Abstract
A ligand consisting of a 2,2′‐bipyridine core and two 4,4′‐bipyridinium arms terminated by a thiol group is prepared following a multistep synthetic procedure. Two of these ligands assemble around a single CuI center as a result of the tetrahedral coordination of their 2,2′‐bipyridine cores by the metal. Both the ligand and the complex adsorb spontaneously on the surface of polycrystalline‐gold electrodes. The surface coverage of the films prepared by immersing a gold substrate into a solution of the ligand increases from monolayer to multilayer values with immersion time. Instead, the complex can only form monolayers. The cyclic voltammograms of the resulting films show the characteristic response for the reversible reduction of the 4,4′‐bipyridinium dications to their radical cations. In the case of the complex, a wave for the monoelectronic oxidation of the metal center can also be observed. The back reduction wave, however, is markedly broader and appears at significantly lower potentials. Model studies in solution indicate that this response is a result of the presence of free thiol groups and is consistent with a change in the coordination geometry of the metal. Specifically, the oxidation of the CuI center to a CuII ion is, presumably, accompanied by the folding of one of the thiol groups back to interact with the metal. Thus, oxidation/reduction cycles of the metal center can, in principle, be exploited to control reversibly large amplitude molecular motions at the electrode/solution interface in the shape of the folding/unfolding of oligomethylene chains.
Multicomponent building blocks incorporating 4,4′‐bipyridinium dications and CuI centers adsorb spontaneously on the surface of polycrystalline‐Au electrodes. Both redox couples can be addressed independently in the resulting electroactive films. The oxidation of the metal center is, presumably, followed by large amplitude motions involving the folding of one of the four 4,4′‐bipyridinium arms (see figure).
