Linear enthalpy relationships in co-ordination reactions of macrocyclic ligands with copper(II)

Abstract

The heats of protonation of 12-(3′,5′-dibromo-2′-hydroxybenzyl)-1,4,7,10-tetraazacyclotridecane-11,13-dione (hdbtado) have been determined in aqueous solution at 25 ± 0.1 °C and I= 0.1 mol dm^–3(KNO₃) by means of a model RD-1 automatic conduction calorimeter. The heats of formation of binary complex compounds of this ligand with Cu^II and ternary complex compounds of this ligand with Cu^II–5-substituted phenanthrolines have also been determined under identical conditions. By utilizing the calorimetric data, the heats of formation of the ternary complex compounds Cu^II–α-amino acid–hdbtado have been evaluated. Some linear enthalpy relationships have been found to exist between the heats of protonation of the ligands and the heats of formation of the ternary complex compounds.