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The protonation constants for the macrocyclic ligands 1,15,18-triaza-3,4;12,13-dibenzo-5,8,11-trioxa cycloeicosane (NdienOdienH4), 1,12,15-triaza-3,4;9,10-dibenzo-5,8-dioxa cycloheptadecane (NdienOenH4), and 1,15-diaza-3,4;12,13-dibenzo-5,8,11-trioxa cycloheptadecane (NenOdienH4) have been determined by the potentiometry in aqueous solutions (25℃, I = 0.1, KNO3). The stability constants for complexes formed in the aqueous solution (25℃, I = 0.1, KNO3) between the above ligands and the metal ions (Co(Ⅱ), Ni(Ⅱ), and Cu(Ⅱ)) have been measured by potentiometry. The rate of the ligand substitution reaction was measured spectrophotometrically by the addition of aqueous solutions of ethylenediamine to the solution of the complex. From the study of the temperature effect on the rate constant (kobs), activation parameters (Ea,△H≠, and △S≠) have been determined. The possible mechanism for the substitution reaction is proposed.
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