Association-gated multiphoton activation of inert haloarenes via sequential electron donor–acceptor assembly

The functionalization of recalcitrant chemical bonds that require extreme reduction potentials is often thwarted by the absence of a defined reaction field to control potent intermediates. Conventional multiphoton photocatalysis generates super-reductants, whose immense energy dissipates through chaotic, diffusion-controlled pathways. Herein, an “association-gated” strategy is introduced that constructs sequential electron donor–acceptor complexes as programmable reaction microenvironments. This system initially captures a single photon through its sulfide/naphthalene monoimide complex. The resulting naphthalene monoimide radical anion serves as a scaffold to pre-organize the haloarene substrate into a second, distinct electron donor–acceptor complex, creating a reaction pocket for the final, energy-storing excitation. Such supramolecular confinement generates an extreme reducing potential at the carbon–halogen bond, suppressing both diffusive side-reactions and parasitic hydrogen atom transfer from amine donors. This unlocks a broad scope of transformations under air-tolerant conditions, providing a versatile tool for late-stage diversification. Extreme photoreduction is often limited by uncontrolled, diffusion-driven reactivity of highly energetic intermediates. Here, the authors report an association-gated photocatalytic strategy that assembles sequential donor–acceptor complexes to create confined reaction pockets, enabling selective activation of strong carbon–halogen bonds.