Electrochemical behavior of the tris(pyridine)-Cu funnel complexes: an overall induced-fit process involving an entatic state through a supramolecular stress.

The electrochemical behavior of the tris(pyridine) calix[6]arene Cu adducts is unique as compared to that of most classical Cu complexes in a strain-free environment. The presence of MeCN buried inside the cavity is a prerequisite for a quasi-reversible behavior in a dynamic mode. The CV behavior assisted by simulation outlines that the coordination adaptability of the Cu(II)/Cu(I) redox states is completely reversed, with a Td geometry enforced at either redox states. Hence, the supramolecular control of the Cu coordination by a protein-like pocket determines the dynamics of the electron transfer process, its thermodynamics, and the kinetics of the reorganizational barrier and generates a preorganized state for oxidation. This redox behavior corresponds to an overall induced-fit process generating a truly entatic highly oxidizing Cu(II) state through a protein-like strain by involvement of the secondary coordination sphere.