HgII-Mediated TlI-to-TlIII Oxidation in Dynamic PbII/Tl Porphyrin Complexes

Compared with their purely organic counterparts, molecular switches that are based on metal ion translocations have been underexplored, and more particularly, it remains challenging to control the translocation of several particles in multisite receptors. Recently, bimetallic complexes that undergo double translocation processes have been developed with bis-strapped porphyrin ligands. To implement a redox control for these systems, we have investigated the formation of heterobimetallic lead/thallium complexes, with thallium in the +I and +III oxidation states. Two different complexes were characterized: 1) a Pb^II/Tl^I complex, in which both metal ions interact with the N-core on its different sides, and 2) a Pb^II/Tl^III complex with Tl^III selectively bound to the N-core and Pb^II selectively bound to the strap opposite to Tl^III. These two complexes undergo interconversion between their two degenerate forms (same coordination of the metal ions but on opposite sides) by different intra or intermolecular translocation pathways. In addition, conversion of the Pb^II/Tl^I complex into its Pb^II/Tl^III counterpart was achieved by addition of a stoichiometric amount of Hg^II salt as a sacrificial electron acceptor. These results further contribute to the elaboration of devices that feature redox-controlled compartmentalized double translocations.