Nickel and copper complexes with few amide-based macrocyclic and open-chain ligands

The present work shows three new amide-based ligands H2L1, H2L2 and H2L3 and their nickel and copper complexes. The X-ray structural analysis substantiate that the ligands constitute a square-based basal plane around the metal center. The crystal structures also show interesting solid state packing due to hydrogen-bonding and various weak C⋯H interactions. The solution-based spectral studies support the solid-state geometry observed for these complexes. The electrochemical results show that the Ni3+/2+ and Cu3+/2+ redox couple primarily depends on the N4 donors composed of Namide and Namine atoms. It was observed that the ligands H2L1 and H2L2 are better suited to stabilize the Cu(III) species whereas ligand H2L3 is ideal for the stabilization of Ni(III) species. On the basis of electrochemical findings, transient Ni3+ species were generated and characterized by the absorption spectroscopy.

The present work shows Ni(II) and Cu(II) coordination chemistry in a set of amide-based macrocyclic and open-chain ligands. The mononuclear complexes have been characterized by crystallographic, spectral and detailed electrochemical techniques.Figure optionsDownload as PowerPoint slideHighlights
► Ni and Cu chemistry with amide-based macrocyclic and open-chain ligands.
► Ligands constitute square-plane around metal ion as revealed by crystallography.
► Solution state structure by NMR, EPR, and UV–Vis spectroscopy.
► Electrochemistry shows metal- and ligand-centered oxidations.
► Electrochemical generation of Ni3+ species and their characterization.