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 CuL2-, CuLH and CuLH2 have been identified and their stability constants determined.

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