Controlling the Size of Molecular Copper Clusters Supported by a Multinucleating Macrocycle

The use of a nonrigid, pyridyldialdimine-derived macrocyclic ligand (³PDAI₂) enabled the synthesis of well-defined mono-, di-, tri-, and tetra-nuclear Cu(I) complexes in good yields through rational synthetic means. Starting from mono- and diargentous ³PDAI₂ complexes, transmetalation to Cu(I) proceeded smoothly with formation of AgX (X = Cl, I) salts to generate mono-, di-, and trinuclear copper complexes. Monodentate supporting ligands (MeCN, xylNC, PMe₃, PPh₃) were found to either transmetallate with or bind various di- and trinuclear clusters. The solution-phase dynamic behaviors of these species were studied through NMR spectroscopic investigations, and an in-depth study of the trinuclear systems revealed a rate dependence on the identity of the supporting ligand, indicating that ligand dissociation reactions were involved in the dynamic exchange processes. Synthetic investigations further found methods for the purposeful interconversion between the di- and trinuclear systems as well as the synthesis of a pseudotetrahedral tetracopper complex with two μ-Ph supporting ligands.