Energy transfer-mediated multiphoton synergistic excitation for selective C(sp)-H functionalization with coordination polymer.

Activation and selective oxidation of inert C(sp)-H bonds remain one of the most challenging tasks in current synthetic chemistry due to the inherent inertness of C(sp)-H bonds. In this study, inspired by natural monooxygenases, we developed a coordination polymer with naphthalenediimide (NDI)-based ligands and binuclear iron nodes. The mixed-valence FeFe species and chlorine radicals (Cl) are generated via ligand-to-metal charge transfer (LMCT) between Fe and chlorine ions. These Cl radicals abstract a hydrogen atom from the inert C(sp)-H bond of alkanes via hydrogen atom transfer (HAT). In addition, NDI converts oxygen to O via energy transfer (EnT), which then coordinates to Fe, forming an Fe = O intermediate for the selective oxidation of C(sp)-H bonds. This synthetic platform, which combines photoinduced EnT, LMCT and HAT, provides a EnT-mediated parallel multiphoton excitation strategy with kinetic synergy effect for selective C(sp)-H oxidation under mild conditions and a blueprint for designing coordination polymer-based photocatalysts for C(sp)-H bond oxidation.