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Amino acid esters (L) react with [Pd(Eten)(H 2 O) 2 ] 2+ (Eten = N -ethyl ethylenediamine) giving mixed ligand complexes of the type [Pd(Eten)L] 2+ . Base hydrolysis of [Pd(Eten)L] 2+ was studied by pH-stat technique from which rate constants for the base hydrolysis of the esters were obtained. The glycine methyl ester hydrolysed significantly, whereas the methionine methyl and histidine methyl esters hydrolysed much slower. The mode of coordination of the ester plays a role in the catalysis, and possible mechanisms for these reactions are considered. Activation parameters were determined for the hydrolysis of the glycine methyl ester. The effect of the dielectric constant of the medium on the hydrolysis process was also investigated. The B3LYP/LANL2DZ method was used for geometric optimization of the free ligand and the complex using the Gaussian 09 program. The calculations are compared with the kinetic data. In addition, the vibrational frequencies of the molecules were computed for the optimized geometries. [ABSTRACT FROM AUTHOR]

Abstract: Formation equilibria of copper(II) complexes of 2-(aminomethyl)-benzimidazole (AMBI) and the ternary complexes Cu(AMBI)L (L=amino acid, amide, dicarboxylic acid or DNA constituents) have been investigated. Ternary complexes of amino acids or amides are formed by a simultaneous mechanism. Amino acids form the complex Cu(AMBI)L, whereas amides form two complex species Cu(AMBI)L and Cu(AMBI)(LH−1). The ternary complexes of copper(II) with AMBI and dicarboxylic acids or DNA units are formed by a stepwise mechanism, whereby binding of copper(II) to AMBI is followed by ligation of the dicarboxylic acids or DNA components. The values of Δ log 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 AMBI and the aromatic side chains of the bio-active ligands. The solid complexes Cu(AMBI)L where L=1,1-cyclobutanedicarboxylic acid (CBDCA) and malonic acid were separated and identified by elemental analysis and infrared spectroscopy and magnetic moment. The decomposition course and steps for the isolated complexes were analyzed and the kinetic parameters of the non-isothermal decomposition were calculated. The hydrolysis of glycine methyl ester (MeGly) is catalyzed by the Cu(AMBI)2+ complex. The kinetic data is fitted assuming that the hydrolysis reaction proceeds in two steps. The first step, involving coordination of the amino acid ester by the amino and carbonyl groups, is followed by rate-determining attack by OH− ion. The second step involves the equilibrium formation of the hydroxo-complex Cu(AMBI)(MeGly)(OH) followed by intramolecular OH− attack. [Copyright &y& Elsevier]

Acid-base equilibria of the iron(III) complexes of Schiff base synthesized from 2,6-diacetylpyridine and amino alcohol as, glucosamine or ethanolamine were investigated. These complexes are abbreviated as [Fe(dapGH 2)(H 2 O) 2 ]3+ and [Fe(dapEH 2)(H 2 O) 2 ]3+ for glucosamine and ethanolamine respectively. The pKa for induce ionization of the alcohol hydrogen atoms and the coordinated water molecules were also determined. The hepta-coordination mode of Fe(III) ion is evidenced by the hydrolysis data. The equilibrium constants were measured by potentiometric titration at 25 °C and ionic strength 0.1 M NaNO 3 using the non linear least-squares program MINIQUAD-75. The speciations of the various complex species were obtained as a function of pH. DFT calculations were carried out for Schiff base that derived from ethanolamine (dapEH 2) and its ferric complex. Molecular docking studies have proved that dapEH 2 and [Fe(dapEH 2)(H 2 O) 2 ]3+ interact with ribosyltransferase (code: 3GEY) through the amino acids active sites. All suggested ligands and their ferric complexes were screened in vitro against some selected bacteria. The antioxidant properties of the ferric complexes were examined by the DPPH test. [Fe(dapEH 2)(H 2 O) 2 ]3+ showed higher antioxidant activity than the [Fe(dapGH 2)(H 2 O) 2 ]3+. The IC 50 values of [Fe(dapEH 2)(H 2 O) 2 ]3+ complex and [Fe(dapGH 2)(H 2 O) 2 ]3+ complex were found to be 160.18 and 394.3 µg/ml respectively. [ABSTRACT FROM AUTHOR]