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Mixed-ligand complexes of bivalent metal ions, viz, Co(II), Ni(II), Cu(II), and Zn(II) of the composition [ML(dan)]Cl (where L = Schiff base ligand, dan = 1,8-diaminonaphthalene and M = Co(II), Ni(II), Cu(II), Zn(II)) have been synthesized and characterized. The stoichiometric ratio of the prepared complexes has been estimated using complementary techniques such as elemental analyses, FT-IR, UV-vis and EPR spectra, magnetic and molar conductivity measurements. The study shows that all the complexes have square planar geometry. The synthesized compounds have been tested in vitro against various types of pathogenic bacteria to weigh up their antimicrobial properties. They have lofty activity against the tested bacteria. The complexes have higher activity than the free ligands. The interaction of synthesized complexes with calf thymus DNA (CT-DNA) has been studied by absorption spectroscopic technique and viscosity measurements. The complexes show a successful interaction with CT-DNA via intercalation mode. In addition, molecular docking approach has been performed for predicting the binding free energy of the synthesized compounds with 1BNA receptor. [ABSTRACT FROM AUTHOR]

Three lanthanide complexes (La(III), Er(III), and Yb(III)) derived from ferrocene-based Schiff base ligand (HL) were synthesized from condensation of 2-aminophenol with 2-acetylferrocene. The ligand and metal complexes were characterized based on elemental analyses, IR, 1H NMR, molar conductance, SEM and thermal analyses (TG, DTG). The molar conductance revealed that all the metal chelates were electrolytes having the general composition [M(L)(Cl)(H2O)3]Cl·4H2O. HL and its complexes were screened for their antibacterial and antifungal activity by agar diffusion method. The results of these studies showed that the metal complexes are more effective antibacterial and antifungal agents as compared with the free ligand. The anticancer activity was screened against human breast cancer cell line (MCF-7). Results indicated that metal complexes showed an increased cytotoxicity in proliferation to cell lines as compared to free ligand. Molecular docking studies were performed to identify the binding orientation or conformation of a complex in the active site of the protein. HL and its complexes were docked with crystal structure of DDB1 of breast cancer, crystal structure of HCV, RNA-dependent RNA polymerase, receptors of HBV core protein, crystal structure of the Fab fragment of anti-HAV. [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]

Amino acid Schiff bases, [NaL]·nH2O (L = N-(2-hydroxy-5-nitrobenzylidene)alaninate,N-(2-hydroxy-5-nitrobenzylidene)valinate, andN-(2-hydroxy-5-nitrobenzylidene)phenylalaninate), were synthesized as monosodium salts (L1Na–L3Na). The structures of the monosodium salts were confirmed on the basis of elemental analysis, conductivity measurements, UV–vis, FT-IR, and 2D NMR (HMQC) spectroscopies.L1Nawas also structurally determined by single-crystal X-ray diffraction. Hydrogen bond between the amino N(2)–H and phenolate O(1) of the salicylidene part of the molecule played important roles in stabilizing the zwitterion crystal structure. The ranges of the D–H…A angles and those of the H…A and D…A distances indicated the presence of short hydrogen bonds in the structure. In addition, the monosodium salts have been evaluated forin vitroantioxidant activity. Iron(III) complexes (L1Fe–L3Fe) have been obtained by reaction of the appropriate ligand with iron(III) chloride in a 2 : 1 M ratio. Fe(III) complexes were characterized by elemental and thermal analysis, conductivity and magnetic susceptibility measurements, UV–vis, FT-IR, and X-ray photoelectron spectroscopy methods. [ABSTRACT FROM PUBLISHER]

Ruthenium(III) complexes of three tetradentate Schiff bases with N2O2donors formulated as [RuCl(LL1)(H2O)], [RuCl(LL2)(H2O)] and [RuCl(LL3)(H2O)] were synthesized and characterized by elemental analyses, molar conductance, FTIR, and electronic spectral measurements. The FTIR data showed that the tetradentate Schiff base ligands coordinate to Ru ions through the azomethine nitrogen and enolic oxygen. The antioxidant activities of the complexes were investigated through scavenging activity on 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2′-azinobis-3-ethylbenzothiazoline-6-sulfonic acid (ABTS) radicals. The DPPH activity for [RuCl(LL2)(H2O)] with IC50 = 0.031 mg mL−1was higher than the values obtained for the other Ru(III) compounds. The study revealed that the synthesized Ru(III) complexes of the tetradentate Schiff base exhibited strong scavenging activities against DPPH and moderate against ABTS radicals. In addition, the antiproliferative studies of the complexes were also tested against human renal cancer cells (TK10), human melanoma cancer cells (UACC62), and human breast cancer cells (MCF7) using the SRB assay. The results indicated that the Ru(III) complexes showed low anticancer activities against the tested human cancer cell lines. [ABSTRACT FROM PUBLISHER]

The heterodinuclear complexes [CuLnL(NO3)2(H2O)3MeOH]NO3·MeOH (Ln?=?Ho (1), Tm (2), Yb (3), and Lu (4); L?=?N,N?-bis(5-bromo-3-methoxysalicylidene)propylene-1,3-diamine) have been synthesized and characterized by elemental analysis, FTIR, thermogravimetric (TG)/differential scanning calorimetry (DSC), TG-FTIR, single crystal X-ray diffraction studies, and magnetic measurements. The isostructural compounds crystallized in the monoclinic space groupP21/n. The rare earth(III) cation is nine coordinate, whereas the coordination number for copper(II) is six. The complexes were stable at room temperature. The thermal decomposition products were mainly CH3OH, H2O, CH3Br, NOx(x?=?1 or 2), CO2, and CO. The magnetic properties of1–3were dominated by the crystal field effect on the LnIIIsite, masking the magnetic interaction between the paramagnetic centers. The CuII–LuIIIpair in4showed no significant interaction, which is in accord with the diamagnetic nature of the ground state for lutetium(III). The heterodinuclear compounds [CuLn(L)(NO3)2(H2O)3MeOH]NO3·MeOH (where Ln?=?Ho (1), Tm (2), Yb (3), and Lu (4)) have been synthesized and characterized by elemental analysis, FTIR, TG/DSC, TG-FTIR, single crystal X-ray diffraction studies, and magnetic measurements. The complexes are isostructural and crystallize in the monoclinic space groupP21/n. The magnetic properties of1,2, and3are dominated by the crystal field effect on the LnIIIsite, masking the magnetic interaction between the paramagnetic centers. [ABSTRACT FROM AUTHOR]

New metallointercalators (1a–1e) have been synthesized using the Schiff base,4-[phenyl(phenylimino)methyl]benzene-1,3-dioland metal(II) ions,viz. Mn(II), Co(II), Ni(II), Cu(II), and Zn(II). They are characterized by analytical and spectral methods. Elemental analyses and molar conductance values reveal that the Schiff base metal(II) complexes have 1?:?2 stoichiometry and are non-electrolytes. The Schiff base (HL) binds with M(II) ions through azomethine and deprotonated phenolic groups. Thermal studies reveal the presence of water in1a–1c. Powder X-ray diffraction and SEM studies show that all the complexes are microcrystalline with homogenous morphology.In vitrobiological activities of HL and1a–1ehave been screened against bacteria and fungi by well diffusion technique, revealing that these complexes are good antimicrobial agents against various pathogens. The complexes exhibit better biological activities than HL. Complex1dbinds with Calf thymus DNA through intercalation and weak covalent interactions. The oxidative cleavage of1a–1ewithpUC19 DNA has also been explored. The results indicate that they bind to DNA through intercalation and are efficient metallointercalators and cleaving agents. The4-[phenyl(phenylimino)methyl]benzene-1,3-diolSchiff base metallointercalators act as efficient DNA binding and cleaving agents. All the complexes arein vitrobiological and antioxidant activators. Cu(II) complex is found to be efficient intercalator than other chelates. [ABSTRACT FROM AUTHOR]

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]

Two structurally similar centrosymmetric phenoxo-bridged dinuclear manganese(III) complexes, [Mn2(L1)2(N3)2] (1) and [Mn2(L2)2(NCS)2] (2), were prepared from the tetradentate bis-Schiff base ligands,N,N’-bis(salicylidene)propane-1,2-diamine (H2L1) andN,N’-bis(salicylidene)ethane-1,2-diamine (H2L2), respectively, in the presence of pseudohalides. The complexes have been characterized by FTIR, elemental analyses, and molar conductivity. Structures of the complexes have been confirmed by single-crystal X-ray determination. The bis-Schiff base ligands coordinate with Mn through their phenolate oxygen and imino nitrogen. Each Mn is an octahedral. The complexes showed that they exhibit high activity in catalytic olefin oxidation. [ABSTRACT FROM AUTHOR]

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

A new tridentate Schiff base, 5-bromosalicylaldehydeS-allylisothiosemicarbazone hydrobromide (H2L), and several new mononuclear complexes of copper(II) and molybdenum(VI) of this ligand with general formulas ([Cu(L)Im] (1)), ([Cu(L)NH3]·4H2O (2)), and ([MoO2(L)1-MeIm] (3), Imidazole: Im, 1-methylimidazole: 1-MeIm) were prepared and characterized by elemental analyses, IR, proton magnetic resonance Spectroscopy, and ultraviolet–visible techniques. The physico-chemical results suggested that the H2L coordinates in the dianionic tridentate form. Crystal structures of the Cu(II) complexes reveal a square planar configuration surrounded by the dianionic tridentate isothiosemicarbazone (ONN) and Im and NH3for1and2, respectively. The L2-, two oxo, and 1-methylimidazole are coordinated to molybdenum(VI) in a distorted octahedral geometry in3. Formation of pure metal oxide residues was confirmed by thermal degradation of the complexes. [ABSTRACT FROM AUTHOR]

The synthesis of new tetradentate Schiff-base containing N4 donors is described along with the preparation of a series of copper complexes derived from this ligand. These complexes have the form [CuLX]X′, X = OH−, X′ =  (1) or X = X′ = Cl− (2); and [CuL]H2O(ClO4)2 (3), in addition to a copper(I) complex [Cu2L2](ClO4)2 (4). The synthesized compounds were spectroscopically characterized, showing the N4 donor ligand. The single-crystal X-ray structural analysis of 4 demonstrated the dimeric structure and univalent copper. This dimer consists of , two uncoordinated , and one acetonitrile. Each ligand is tetradentate via pyridyl and azomethine nitrogen atoms, providing a strongly distorted tetrahedron around copper(I) despite the pseudo-macrocyclic skeleton of the ligand. These complexes have been evaluated as functional model systems for catechol oxidase enzyme using 3,5-di-tert-butylcatechol (3,5-DTBC) as the test substrate. The catalytic performance of the air oxidation of 3,5-DTBC to the corresponding light absorbing 3,5-di-tert-butylquinone (3,5-DTBQ) at ambient conditions was studied using UV-Vis absorption spectra. Complex 4 exhibits the highest catalytic activity with turnover number of 33 h−1. A kinetic treatment on the basis of the Michaelis–Menten model was applied. Correlation among reactivity, binding constants, electrochemical properties, and the geometry was determined. These correlations showed that the rate of oxidation is linearly correlated with the binding constants for the five coordinate 1 and 2. The catalytic investigations demonstrate that geometrical effects are only one facet of the activity. The probable mechanistic implications of the catalyzed oxidation reactions are discussed. [ABSTRACT FROM PUBLISHER]