Synthesis and characterization of N,N-diethylnicotinamide-acetylsalicylato complexes of Co(II), Ni(II), Cu(II), and Zn(II)

N,N-diethylnicotinamide-acetylsalicylato complexes of Co(II), Ni(II), Cu(II), and Zn(II) were synthesized and investigated by elemental analysis, magnetic susceptibility, solid state UV–Vis, direct injection probe mass spectra, FTIR spectra and thermoanalytic TG-DTG methods. The complexes contain two waters, two acetylsalicylate (asa) and two N,N-diethylnicotinamide (dena) ligands per formula unit. The acetylsalicylate and N,N-diethylnicotinamide are monodentate through acidic oxygen and nitrogen of pyridine ring. Decomposition of each complex starts with dehydration then decomposition of N,N-diethylnicotinamide and acetylsalicylate, respectively. The thermal dehydration of the complexes takes place in one or two steps. The decomposition mechanism and thermal stability of the investigated complexes are interpreted in terms of their structures. The final decomposition products are found to be metal oxides.     

Synthesis,characterization and biological studies of Co(II), Ni(II), Cu(II) and Zn(II) complexes with pyrral-l-histidinate

The Schiff base ligand, pyrral-l-histidinate(L) and its Co(II), Ni(II), Cu(II) and Zn(II) complexes were synthesized and characterized by elemental analysis, mass, molar conductance, IR, electronic, magnetic measurements, EPR, redox properties, thermal studies, XRD and SEM. Conductance measurements indicate that the above complexes are 1:1 electrolytes. IR data show that the ligand is tridentate and the binding sites are azomethine nitrogen, imidazole nitrogen and carboxylato oxygen atoms. Electronic spectral and magnetic measurements indicate tetrahedral geometry for Co(II) and octahedral geometry for Ni(II) and Cu(II) complexes, respectively. The observed anisotropic g values indicate the presence of Cu(II) in a tetragonally distorted octahedral environment. The redox properties of the ligand and its complexes have been investigated by cyclic voltammetry. Thermal decomposition profiles are consistent with the proposed formulations. The powder XRD and SEM studies show that all the complexes are nanocrystalline. The in vitro biological screening effects of the synthesized compounds were tested against the bacterial species, Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus; fungal species, Aspergillus niger, Aspergillus flavus and Candida albicans by the disc diffusion method. The results indicate that complexes exhibit more activity than the ligand. The nuclease activity of the ligand and its complexes were assayed on CT DNA using gel electrophoresis in the presence and absence of H₂O₂.     

Synthesis, spectral and thermal studies of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complex dyes based on hydroxyquinoline moiety

A series of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes of azo-compounds containing hydroxyl quinoline moiety have been synthesized and characterized by elemental analysis, molar conductance, magnetic moments, IR, electronic and ESR spectral studies. The results revealed the formation of 1:1 and 1:2 (L:M) complexes. The molar conductance data reveal that the chelates are nonelectrolyte. IR spectra indicate that the azodyes behave as monobasic bidentate or dibasic tetradentate ligands through phenolate or carboxy oxygen, azo N for 1:1 (L:M) complexes beside phenolate oxygen and quinoline N atoms for 1:2 (L:M) complexes. The thermal analyses (TG and DTA) as well as the solid electrical conductivity measurements are also studied. The molecular parameters of the ligands and their metal complexes have been calculated.     

Synthesis and characterization of Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes with N-salicydene-o-hydroxymethyleneaniline

The new Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) complexes with tridentate Schiff base, the product of condensation of o-aminobenzyl alcohol with salicylaldehyde have been synthesized and characterized by elemental analysis, IR, electronic, EPR and Mössbauer spectra, thermal analysis, magnetic susceptibility and molecular weight measurements. Dimeric or polymeric structures for the investigated complexes were proposed. The interaction of the cobalt complex with dioxygen is also described.     

Synthesis, spectral characterization, solution equilibria, in vitro antibacterial and cytotoxic activities of Cu(II), Ni(II), Mn(II), Co(II) and Zn(II) complexes with Schiff base derived from 5-bromosalicylaldehyde and 2-aminomethylthiophene

Schiff base namely 2-aminomethylthiophenyl-4-bromosalicylaldehyde (ATS)(4-bromo-2-(thiophen-2-yl-imino)methylphenol) and its metal complexes have been synthesized and characterized by elemental analyses, IR, 1H NMR, solid reflectance, magnetic moment, molar conductance, mass spectra, ESR and thermal analysis (TGA). The analytical data of the complexes show the formation of 1:2 [M:L] ratio of the formula [ML2], where M represents Ni(II), Zn(II) and Cu(II) ions, while L represents the deprotonated Schiff base. IR spectra show that ATS is coordinated to the metal ions in a bidentate manner through azomethine-N and phenolic-oxygen groups. The ligand and their metal chelates have been screened for their antimicrobial activities using the disc diffusion method against the selected bacteria. A cytotoxicity of the compounds against colon (HCT116) and larynx (HEP2) cancer cells have been studied. Protonation constants of (ATS) ligand and stability constants of its Cu2+, Co2+, Mn2+, Zn2+ and Ni2+ complexes were determined by potentiometric titration method in 50% (v/v) DMSO-water solution at ionic strength of 0.1 M NaNO3.     

Synthesis,spectroscopic, and thermal analyses of trinuclear Mn(II), Co(II), Ni(II), and Zn(II) complexes with some sulfa derivatives

New bi- and trihomonuclear Mn(II), Co(II), Ni(II), and Zn(II) complexes with sulfa-guanidine Schiff bases have been synthesized for potential chemotherapeutic use. The complexes are characterized using elemental and thermal (TGA) analyses, mass spectra (MS), molar conductance, IR, ¹H-NMR, UV-Vis, and electron spin resonance (ESR) spectra as well as magnetic moment measurements. The low molar conductance values denote non-electrolytes. The thermal behavior of these chelates shows that the hydrated complexes lose water of hydration in the first step followed by loss of coordinated water followed immediately by decomposition of the anions and ligands in subsequent steps. IR and ¹H-NMR data reveal that ligands are coordinated to the metal ions by two or three bidentate centers via the enol form of the carbonyl C=O group, enolic sulfonamide S(O)OH, and the nitrogen of azomethine. The UV-Vis and ESR spectra as well as magnetic moment data reveal that formation of octahedral [Mn₂L¹(AcO)₂(H₂O)₆] (1), [Co₂(L¹)₂(H₂O)₈] (2), [Ni₂L¹(AcO)₂(H₂O)₆] (3), [Mn₃L²(AcO)₃(H₂O)₉] (5), [Co₃L²(AcO)₃(H₂O)₉] · 4H₂O (6), [Ni₃L²(AcO)₃(H₂O)₉] · 7H₂O (7), [Mn₃L³(AcO)₃(H₂O)₆] (9), [Co₂(HL³)₂(H₂O)₈] · 4H₂O (10), [Ni₃L³(AcO)₃(H₂O)₉] (11), [Mn₃L⁴(AcO)₃(H₂O)₉] · H₂O (13), [Co₂(HL⁴)₂(H₂O)₈] · 5H₂O (14), and [Ni₃L⁴(AcO)₃(H₂O)₉] (15) while [Zn₂L¹(AcO)₂(H₂O)₂] (4), [Zn₃L²(AcO)₃(H₂O)₃] · 2H₂O (8), [Zn₃L³(AcO)₃(H₂O)₃] · 3H₂O (12), and [Zn₃L⁴(AcO)₃(H₂O)₃] · 2H₂O (16) are tetrahedral. The electron spray ionization (ESI) MS of the complexes showed isotope ion peaks of [M]⁺ and fragments supporting the formulation.     

Synthesis,spectral characterization and biological activity of benzofuran Schiff bases with Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II) complexes

New Schiff bases have been synthesized from benzofuran-2-carbohydrazide and benzaldehyde, [BPMC] or 3,4-dimethoxybenzaldehyde, [BDMeOPMC]; complexes of the type MLX₂, where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II), L = BPMC or BDMeOPMC and X = Cl, have been prepared. Structures have been elucidated on the basis of elemental analysis, conductance measurements, magnetic properties, spectral studies i.e., ¹H NMR, electronic, ESR and IR studies show that the Schiff bases are bidentate through the azomethine nitrogen and oxygen of the carbonyl. We propose tentative structures for all of these complexes. The antifungal and antibacterial activities of the ligands and their metal complexes have been screened against fungi Aspergillus niger and Aspergillus fumigatus and against bacteria Escherichia coli and S. aurious.     

Synthesis,spectral characterization,electrochemical and biological studies of Co(II), Ni(II) and Cu(II) complexes with thiocarbohydrazone

A series of metal complexes of Co(II), Ni(II) and Cu(II) have been synthesized with the Schiff base derived from thiocarbohydrazide and 8-formyl-7-hydroxy-4-methylcoumarin. The structures of the complexes have been proposed by elemental analyses, molar conductance, spectral (IR, UV-Vis, ESR and FAB-mass), magnetic, thermal and electrochemical studies. These complexes are soluble in DMF and DMSO and molar conductance values indicate that they are non-electrolytes. Elemental analyses of the complexes confirm stoichiometry ML ·; 2H₂O [M=Co(II), Ni(II) and Cu(II)]. Spectroscopic studies indicate coordination occurs through phenolic oxygen after deprotonation and nitrogen of azomethine. The Schiff base and its complexes have also been screened for antibacterial (Escherichia coli, Streptococcus aureus, Streptococcus pyogenes and Pseudomonas aeruginosa) and antifungal activities (Aspergillus niger, Aspergillus flavus and cladosporium) by the MIC method. The brine shrimp bioassay was also carried out to study their in vitro cytotoxic properties.     

Synthesis and spectral studies of pyranone derivative and its Cu(II), Co(II), Ni(II) and Zn(II) complexes

Under the thermolysis condition, 5-phenyl-2,3-dihydro-2,3-furandione (IV) in inert aprotic solvents as p-xylene at 130–140°C yields 3-benzoyl-4-hydroxy-6-phenyl-2H-pyran-2-one (VI) via phenyl ketene (V). The compound (VI) was converted into the corresponding 3-benzoyl-4-hydroxy-6-phenylpyridin-2(1H)-one (VII), and 3-benzoyl-2-oxo-6-phenyl-2H-pyran-4-yl acetate (VIII), by its reactions with ammonium hydroxyde, and acetic anhydride, respectively. On the other hand, a series of new various metal complexes (IX-XIa, XIb) of VI was synthesized. The results suggest that the compound VI as bidentate ligand indicate a binuclear structure for the Cu(II) complex with square-planar geometry. The Ni(II) and Zn(II) complexes are of tetrahedral and the Co(II) complex is also octahedral geometry with water molecules at the axial positions. The structures of compounds and complexes were characterized on the basis of elemental analysis, Mass, IR, ¹H, and ¹³C NMR spectra. The text was submitted by the authors in English.     

Synthesis, thermal and other studies of 2,4'-bipyridine-dichloroacetato complexes of Mn(II), Co(II), Ni(II) and Cu(II)

Four new mixed ligand complexes were prepared by the reaction of title metal dichloroacetates and 2,4'-bipyridine. The general formulae of synthesized compounds are M(2,4'-bpy)₂(CCl₂HCOO)₂·nH₂O (where M(II)=Mn, Co, Ni, Cu; 2,4'-bpy=2,4'-bipyridine, n=2 or 4). The complexes have been isolated from aqueous media and characterized by chemical analysis, molar conductance (in MeOH, DMSO and DMF), magnetic, IR and VIS spectral studies. The nature of metal(II)-ligand coordination is discussed. The thermal behaviour of obtained complexes was studied by thermal analysis and TG-MS techniques in air. IR, X-ray powder diffraction and thermoanalytical data were used for the determination of solid intermediate products of the thermal decomposition. The principal volatile products of thermal decomposition of complexes were proved by mass spectroscopy: H₂O⁺, CO⁺ ₂, HCl⁺ ₂, Cl⁺ ₂, NO⁺ and other. This revised version was published online in July 2006 with corrections to the Cover Date.     

Synthesis and characterization of bis(nicotinamide) m-hydroxybenzoate complexes of Co(II), Ni(II), Cu(II), and Zn(II)

Mixed-ligand m-hydroxybenzoate complexes of Co(II), Ni(II), Cu(II), and Zn(II) with nicotinamide were synthesized and characterized by elemental analysis, FT-IR spectrometry, solid state UV-vis spectrometry, and magnetic susceptibility measurements. The thermal behavior of the complexes was studied by simultaneous TG-DTA methods in static air atmosphere. The infrared spectral characteristics of the complexes are discussed and the mass spectra data are recorded. The complexes contain two water molecules, two m-hydroxybenzoato (m-hba), and two nicotinamide (na) ligands per formula unit. In these complexes, the m-hydroxybenzoate and nicotinamide behave as a monodentate ligand through acidic oxygen and nitrogen of the pyridine ring. The decomposition pathways and the stability of the complexes are interpreted in terms of the structural data. The final decomposition products were found to be the respective metal oxides. The text was submitted by the author in English.     

Synthesis,characterization and biological properties of Co(II), Ni(II), Cu(II) and Zn(II) complexes with an SNO functionalized ligand

Some new metal(II) complexes, ML₂[M = Co, Ni, Cu and Zn], of 2-acetylthiophene benzoylhydrazone ligand (HL) containing a trifunctional SNO-donor system have been synthesized and characterized on the basis of physicochemical data by elemental analysis, magnetic moment, molar conductance, thermogravimetric and spectroscopic (electronic, IR, ¹H NMR and ¹³C NMR) data. The ligand functions as monobasic SNO tridentates where the deprotonated enolic form is preferred in the coordination producing distorted octahedral complexes.     

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

A series of metal complexes of cobalt(II), nickel(II), copper(II), and zinc(II) have been synthesized with newly-derived biologically active ligands. These ligands were synthesized by condensation of 3-substituted-4-amino-5-hydrazino-1,2,4-triazole and orthophthalaldehyde. The probable structure of the complexes has been proposed on the basis of elemental analyses and spectral (IR, ¹H-NMR, UV-vis, magnetic, ESR, FAB-mass and thermal studies) data. Electrochemical study of the complexes is also made. All complexes are nonelectrolytes in N,N-dimethyl formamide and DMSO. The Schiff bases and their Co(II), Ni(II), Cu(II), and Zn(II) complexes have been screened for antibacterial (Escherichia coli, Staphylococcus aureus, Streptococcus pyogenes, and Pseudomonas aeruginosa) and antifungal (Aspergillus niger, Aspergillus flavus, and cladosporium) activities by minimum inhibitory concentration method. DNA cleavage is also carried out.     

Synthesis and characterization of oxazolone complexes with Fe(III), Co(II), Ni(II), Cu(II) and Zn(II) in different counterions

Oxazolone forms (1:1) complexes with Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ chlorides, as well as forms (1:1) complexes with Co²⁺ and Cu²⁺ acetates. All the complexes are found to be non-electrolytes in DMF; tetrahedral, square-planar and octahedral structures are assigned to them based on electronic and magnetic data. IR studies reveal that the complexes are formed by donating the lone-pair electron from O and N atoms to the metal ion. The thermal decomposition of the [ML·mX·nH₂O]_y·H₂O chelates was studied by TG–DTA techniques. The mechanism of the decomposition has been established from TG–DTA data. The kinetic parameters, activation energy (E_a) and pre-exponential factor (A), were calculated from TG curves using Coats and Redfern method. Relative thermal stabilities of the chelates have been evaluated on the basis of these parameters.     

Synthesis,structural studies and bio-activity of Mn(II), Co(II), Ni(II), Cu(II) and Zn(II) complexes with p -amino acetophenone salicyloyl hydrazone

Complexes of the type [M(pash)Cl] and [M(Hpash)(H₂O)SO₄] (M=Mn(II), Co(II), Ni(II), Cu(II) and Zn(II); Hpash = p-amino acetophenone salicyloyl hydrazone) have been synthesized and characterized by elemental analyses, molar electrical conductance, magnetic moments, electronic, ESR and IR spectra, thermal studies and X-ray powder diffraction. All the complexes are insoluble in common organic solvents and are non-electrolytes. The magnetic moment values and electronic spectra indicate a square-planar geometry for Co(II), Ni(II) and Cu(II) chloride complexes and spin-free octahedral geometry for the sulfato complexes. The ligand coordinates through >C=N–,–NH₂ and a deprotonated enolate group in all the chloro complexes, and through >C=N–, >C=O and–NH₂ in the sulfato complexes. Thermal analyses (TGA and DTA) of [Cu(pash)Cl] show a multi-step exothermic decomposition pattern. ESR spectral parameters of Cu(II) complexes in solid state at room temperature suggest the presence of the unpaired electron in d _{x ² ? y ²} . X-ray powder diffraction parameters for [Cu(pash)Cl] and [Ni(Hpash)(H₂O)SO₄] correspond to tetragonal and orthorhombic crystal lattices, respectively. The complexes show a fair degree of antifungal activity against Aspergillus sp., Stemphylium sp. and Trichoderma sp. and moderate antibacterial activity against E. coli and Clostridium sp.     

Synthesis,characterization, thermal and redox behavior,and biological activity of Ni(II), Cu(II), and Zn(II) complexes containing pyridoxine and imidazole moieties

Several mixed ligand complexes [M(II)(PN)(B)] [M(II) = Ni(II), Cu(II), and Zn(II)] derived from pyridoxine (PN) and imidazoles (B), namely imidazole (him), benzimidazole (bim), histamine (hist), and L-histidine (his), were synthesized. The complexes are characterized by elemental analysis, IR, UV-Vis ¹H NMR, and ESR spectroscopy. In [M(II)(PN)B], the monovalent anion of PN is bidentate to M(II) (–O, –OH), him, bim monodentate (–N), hist bidentate (–N, –N), and his tridentate (–O, –N, –N). Magnetic moment studies showed that the Ni(II) complexes and Cu(II)–PN–his have octahedral configuration while the other Cu(II) complexes have distorted tetrahedral geometry. The g _∥/A _∥ values calculated from the X-band ESR spectra of Cu(II) complexes in DMSO at 300 and 77 K supports the geometry. The thermal behavior (TG/DTA) of the synthesized complexes indicates the presence of lattice as well as coordinated water in the complexes. The in vitro biological activity of the mixed ligand complexes was tested against common bacteria, yeast, and fungi. The results in comparison with the control indicate that most of the complexes exhibit higher biological activities. The oxidative DNA cleavage studies of the mixed ligand complexes were performed using gel electrophoresis.     

Synthesis and characterization of heterocyclic Schiff base and its complexes with Cu(II), Ni(II), Co(II), Zn(II), and Cd(II)

A new Schiff base, {1-[(2-hydroxy-naphthalen-1-ylmethylene)-amino]-4-phenyl-2-thioxo-1, 2-dihydro-pyrimidin-5-yl}-phenyl-methanone, has been synthesized from N-amino pyrimidine-2-thione and 2-hydroxynaphthaldehyde. Metal complexes of the Schiff base were prepared from acetate/chloride salts of Cu(II), Co(II), Ni(II), Zn(II), and Cd(II) in methanol. The chemical structures of the Schiff-base ligand and its metal complexes were confirmed by elemental analyses, IR, ¹³C-NMR, ¹H-NMR, API-ES, UV-Visible spectroscopy, magnetic susceptibility, and thermogravimetric analyses. The electronic spectral data and magnetic moment measurements suggest mononuclear octahedral and mononuclear or binuclear square planar structures for the metal complexes. In light of these results, it was suggested that this ligand coordinates to each metal atom by hydroxyl oxygen, azomethine nitrogen, and thione sulfur to form octahedral complexes with Cd(II) and Zn(II).     

Structure of Mn(II), Co(II), Ni(II), and Cu(II) complexes with triformylmethane

Previously unknown [ML₂(H₂O) _n ] bischelates, where M is Mn(II), Co(II), Ni(II), or Cu(II) and L is deprotonated triformylmethane, are studied by X-ray diffraction analysis. It is revealed that in the crystals of all compounds there are multiple hydrogen bonds linking bischelate molecules into polymer layers or a single framework. The character of the temperature dependence of the effective magnetic moment [ML₂(H₂O) _n ] indicates the existences of weak intracrystalline exchange interactions between the unpaired electrons of the paramagnetic centers.