Role of metals in enzymatic reactions. Part 5.—Kinetics of ternary complex formation between magnesium and manganese(II) species and 8-hydroxyquinoline

Abstract

The temperature-jump relaxation method has been used to measure the activation parameters for the formation and dissociation of the 1:1 complexes between magnesium and manganese(II) and 8-hydroxyquinoline (oxine) and of the ternary complexes between oxine and the magnesium and manganese(II) complexes of nitrilotriacetate, uramil-NN-diacetate, adenosine-5′-diphosphate, adenosine-5′-triphosphate and polytriphosphate. The results strengthen the previous conclusion that the first ligand has comparatively little influence on the kinetics of the reaction of magnesium with a second ligand, whereas manganese(II) shows similarities to zinc in the reactivity of its complexes. The enzymatic behaviour of magnesium and manganese(II) is discussed in the light of these results.