Feature Article: Macromolecules Containing Pendent Cationic Cyclopentadienyliron Moieties

This feature article describes the synthesis of various classes of monomers and polymers incorporating organoiron moieties. Polyethers incorporating η6-substituted-arene-η5-cyclopentadienyliron moieties were synthesized via metal-mediated nucleophilic aromatic substitution reactions. Linear polymers incorporating both cationic and neutral organoiron units were prepared; these polymers underwent two electrochemical processes, oxidation of the neutral iron species occurred between 0.89 and 1.0 V and reduction of the cationic iron groups occurred between −1.10 and −1.45 V. Polynorbornenes, polymethacrylates, and polystyrenes were prepared via radical and condensation polymerization of organoiron functionalized monomers. The incorporation of azo dyes into the polymers gave rise to a variety of colored materials that could be photobleached in the presence of hydrogen peroxide. The incorporation of benzothiazole-based dyes resulted in colored polymers with higher λmax values than azobenzene-based dyes. Photolytic decoordination of the cationic cyclopentadienyliron moieties resulted in the formation of organic analogs or neutral polyferrocenes depending on the nature of the starting polymers. A number of 3-arm star-shaped molecules were also prepared; electrochemical studies showed that the inner and outer iron moieties are reduced at different potentials.