Hydrated metal charge density as a universal descriptor explaining mechanistic variations in periodate activation toward pollutant degradation.

Although activation mechanisms of oxidants diverge significantly across different transition metals, whether the universal descriptor exists that can unify these pathways remains unknown. Herein, taking periodate (PI) as an example, we systematically explored the connection among Group VIII (8) metals (Fe(II), Ru(III), Os(III)). While all three metals activate PI effectively, Os(III) exhibits fundamentally different activation behavior compared to Fe(II) and Ru(III). PI activation by Os(III) primarily generated ·OH, promoting hydroxylated products formation; whereas high-valent metal-oxo species dominate in Fe(II) and Ru(III) systems, yielding epoxy products. Theoretical calculations indicate that Os(III) possesses a significantly higher positive charge density than that of Fe(II) and Ru(III). The high charge density of Os(III) enhances oxygen affinity, and reduces the energy barrier for single-electron transfer to water ligands, thereby promoting radical generation. Conversely, the lower charge density of Fe(II) and Ru(III) indicates a stronger affinity for electrons, favoring the oxygen atom transfer process. This work identifies metal charge density as a key descriptor modulating reaction mechanisms of oxidants and informs the design of tunable oxidation processes.