Kinetic and mechanistic studies on the interaction between glycylglycine and cis-diaqua-bis-(bipyridine)-ruthenium(II) complex in aqueous medium

Abstract

The kinetics of interaction between glycylglycine and cis-[Ru(bipy) 2 (H 2 O) 2 ] 2+ have been studied spectrophotometrically as a function of [Ru(bipy) 2 (H 2 O) 2 2+ ], [diglycine] and temperature at a particular pH (4.8), where the substrate complex exists predominantly as the diaqua species and diglycine as the zwitter ion. The reaction has been found to proceed via two consecutive steps. The first step involves the ligand-assisted anation, while the second step involves chelation when the second aqua ligand is displaced. Rate constants have been evaluated and activation parameters calculated. The low enthalpy of activation and large negative values of entropy of activation indicate an associative mode of activation for both steps.

Mechanistic aspects of ligand substitution on cis-diaqua(cis-1,2-diaminocyclohexane)platinum(II) by Glycine-l-Leucine

“…The spectrum suggests that the final product is an (N, O) coordinated chelate in which Glyleu behaves as a bidentate ligand. This observation is consistent with other studies [28,29] where (N, N)-platinum complexes bind to amino acids, substituted amino acids and dipeptides through O and N . The molar conductance measurement also provides evidence in favor of the interaction between cis-[Pt(cisdach)(OH 2 )] 2?…”

Kinetic study of the interaction of three glycine‐containing dipeptides with diaquaethylenediamineplatinum(II) in aqueous medium

“…The spectrum suggests that the final product is an (N, O) coordinated chelate in which peptides behave as a bidentate ligand. This observation is consistent with other studies [25,26] where (N,N)-platinum complexes bind to amino acids, substituted amino acids, and dipeptides through O and N.…”

Surface-enhanced Raman spectrum of Gly-Gly adsorbed on the silver colloidal surface

“…So when the pH of the solution is at 3.5, which is just above the pK 1 of the Gly-Gly, the net charge of Gly-Gly is positive and thus amino groups of this sample cannot adsorbed on the positively charged silver surface. As pH value of the solution is 7.5, which is close to the pK 2 of Gly-Gly (8.13) [26], as discussed above, the amino group is attached to the silver surface and deprotonated while small contributions come from the carboxylate group. In addition, the amide group of Gly-Gly adsorbs directly with the silver surface.…”

“…The pK 1 of Gly-Gly is 3.21 [26], and thus some of the carboxylate groups of Gly-Gly have negative charge and most of the amino groups have the positive charge. So when the pH of the solution is at 3.5, which is just above the pK 1 of the Gly-Gly, the net charge of Gly-Gly is positive and thus amino groups of this sample cannot adsorbed on the positively charged silver surface.…”