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)₂O₂ and N(imine)₂O₂ 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)₂O₂ to the N(imine)₂O₂ coordination site and one of the propionitrile pendant arms is removed. The heterodinuclear complexes [ZnL²Cu(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.

Keywords:

• Heterodinuclear complex
• Pendant arm ligand
• Unsymmetrical compartmental ligand
• Macrocyclic ligand
• Copper migration
• Crystal structure

Acknowledgments

We are grateful to Mazandaran University of the Islamic Republic of Iran for the financial support. We also express our appreciation to Dr Sahar Rashid Nadimi for measuring the cyclic voltammogram of the samples.