Electroactive films of polypyrroles containing complexing cavities preformed by entwining ligands on metallic centers

Article abstract of DOI:10.1021/ja00041a012

New functionalized polypyrrole films containing transition metal complexes have been prepared and studied. The strategy is based on the three-dimensional template effect of a metal center (Cu¹, Co^II, Zn^II, Ag¹) able to entwine two end-functionalized chelating ligands before polymerization (Figure 2). The ligands used consist of a 2,9-diphenyl-l, 10-phenanthroline subunit (dpp) bearing two pyrrole nuclei. The pseudotetrahedral geometry of the precursor complex is such that after polymerization of the N-anchored pyrrole rings, a highly entangled network is obtained. The rigidity of the polymer matrix is sufficient to allow demetalation of the template center (by CN^- or SCN^-) without collapse of the three-dimensional structure. Such a property is related to the expected complex topology of the material prepared. The organic backbone certainly contains interlocking rings and various network substructures. The free ligand polymer film can be recomplexed using an appropriate metal source. The polymer matrix thus keeps a memory of the templating metal used for building it. Copper(I) turned out to be the most convenient template during the polymer electrosynthesis and seemed to lead to the most structured network. The various complexes obtained using the electrosynthesis method display electrochemical properties analogous to those of the corresponding catenates in solution. Here again, low oxidation states like copper(I), cobalt(I), formal zinc(I), and silver(0) are remarkably stabilized by the entwined and entangled system. Conductivity measurements and detailed electrochemical and spectroelectrochemical studies on several films have been carried out.