Synthesis and Characterization of an Iron(II) Bipyridine Redox-Active Polymer

Soluble redox-active polymers (RAPs) are promising materials for energy storage applications in redox flow batteries. Here, we present the synthesis and characterization of a new metal-based Redox-Active Polymer (RAP) based on iron(II) bipyridine pendants and a modified polyvinyl benzyl chloride (PVBC) as backbone structure. Our metallopolymer called Fe-RAP was characterized by Fourier transform infrared spectroscopy (FTIR), inductively coupled plasma optical emission spectroscopy (ICP-OES), ultraviolet-visible spectroscopy (UV-Vis) and dynamic light scattering (DLS). FTIR results showed the disappearance of the -CH2-Cl band at 1264 cm-1, and subsequent appearance of a quaternary salt due the insertion of (CH3)2N-phen, later to be modified for redox activity with [Fe(Cl2)(Bpy)2]. ICP suggested that about 75% of the available sites of the original PVBC backbone were modified with Fe. Electronic spectra in the UV-Vis region reinforce the presence of Fe(II) metallocentre in the polymer due the charge-transfer metal-to-ligand (MLCT) in 520nm. Finally, DLS showed that the polymer is free of small molecules or precursors. Cyclic voltammetry at an ultramicroelectrode showed redox activity at 0.6 V vs Fc+.