Synthesis, characterization, solution stability studies, electrochemistry, and DNA-binding behavior of Cu(II) complexes of D-gluconic acid

The chemistry of saccharides has emerged as a new subarea of pharmaceuticals. Condensation reactions of D-gluconic acid with [M(en)(2) ]Cl-2 /[M(ea)(2) ]Cl-2 where M=Cu, Ni, en=ethylenediamine, and ea=ethanolamine were carried out and a new series of chiral complexes have been isolated and characterized. Molar conductance measurements show that the complexes are ionic, and the spectral data are indicative of octahedral geometry of the complexes [Cu(D-GlcCO(2) H en*)(2) (H2O)(2) ] center dot Cl-2 (1b), [Cu(D-GlcCO(2) H ea*) (H2O)(2) ] center dot Cl-2 (3b) and [Ni(D-GlcCO(2)H ea*) (H2O)(2)] center dot Cl-2 (4), and the square planar geometry of complex [Ni(D-GlcCO(2)H en*)(2) ] center dot Cl-2 (2b). Polarimetric data along with CD spectra establish the chiral nature of complexes. Solution stabilities of these complexes were evaluated by cyclic voltammetric techniques as a function of pH. Electrochemical behavior of the complexes was studied in aqueous solution and showed an irreversible Cu-II /Cu-I couple. Kinetic studies of complex 1b and 3b with calf thymus DNA have been investigated spectrophotometrically under pseudo-first order conditions, and k(obs) values have been evaluated. Circular dichroism, cyclic voltammetry determinations, and viscosity measurements have also been carried out to authenticate the binding of DNA with metal complexes. Complexes 1b and 3b bind to DNA by covalent bond formation.