Kinetics of ternary complex formation between magnesium species and 5-nitrosalicylic acid

Abstract

The temperature-jump relaxation method has been used to measure the rate constants and activation parameters for the formation and the dissociation of the 1 : 1 complex between magnesium and 5-nitrosalicylic acid (nsa) and of the ternary complexes between nsa and the magnesium-nitrilo-triacetate, -adenosine-5′-triphosphate and -polytriphosphate complexes. The results are compared with those of a previous study with 8-hydroxyquinoline (oxine) and it is shown that the complex formation data can be rationalized in terms of the normal dissociative model provided the local charge densities on the metal ion and the coordinating atom of the incoming ligand are considered rather than the overall charges. The Hückel LCAO method has been used to estimate the net charges on the various atoms of nsa^2– and the oxine molecule and monoanion.