The Mn 4 V 4 O 17 ( OAc ) 3 3 − polyoxometalate is a water oxidation catalyst featuring a Mn 4 O 4 6 + cubane core reminiscent of the natural oxygen-evolving complex. Here, we investigate how polymer-brush confinement modulates the reduction potentials of two catalytical relevant couples, comparing dry acetonitrile, a mixture of 5 vol% water in acetonitrile, and a poly( N,N -dimethylaminoethyl methacrylate) brush that biomimics a hierarchically structured environment. To this end, we leverage Marcus theory, molecular dynamics simulations and multiscale QM/MM single point calculations employing density functional theory. In homogeneous solution, calculated reduction potentials reproduce experimental trends and show that solvent composition primarily governs redox energetics, while counterion effects depend on ion pairing. The Mn III Mn 3 IV ⇌ Mn 4 IV + e − reaction exhibits enhanced solvent sensitivity due to oxidation-state-dependent counterion redistribution. Under polymer-brush confinement, reduction potentials decrease by up to 1 V relative to bulk solution, indicating destabilization of reduced states. Structural analysis reveals that electrostatic interactions with protonated DMAEMA units modify microsolvation structure within the brush. Overall, this study demonstrates that redox potentials of polyometalate catalysts are highly sensitive to electrostatics, solvation environment and confinement, providing guidance in the design of related polyometalate water oxidation catalysts in structure environments. • Reduction potentials of a MnV polyoxometalate water-oxidation catalyst differ significantly between solvent and polymer brush environment. • Polymer brush confinement results in lower redox potentials. • Oxidation states of MnV polyoxometalate guide mobility within polymer brush.
Tippner et al. (Fri,) studied this question.