Homo and heterodinuclear complexes derived from unsymmetrical macrocyclic ligands with two coordination sites: Removal of a pendant arm and migration of copper ion upon cyclization

Abstract

The dinucleating macrocyclic ligands (L 2a) 2- and (L 2b) 2- were prepared by [1:1] cyclic condensation of N,N′-dipropionitrile-N,N′-ethylene-di(5-methyl-3-formyl-2- hydroxybenzylamine or N,N′-dipropionitrile-N,N′-ethylene-di(5-bromo- 3-formyl-2-hydroxybenzylamine with 1,3-diaminopropane. The ligands include dissimilar N(amine) 2O 2 and N(imine) 2O 2 coordination sites sharing two phenolic oxygen atoms and containing two propionitrile pendant arms on the amine nitrogen atoms. A series of mono- and dinuclear complexes were synthesized and characterized on the basis of elemental analysis, molar conductance measurement, X-ray crystallography, IR, NMR, and UV-Vis spectroscopies as well as cyclic voltammetric measurements. During the cyclization copper(II) migrates from the N(amine) 2O 2 to the N(imine) 2O 2 coordination site and one of the propionitrile pendant arms is removed. The heterodinuclear complexes [ZnL 2Cu(OAc)] + were prepared by a transmetallation reaction. The characterization results showed that the two metal ions are bridged by two phenolic oxygen atoms and an acetate group, providing distorted five-coordinate geometries for both metals. © 2012 Taylor & Francis.