Cu²⁺ complexes of tetraazacyclododecanes functionalized with benzyl side chains carrying carboxylic or phenolic groups

Abstract

A series of tetra-N-functionalized 1,4,7,10-tetraazacyclododecanes with benzyl side chains carrying carboxylic or phenolic groups have been synthesized. All of these ligands form Cu²⁺ complexes, which have been characterized by elemental analysis, absorption spectra and in two cases (ligands 4 and 7) by an X-ray diffraction study. In both cases the Cu²⁺ is co-ordinated by the four nitrogens of the macrocycle folded in the trans-I configuration and an additional ligand. The additional ligand is CI⁻ for the complex with 4, and a side chain carboxylate group for the complex with 7. In addition potentiometric and spectrophotometric equilibrium measurements of Cu²⁺ with 7 have been run. Three species CuL^2-, CuLH⁻ and CuLH₂ have been identified and their stability constants determined.