Redox-driven intramolecular anion translocation between a metal centre and a hydrogen-bond-donating compartment

Dicationic ligands incorporating two 2,2'-bipyridine units and two imidazolium moieties, [1](2+) and [2](2+), form stable chelate complexes with Cu-II and Cu-I in acetonitrile solution. Each Cu-II complex binds two X- ions according to two stepwise equilibria, the first involving the Cu-II centre and the second involving the bis-imidazolium compartment. Cu-I complexes are able to host only one NO3- ion in the bis-imidazolium cavity, while other anions induce demetallation. Thus, in the presence of one equivalent of NO3-, the Cu-II/Cu-I redox change makes the anion translocate quickly and reversibly from one binding site to the other within the [Cu-II,Cu-I(1)](4+/3+) system, as demonstrated by cyclic voltammetry and controlled-potential electrolysis experiments.