazole Schiff bases

A series of metal complexes of cobalt(II), nickel(II) and copper(II) have been synthesized with newly derived biologically active ligands. These ligands were synthesized by the condensation of 3-substituted-4-amino-5-hydrazino-1,2,4-triazole and 8-formyl-7-hydroxy-4-methylcoumarin. The probable structure of the complexes has been proposed on the basis of elemental analyses and spectral (IR, Uv-Vis, magnetic, ESR, FAB-mass and thermal studies) data. Electro chemical study of the complexes is also reported. All these complexes are non-electrolytes in DMF and DMSO. All the ligands and their Co(II), Ni(II) and Cu(II) complexes were screened for their antibacterial (Escherichia coli, Staphylococcus aureus, Staphylococcus pyogenes and Pseudomonas aeruginosa) and antifungal (Aspergillus niger, Aspergillus flavus and cladosporium) activities by MIC method. The brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties.     

Antibacterial and Antifugal Mono- and Di-substituted Symmetrical and Unsymmetrical Triazine-derived Schiff-bases and their Transition Metal Complexes

A new series of antibacterial and antifungal triazine-derived mono- and di-substituted (symmetrical and unsymmetrical) Schiff-bases and their cobalt(II), copper(II), nickel(II) and zinc(II) metal complexes have been synthesized and characterized by their elemental analyses, molar conductances, magnetic moments and IR and electronic spectral measurements. IR spectra indicated the ligands to act as tridentate towards divalent metal ions via a trazine-N, the azomethine-N and, indole-NH and deprotonated-O of salicylaldehyde. The magnetic moments and electronic spectral data suggest octahedral geometry for the Co(II), Ni(II) and Zn(II)complexes and square-pyramid for Cu(II) complexes. NMR spectral data of the ligands and their diamagnetic zinc(II) complexes well-define their proposed structures/geometries. Elemental analyses data of the ligands and metal complexes agree with their proposed structures/geometries. The synthesized ligands, along with their metal complexes were screened for their antibacterial activity against Escherichia coli, Bacillus subtillis, Shigella flexneri, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi and for antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The results of these studies show the metal complexes to be more antibacterial/antifungal against two or more species as compared to the uncomplexed Schiff-base ligands.     

Antibacterial and antifugal mono- and di-substituted symmetrical and unsymmetrical triazine-derived Schiff-bases and their transition metal complexes

A new series of antibacterial and antifungal triazine-derived mono- and di-substituted (symmetrical and unsymmetrical) Schiff-bases and their cobalt(II), copper(II), nickel(II) and zinc(II) metal complexes have been synthesized and characterized by their elemental analyses, molar conductances, magnetic moments and IR and electronic spectral measurements. IR spectra indicated the ligands to act as tridentate towards divalent metal ions via a trazine-N, the azomethine-N and, indole-NH and deprotonated-O of salicylaldehyde. The magnetic moments and electronic spectral data suggest octahedral geometry for the Co(II), Ni(II) and Zn(II)complexes and square-pyramid for Cu(II) complexes. NMR spectral data of the ligands and their diamagnetic zinc(II) complexes well-define their proposed structures/geometries. Elemental analyses data of the ligands and metal complexes agree with their proposed structures/geometries. The synthesized ligands, along with their metal complexes were screened for their antibacterial activity against Escherichia coli, Bacillus subtillis, Shigella flexneri, Staphylococcus aureus, Pseudomonas aeruginosa and Salmonella typhi and for antifungal activity against Trichophyton longifusus, Candida albicans, Aspergillus flavus, Microsporum canis, Fusarium solani and Candida glaberata. The results of these studies show the metal complexes to be more antibacterial/ antifungal against two or more species as compared to the uncomplexed Schiff-base ligands.