One-pot synthesis, characterisation and kinetic stability of novel side-bridged pentaazamacrocyclic copper(ii) complexes

Single-step synthetic protocols are reported for novel macrocyclic copper(ii) complexes incorporating a piperazine unit in the ligand backbone. Synchrotron X-ray structure determination confirmed the copper(ii) coordination geometry in the solid state as distorted square pyramidal with chloride occupying the axial position above the N4 ligand plane. DFT calculations, electrochemical studies and UV/vis investigations in biological media all confirmed that compounds in this class have high stability, and compare well in both thermodynamic and kinetic terms with the ubiquitous Cu(ii) cyclam compounds, and are therefore of relevance for future use as synthetic scaffolds for the binding, transport and tracing of copper ions in vitro.