Synthesis and biophysicochemical studies of some transition metal complexes from benzimidazole derivatives and some bioactive ligands / Mohammad Saied Ali Esmail Mansour ; Supervised Fakiha Eltaib Heakal , Ahmed A. Elsherif

Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Inorganic Chemistry

Binary and mixed-ligand complexes of zinc(II) involving 1-H-benzimidazole-2-carboxylic acid (BCA) and amino acids, peptides (HL), dicarboxylic acid or DNA constituents have been investigated. The stepwise stability constants of BCA with some selected bivalent transition metal ions were also determined in 0.1 mol.dm⁻³ NaNO₃. In terms of the nature of metal ion, the complex stability follows the trend Cu²⁺ > Ni²⁺ > Co²⁺ > Zn²⁺, being in agreement with the Irving-Williams{u2019} order of metal ions. Thermodynamic parameters for Zn(II)-BCA complex as a representative example of M(II)-BCA complex formation were derived and discussed. Amino acids form the complex Zn(BCA)L, whereas amides form two complex species Zn(BCA)L and Zn(BCA)(LH-1).Stability of the ternary complexes was quantitatively compared with their corresponding binary complexes in terms of the parameters xlog K, log ÝStat and log X. The effect of side chains of amino acid ligands (xR) on the complex formation was discussed. Values of xlog K indicate that the ternary complexes containing aromatic amino acids are significantly more stable than the complexes containing alkyl- and hydroxyalkyl-substituted amino acids. This may be taken as an evidence for a stacking interaction between the aromatic moiety of BCA and the aromatic side chains of the bio-active ligands. Concentration distributions of various species formed in solution were also evaluated as a function of pH. The structure of the M(II) complexes have been geometrically optimized and results of molecular parameters support well the experimental formation constants of these complexes. The synthesized complexes were characterized using different tools of analysis and their biological activities were investigated

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