Synthesis of A Novel Spirobisnitroxide Polymer and its Evaluation in an Organic Radical Battery

A straightforward synthesis of a novel spirobisnitroxide 6 has been developed. Cyclovoltammetry of 6 revealed two distinct reversible oxidation/reduction steps separated by ca. 740 mV indicating the formation of the corresponding oxoammonium cations. Rhodium-catalyzed polymerization of 6 afforded the polyacetylene polymer 7 bearing the pending spirobisnitroxide groups. Additionally, cross-linked 7 was prepared in the presence of 3 mol % of N,N′-diprop-2-ynyl-oxalamide. If oxidation of both nitroxide groups is considered, 7 possesses an unprecedented high theoretical charge capacity of 174 mA h g−1. Evaluation of the cross-linked polymer 7 as a cathode material for an organic radical battery showed very good cycling stability when the potential was kept below the oxidation potential of the five-membered nitroxide subunit of 6. A presumable irreversible degradation of the polymeric backbone of 7 occurred at higher potentials, limiting the experimentally obtained charge capacity to 73 mA h g−1.