Potential biochromium sources; kinetic studies on acid- and base-catalyzed aquation of [Cr(ox)2(2-(aminomethyl)pyridine]−

Abstract

Acid-and base-catalyzed hydrolysis of [Cr(ampy)(ox) 2 ] -, where ampy = 2-(aminomethyl)pyridine, leads to successive dissociation of the ligands via concurrent reaction paths, whereas at pH 1-9 only ampy is liberated as a result of spontaneous processes. The first ligand dissociation proceeds via aqua intermediates with one-end bonded ampy (1) or ox ligands (2), respectively, which in alkaline media undergo rapid deprotonation to give the appropriate hydroxo-forms. The kinetics of two reaction stages, namely the chelate ring opening and the ligand liberation, were studied spectrophotometrically. In acidic media, the first stage is much faster than the second, whereas in alkaline solutions, both the stages are characterized by similar rate constants. The dependences of k obs on [H ? ] are as follows: k obs1,H = a 1 ? b 1 /[H ? ], k obs2,H = a 2 ? b 2 [H ? ]. At pH [ 13, rate constants k obs1 , OH and k obs2 , OH are [OH -] independent. The effect of pH on the complex reactivity was rationalized based on proposed mechanisms.

Kinetic studies on acid-catalysed aquation of some [Cr(ox)2(amino acid)]2− complexes

“…In that case, only one possibility of proton attachment (to the coordinated carboxylate group) exists. However, the other possibility is also worth consideration, as it was established for acid-catalysed aquation of Cr ox ð Þ 2 Â ampy ð Þ À , where ampy is 2-(aminomethyl)pyridine [20]. The metastable intermediate (P 1,Aa ) subsequently liberates the monodentate Aa ligand to produce the cis-[Cr(ox) 2 (H 2 O) 2 ] -anion, which under the conditions used in this study does not undergo further ligand substitution.…”

Pyridine: the scaffolds with significant clinical diversity

“…26 Mansour et al investigated the cytotoxicity against MCF-7 and MDA-MB-231 cell lines for some new chemical entities at different concentrations (0-100 mg mL À1 ) via the MTT assay. Compounds (45)(46)(47)(48) were found with the lowest half-maximal inhibitory concentrations (IC 50 ) against those cell lines by cytotoxicity assays. 27 Barresi et al reported vinyl-substituted pyridine (50,51) compounds showing the antitumor activities (in vitro) of the synthesized compounds.…”

“…Both the acetylated compounds exhibited an excellent anti-inammatory activity. [45][46][47] Pavlova et al reported nicotinic acid amides derivatives to have both anti-inammatory and antimicrobial activities. 48 Compound 71 exerted the highest activity.…”