Surface Immobilization of [M(mcp)L ₂ ] Complexes Using Conducting Redox Polymers

We report the synthesis of an EDOT-functionalized mcp ligand that enables direct immobilization of [M(mcp)X2] complexes (M = Fe, Co, Cu, Ru) into conducting redox polymers (CRPs) via electropolymerization. Poly(EDOT-co-[Fe(EDOT-mcp)X2]) films were thoroughly characterized in both acetonitrile and water using cyclic voltammetry, in situ conductance measurements, and in situ UV/Vis spectroelectrochemistry. These operando studies disentangle backbone doping from the Fe(III)/Fe(II) pendant group redox transition, revealing that charge transport proceeds predominantly through the polymer backbone, while the pendant complexes operate as discrete electroactive sites. The Fe redox potential is highly sensitive to electrolyte anion coordinating strength and concentration, reflecting ligand exchange at the labile sites. In water, the electrochemical response is governed by proton-coupled electron transfer and is strongly affected by pH and buffer identity. Only when buffer ions penetrate the polymer bulk─at sufficiently high buffer concentrations─do the pendant groups experience the same effective proton activity as the surrounding electrolyte. Although attempts at catalytic water oxidation confirm Fe-centered oxidation chemistry, the material undergoes rapid conductivity loss at anodic potentials, indicating backbone degradation under turnover conditions. These findings establish the EDOT-mcp platform as a versatile immobilization strategy for mcp-type metal complexes and highlight design requirements for improving stability in oxidative catalysis.