Adel A.A. Emara

Structural, spectral and biological studies of binuclear tetradentate metal complexes of N3O Schiff base ligand synthesized from 4,6-diacetylresorcinol and diethylenetriamine.

The binuclear Schiff base, H2L, ligand was synthesized by reaction of 4,6-diacetylresorcinol with diethylenetriamine in the molar ratio 1:2. The coordination behavior of the H2L towards Cu(II), Ni(II), Co(II), Zn(II), Fe(III), Cr(III), VO(IV) and UO2(VI) ions has been investigated. The elemental analyses, magnetic moments, thermal studies and IR, electronic, 1H NMR, ESR and mass spectra were used to characterize the isolated ligand and its metal complexes. The ligand acts as dibasic with two N3O-tetradentate sites and can coordinate with two metal ions to form binuclear complexes. The bonding sites are the nitrogen atoms of the azomethine and amine groups and the oxygen atoms of the phenolic groups. The metal complexes exhibit either square planar, tetrahedral, square pyramid or octahedral structures. The Schiff base ligand and its metal complexes were tested against four pathogenic bacteria (Staphylococcus aureus and Streptococcus pyogenes) as Gram-positive bacteria, and (Pseudomonas fluorescens and Pseudomonas phaseolicola) as Gram-negative bacteria and two pathogenic fungi (Fusarium oxysporum and Aspergillus fumigatus) to assess their antimicrobial properties. Most of the complexes exhibit mild antibacterial and antifungal activities against these organisms.

Metal complexes of some thiocarbohydrazone ligands: synthesis and structure

The synthesis, structure, physico-chemical investigation and biological studies of some metal complexes of thiocarbohydrazone ligands are described. The ligands were obtained by condensation of N,N′-thiocarbohydrazide with carbonyl compounds such as 2-hydroxyacetophenone or 5-chlorosalicylaldehyde. A variety of binuclear or mononuclear complexes were obtained with the ligands in mono-, bi- and/or tri-deprotonated forms. The bonding sites are the azomethine nitrogen atom, phenolic oxygen atom and thiol sulfur atom. The metal complexes exhibit either tetrahedral or octahedral structures. Preliminary antimicrobial screening showed that the ligands and their metal complexes possess antimicrobial activity towards bacteria and fungi.

INTERMEDIATES IN THE THERMAL DECOMPOSITION OF NORMAL COPPER(II), NICKEL(II) AND COBALT(II) SELENITE DIHYDRATES

Abstract Thermal decomposition of normal transition metal selenite dihydrates, MSeO2.2H2O; M [dbnd] Cu(II), Ni(II), Co(II) was traced by TGA/DTA measurements from 50–700°C. The thermal products were obtained by heating the selenites in an air-oven to different temperatures, as determined from TGA/DTA curves, where different coloured products are obtained. The structures of the start selenites and the thermal intermediates were determined by chemical analyses and FT-IR spectral measurements. The start selenites proved to be equilibrium mixtures of the selenite, hydrogenselenite and/or pyroselenite anions. Gradual changes occurred in the FT-IR spectra of the nickel and cobalt selenites on thermal treatment till 225°C where, due to water loss, merely selenite anions are observed. In the case of the copper selenite, the selenito mixture persists till 250°C and the only change observed in the final product is the disappearance of one of the structurally non-equivalent water molecules present in the start selen...

Novel transition metal complexes of 4-hydroxy-coumarin-3-thiocarbohydrazone: pharmacodynamic of Co(III) on rats and antimicrobial activity.

A new series of stable transition metal complexes of the formula M(L)X·S, where M = Cu(II), Ni(II), Co(III), Cr(III) and Fe(III) and L is the deprotonated ligand of 4-hydroxy-coumarin-3-thiocarbohydrazone, X = Cl(-), NO(3)(-) or CH(3)COO(-) and S = H(2)O and/or EtOH. The HL ligand was prepared by the reaction of 3-formyl-4-hydroxy-coumarine with thiocarbohydrazide in the molar ratio 1:1. The HL ligand and its metal complexes were characterized by elemental analysis, (1)H NMR, IR and electronic spectra, and molar conductance and magnetic measurements and thermal gravimetric analysis (TGA). The HL ligand acts as a monobasic tridentate ONS donor in all metal complexes, and coordinated through the phenolic OH, azomethine nitrogen and thione sulfur. Electronic spectra with magnetic moments suggested varieties of geometries around the central metal atoms. Thermal gravimetric analysis indicates that the complexes are stable up to 300°C, and release the uncoordinated and/or coordinated H(2)O/solvent molecules, which is accompanied by a color change. The formed complexes after releasing the solvent were investigated and their structures are suggested to have square planar or octahedral arrangement. Pharmacodynamic of cobalt(III) complex on some biochemical parameters and histological studies in serum and heart tissue in rats have been studied. Although the complexes demonstrated a significant effect at low dose than the high dose, the ligand showed significant good effects in both high and low doses on the biochemical analysis in serum and heart tissue. Cobalt complex was screened in order to evaluate its antifungal activity against the filamentous fungi Aspergillus niger, Aspergillus fumigatus, and Aspergillus flavus, and antibacterial activity against the Candida albicans, Escherichia coli, Klebseilla pneumoniae and Pseudomonas aeruginosa.

Novel Asymmetric Tetradentate Schiff Base Ligands Derived from 6-Metwia-Formyl4-Hydroxy-2-(1H)-Quinolone and Their Metal Complexes

Abstract Novel asymmetric, tetradentate, dibasic Schiff base ligands were synthesized by the condensation of the half-unit Schiff base ligand 3-[o-aminophenyliminomethyl]-4-hydroxy-6-methyl-2-(1H)-quinolone with acetylacetone and salicylaldehyde. Cu(II), Ni(II), UO2 (VI) and Fe(III) complexes of both ligands were prepared using different salts in the case of Cu(II) and Ni(II) cations The structures of the ligands and the complexes were elucidated by chemical analyses, IR, UV-visible, mass spectra and magnetic moment measurements. Both Cu(II) and Ni(II) cations are initially coordinated to the N2O2 coordinating sites of the ligands The Cu(II) complexes were either square-planar mononuclear compounds, [LCu]. xH2O, or dinuclear compounds, [LCu2(OAc)2], where both square-planar and octahedral geometries exist in the same complex molecule, while the Ni(II) complexes were either diamagnetic square-planar or paramagnetic compounds where both octahedral and square-planar geometries do exist, indicating their anom...

Copper(II), Nickel(II), Oxovanadium(IV) and Dioxouranium(VI) Complexes of Novel Asymmetric Tetradentate Schiff Base Ligands Derived from 6-Methyl-3-Formyl-4-Hydroxy-2-(1H)-Quinolone. Part V

Abstract The novel, half-unit ligand obtained by the single condensation of 6-methyl-3-formyl-4-hydroxy-2-(1H)-quinolone and p-phenylenediamine, was condensed with either acetylacetone or salicylaldehyde to yield novel, asymmetric tetradentate Schiff base ligands, H2La and H2Lb, respectively. The reactions of the ligands with Cu2+, Ni2+, VO2+ and UO2 2+ salts yielded complexes of the general formula [L2M2 nH2O, except that of the uranyl complex of the ligand H2La which has the formula [LaUO2)2(OAc)2(OH2)2]. The ligands and metal complexes were characterized by elemental analyses, IR, UV-visible, mass and ESR spectra and magnetic measurements. The Cu2+ complexes are distored tetrahedral, the Ni2+ complexes are octahedral, the VO2+ complexes are square pyramidal and the UOz z+ complexes are pentagonal bipyramidal The vanadyl and nickel complexes showed antiferromagnetic interaction between adjacent metal cations.

Synthesis, spectroscopic investigations, and biological activity of metal complexes of N-benzoylthiosemicarbazide

N-Benzoylthiosemicarbazide, HL, was obtained by fusion of benzoylhydrazide and ammonium thiocyanate. Reactions of HL with cobalt(II), nickel(II), copper(II), zinc(II), iron(III), cadmium(II), oxovanadium(IV), and dioxouranium(VI) in 1 : 1 molar ratio yield the corresponding complexes. The N-benzoylthiosemicarbazide may act as a neutral or monobasic bidentate ligand coordinated through NS or NO sites. The structures of the HL ligand and its complexes were identified by elemental analysis, infrared, electronic, mass, 1H-NMR, and ESR spectra as well as magnetic susceptibility and molar conductivity measurements. Different geometries were obtained for the metal complexes. The ligand and its metal complexes were investigated for antibacterial and antifungal properties. Two Gram-positive bacteria, Staphylococcus aureus and Streptococcus pyogenes, two Gram-negative, bacteria, Pseudomonas fluorescens and Pseudomonas phaseolicola and two fungi, Fusarium oxysporum and Aspergillus fumigatus, were used in this study. The metal complexes were more effective than the free ligand.

Synthesis, spectroscopic properties, molecular docking, anti-colon cancer and anti-microbial studies of some novel metal complexes for 2-amino-4-phenylthiazole derivative.

This article describes the synthesis of novel bidentate Schiff base (H2L) from condensation of 2-amino-4-phenylthiazole (APT) with 4,6-diacetylresorcinol (DAR) in the molar ratio 2:1. We studied interaction of ligand (H2L) with transition metal ions such as Cr(III), Fe(III), Cu(II), Zn(II) and Cd(II). The ligand (H2L) has two bidentate sets of (N-O) units which can coordinate with two metal ions to afford novel binuclear metal complexes. The directions of coordinate bonds are from nitrogen atoms of azomethine groups and oxygen atoms of the phenolic groups. Structures of the newly synthesized complexes were confirmed by elemental analysis, IR, UV, (1)H NMR, ESR, TGA and mass spectral data. All of the newly synthesized complexes were evaluated for their antibacterial and anti-fungal activities. They were also evaluated for their in vitro anticancer activity against human colon carcinoma cells (HCT-116) and mammalian cells of African green monkey kidney (VERO). The Cu(II) complex with selectivity index (S.I.)=21.26 exhibited better activity than methotrexate (MTX) as a reference drug with S.I. value=13.30, while Zn(II) complex with S.I. value=10.24 was found to be nearly as active as MTX. Molecular docking studies further helped in understanding the mode of action of the compounds through their various interactions with active sites of dihydrofolate reductase (DHFR) enzyme. The observed activity of Fe(III) and Cu(II) complexes gave rise to the conclusion that they might exert their action through inhibition of the DHFR enzyme.

Synthesis, characterization and oxygen affinity of Mn(II), Co(II) and Ni(II) complexes of diethylenetriamine Schiff bases

N,N′-diethyleneamine bis(salicylideneimine); H2DETS and N,N′-diethyleneamine bis(o-hydroxyacetophenoneimine); H2DETHA have been prepared to produce Mn(II), Co(II) and Ni(II) complexes by the addition of the synthesized Schiff bases to the studied ions under nitrogen. H2DETS and H2DETHA are neutral tridentate in the nitrato complexes and binegative pentadentate in the other complexes. A square pyramidal structure was suggested for all complexes based on elemental analysis, molar conductivity, infrared, electronic spectra and magnetic moment measurements. The oxygen absorption properties were studied for the isolated complexes by considering the solubility, oxygen affinity and stability. [Co(DETS)]·4H2O has the highest affinity. Different concentrations for the Co(II) complex were studied.

DI-, TRI- AND POLY-NUCLEAR TRANSITION METAL COMPLEXES OF 3,4-DIACETYL-2,5-HEXANEDIONE

Abstract 3,4-Diacetyl-2,5-hexanedione (tetraacetylethane) is a tetradentate dibasic ligand and constitutes two acetylacetone molecules linked together through the central carbon. The ligand is thus capable of coordinating two metal cations. Its reaction with Cu(II), Ni(II), Co(II), Fe(III) and Cr(III) yielded the corresponding complexes, [(M(L-2H)] for Cu(II) and Ni(II), basic Co(III) complex [Co(L-2H)(OH)] and [M(2L-3H) for Fe(III) and Cr(III). These complexes were characterized by their IR, visible and mass spectra and by magnetic measurements. All complexes have octahedral configurations. The mass spectra of the complexes indicated peaks with m/e values higher than the parent peaks, where Ni(II), and Co(III) complexes are dimers and the Cu(II) complex is trimeric. This coupled with the insolubility of the complexes in all common solvents indicates the polymeric nature of the products.