Thermodynamics and kinetics of dioxygen binding to Co(II) complexes with saturated macrocyclic tetraamines

Some thermodynamic and kinetic aspects of the reactions of dioxygen binding to Co(II) complexes with the two cyclic tetraamines 1,4,7,10-tetraazacyclododecane ([12]aneN(4)) and 1,4,8,11-tetraazacyclotridecane ([13]aneN(4)) are examined. Specifically, results are reported on: (1) the determination of the protonation constants and protonation enthalpies for both [12]aneN(4) and [13]aneN(4) ligands; (2) the study of the kinetics of the formation of the precursor CoL complexes for L = [12]aneN(4) and [13]aneN(4) carried out by monitoring the uptake rate of molecular dioxygen; (3) the recognition of the type of dioxygen adducts formed at various pH values; (4) the determination of the kinetic and thermodynamic data characterising the reactions of isomerization of monobridged mu-peroxo-monohydroxo (CoL)(2)(mu-O(2))(OH) complexes into the dibridged mu-peroxo-mu-hydroxo (CoL)(2)(mu-O(2))(mu-OH) complexes, and the reactions of conversion of the dibridged mu-peroxo-mu-hydroxo (CoL)(2)(mu-O(2))(mu-OH) complexes into the monobridged mu-peroxo-dihydroxo (CoL)(2)(mu-O(2))(OH)(2) complexes. (C) 1999 Elsevier Science Ltd. All rights reserved.