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Proton-ligand association constants of 1-benzoyl(1,2,4-triazol-3-yl)thiourea (BTTU) and its complex formation constants with some bivalent metal ions Ni(II), Co(II), Mn(II), Zn(II), and Cu(II), have been determined potentiometrically in 50% EtOH–H2O and 0.1 M NaNO3. The complexes formed in solution have a stoichiometry of 1:1 and 1:2 [M:L], where M represents the metal ion and L the BTTU ligand. The corresponding thermodynamic parameters are derived and discussed. The complexes are stabilized by enthalpy changes and the results suggest that complexation is an enthalpy-driven process. The effects of metal ion, ionic radius, electronegativity, and nature of ligand on the formation constants are discussed. The formation constants of the complexes with 3d transition metals follow the order Mn2+ < Co2+ < Ni2+ < Cu2+ > Zn2+. The metal complexes were synthesized and characterized by elemental analyses, conductance, IR,1H NMR, and magnetic measurements. The low magnetic moment of 0.11 BM for the Cu(II) complex is suggestive of dimerization through Cu–Cu interaction. The concentration distribution diagrams of the complexes were evaluated. The ligands and their metal complexes have been screenedin vitroagainst some bacteria and fungi. [ABSTRACT FROM AUTHOR]

Abstract: Pd(DHP)Cl2 and Pd(DHP)(CBDCA) complexes (DHP=1,3-diamino-2-hydroxopropane and CBDCA=1,1-cyclobutanedicarboxylate), were synthesized and characterized by elemental analysis, IR and NMR spectral measurements. The coordination of [Pd(DHP)(H2O)2]2+ with some selected bio-relevant ligands, containing different functional groups was investigated. The ligands used are amino acids, peptides, DNA constituents and dicarboxylic acids. Stoichiometry and stability constants of the complexes formed are reported at 25°C and 0.1M ionic strength. The results show the formation of 1:1 complexes with amino acids and dicarboxylic acids. DNA constituents form 1:1 and 1:2 complexes. Peptides form both 1:1 complexes and the corresponding deprotonated amide species. The effect of chloride ion concentration and dioxane on the acid dissociation constants of 1,1-cyclobutane dicarboxylic acid (CBDCAH2) and the formation constant of its complex with Pd(DHP)2+ was reported. The equilibrium constants for the displacement of coordinated ligands as uracil, glycine or methionine by cysteine are calculated. The results are expected to contribute to the chemistry of antitumour agents. [Copyright &y& Elsevier]