Metal Complexes of Schiff Bases: Preparation, Characterization, and Biological Activity

Authors : Gehad Geindy MOHAMED, Mohamed Mohamed OMAR, Ahmed Mohamed HINDY

Pages : 361-382

View : 17 | Download : 8

Publication Date : 0000-00-00

Article Type : Research Paper

Abstract :Metal complexes of Schiff bases derived from 2-furancarboxaldehyde and o-phenylenediamine insert ignore into journalissuearticles values(L1);, and 2-thiophenecarboxaldehyde and 2-aminothiophenol insert ignore into journalissuearticles values(HL2); are reported and characterized based on elemental analyses, IR 1H NMR, solid reflectance, magnetic moment, molar conductance, and thermal analysis insert ignore into journalissuearticles values(TGA);. The ligand dissociation, as well as the metal-ligand stability constants were calculated, pH-metrically, at 25 °C and ionic strength m = 0.1 insert ignore into journalissuearticles values(1 M NaCl);. The complexes are found to have the formulae [Minsert ignore into journalissuearticles values(L1);insert ignore into journalissuearticles values(H2O);2]insert ignore into journalissuearticles values(Cl);n \cdot yH2O insert ignore into journalissuearticles values(where M = Feinsert ignore into journalissuearticles values(III);, Niinsert ignore into journalissuearticles values(II);, Cuinsert ignore into journalissuearticles values(II);; n = 2-3, y = 2-4);; [Minsert ignore into journalissuearticles values(L1);]insert ignore into journalissuearticles values(X);2 \cdot yH2O insert ignore into journalissuearticles values(where M = Coinsert ignore into journalissuearticles values(II);, Zninsert ignore into journalissuearticles values(II);, UO2insert ignore into journalissuearticles values(II);, X = Cl, AcO or NO3, y = 1-3);; [Minsert ignore into journalissuearticles values(L2);2] \cdot yH2O insert ignore into journalissuearticles values(where M = Coinsert ignore into journalissuearticles values(II);, Niinsert ignore into journalissuearticles values(II);, Cuinsert ignore into journalissuearticles values(II);; X = Cl; y = 0-2 and Zninsert ignore into journalissuearticles values(II);; X = AcO, y = 0);; and [Feinsert ignore into journalissuearticles values(L2);2]Cl \cdot 2H2O and [UO2insert ignore into journalissuearticles values(HL2);2]insert ignore into journalissuearticles values(NO3);2. The molar conductance data reveal that all the metal chelates of the L1 ligand, and Feinsert ignore into journalissuearticles values(III); and UO2insert ignore into journalissuearticles values(II); chelates of HL2 are electrolytes, while Coinsert ignore into journalissuearticles values(II);, Niinsert ignore into journalissuearticles values(II);, Cuinsert ignore into journalissuearticles values(II);, and Zninsert ignore into journalissuearticles values(II); chelates of HL2 are non-electrolytes. IR spectra show that L1 is coordinated to the metal ions in a tetradentate manner, with ONNO donor sites of azomethine--N and furan-O, whereas the HL2 ligand is coordinated to the metal ions in a terdentate manner with SNS donor sites of azomethine--N, thiophene-S, and thiol-S. From the magnetic and solid reflectance spectra, it is found that the geometrical structures of these complexes are octahedral and tetrahedral. The thermal behavior of these chelates shows that the hydrated complexes lose water molecules of hydration in the first step and is immediately followed by decomposition of the anions and ligand molecules in the subsequent steps. The activation thermodynamic parameters, such as E*, D H*, D S*, and D G*, are calculated from the DrTG curves using the Coats-Redfern method. The synthesized ligands, in comparison to their metal complexes, were also screened for their antibacterial activity against bacterial species, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus Pyogones, as well as fungi insert ignore into journalissuearticles values(Candida);. The activity data show the metal complexes to be more potent antibacterials than the parent Schiff base ligand against one or more bacterial species.
Keywords : 2 thiophenecarboxaldehyde, 2 furancarboxaldehyde, 2 aminothiophenol, o phenylenediamine, transition metal complexes, stability constants, IR, 1H NMR, conductance, solid reflectance, magnetic moment, thermal analysis, biological activity