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AbstractA Schiff base (imine) ligand, (E)-4-((2-hydroxy-3,5-diiodobenzylidene)amino)-N-(4,6-dimethylpyrimidin-2-yl)benzenesulfonamide (HL), was synthesized by condensation of 3,5-diiodosalicylaldehyde with sulfamethazine. The ligand was then complexed with Zn(II), Cu(II), Ni(II), Co(II) and Fe(II) employing a metal to ligand ratio of 1:2 to form chelates (1-5), [M(L)2(H2O)2]. Characterization was done by UV-visible, FTIR, 1H and 13C NMR spectroscopy, elemental analysis, magnetic moments, thermogravimetric analyses (TGA) and conductance studies. The Schiff base behaved as a bidentate ligand and metal chelates assumed octahedral geometry. MOE-docking was employed to assess binding of the Schiff base (HL) and its chelates (1-5) with 1T2P, 1VVQ, 2W61, 3U2D, 4H8E and 5K18 proteins. Results indicated that Zn(II) chelate (1) and Fe(II) chelate (5) are the most potent compounds. Antibacterial and antibiofilm activities were executed against Enterococcus faecalis, Staphylococcus aureus, Proteus mirabilis and Klebsiella pneumoniae. Antifungal activities were performed against Candida albicans and Aspergillus niger. The Schiff base exhibited moderate antibacterial/antifungal activities that were enhanced on chelation with metal ions. Zinc(II) chelate (1) and Fe(II) chelate (5) show excellent antibacterial/antifungal activities. Complex 2 exhibited good antibiofilm activity. [ABSTRACT FROM AUTHOR]

To investigate how modification in the structure of 1,3-propanediamine chain of 1,3-pdta (1,3-propanediamine-N,N,N′,N′-tetraacetate) ligand affects the structural and biological properties of the corresponding metal complexes, two new octahedral complexes, [Co(H2O)5Co(2,2-diMe-1,3-pdta)]·H2O (1) and [Mg(H2O)5Mg(2,2-diMe-1,3-pdta)]·1.5H2O (2) (2,2-diMe-1,3-pdta = 2,2-dimethyl-1,3-propanediamine-N,N,N′,N′-tetraacetate), were synthesized and characterized by IR spectroscopy and single-crystal X-ray diffraction analysis. Additionally, UV-Vis and NMR spectroscopic methods were applied for the characterization of 1 and 2, respectively. Crystallographic data indicate that these complexes contain 2,2-diMe-1,3-pdta coordinated to the metal ion through 2 N and 4 O atoms forming [M(H2O)5M′(2,2-diMe-1,3-pdta)] complex unit (M, M′ = Co(II), Co(II) (1) and M, M′ = Mg(II), Mg(II) (2)), which is composed of [M′(2,2-diMe-1,3-pdta)]2− and [M(H2O)5O]2+ octahedra bridged by one of the axial carboxylate groups. The antimicrobial activities of 1 and 2 were evaluated against different bacteria and Candida spp., while their cytotoxic effect was tested on the normal human lung fibroblasts (MRC-5). The ability of 1 and 2 to inhibit formation of C. glabrata biofilms was also assessed. The obtained structural parameters and biological properties of the two complexes were compared to Co(II) and Mg(II) complexes with 1,3-pdta ligand. [ABSTRACT FROM AUTHOR]

By using a half-salen ligand (HL) and substituted salicylaldehydes, new unsymmetrical salen-type ligands (H2L1, H2L2, and H2L3) and their Ni(II), Zn(II) and Fe(III) complexes were synthesized. The compounds were characterized based on elemental analysis, IR, 1H NMR, X-ray diffraction (for HL), spectroscopy, mass spectrometry, magnetic moment, molar conductance measurements, and thermal analysis (TGA). The unsymmetrical salen ligands, during complexation, are attached to the metal by two imine nitrogen atoms and two phenolic oxygen atoms in all complexes; in the Fe(III) complexes, the fifth coordination is completed by chloride. Square planar geometry or distorted square planar geometry for [NiL1-3], [ZnL1-3], and square pyramidal geometry for [FeL1-3Cl] are proposed. Conductance measurements suggest non-electrolytic nature of the metal complexes. Thermogravimetric analysis showed that the complexes exhibit higher stability than the ligands. The electrochemical properties of the compounds were studied by cyclic voltammetry. HOMO-LUMO energy levels and electrochemical band gaps (E′g) were calculated. The solid state electrical conductivity of the iodine-doped compounds was measured and their semiconductor properties were determined. In addition, fluorescence properties of ligands and Zn(II) complexes were investigated. [ABSTRACT FROM AUTHOR]

New air stable N-heterocyclic carbene functionalized Schiff base ligands (L) of the type 2-[-2-[3-(R)imidazol-1-yl]ethyliminomethyl]phenol [R = methyl (2), 2-pyridylmethyl (3)] were synthesized and characterized by NMR, IR, MS, and CHN analysis. Single crystal X-ray structural analysis of their Ni(II) complexes revealed square planar arrangement of the chelating ligands coordinated in tridentate (2, C^N^O) and tetradentate (3, N^C^N^O) modes around the metal. The three new isolated and fully characterized complexes were utilized as catalysts for the catalytic transfer hydrogenation of aliphatic ketones in 2-propanol as solvent and source of hydrogen. Based on 0.2 mol% catalyst concentration, the complexes showed activity for aliphatic ketones and 100% conversion (turnover number of 500) for cyclohexanone and all the aromatic ketones tested. [ABSTRACT FROM AUTHOR]

Eight substituted bidentate Schiff base ligands HOC6H4CH=N-R (HL) (HL1: R = 4-ClC6H4, HL2: R = 2-ClC6H4, HL3: R = 4-NO2C6H4, HL4: R = 4-MeC6H4, HL5: R = 2,6-Me2C6H3, HL6: R = 2,46-Me3C6H2, HL7: R = CH2C6H5, and HL8: R = n-Pr) were synthesized by the typical condensation reaction. Interaction ofcis-[Ru(bpy)2Cl2]⋅2H2O (bpy = 2,2′-bipyridine) with one equivalent of HLligand in the presence of KPF6afforded the cationic ruthenium(II) complexes of the type [Ru(bpy)2(L)](PF6) (1–8). The reaction ofcis-[Ru(phen)2Cl2]⋅2H2O (phen = 1,10-phenanthroline) and HL1under similar condition gave complex [(phen)2Ru(L)](PF6) (1a). Treatment ofcis-[Ru(phen)2Cl2]⋅2H2O with two equivalents of HLin the presence of KPF6resulted in isolation of the cationic ruthenium(III) complexes of the type [Ru(phen)(L)2](PF6) (9-16). All complexes have been spectroscopically characterized. The structures of1a⋅CH2Cl2,2⋅½CH2Cl2,3⋅CH3CN,5⋅½H2O,6,12⋅½HOCH2CH2OH,13⋅CH3CN,15⋅H2O, and16have been determined by single-crystal X-ray diffraction. [ABSTRACT FROM PUBLISHER]

Two new palladium complexes, [Pd(dpbs)Cl] (1) and [Pd4(dbbs)4] (2) (where (dpbs)2 = o,o′-(N,N′-dipicolinyldene)diazadiphenyl disulfide and (dbbs)2 = N,N′-(1,1′-dithio-bis(phenylene))-bis(salicylideneimine)), have been synthesized and characterized by analytical and spectral (electronic, IR,1H,13C spectroscopy) techniques. The structures of1and2have been solved by single-crystal X-ray diffraction experiments, which indicate distorted square planar coordination geometries around palladium(II) by O, N, and S donors. The metal chelates have been screened for their antibacterial and antioxidant activities, and compared with their respective ligands. The binding properties of the complexes have been studied by electronic absorption, emission spectroscopy, and viscosity measurements. The competitive fluorescence study with ethidium bromide and the effect of iodide concentration on fluorescence of the complex-DNA system have been investigated. All these experimental results suggest that palladium complexes strongly bind to DNA, presumably via groove binding. The thermodynamic parameters, enthalpy change (ΔH°), and entropy change (ΔS°) were calculated by the Van’t Hoff equation, suggesting hydrogen bonds play a predominant role in the binding of complexes to DNA. [ABSTRACT FROM AUTHOR]

The reaction of europium(III) or gadolinium(III) acetates with a Schiff base ligand {HL(C22H21N3O) = ((E)-9-((quinolin-8-ylimino)methyl)-1,2,3,5,6,7-hexahydropyrido[3,2,1-ij]quinolin-8-ol)} in methanol affords two dinuclear complexes which have been characterized by powder X-ray diffraction, Raman spectroscopy, scanning electron microscope–electron dispersive spectroscopy, absorption and emission spectroscopies as well as single-crystal X-ray diffraction. [Eu2L2(CH3COO)4(CH3OH)2] (1) and [Gd2L2(CH3COO)4(CH3OH)2] (2) are iso-structures, each consisting of two M : L : CH3COO : CH3OH (1 : 1 : 1 : 1) units bridged by two acetate anions with the metal center in a distorted capped square antiprismatic coordination geometry. Their vibration modes, electronic structures, and photoluminescent properties are reported. [ABSTRACT FROM AUTHOR]

Reaction of Cu(II) nitrate with a new pyrazole-based Schiff base ligand, 5-methyl-3-formylpyrazole-N-(2′-methylphenoxy)methyleneimine (MPzOA), afforded two types of Cu(II) complexes at different reaction temperatures, [Cu(MPzOA)(NO3)]2(1) and [Cu(3,7,11,15-tetramethylporphyrin)(H2O)](NO3)2(2), reported together with a Ni(II) complex, [Ni(MPzOA)2(H2O)2]Br2(3). The compounds are characterized by single crystal X-ray structure analyses along with several physico-chemical and spectral parameters. Complex1is authenticated as a bis(μ-pyrazolato)dicopper(II), while2is a porphyrinogen and3is a distorted octahedral complex. Structural analyses of the complexes reveal that1crystallized in monoclinicP21/nspace group while2and3crystallized in monoclinicC2/cspace group. DNA-binding studies of the complexes have shown that the complexes interact with CT-DNA. DNA-cleavage studies with plasmid DNA have shown that1and2induce extensive DNA cleavage in the presence of H2O2as an additive, whereas there is no change in degradation of super-coiled DNA by3in the presence of additive. The antimicrobial studies of the complexes againstEscherichia coliDH5α bacteria strain indicated that all the complexes were capable of killingE. coliwith different LD50 values. [ABSTRACT FROM AUTHOR]

Reactions of 1,2-di(o-aminophenylthio)ethane with 3-ethoxy-2-hydroxybenzaldehyde yield the new hexadentate N2S2O2donor thioether Schiff base 1,2-bis(2-((2-(thio)phenylimino)methyl)-6-ethoxyphenol)ethane (H2L). Ni(II), Zn(II), Cd(II), and Hg(II) complexes of this ligand were prepared. Of these complexes, [NiL]·2H2O has been structurally characterized by X-ray crystallography. The coordination geometry around Ni(II) was described as octahedral. Zn(II), Cd(II), and Hg(II) complexes and the Schiff base ligand have been characterized by CHN analyses, molar conductivity, UV–vis, FT-IR,1H, and13C NMR spectroscopy. [ABSTRACT FROM AUTHOR]

This article reports the synthesis and characterization of four Ni(II) Schiff base complexes, [Ni(L)(H2O)], where H2L = N-(dehydroacetic acid)-thiosemicarbazide (H2dha-tsc), N-(dehydroacetic acid)-4-methyl-3-thiosemicarbazide (H2dha-mtsc), N-(dehydroacetic acid)-4-phenyl-3-thiosemicarbazide (H2dha-ptsc), or N-(dehydroacetic acid)-4-phenylsemicarbazide (H2dha-psc). The nature of bonding and stereochemistry of these complexes have been deduced from elemental analysis, infrared and electronic spectral studies, molar conductance, magnetic measurements, mass spectrometry, thermogravimetric analysis,1H NMR and13C NMR studies, and cyclic voltammetry. The stabilities of the complexes were determined in both solid state and solution. Molecular geometry optimizations and vibrational frequency calculations were performed with Gaussian 09 software package using density functional theory (DFT) with B3LYP/6-311G for a ligand (dha-ptscH2) and B3LYP/LANL2DZ combination for [Ni(dha-mtsc)(H2O)]. Based on the combined experimental and theoretical studies, square planar geometry has been proposed for the Ni(II) complexes. The Schiff base ligands and their metal complexes were screened for antibacterial activities against gram-negative bacteria (Escherichia coli) at different concentrations to get their minimum inhibition concentration values. The bactericidal activity was enhanced in metal complexes as compared to free ligands. [ABSTRACT FROM AUTHOR]

Co(II), Ni(II), Cu(II) and Zn(II) Schiff base complexes derived from 3-hydrazinoquionoxaline-2-one and 1,2-diphenylethane-1,2-dione were synthesized. The compounds were characterized by elemental analyses, molar conductance, magnetic susceptibility measurements, FTIR, UV–vis,1H NMR,13C NMR, ESR, and mass spectral studies. Thermal studies of the ligand and its metal complexes were also carried out to determine their thermal stability. Octahedral geometry has been assigned for Co(II), Ni(II), and Zn(II) complexes, while Cu(II) complex has distorted octahedral geometry. Powder XRD study was carried out to determine the grain size of ligand and its metal complexes. The electrochemical behavior of the synthesized compounds was investigated by cyclic voltammetry. For all complexes, a 2 : 1 ligand-to-metal ratio is observed. The ligand and its metal complexes were screened for their activity against bacterial species such asE. coli,P. aeruginosa,andS. aureusand fungal species such asA. niger,C. albicans,andA. flavusby disk diffusion method. The DNA-binding of the ligand and its metal complexes were investigated by electronic absorption titration and viscosity measurement studies. Agarose gel electrophoresis was employed to determine the DNA-cleavage activity of the synthesized compounds. Density functional theory was used to optimize the structure of the ligand and its Zn(II) complex. [ABSTRACT FROM PUBLISHER]

The chitosan–(Fe(II), Co(II), and Cu(II)) complexes were prepared by mixing chitosan (Chi) powder with a salicylaldehyde (Sal, 5-hydrogen (–H)) and their 5-bromo (–Br), 5-chloro (–Cl), 5-methoxy (–OCH3), 5-fluoro (–F), 5-methyl (–CH3), and 5-nitro (–NO2) derivatives (groups R) and mixing these with FeCl2and CuCl2in ethanol and with Co(CH3COO)2solutions in butanol at 80 °C over 8 h in heterogeneous phase, followed by extraction with ethanol and butanol, respectively. The complexes were characterized by FTIR and UV–vis spectroscopy, elemental analysis, and cyclic voltammetry. A linear correlation between the metal formal potentialversusthe Hammett parameters of the substituents was observed. The electron-withdrawing groups shift the redox potential to positive values, as a result of lowering the energy of the highest occupied molecular orbital. The formal potential was used as a measurement for the driving force of chitosan complexes for redox reactions. [ABSTRACT FROM PUBLISHER]

Ni(II), Cu(II), and Co(II) complexes, ML2, with a new thioether containing ONS donors were synthesized, where L = deprotonated Schiff base. The analytical, spectral (FTIR,1H NMR, and UV-vis), conductivity, and magnetic studies show that the metal complexes possess octahedral geometry and are non-electrolytes. The coordination mode of ligand,1, and nickel(II) complex, NiL2,2, was determined by single-crystal X-ray diffraction studies. Here, the nickel is coordinated to two oxygens, two nitrogens, and two sulfurs of two tridentate ligands with slightly distorted octahedral environment around nickel. The copper complex shows very good catalytic activities towards oxidation of organic thioethers to the corresponding sulfoxide predominantly using H2O2as the oxidant. A series of Ni(II), Cu(II), and Co(II) complexes, ML2, of a new thioether containing ONS donors have been synthesized, where L = deprotonated Schiff base. The analytical, spectral (FTIR,1H NMR, UV–vis), conductivity, and magnetic studies showed that the metal complexes possess octahedral geometry and are non-electrolytes. The structures of ligand as well as nickel(II) complex, NiL2,2, were determined by single-crystal X-ray diffraction studies. The copper complex shows very good catalytic activities towards oxidation of organic thioethers to the corresponding sulfoxide predominantly using H2O2as the oxidant. [ABSTRACT FROM PUBLISHER]

Ten new complexes, [Cu2(L1)(NO3)2]·2H2O (1), [Cu4(L1)2]·4ClO4·H2O (2), [Cu2(L1)(H2O)2]·(adipate) (3), [Cu6(L1)2(m-bdc)4]·2DMF·5H2O (4), [Cu2(L1)(Hbtc)]·5H2O (5), [Cu2(L1)(H2O)2]·(ntc)·3H2O (6), [Co2(L2)]·[Co(MeOH)4(H2O)2] (7), [Co3(L2)(EtOH)(H2O)] (8), [Ni6(L2)2(H2O)4]·H2O (9) and [Zn4(L2)(OAc)2]·0.5H2O (10), have been synthesized.1displays a [Cu2(L1)(NO3)2] monomolecular structure.2shows a supramolecular chain including [Cu2L1]2+. In3, two Cu(II) ions are connected by L1to form a [Cu2(L1)(H2O)2]2+cation. In4, them-bdc anions bridge Cu(II) ions and L1anions to form a layer. Both5and6display 3-D supramolecular structures.7consists of both [Co2L2]2?and [Co(MeOH)4(H2O)2]2+units.8and9show infinite chain structures. In10, Zn(II) dimers are linked by L2to generate a 3-D framework. The magnetic properties for4and8and the luminescent property for10have been studied. [ABSTRACT FROM AUTHOR]

Ruthenium(II) complexes with 2-acetylpyridine-thiosemicarbazones (L1–L4) were synthesized and characterized by analytical and spectral (FT-IR, UV–vis, NMR [1H,13C and31P], and ESI-Mass) methods. Systematic biological investigations, free radical scavenging, anticancer activities, and DNA cleavage studies, were carried out for the complexes. Antioxidant studies showed that the complexes have significant antioxidant activity against DPPH, hydroxyl, nitric oxide radicals and hydrogen peroxide assay. Thein vitrocytotoxicity of complexes against breast cancer (MCF-7) cell line was assayed showing high cytotoxicity with low IC50values indicating their efficiency in destroying the cancer cells even at very low concentrations. The DNA cleavage studies showed that the complexes efficiently cleaved DNA. [ABSTRACT FROM PUBLISHER]

Schiff bases (SBs) are aldehyde- or ketone-like compounds in which the carbonyl group is replaced by an imine or azomethine. In spite of the large interest always shown in the coordination properties of Schiff base ligands and the attention paid in recent years to the possible variable biological activities of their metal complexes, studies dealing with protonation and formation equilibria of Schiff bases and their complexes are still very rare. Thus, the importance of the determination of the equilibrium constants of Schiff bases and their complex formation equilibria is of paramount importance to understand the complicated biological reactions like transamination, racemization and decarboxylation. The 33 ligands considered herein include salicylaldehyde/substituted salicylaldehyde SBs and salicylaldehyde/substituted salicylaldehyde amino acid SBs. This article is focused on protonation and complex-formation equilibria of salicylaldehyde or substituted salicylaldehyde SBs and salicylaldehyde amino acid SBs in aqueous and nonaqueous solutions, taking into account also the structure-activity correlation of SBs and their metal(II) complexes based on their stability constants. Activity of SBs enhances upon complexation and the order of activity is nearly in accord with the order of the formation constants of metal ions. The few enthalpy and entropy changes available for such protonation and complex-formation reactions are reported and discussed. [ABSTRACT FROM AUTHOR]

Treatment of [RuHCl(CO)(PPh3)3] with equal amounts of equiv. bidentate Schiff base 2[(4-chloro-phenylimino)-methyl]-phenol (HL-Cl) or 2(p-tolylimino-methyl)-phenol (HL-Me) or 2[(4-nitro-phenylimino)-methyl]-phenol (HL-NO2) in the presence of triethylamine afforded [RuCl(?2-N,O-L-Cl)(CO)(PPh3)2] (1), [RuCl(?2-N,O-L-Me)(CO)(PPh3)2] (2), and [RuCl(?2-N,O-L-NO2)(CO)(PPh3)2] (3), respectively. The molecular structures of1,2, and3·1.5C6H14have been determined by single-crystal X-ray crystallography. Complexes1–3were used for oxidation of primary and secondary alcohols to aldehydes and ketones as catalysts in the presence ofN-methylmorpholine-N-oxide. [ABSTRACT FROM AUTHOR]

The reactions of HL1[2-((2-(benzylthio)phenylimino)methyl)phenol] and HL2[3-((2-(benzylthio)phenylimino)methyl)-2-hydroxy-5-methylbenzaldehyde] separately with Cu(OAc)2·H2O afforded new Cu(II) complexes [Cu(L1)(OAc)] (1) and [Cu(L2)2] (2), respectively. These are characterized by microanalytical data and spectroscopic studies. UV–vis spectra of the complexes show intense low-energy transitions ∼ 420 nm which are ligand to metal charge transfer (LMCT) transitions. The single-crystal X-ray structures were determined for1and2. Reactions of [Cu(L1)(OAc)] (1) with, SCN–andshow the replacement of weakly coordinated acetate yielding [Cu(L1)(N3)], [Cu(L1)(SCN)] and [Cu(L1)(NO2)], respectively. Unequivocal characterization of the substituted products has been done by single-crystal X-ray study of [Cu(L1)(N3)]. HL2and its Cu(II) complex exhibited low-intensity emission bands at ∼575 nm upon excitation at 375 nm and at 420 nm, respectively. Redox properties of the complexes were determined electrochemically. Density functional theory (DFT) computations have been carried out to explain the spectroscopic and redox properties of the complexes. [ABSTRACT FROM AUTHOR]

This article presents the synthesis, physico-chemical, in particular voltammetric, characteristics of two iron(III) complexes with pyridoxal aminoguanidine (PLAG), [Fe(PLAG)Cl2(H2O)]Cl (1) and [Fe(PLAG)2](NO3)3 (2). As expected, the zwitterion of the chelate ligand is coordinated tridentate through oxygen of phenol and nitrogen atoms of azomethine and imino groups of the aminoguanidine fragment. In both complexes, Fe(III) is distorted octahedral. [Fe(PLAG)2](NO3)3 (2) is the first bis(ligand) complex with this ligand. Cyclic voltammetric characteristics of the ligand and complexes were studied in DMF in the presence of TBAP or LiCl as supporting electrolytes. The complexes are unstable in this solvent, especially in the presence of an excess of chloride, thus forming several reducible species whose stabilities and behaviors were characterized. [ABSTRACT FROM AUTHOR]

Schiff bases o-vanilidene-1-aminobenzene (HL1) and o-vanilidene-2-methyl-1-aminobenzene (HL2) lead to the formation of mono- and bis-[(Cl)Zn(L1)] (1), [(Cl)Zn(L2)] (2), [(Cl)Hg(L1)] (3), [(Cl)Hg(L2)] (4), [Zn(L1)2] (5), [Zn(L2)2] (6), [Hg(L1)2] (7), and [Hg(L2)2] (8) complexes by reactions of zinc(II) and mercury(II) chlorides in different mole ratio(s). Complexes 1–8 have been characterized by elemental analyses (Zn, Hg, C, H, Cl, and N), melting point and spectral (IR, 1H-NMR), PXRD, molar conductivity measurement, and TGA. Conductivity measurements suggest non-electrolytes. Structural compositions have been assigned by mass spectral studies. Four-coordinate geometry may be assigned to these complexes tentatively. Structural study reveals that in 1–4 two metal centers are held together by two bridged (μ2-Cl) chlorides, whereas 5–8 contain two bidentate Schiff-base ligands around one metal-producing monomers. [ABSTRACT FROM AUTHOR]

[Cu2(H4L)(OCH3)(H2O)] · 2MeOH (1) has been synthesized from the reaction of 2-hydroxy-5-methylisophthalaldehyde, tris(hydroxymethyl)aminomethane and copper(II) perchlorate in methanol with the Schiff-base polyhydroxyl ligand (H4L)3− formed in situ. Single-crystal X-ray structure analysis of 1 reveals a binuclear structure with Cu(II) asymmetrically bridged by a methoxo and a phenoxo group with Cu–O–Cu bridging angles of 102.93(7)° and 100.17(7)°, respectively. The binuclear Cu(II) moieties utilize the coordinated and noncoordinated alkoxyl groups for formation of intermolecular hydrogen bonds, thus affording a 3-D supramolecular structure. Variable temperature magnetic measurements reveal strong antiferromagnetic coupling in 1 with the 2J-value of −729 cm−1, which was mediated cooperatively by the methoxo and phenoxo bridges. Magneto-structural correlations are discussed based on the crystal structure. [ABSTRACT FROM PUBLISHER]

Four mononuclear complexes of Cu(II) and Zn(II) having a Schiff-base ligand and 1,10-phenanthroline/2,2′-bipyridine have been synthesized and characterized. From electronic spectral and magnetic susceptibility data, octahedral geometry has been proposed for the complexes. DNA-binding behaviors of these complexes are studied by absorption titration, electrochemical, and viscosity methods. The results indicate that the complexes bind to calf thymus DNA in an intercalative mode. The gel electrophoresis results reveal that 1 cleaves pBR322 DNA effectively. The ligand and its complexes have been screened for their antimicrobial activities against a few microorganisms. The data exhibit that they are better antimicrobial agents than the ligand. [ABSTRACT FROM PUBLISHER]

A new symmetrical tetradentate Schiff base was prepared by the condensation of 5-nitro-o-vanillin and diaminoethane. Its complexes were synthesized and characterized by elemental analysis, magnetic moment, molar conductance, UV-Vis, IR, 1H NMR, ESI-mass, and EPR spectra. The DNA-binding behavior of these complexes was investigated by absorption spectra, cyclic voltammetry, and viscosity measurements. The DNA-binding constants for Co(II), Ni(II), Cu(II), and Zn(II) complexes were 1.58 × 104, 1.65 × 104, 2.71 × 104, and 1.83 × 104 (mol L−1)−1, respectively. The results suggest that the complexes intercalate between DNA base pairs. Further, all these complexes exhibit moderate to high ability to cleave pUC19 DNA. The ligand and its complexes have been screened for antimicrobial activities using the disc diffusion method against selected bacteria and fungi. Antibacterial activity was greater against Gram-positive than Gram-negative bacteria for Cu(II) complex and antifungal activity was greater against Aspergillus niger and Candida albicans for the Cu(II) complex. [ABSTRACT FROM PUBLISHER]

A new Schiff base, (pyridin-2-yl)-N-(3,5-di(pyridin-2-yl)-4H-1,2,4-triazol-4-yl)methanimine, (L), was synthesized. Reaction of [(η6-arene)Ru(µ-Cl)Cl]2 and [Cp*M(µ-Cl)Cl]2 (M = Rh and Ir) with one equivalent of L in the presence of NH4PF6 in methanol yielded dinuclear complexes, [(η6-arene)2Ru2(L-OH)Cl](PF6)2 {arene = C6H6 (1), p-iPrC6H4Me (p-cymene) (2) and C6Me6 (3)}, and [Cp*2M2(L-OH)Cl](PF6)2 [M = Rh (4) and Ir (5)], respectively, leading to the formation of five new chiral complexes with –OH on the azomethine carbon. L is a pentadentate ligand where one of the metal centers is coordinated to two nitrogen atoms in a bidentate chelating fashion while the other metal is bonded tridentate to three nitrogen atoms. Although the ligand is neutral before coordination, after complexation it is anionic (uni-negative) with negative charge on the azo nitrogen {see the structures: N(5) in 2[PF6]2 and N(3) for 4[PF6]2}. The complexes have been characterized by various spectroscopic methods including infrared and 1H NMR and the molecular structures of the representative complexes are established by single-crystal X-ray diffraction studies. [ABSTRACT FROM AUTHOR]

Complexes [M(L)(L′)Cl · H2O], where M = Co(II), Ni(II), Cu(II), Zn(II), Cd(II), and Hg(II), L = ligand derived from reaction between benzofuran-2-carbohydrazide and 3,4,5-trimethoxybenzaldehyde (TMeOBFC) and L′ = 2-aminothiophenol (2-atp), have been synthesized. The structures of the complexes have been proposed from analytical data, IR, UV-Vis, 1H NMR, direct analysis in real time-mass spectra, ESR spectral data, magnetic, and thermal studies. The complexes are soluble in DMF and DMSO. Molar conductance values indicate that the complexes are non-electrolytes. Antibacterial and antifungal activities of the ligands and their metal complexes have been obtained against bacteria Escherichia coli and Staphylococcus aureus and against fungi Aspergillus niger and Aspergillus flavus. [ABSTRACT FROM AUTHOR]

Four water-soluble dinuclear Zn(II) complexes (1–4) of compartmental ligand L = 2,6-bis(R-iminomethyl)-4-R′-phenolate (where R = N-ethylpiperidine or R = N-ethylpyrrolidine, R′ = methyl or tert-butyl) have been synthesized, characterized, and their DNA cleavage activity and cytotoxicity toward HepG2 cancerous cells are evaluated. The dinuclear complexes are formed by a pentadentate-substituted phenolate ligand chelating the metal ions separated by ca 3.27 Å. Each metal is a distorted trigonal bipyramid, completing the coordination sphere through acetate. The X-ray structural determination of 2 shows that the complex is counterbalanced by half (formulation [Zn2L2(CH3CO2)2][(Zn(SCN)4]0.5), while in 1 and 3 two crystallographically-independent complexes are present in the unit cell with a . Among the four complexes only the 4-tert-butyl-phenolato derivatives (3 and 4) show DNA cleavage activity in in-vivo conditions and appear to be promising toward metal complexes to be used as anticancer agents. The cytotoxicity of the complexes, investigated through MTT assay, suggests that 4 is a better choice as artificial nuclease. [ABSTRACT FROM AUTHOR]

A series of binuclear Schiff-base complexes of zinc(II) and mercury(II) containing bidentate ligands (HL) [HL = salicylidene-2-methyl-1-aminobenzene (HL1), salicylidene-2-aminopyridine (HL2), and salicylidene-3-nitro-1-aminobenzene (HL3)] with 'N' and 'O' donors have been synthesized by simple metathetic reactions of anhydrous metal chlorides with sodium salts of Schiff bases (in tetrahydrofuran (THF)/MeOH) in equimolar ratio to produce [(µ-Cl)2M2(L)2 · xTHF] [where M = Zn(II) and Hg(II); L = HL1, HL2, and HL3; x = 0 for (1), (4), (6) and x = 2 for (2), (3), (5)]. The main emphasis on the complexes [(µ-Cl)2M2(L)2 · 2THF] (2), (3), and (5) is given due to their five-coordinate environment around metal ions. The complexes have been characterized by elemental analyses (M, Cl, C, H, N), melting point, and spectral (FT-IR, 1H-NMR, and 13C-NMR) studies. The structural composition of the complexes has been determined by FAB-MS spectral studies. FAB-MS showed the isotopic molecular ion peak [M+] and fragments supporting the formulation. Powder X-ray diffraction study of 6 is also reported showing the crystallite size (404.5 Å) of the complex. [ABSTRACT FROM AUTHOR]

Mixed ligand complexes of iron(III), [Fe(sb)2(py)Cl] · 2H2O (1-9) [where sbH = Schiff bases (derived from condensation of 2-aminopyridine (sapH), 2-aminophenol (saphH), o-toluidine (o-smabH), aminobenzene (sabH), p-toluidine (p-smabH), 3-nitroaniline (snabH), and anthranilic acid (saaH) with salicylaldehyde and substituted (mercapto-)benzimidazole (mbzH), {2-(o-hydroxyphenyl)}benzoxazole, (pboxH)], have been synthesized by the interactions of iron(III) chloride with corresponding ligands in 1 : 2 molar ratio in refluxing pyridine. These complexes have been characterized by elemental analyses, melting points, spectral, and magnetic studies. Powder X-ray diffraction studies of some representative complexes are also reported herein. The antibacterial and antifungal activities of the free ligands and their iron(III) complexes were found in vitro. The complexes showed good antibacterial and antifungal effect to some bacteria and fungi. Two standard antibiotics (chloromphenicol and terbinafine) were used for comparison with these complexes. [ABSTRACT FROM AUTHOR]

A new Schiff-base 3-chloro-N'-(2-hydroxybenzylidene)benzohydrazide (H2BBH) and its oxovanadium(V) complex [VO(BBH)(OCH3)]2 have been synthesized and characterized by elemental analysis, infrared (IR) spectra, and single-crystal X-ray determination. Both the ligand and the complex crystallized in the monoclinic space group P21/c. The Schiff-base coordinates to V through the phenolate O, the imine N, and the enolic O. In the centrosymmetric dimeric oxovanadium(V) complex, the V atom is six-coordinate in an octahedral geometry. The bond lengths related to the donor atoms in the complex are different from those in the ligand. The coordination of the ligand to V is also supported by IR spectra. [ABSTRACT FROM AUTHOR]

Tridentate chelate complexes M[LX · 2H2O], where M = Co(II), Ni(II), Cu(II), Zn(II), and Cd(II) have been synthesized from the Schiff base L = N-[1-(3-aminopropyl)imidazole]salicylaldimine and X = Cl. Microanalytical data, UV-Vis, magnetic susceptibility, IR, 1H-NMR, mass, and EPR techniques were used to confirm the structures. Electronic absorption spectra and magnetic susceptibility measurements suggest square-planar geometry for copper complex and octahedral for other metal complexes. EPR spectra of copper(II) complex recorded at 300 K confirm the distorted square-planar geometry of the copper(II) complex. Biological activities of the ligand and metal complexes have been studied on Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans by the well diffusion method. The activity data show the metal complexes to be more potent than the parent ligand against two bacterial species and one fungus. The electrochemical behavior of the copper complex was studied by cyclic voltammetry. [ABSTRACT FROM AUTHOR]

A dinuclear copper(II) complex with a newly synthesized tridentate Schiff-base ligand 2-[(2-hydroxy-ethylimino)-methyl]-4,6-diiodo-phenol (HL), of formula [Cu2L2Cl2 · C4H8O] (1), was prepared. Both the ligand and the complex were characterized by X-ray crystallography, confirming that the Schiff base is tridentate and its dinuclear copper(II) complex is five-coordinate from one nitrogen and two oxygens from L and two chlorides. The complex was assayed for antibacterial (Bacillus subtilis, Staphylococcus aureus, Streptococcus faecalis, Pseudomonas aeruginosa, Escherichia coli, and Enterobacter cloacae) activities by the MTT method. Complex 1 exhibited better antimicrobial activity than the ligand. [ABSTRACT FROM AUTHOR]

A new series of acyclic mononuclear copper(II) complexes have been prepared by Schiff-base condensation derived from 5-methylsalicylaldehyde, diethylenetriamine, tris(2-aminoethyl) amine, triethylenetetramine, N,N-bis(3-aminopropyl)ethylene diamine, N,N-bis(aminopropyl) piperazine, and copper perchlorate. All the complexes were characterized by elemental and spectral analyses. Electronic spectra of the complexes show a d-d transition in the range 500-800 nm, electrochemical studies of the complexes show irreversible one-electron-reduction process around -1.10 to -1.60 V. The reduction potential of the mononuclear copper(II) complexes shifts toward anodic direction upon increasing the chain length of the imine compartment. ESR spectra of the mononuclear copper(II) complexes show four lines, characteristic of square-planar geometry, with nuclear hyperfine spin 3/2. The copper(II) complexes show a normal room temperature magnetic moment value μeff = 1.72-1.76 BM, close to the spin-only value of 1.73 BM. Electrochemical and catalytic studies of the complexes were compared on the basis of increasing the chain length of the imine compartment. All the complexes were screened for antifungal and antibacterial activities. [ABSTRACT FROM AUTHOR]

Two isoniazid Schiff bases, N-isonicotinamido-2-furanketimine (INH-F1) and N-isonicotinamido-5-methyl-2-furanketimine (INH-F2), possessing potential N and O coordination sites have been prepared by the reaction of isoniazid with 2-acetylfuran and 2-acetyl-5-methylfuran, respectively. Complexes of Pd(II) and Pt(II) have been prepared and characterized by elemental analyses, melting point determinations and electronic, infrared, 1H NMR, 13C NMR spectral studies, and X-ray powder diffraction studies. In all the complexes, the monobasic bidentate nature of the ligand is evident. Antibacterial and antifungal studies of these compounds against various pathogenic bacterial and fungal strains have been carried out. Both the ligands and their metal chelates were active against all the microbial strains investigated. However, the chelates were found to be more active than the ligands. The antimycobacterial activity of the ligands and their metal complexes has been evaluated against Mycobacterium smegmatis, which showed clear enhancement in this activity upon metal complexation with Schiff bases. [ABSTRACT FROM AUTHOR]

Schiff bases (L) viz, N,N',N'',N'''-tetra-3,4-dimethoxybenzalidene-3,3'-diaminobenzidine (TDBD), N,N',N'',N'''-tetra-4-hydroxy-3-methoxybenzalidene-3,3'-diaminobenzidine (THMBD), and N,N',N'',N'''-tetra-3-hydroxy-4-nitrobenzalidene-3,3'-diaminobenzidine (THNBD) afford binuclear [M2LCl4] complexes where M = Cu(II) or Zn(II). These Schiff bases and their binuclear complexes have been characterized by analytical and spectral data showing square-planar geometry on metalation with Cu2+. Intercalative binding of these complexes with DNA has been investigated by electronic absorption spectroscopy, viscosity measurements, cyclic voltammetry, and differential pulse voltammetry. Control DNA cleavage experiments using pUC19 supercoiled (SC) DNA and minor groove binder distamycin suggest that these synthesized complexes bind to the major groove. In the presence of a reducing agent like 3-mercaptopropionic acid (MPA), they show chemical nuclease activity. They also show an efficient photo-induced DNA cleavage on irradiation with a monochromatic UV light of 360 nm in the presence of inhibitors. Control experiments indicate the inhibition of cleavage in the presence of singlet oxygen quencher like sodium azide and the enhancement of cleavage in D2O show the formation of singlet oxygen as reactive species. The superoxide dismutase (SOD)-mimetic activity of the synthesized complexes has been assessed for their ability to inhibit the reduction of nitroblue tetrazolium chloride (NBT). The complexes have promising SOD-mimetic activity. The antimicrobial results indicate that the complexes inhibit the growth of bacteria and fungi more than free ligands. [ABSTRACT FROM AUTHOR]

Adduct formation between R2SnCl2 (R = methyl and phenyl) and PhSnCl3 as acceptors and Cu(II) complexes of tetradentate Schiff-base ligands [CuL], where L = [Salen, bis(salicylaldehyde)ethylenediimine], [3-MeOSalen, N,N'-bis(3-methoxysalicylaldehyde)ethylenediimine], [5-MeOSalen, N,N'-bis(5-methoxysalicylaldehyde)ethylenediimine], [5-BrSalen, N,N'-bis(5-bromosalicylaldehyde)ethylenediimine], [salpn, N,N'-bis(salicylaldehyde)1,3-propanediimine], [Salophen, bis(salicylaldehyde)phenylenediimine], [3-MeOSalophen, N,N'-bis(3-methoxysalicylaldehyde)phenylenediimine], and [5-MeOSalophen, N,N'-bis(5-methoxysalicylaldehyde)phenylenediimine], as donors have been investigated in acetonitrile by UV-Vis spectrophotometric analysis. The formation constants and thermodynamic free energies were measured using UV-Vis titration for 1 : 1 adduct formation at various temperatures (T = 293-313 K). The trend of adduct formation for copper Schiff-base complexes with a given tin acceptor decreases as follows: [image omitted] [image omitted]; [image omitted] The trend of the reaction of RnSnCl4-n acceptors toward a given copper Schiff-base complex is PhSnCl3 > Ph2SnCl2 > Me2SnCl2. The reactivity of PhSnCl3 toward Cu(Salen), Cu(Salpn), and Cu(Salophen) increases with increasing temperature. [ABSTRACT FROM AUTHOR]

Reaction of the N-tosyl-1,2-diaminopropane or N-tosyl-1,2-diaminobenzene with salicylaldehyde forms two new asymmetric sulfonamide Schiff bases, N-[2-(2-hydroxybenzylideneamino)propyl]-4-methylbenzenesulfonamide (H2L1) and N-[2-(2-hydroxybenzylideneamino)phenyl]-4-methylbenzenesulfonamide (H2L2). Two new complexes [CuLx(H2O)] (x = 1 for 1, x = 2 for 2) constructed from H2Lx have been prepared and characterized via X-ray single-crystal diffraction, elemental analysis, FT-IR, UV-Vis, TGA, quantum chemical calculations, and photoluminescence measurements. Weak C-H ··· π, hydrogen bonds, π-π, and Cu ··· O weak interactions lead to 3-D supramolecular architecture, 1, and 1-D double chain, 2. [ABSTRACT FROM AUTHOR]

Knoevenagel condensate-based Schiff base ligands (L) containing N and S donor sites have been designed and synthesized [L = 3-cinnamalideneacetylacetonethiosemicarbazone (CAT)/3-cinnamalideneacetylacetoneethylthiosemicarbazone (CAET)/3-cinnamalideneacetylacetonephenylthiosemicarbazone (CAPT)]. They afford complexes of the type [ML] [M = Cu(II) and Zn(II)]. Both the ligands and their complexes were characterized by analytical and spectral data. Intercalative binding of these complexes with DNA has been investigated by electronic absorption spectroscopy, viscosity measurements, cyclic voltammetry, and differential pulse voltammetry. Electrophoretic study of the complexes indicates that they efficiently cleave supercoiled pUC19 DNA in the presence of hydrogen peroxide. [ABSTRACT FROM AUTHOR]

The calix[4]arene-based podand which incorporates two salicylideneamine units in 1,3-alternate positions of the lower rim has been prepared and subjected to complexation studies with transition metal ions. The nickel and copper complexes form a 2 : 2 stoichiometric metallic macrocyclic framework. [ABSTRACT FROM AUTHOR]

Three asymmetric Schiff-base tetradentate diimines H2L1, H2L2, and H2L3 [(2-OH)C6H4N=CHC6H42-N=CHC6H3(2-OH)(5-X), X = H, CH3, Cl respectively] have been synthesized by a two step process. The reaction of 2-hydroxy aniline with 2-nitro-benzaldehyde in EtOH gave the starting Schiff base, 2-hydroxy-N-(2-nitrobenzylidene)aniline (SB-NO2), which was reduced into the amino derivative (SB-NH2) in solution. Reacting SB-NH2 with 2-hydroxybenzaldehyde, 2-hydroxy-5-methylbenzaldehyde and 2-hydroxy-5-chlorobenzaldehyde gave the three new ligands H2L1, H2L2, and H2L3 respectively. Their dimeric, binuclear metal complexes with Ni(II) and Fe(III) have also been synthesized. The ligands and their complexes were characterized by elemental analyses, LC-MS, IR, electronic, 1H and 13C-NMR spectra, TGA, conductivity and magnetic measurements. All of the spectroscopic, analytical and other data indicate octahedral geometry M2L2(H2O)X2 (M: Ni,Co;X: Cl or H2O), except for NiL2 which is monomeric. Antimicrobial activities of the ligands and the complexes were evaluated against five bacteria. While the ligands and the Ni complexes are inactive towards Pseudomonas aeruginosa and Staphylococcus aureus, Fe complexes are active; only Fe complexes are inactive against Escherichia coli. All of the compounds have antimicrobial activities against Bacillus subtilis, and Yersinia enterecolitica. [ABSTRACT FROM AUTHOR]

Four heterocyclic Schiff-base ligands derived from condensation of 4-amino-1,3 dimethyl-2,6 pyrimidine-dione with 2-hydroxybenzaldehyde, 2-methoxybenzaldehyde, 4-hydroxy-3-methoxybenzaldehyde and 4-(dimethylamino) benzaldehyde, (HL1, L2, HL3and L4), respectively, and their Co(II) and Ni(II) complexes have been prepared and characterized via elemental analysis, molar conductance, magnetic moment, thermal and XRPD analysis as well as spectral data (IR, 1H-NMR, mass and solid reflectance). IR data reveal that the ligands are bidentate neutral ligands except HL1, which is monobasic tridentate with coordination sites azomethine (N), carbonyl (O) and phenolic (O). Conductance data suggest that all complexes are non-electrolytes, except cobalt(II) complexes of L2and HL3are 1 : 1 electrolytes. The mass spectra confirm the proposed structure of the ligands and their complexes. The solid reflectance spectral data and magnetic moment measurements suggest octahedral, tetrahedral and square planar geometrical structures for the metal complexes. The spectral data were utilized to compute the important ligand field parameters B, β and Dq; LFSE also was calculated. The thermal behavior is also studied. Antibacterial and antifungal properties of the ligands and their complexes show broad-spectrum activities and the metal complexes show higher activity than the free ligands. [ABSTRACT FROM AUTHOR]

Schiff-base complexes [ML(H2O)2(Ac)]nH2O (M = Co(II), Ni(II) and Zn(II); L = Schiff-base ligand derived from 2-acetylpyridine and alanine and n = 1-3/2) were synthesized and characterized by elemental analysis, spectral (FTIR, UV/Vis, MS, 1H-NMR), thermal (TGA), conductance and magnetic moment measurements. The results suggest octahedral geometry for all the isolated complexes. IR spectra show that the ligand coordinates to the metal ions as mononegative tridentate through pyridyl nitrogen, azomethine nitrogen and carboxylate oxygen after deprotonation of the hydroxyl group. Semi-empirical calculations PM3 and AM1 have been used to study the molecular geometry and the harmonic vibrational spectra to assist the experimental assignments of the complexes. [ABSTRACT FROM AUTHOR]

Four new heterobimetallic complexes [CuL 1 ][MnCl 4 ] ( 1 ), [CuL 2 ][MnCl 4 ] ( 2 ), [NiL 1 ][MnCl 4 ] ( 3 ), [NiL 2 ][MnCl 4 ] ( 4 ) (L 1 = 4,6,6-trimethyl-1,9-diamino-3,7-di-aza-nona-3-ene; L 2 = 1,15-dihydroxy-7,9,9-trimethyl-3,6,10,13-tetra-aza-pentadeca-6-ene) have been prepared from elemental metals, ethylenediamine dihydrochloride or its N-(2-hydroxyethyl) derivative and acetone by the template condensation reaction. All complexes have been characterized by elemental analysis, IR and UV-Visible spectroscopy. The structures of 2 and 3 have been determined by X-ray crystallography ( 2 : Orthorhombic, Pna2 1, a = 20.136(4), b = 11.185(2), c = 10.251(2)Å, Z = 4; 3 : Orthorhombic, Pca2 1, a = 14.335(2), b = 11.405(2), c = 11.154(2)Å, Z = 4 ). Both crystals consist of alternating complex cations [ML] 2+ and anions [MnCl 4 ] 2- linked together by N-H···Cl-Mn and O-H···Cl-Mn hydrogen bonds forming 2D corrugated sheets in ( 2 ) and 1D helical chains in ( 3 ). Complex 2 represents the first single crystal structure elucidation of the complex containing L 2 . [ABSTRACT FROM AUTHOR]