Tuning the structural and catalytic properties of copper(II)-based complexes containing pyridine-2,6-diimines.

Four mononuclear penta coordinated copper(II) chelates, [CuLnBr2] nH2O, containing the tridentate neutral ligands, pyridine-2,6-diimine (Ln), were prepared via the template technique. Analytical and several physicochemical methods have been used to characterize the prepared metal chelates. Square-pyramidal stereochemistry was described to the current copper(II) complexes. DFT technique has been applied to optimize the structure of the running diimines and their corresponding copper-based compounds. Ligand substitution study performed to link the catalytic potency of the candidate oxidase mimics and their lability characters. Spectral investigations reveal that nature of substituents of the chelated ligands effectively tuning the Lewis acidity of copper(II) centers. Biomimetics of redox proteins specifically containing copper were examined towards the aerobic oxidation of polyphenol. Kinetic studies with the stopped-follow technique showed a close association between the Lewis acidity of the copper(II) nuclei of the prepared chelates and their oxidase-like activity. The catalytic activity of the natural enzyme (catechol oxidase from sweet potatoes) measured and compared with that for the present CuII chelates. The thermodynamic parameter drive force (ΔG° or λ) of the performed oxidation processes was determined from the values of redox potential of the chemical species involved in these catalytic reactions. The proposed catalytic reactions pathways have been discussed based on the outcomes of the kinetic investigations.Communicated by Ramaswamy H. Sarma.

Spectroscopic, thermal and antitumor investigations of sulfasalazine drug in situ complexation with alkaline earth metal ions.

The complexes of sulfasalazine (H(3)Suz) with some of alkaline metals Mg(II), Ca(II), Sr(II) and Ba(II) have been investigated. Sulfasalazine complexes were synthesized and characterized by spectroscopic tools; infrared spectra, electronic and mass spectra. The IR spectra of the prepared complexes were suggested that the H(3)Suz behaves as a bi-dentate ligand through the carboxylic and phenolic groups. The molar conductance measurements gave an idea about the non-electrolytic behavior of the H(3)Suz complexes. The thermal decomposition processes for metal(II) complexes of H(3)Suz viz: [M(HSuz)(H(2)O)(4)] (where M = Mg(II), Ca(II), Sr(II) or Ba(II)) have been accomplished on the basis of TG/DTG and DTA studies, and the formula conforms to the stoichiometry of the complexes based on elemental analysis. The kinetic analyses of the thermal decomposition were studied using the Coats-Redfern and Horowitz-Metzger equations. The antitumor and antimicrobial activities of the H(3)Suz and their alkaline metal(II) complexes were evaluated.