Two novel macrocyclic monooxo-tetraamines and the stabilities of their Cu(II) complexes

The synthesis and characterization of two novel macrocyclic monooxo-tetraamines: 1,4,8,11-tetraazacyclotetradecane-3-one (1) and 1,4,7,10-tetraazacyclododecane-2-one (2) are described. Equilibrium constants for their Cu(II) complexes were determined by direct potentiometry. The formation constants (KMH−1L=[MH−1L]/[M][L][H−1]) of Cu(II)−1 in 0.100 M KCl at 25.0 °C is 1013.26; that for the 2 isomer is 103.35. The pM values of ligands 1 and 2 are 17.9 and 8.5, respectively. The results are compared with three monooxo-macrocyclic tetraamines (3, 4, 5) and some dioxomacrocyclic tetraamines.