Hanan F. Abd El-Halim

Synthesis, structural, thermal studies and biological activity of a tridentate Schiff base ligand and their transition metal complexes.

Schiff base (L) ligand is prepared via condensation of pyridine-2,6-dicarboxaldehyde with -2-aminopyridine. The ligand and its metal complexes are characterized based on elemental analysis, mass, IR, solid reflectance, magnetic moment, molar conductance, and thermal analyses (TG, DTG and DTA). The molar conductance reveals that all the metal chelates are non-electrolytes. IR spectra shows that L ligand behaves as neutral tridentate ligand and bind to the metal ions via the two azomethine N and pyridine N. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral (Cr(III), Fe(III), Co(II), Ni(II), Cu(II), and Th(IV)) and tetrahedral (Mn(II), Cd(II), Zn(II), and UO2(II)). The thermal behaviour of these chelates shows that the hydrated complexes losses water molecules of hydration in the first step followed immediately by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as, E*, ΔH*, ΔS* and ΔG* are calculated from the DTG curves using Coats-Redfern method. The synthesized ligand, in comparison to their metal complexes also was screened for its antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, Staphylococcus pyogones and Fungi (Candida). The activity data shows that the metal complexes to be more potent/antibacterial than the parent Schiff base ligand against one or more bacterial species.

Ligational behaviour of lomefloxacin drug towards Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO2(VI) ions: Synthesis, structural characterization and biological activity studies

Nine new mononuclear Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), Th(IV) and UO(2)(VI) complexes of lomefloxacin drug were synthesized. The structures of these complexes were elucidated by elemental analyses, IR, XRD, UV-vis, (1)H NMR as well as conductivity and magnetic susceptibility measurements and thermal analyses. The dissociation constants of lomefloxacin and stability constants of its binary complexes have been determined spectrophotometrically in aqueous solution at 25±1°C and at 0.1 M KNO(3) ionic strength. The discussion of the outcome data of the prepared complexes indicate that the lomefloxacin ligand behaves as a neutral bidentate ligand through OO coordination sites and coordinated to the metal ions via the carbonyl oxygen and protonated carboxylic oxygen with 1:1 (metal:ligand) stoichiometry for all complexes. The molar conductance measurements proved that the complexes are electrolytes. The powder XRD study reflects the crystalline nature for the investigated ligand and its complexes except Mn(II), Zn(II) and UO(2)(II). The geometrical structures of these complexes are found to be octahedral. The thermal behaviour of these chelates is studied where the hydrated complexes lose water molecules of hydration in the first steps followed by decomposition of the anions, coordinated water and ligand molecules in the subsequent steps. The activation thermodynamic parameters are calculated using Coats-Redfern and Horowitz-Metzger methods. A comparative study of the inhibition zones of the ligand and its metal complexes indicates that metal complexes exhibit higher antibacterial effect against one or more bacterial species than the free LFX ligand. The antifungal and anticancer activities were also tested. The antifungal effect of almost metal complexes is higher than the free ligand. LFX, [Co(LFX)(H(2)O)(4)]·Cl(2) and [Zn(LFX)(H(2)O)(4)]·Cl(2) were found to be very active with IC50 values 14, 11.2 and 43.1, respectively. While, other complexes had been found to be inactive at lower concentration than 100 μg/ml.

Lanthanide amino acid Schiff base complexes: synthesis, spectroscopic characterization, physical properties and in vitro antimicrobial studies

Abstract Complexes of La (III), Nd(III), Gd(III), Sm(III), and Ce(IV) were synthesized with Schiff base [(3,5-di-tert-butyl-2-hydroxybenzyl) amino] acetic acid (H 3 L). The ligand and its complexes were synthesized and characterized based on the following analysis: elemental analyses, FAB-mass, molar conductance measurements, magnetic measurement, UV-visible, IR, and NMR spectral studies. The spectral data revealed that the ligand acted as a neutral tridentate coordinating to metal ion through ONO donor sequence. Thermal degradation studies of the ligand and its complexes showed that the previous lanthanide complexes were more thermally stable than the ligand itself. The Schiff base and its complexes were screened for their antibacterial ( Escherichia coli, Staphylococcus aureus ) and antifungal ( Aspergillus flavus and Candida Albicans ).

Metalloantibiotics: Synthesis and Antimicrobial Activity of Clotrimazole Metal Chelates, Spectroscopic, and Thermal Characterization

Metal complexes of clotrimazole (CLMZ) drug were prepared and characterized based on elemental analyses, IR, magnetic moment, molar conductance, and thermal analyses techniques. The complexes have the general formulae [MCl2(H2O)2(L)2].yH2O (where M = Mn(II), Cu(II)), Co(II), Ni(II), Zn(II), y = 0 − 3) and [MCl2(H2O)2(L)2]Cl.yH2O (where M = Cr(III) and Fe(III), y = 0 − 3). The molar conductance data reveal that bivalent metal chelates are non-electrolytes while Cr(III) and Fe(III) chelates are of 1:1 electrolytes. IR spectra show that CLMZ is coordinated to the metal ions in a neutral unidentate manner with N donor site of the imidazole–N. The geometrical structures of these complexes are octahedral. The thermal behaviour of these chelates was studied and the activation thermodynamic parameters are calculated using Coats-Redfern method. CLMZ and its metal complexes were screened for their antibacterial activity against bacterial and fungi species. The metal complexes are found to have more biological activity than the parent CLMZ drug.