Synthesis and spectroscopic studies of binuclear metal complexes of a tetradentate N2O2 Schiff base ligand derived from 4,6-diacetylresorcinol and benzylamine

A tetradentate N2O2 donor Schiff base ligand, H2L, was synthesized by the condensation of 4,6-diacetylresorcinol with benzylamine. The structure of the ligand was elucidated by elemental analyses, IR, 1H NMR, electronic and mass spectra. Reaction of the Schiff base ligand with nickel(II), cobalt(II), iron(III), cerium(III), vanadyl(IV) and uranyl(VI) ions in 1:2 molar ratio afforded binuclear metal complexes. Also, reaction of the ligand with several copper(II) salts, including Cl-, NO3-, AcO-, ClO4- and SO42- afforded different metal complexes that reflect the non-coordinating or weakly coordinating power of the ClO(4)(-) anion as compared to the strongly coordinating power of SO42- and Cl- anions. Characterization and structure elucidation of the prepared complexes were achieved by elemental and thermal analyses, IR, 1H NMR, electronic, mass and ESR spectra as well as magnetic susceptibility measurements. The metal complexes exhibited different geometrical arrangements such as square planar, octahedral, square pyramidal and pentagonal bipyramidal arrangements. The variety in the geometrical arrangements depends on the nature of both the anion and the metal ion.     

Synthesis and spectroscopic studies of new binuclear transition metal complexes of Schiff bases derived from 4,6-diacetylresorcinol

Two new series of copper(II), nickel(II), cobalt(II), zinc(II), iron(III), chromium(III), vanadyl(IV) and uranyl(VI) complexes with two bifunctional tridentate Schiff base, H₄L¹ and H₂L² ligands have been prepared. The Schiff base, H₄L¹ and H₂L², ligands were synthesized by the condensation of 4,6-diacetylresorcinol with o-aminophenol or o-phenylenediamine. The ligands are either di- or tetra-basic with two symmetrical sets of either OON or NNO tridentate chelating sites. The ligands and their metal complexes have been characterized by elemental analysis, ¹H-n.m.r., FT-IR, mass, electronic, esr spectra and thermal gravimetric analysis and magnetic susceptibility. With the exception of Co^II ion with H₂L² which afforded a trinuclear complex, a variety of binuclear complexes for the rest of the metal complexes were obtained with the ligands in its di- or tetra-deprotonated forms. The bonding sites are the azomethine and amino nitrogen atoms, and phenolic oxygen atoms. The metal complexes exhibit different geometrical arrangements such as square planar, tetrahedral, square pyramid and octahedral arrangement.     

Synthesis,structural characterization and biological activities of metal(II) complexes with Schiff bases derived from 5-bromosalicylaldehyde: Ru(II) complexes transfer hydrogenation

In this study, two novel Schiff base ligands (L¹ and L²) derived from condensation of methyl 2-amino-6-methyl-4,5,6,7-tetrahydrothieno[2,3-c]pyridine-3-carboxylate and methyl 2-amino-6-phenyl-4,5,6,7-tetrahydrobenzo[b]thiophene-3-carboxylate, both starting matter with 5-bromo-salicylaldehyde, and their Zn(II) and Ni(II) metal complexes have been prepared using a molar ratio of ligand:metal as 1:1 except the Ru(II) complexes 1:0.5. The structures of the obtained ligands and their metal complexes were characterized by elemental analysis, FT-IR, ¹H NMR, ¹³C NMR, UV–vis, thermal analysis methods, mass spectrometry, and magnetic susceptibility measurements. Antioxidant and antiradical activity of Schiff base ligands and their metal complexes were been evaluated in vitro tests. Antioxidant activities of metal complexes generally were more effectives than free Schiff bases. 1c and 2c were used as catalysts for the transfer hydrogenation (TH) of ketones. 1c, 2c complexes were found to be efficient catalyst for transfer hydrogenation reactions.     

Synthesis,spectral, thermal,potentiometric and antimicrobial studies of transition metal complexes of tridentate ligand

A series of metal complexes of Cu(II), Ni(II), Co(II), Fe(III) and Mn(II) have been synthesized with newly synthesized biologically active tridentate ligand. The ligand was synthesized by condensation of dehydroacetic acid (3-acetyl-6-methyl-(2H) pyran-2,4(3H)-dione or DHA), o-phenylene diamine and fluoro benzaldehyde and characterized by elemental analysis, molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, ¹H-NMR, UV–Vis spectroscopy and mass spectra. From the analytical data, the stoichiometry of the complexes was found to be 1:2 (metal:ligand) with octahedral geometry. The molar conductance values suggest the non-electrolyte nature of metal complexes. The IR spectral data suggest that the ligand behaves as a dibasic tridentate ligand with ONN donor atoms sequence towards central metal ion. Thermal behaviour (TG/DTA) and kinetic parameters calculated by the Coats–Redfern and Horowitz–Metzger method suggest more ordered activated state in complex formation. To investigate the relationship between stability constants of metal complexes and antimicrobial activity, the dissociation constants of Schiff bases and stability constants of their binary metal complexes have been determined potentiometrically in THF–water (60:40%) solution at 25 ± 1 °C and at 0.1 M NaClO₄ ionic strength. The potentiometric study suggests 1:1 and 1:2 complexation. Antibacterial and antifungal activities in vitro were performed against Staphylococcus aureus, Escherichia coli and Aspergillus niger, Trichoderma, respectively. The stability constants of the metal complexes were calculated by the Irving–Rosotti method. A relation between the stability constant and antimicrobial activity of complexes has been discussed. It is observed that the activity enhances upon complexation and the order of antifungal activity is in accordance with stability order of metal ions.     

Antibacterial evaluation of some Schiff bases derived from 2-acetylpyridine and their metal complexes

A series of Schiff bases derived from 2-acetylpyridne and their metal complexes were characterized by elemental analysis, NMR, FT-IR and UV-Vis spectral studies. The complexes were screened for anti-bacterial activity against Methicillin-resistant Staphylococcus aureus (MRSA), Acinetobacter baumanni (AC), Klebsiella pneumonie (KB) and Pseudomonas aeruginosa (PA) using the disc diffusion and micro broth dilution assays. Based on the overall results, the complexes showed the highest activities against MRSA while a weak antibacterial activity was observed against A. baumanii and P. aeruginosa.     

Spectroscopic investigations of new binuclear transition metal complexes of Schiff bases derived from 4,6-diacetylresorcinol and 3-amino-1-propanol or 1,3-diamino-propane

The bifunctional carbonyl compound; 4,6-diacetylresorcinol (DAR) serves as precursor for the formation of different Schiff base ligands, which are either di- or tetra-basic with two symmetrical sets of either O2N or N2O tridentate chelating sites. The condensation of 4,6-diacetylresorcinol with 3-amino-1-propanol (3-AP) or 1,3-diaminopropane (DAP), yields the corresponding hexadentate Schiff base ligands, abbreviated as H4La and H2Lb, respectively. The structures of these ligands were elucidated by elemental analyses, IR, mass, 1H NMR and electronic spectra. Reaction of the Schiff base ligands with copper(II), nickel(II), cobalt(II), zinc(II), cadmium(II), iron(III), chromium(III), vanadyl(IV) and uranyl(VI) ions in 1:2 molar ratio afforded the corresponding transition metal complexes. A variety of binuclear complexes for the metal complexes were obtained with the ligands in its di- or tetra-deprotonated forms. The structures of the newly prepared complexes were identified by elemental analyses, infrared, electronic, mass, 1H NMR and ESR spectra as well as magnetic susceptibility measurements and thermal gravimetric analysis (TGA). The bonding sites are the azomethine and amino nitrogen atoms, and phenolic and alcoholic oxygen atoms. The metal complexes exhibit different geometrical arrangements such as square planar, tetrahedral, square pyramid and octahedral arrangement.     

Synthesis,spectral studies,and antimicrobial activity of binary and ternary Cu(II), Ni(II), and Fe(III) complexes of new hexadentate Schiff bases derived from 4,6-diacetylresorcinol and amino acids

Two new hexadentate N₂O₄ donor Schiff bases, H₄L¹ and H₄L², were synthesized by condensation of 4,6-diacetylresorcinol with glycine and alanine, respectively. The structures of the ligands were elucidated by elemental analyses, IR, ¹H NMR, electronic, and mass spectra. Reactions of the Schiff bases with copper(II), nickel(II), and iron(III) nitrates in 1 : 2 molar ratio gave binuclear metal complexes and, in the presence of 8-hydroxyquinoline (8-HQ) or 1,10-phenanthroline (Phen) as secondary ligands (L′), mixed-ligand complexes in two molar ratios 1 : 2 : 2 and 1 : 2 : 1 (L¹/L² : M : L′). The complexes were characterized by elemental and thermal analyses, IR, electronic, mass, and ESR spectral studies, as well as conductivity and magnetic susceptibility measurements. The spectroscopic data reveal that the Schiff-base ligands were dibasic or tetrabasic hexadentate ligands. The coordination sites with the metal ions are two azomethine nitrogens, two oxygens of phenolic groups, and two oxygens of carboxylic groups. Copper(II) complexes were octahedral and square planar while nickel(II) and iron(III) complexes were octahedral. The Schiff bases, H₄L¹ and H₄L², and some of their metal complexes showed antibacterial activity towards Gram-positive (Staphylococcus aureus and Streptococcus pyogenes) and Gram-negative (Pseudomonas fluorescens and Pseudomonas phaseolicola) bacteria and antifungal activity towards the fungi Fusarium oxysporium and Aspergillus fumigatus.     

Coordination polymers of glutaraldehyde with glycine metal complexes: synthesis,spectral characterization,and their biological evaluation

Glycine metal complexes were prepared by the reaction of glycine with Mn(II), Co(II), Ni(II), Cu(II), and Zn(II) in 1?:?2 molar ratio. Thereafter their condensation polymerization was done with glutaraldehyde to obtain polymer metal complexes. All the synthesized polymer metal complexes were characterized by elemental analysis, FT-IR, ¹H-NMR, and UV-Vis spectrometry, magnetic susceptibility, and thermogravimetric studies. The analytical data of all the polymers agreed with 1?:?1 molar ratio of metal complex to glutaraldehyde and magnetic moment data suggest that PGG–Mn(II), PGG–Co(II), PGG–Ni(II), and PGG–Cu(II) have an octahedral geometry around the metal atom, whereas the tetrahedral geometry was proposed for PGG–Zn(II) polymer. The PGG–Mn(II) and PGG–Cu(II) showed octahedral geometry. Thermal behavior of the polymer metal complexes was obtained at a heating rate of 10°C?min^?1 under nitrogen atmosphere from 0°C to 800°C. The antimicrobial activities of synthesized polymers were investigated against Streptococcus aureus, Escherichia coli, Bacillus sphaericus, Salmonella sp. (Bacteria), Fusarium oryzae, Candida albicans, and Aspergillus niger (Yeast).     

Antimicrobial and anticancer activities of Schiff base ligand and its transition metal mixed ligand complexes with heterocyclic base

A new Schiff base ligand (HL) was prepared via a condensation reaction of quinoline‐2‐carboxaldhyde with 2‐aminophenol in a molar ratio of 1:1. Its transition metal mixed ligand complexes with 1,10‐phenanthroline (1,10‐phen) as co‐ligand were also synthesized in a 1:1:1 ratio. HL and its mixed ligand complexes were characterized using elemental analysis, infrared, ¹H NMR, mass and UV–visible spectroscopies, molar conductance, magnetic measurements, solid reflectance, thermal analysis, electron spin resonance and X‐ray diffraction. Molar conductance measurements showed that all complexes have an electrolytic nature, except Cd(II) complex. From elemental and spectral data, the formulae [M(L)(1,10‐phen)(H₂O)]Cl_x?nH₂O (where M = Cr(III) (x = n = 2), Mn(II) and Ni(II) (x = 1, n = 2), Fe(III) (x = n = 2), Co(II), Cu(II) and Zn(II) (x = 1, n = 2)) and [Cd(L)(1,10‐phen)Cl]?3H₂O for the metal complexes have been proposed. The geometric structures of complexes were found to be octahedral. Powder X‐ray diffraction reflected the crystalline nature of the complexes; however, the Schiff base is amorphous. HL and its mixed ligand complexes were screened against Gram‐positive bacteria (Streptococcus pneumoniae and Bacillus subtilis) and Gram‐negative bacteria (Pseudomonas aeruginosa and Escherichia coli). Antifungal activity was determined against Aspergillus fumigatus and Candida albicans, the data showing that most complexes had activity less than that of the Schiff base while Mn(II), Fe(III) and Ni(II) complexes showed no significant antifungal activity. The anticancer activity of HL and its metal complexes was also studied against breast and colon cell lines. The metal complexes showed IC₅₀ higher than that of HL, especially the Cu(II) complex which showed the highest IC₅₀ against breast cell line.     

Spectral characterization,electrochemical, antimicrobial and cytotoxic studies on new metal(II) complexes containing N2O4 donor hexadentate Schiff base ligand

We report the biological activity of the new Schiff base ligand H₂L (H₂L = 6,6′-((1E,11E)-5,8-dioxa-2,11-diazadodeca-1,11-diene-1,12-diyl)bis(2,4-dichlorophenol)), its derived metal(II) complexes [Cu(L)] (1), [Co(L)] (2), [Ni(L)] (3) and [Zn(L)] (4), along with their structural characterizations by using various analytical and spectroscopic techniques. Electrochemical investigations showed that all of these Cu(II), Co(II) and Ni(II) complexes were reversibly reducible. Although the change of the number of unpaired electrons are different of the metal cations, they have an effect on the redox potentials of the Co(II)/(I), Ni(II)/(I) and Cu(II)/(I) couples. The ¹H NMR and FTIR data concluded that the Schiff base ligand H₂L acts as a hexadentate ligand coordinating with metal(II) ions through the oxygen atoms of the (COC), phenolic (COH) groups and nitrogen atom of the azomethine (CHN) group. UV-Visible absorption spectra studies clearly revealed the octahedral geometry of the prepared metal(II) complexes. Complexes 1 and 4 were found to be efficient in bringing about antimicrobial activities. The proposed mechanism of their antimicrobial activities has been discussed. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay showed the remarkable cytotoxicity of complex 1 (IC50 = 17 ± 1.3 μg/mL) on human breast cancer MCF-7 cells than Schiff base ligand H₂L and complexes 2–4. Moreover, AO/EB staining assay revealed cell death due to apoptosis in MCF-7 cells and the generation of ROS by the Schiff base ligand H₂L and its derived metal(II) complexes 1–4 may be a possible cause for their cytotoxic activity.     

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 biological and anticancer studies of mixed ligand complexes with Schiff base and 2,2′‐bipyridine

New mixed ligand complexes of transition metals were synthesized from a Schiff base (L¹) obtained by the condensation reaction of oxamide and furfural as primary ligand and 2,2′‐bipyridine (L²) as secondary ligand. The ligands and their metal complexes were studied using various spectroscopic methods. Also thermal analyses were conducted. The mixed ligand complexes were found to have formulae [M(L¹)(L²)]Cl_m ⋅n H₂O (M = Cr(III) and Fe(III): m  = 3, n  = 0; M = Cu(II) and Cd(II): m  = 2, n  = 1; M = Mn(II), Co(II), Ni(II) and Zn(II): m  = 2, n  = 0). The resultant data revealed that the metal complexes have octahedral structure. Also, the mixed ligand complexes are electrolytic. The biological and anticancer activities of the new compounds were tested against breast cancer (MCF‐7) and colon cancer (HCT‐116) cell lines. The results showed high activity for the synthesized compounds.     

Spectroscopic and biological properties of platinum complexes derived from 2-pyridyl Schiff bases

The reactions of a range of aromatic primary amines with pyridine-2-carboxaldehyde were reported, highlighting the effect of the substituents of the amine on the outcomes of the Schiff base reactions. The variant products of the Schiff base reactions were reacted with cis-[PtCl₂(DMSO)₂], generating platinum(II) complexes with PtCl₂(N^N) general formula. The ligands and platinum(II) complexes were identified and characterized by IR and NMR spectroscopic methods. Single crystal XRD offered structural confirmation for three of the organic compounds and two platinum complexes. The spectral, antimicrobial, DNA-binding and molecular docking of the platinum complexes were studied, highlighting the effect of the different functional group in the Schiff base ligands on their properties. In general, introducing the electron-withdrawing group nitro or acetyl in the 2-pyridyl Schiff base ligands, results in a red-shift in the absorption maxima of the platinum complex. In addition, the enhancement in the antimicrobial activities and the increase in the ct-DNA-binding affinity were also observed when the nitro or acetyl functional group is introduced to the Schiff base ligand in the platinum(II) complex.     

Synthesis,characterization, potentiometry,and antimicrobial studies of transition metal complexes of a tridentate ligand

Complexes of Cu(II), Ni(II), Co(II), Mn(II), and Fe(III) with the tridentate Schiff base, 4-hydroxy-3(1-{2-(benzylideneamino)-phenylimino}-ethyl)-6-methyl-2H-pyran-2-one (HL) derived from 3-acetyl-6-methyl-(2H)-pyran-2,4(3H)-dione (dehydroacetic acid or DHA), o-phenylenediamine, and benzaldehyde were characterized by elemental analysis, molar conductivity, magnetic susceptibility, thermal analysis, X-ray diffraction, IR, ¹H-NMR, UV-Vis spectroscopy, and mass spectra. From analytical data, the stiochiometry of the complexes was found to be 1?:?2 (metal?:?ligand) with octahedral geometry. The molar conductance values suggest nonelectrolytes. X-ray diffraction data suggest monoclinic crystal systems. IR spectral data suggest that the ligand is dibasic tridentate with ONN donors. To investigate the relationship between formation constants of metal complexes and antimicrobial activity, the dissociation constants of Schiff base and stability constants of its binary metal complexes have been determined potentiometrically in THF–water (60?:?40) at 30?±?1°C and at 0.1?mol?L^?1 NaClO₄ ionic strength. The potentiometric titrations suggest 1?:?1 and 1?:?2 complexation. Antibacterial and antifungal activities in vitro were performed against Staphylococcus aureus, Escherichia coli, Aspergillus niger, and Trichoderma with determination of minimum inhibitory concentrations of ligand and metal complexes. The structure–activity correlation based on stability constants of metal complexes is discussed. Activity enhances upon complexation and the order of activity is in accord with the stability order of metal ions.     

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).     

Transition metal complexes of Schiff base ligand based on 4,6-diacetyl resorcinol

Novel Schiff base ligand based on the condensation of 4,6-diacetyl resorcinol with 2-amino-4-methylthiazole in addition to its metal complexes with Cr (III), Mn (II), Fe (III), Co (II), Ni (II), Cu (II), Zn (II) and Cd (II) ions have been synthesized. The structure, electronic properties, and thermal behaviour of Schiff base and its metal complexes have been studied by elemental analysis, mass, ¹H NMR, IR spectra, thermal analysis, and theoretically by density function theory. The ligand acted as mononegative bidentate (NO) ligand and all complexes showed octahedral geometry except Cu (II) showed tetrahedral geometry as indicated from the spectral and magnetic studies. The Cu (II), Zn (II) and Cd (II) complexes were non electrolytes while the rest of the complexes were electrolytes. The antibacterial plus anticancer activities of the parent Schiff base and its metal complexes were screened. In addition, the molecular docking study was performed to explore the possible ways for binding to Crystal Structure of Human Astrovirus capsid protein (5ibv) receptor.     

Synthesis,characterization, and anticancer activity of some metal complexes with a new Schiff base ligand

A new Schiff base ligand, 2-((E)-((4-(((E)-benzylidene)amino)phenyl)imino)methyl)-naphthalene-1-ol, was prepared by the reflux condensation of p-phenylenediamine with 2-hydroxy-1-naphthaldehyde and benzaldehyde. Metal complexes were prepared by reacting the ligand with metal salts: VCl₃, CrCl₃·6H₂O, MnCl₂·3H₂O, FeCl₃·6H₂O, CoCl₃·6H₂O, NiCl₂·6H₂O, CuCl₂·2H₂O, and ZnCl₂. The ligand and its metallic complexes were characterized by various techniques such as elemental analysis, AAS, NMR, IR, UV–Vis, TGA, DTA, XRD and TEM. The data confirmed that the ligand coordinated with the metal ions in a bidentate nature, bonding through its azomethine nitrogen atom and phenolic oxygen atom; this gave an octahedral geometry. The XRD patterns of the complexes indicated that they were of various structures: the Mn(II), Co(III), and Cu(II) complexes were triclinic, the ligand and Ni(II) complex were orthorhombic, the V(III) and Zn(II) complexes were hexagonal, the Cu(II) complex was monoclinic, and the Fe(II) complex was cubic. TEM analysis confirmed that the complexes were nanoscale in nature. The antibacterial and antifungal activities of the ligand and its complexes against Salmonella enterica serovar typhi and Candida albicans were investigated by the hole plate diffusion method. It was observed that the Co(II) and Zn(II) complexes had intermediate antibacterial activities, while the V(III) complex had the highest activity against C. albicans fungi. The in vitro anticancer activities of the ligand and its metal complexes were tested towards PC-3, SKOV3, and HeLa tumour cell lines, where they exhibited higher antitumour activities against these selected human cell lines than clinically used drugs such as cisplatin, estramustine, and etoposide.     

Syntheses, spectroscopic characterization and thermal behavior on novel binuclear transition metal complexes of hydrazones derived from 4,6-diacetylresorcinol and oxalyldihydrazine

4,6-Diacetylresorcinol (DAR) serves as precursor for the formation of different hydrazone ligands, which are di-, tetra- or hexa-basic with two symmetrical sets of O(2)N tridentate, O(2)N(2) tetradentate or O(4)N(2) hexadentate chelating sites. The condensation of 4,6-diacetylresorcinol (DAR) with oxalyldihydrazine (ODH), in the molar ratio 1:1 and 1:2, yields the corresponding hydrazone, H(6)L(a) and H(4)L(b), ligands, respectively. The structures of these ligands were elucidated by elemental analyses and IR, mass, (1)H NMR and UV-vis spectra. Reactions of the hydrazone ligands with cobalt(II), nickel(II), copper(II), zinc(II), cadmium(II), iron(III) and chromium(III) ions in 1:2 molar ratio afforded the corresponding transition metal complexes. A variety of binuclear transition metal complexes were obtained in its di-, tetra- or hexa-deprotonated forms. The structures of the newly prepared complexes were identified by elemental analyses and IR, UV-vis, mass, (1)H NMR and ESR spectra, as well as, magnetic susceptibility measurements and thermal gravimetric analysis (TGA). The bonding sites are the azomethine and CO oxygen atoms in either keto or enol forms and amino nitrogen atoms, and phenolic oxygen atoms. The metal complexes exhibit different geometrical structures such as tetrahedral and octahedral arrangements.