Functionalization of Water-Soluble Metallopolymer Electrocatalysts for Water-Splitting Using Atom Transfer Radical Polymerization and Click Chemistry

The diverse functionalization of the polymeric support phase of diiron disulfide [2Fe-2S] metallopolymer electrocatalysts offers a route to the enhanced generation of molecular hydrogen via water-splitting. Click chemistry has been shown to be a useful tool in post-polymerization functionalization for a wide range of polymeric materials under mild conditions, which is a requirement for [2Fe-2S] metallopolymers due to the presence of iron carbonyl (Fe-CO) bonds in the active site. In this study, we developed a new synthetic methodology to functionalize [2Fe-2S] metallopolymers using atom transfer radical polymerization (ATRP) and post-polymerization functionalization using azide-alkyne "click" cycloaddition. Azide functional [2Fe-2S] metallopolymers were prepared by the ATRP of 3-azidopropyl methacrylate (AzPMA) with either methyl methacrylate (MMA) or 2-(dimethylamino)ethyl methacrylate (DMAEMA), followed by copper-catalyzed "click" cycloaddition with functional terminal alkynes. Both families of PMMA and PDMAEMA functional [2Fe-2S] metallo-copolymers were found to retain Fe-CO bonds from the catalyst active site after the click chemistry reactions and, more importantly, exhibited high electrocatalytic activity for electrochemical water-splitting under pH-neutral aqueous conditions.