Supramolecular effects on the potential of redox units—nanoscaffolds internally functionalised with ferrocene units

Abstract

Redox-active nanoscale racks and nanoladders were prepared as proof of principle in a directional heteroleptic approach towards internally functionalised aggregates. Using the HETTAP concept, zinc(II) phenanthroline terpyridine nanoladder and nanorack structures with internal ferrocene units were prepared. Proximal effects exerted by the ferrocene units in the nanoladders could be read out by comparison of their redox potentials with those of nanorack R1 and of the parent ligand. The increasing compression of the ferrocene units when going from the larger nanoladder L1 to the smaller aggregate L2 manifested itself in an enlarged anodic shift. Thus, the redox potential series (vs. DMFc: E_1/2 = 0.462 V for R1, 0.480 V for L1 and 0.491 V for L2) reveals convincingly the supramolecular effect on a redox transition. At cathodic potentials the zinc(II) phenanthroline terpyridine complexes were decomposed due to a reduction of the ligands, as could be detected from an evaluation of the ferrocene redox potential.