Dioxygen dinuclear complex formation of Co(II) with the macrocyclic ligand 3,6,9,17,20,23-hexaazatricyclo[23.3.1.111,15]triaconta-1(29),11(30),12,14,25,26,27-hexaene

Potentiometric equilibrium studies, UV-Vis spectrophotometric and voltammetric measurements were carried out to determine the degree of binding of 4-methoxy-1,2-phenylenediamine with dicobalt(II)-BMXD complexes (BMXD is 3,6,9,17,20,23-hexaazatricyclo[23.3.1.1(11,15)]-triaconta-1(29),11(30),12,14,25,26,27-hexaene) in the absence and presence of dioxygen. Equilibrium constants for complexes formed are reported, the results are presented in the form of distribution diagrams showing the concentrations of individual complexes as a function of p[H]. The log Ks for the oxygenation constants are: 1.74 and 2.02 for mono and dihydroxo complexes, respectively. The mu-peroxo monohydroxo complex is stabilized with an aromatic diamine substrate and the log of the association constant was found to be 4.57. (C) 2003 Elsevier B.V. All rights reserved.