Fine-tuning the electronic properties of highly stable organometallic Cu^III complexes containing monoanionic macrocyclic ligands

A family of highly stable organometallic CuIII complexes with monoanionic triazamacrocyclic ligands (L′) with general formula [CuL′]+ have been prepared and isolated, and their structural, spectroscopic, and redox properties thoroughly investigated. The HL' ligands have been designed in order to understand and quantify the electronic effects exerted by electron donor and electron-withdrawing groups on either the aromatic ring or the central secondary amine or on both. In the solid state the Cu III complexes were mainly characterized by single-crystal X-ray diffraction analysis, whereas in solution their structural characterization was mainly based on 1H NMR spectroscopy given the diamagnetic nature of the d8 square-planar CuIII complexes. Cyclic voltammetry together with 1H NMR and UV/Vis spectroscopy have allowed us to quantify the electronic effects exerted by the ligands on the CuIII metal center. A theoretical analysis of this family of CuIII complexes has also been undertaken by DFT calculations to gain a deeper insight into the electronic structure of these complexes, which has in turn allowed a greater understanding of the nature of the UV/Vis transitions as well as the molecular orbitals involved. © 2005 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.