Electroorganic reactions.: Part 55.: Quinodimethane chemistry.: Part 3.: Transition metal complexes as inter- and intra-molecular redox catalysts for the electrosynthesis of poly(p-xylylene) (PPX) polymers and oligomers

The role of metal complexes as redox mediators in the electrosynthesis of poly(p-xylylenes) (PPXs) has been explored, with a view to designing metal-containing precursors that can act both as mediators and starting materials for metal-containing polymers. A number of transition metal complexes [Cr(iii), Ni(II) and Co(ii)] are efficient-redox catalysts for production of quinodimethanes, and hence PPXs. Following encouraging results from experiments using mediators based on anthranilic acid and salicylaldehyde ligands a macrocyclic compound was designed, and successfully prepared by a convergent route that incorporated both a 1,4-bis(chloromethylarene) function as a precursor to a quinodimethane and a Ni(II) salen unit as an intramolecular redox catalyst. The macrocycle was successfully reduced cathodically to yield a PPX polymer with bound Ni(ii). Evidence is presented for the operation of intramolecular redox catalysis (homomediation).