Complexation of Pendant Arm Macrocycles with Cu(II) Hydroxo Complexes in Strongly Alkaline Solutions. Investigation of pH Dependences

Abstract

Abstract The complexation kinetics of fully deprotonated pendent arm macrocyclic ligands with Cu(II) hydroxo species had been investigated in aqueous solution at high pH. The pH dependence of the initial second order reaction is explained by the different reactivities for the tris- and tetra-hydroxo species of Cu(II). In some instances, the pendent arms accelerate the rates of the complex formation reaction. An intermediate complex is observed which reacts in a first order reaction to the final complex. The pH dependence of this reaction is the result of the existence of different numbers of aquo and hydroxo ligands additionally coordinated to the metal. Spectral changes for this second step are small, suggesting an isomerisation reaction is taking place.