Intercepting Photogenerated Aminyl Radicals at Metal‐Halide Perovskite Microcrystals to Forge C─N Bonds With Non‐Preactivated Substrates

: Visible-light-driven C─N bond formation from non-preactivated partners remains a central challenge in oxidative synthesis, particularly when selective control over N-centered radical intermediates is required. Here, lead-halide perovskite microcrystals are shown to mediate cross-dehydrogenative C─N coupling of aromatic heterocyclic amines in air at room temperature by controlling complementary radical species at semiconductor interfaces. Phenoxazine undergoes efficient oxidative dimerization, whereas closely related scaffolds such as phenothiazine and 9,9-dimethyl-9,10-dihydroacridine display markedly different reactivity profiles despite comparable oxidation potentials. Combined electrochemical, spectroscopic, and radical-trapping experiments reveal that efficient C─N bond formation correlates with the concurrent generation of radical cation and neutral aminyl species at the catalyst-substrate interface. UV-vis monitoring under controlled atmospheres establishes the necessity of oxygen for sustaining complementary radical populations, while spin-unrestricted DFT calculations identify substrate-dependent spin localization, as well as distinct N─H activation barriers, as key factors of coupling efficiency. Interception of the photogenerated aminyl radicals enables hetero-cross-dehydrogenative coupling with naphthol and naphthylamine derivatives. These findings delineate mechanistic principles governing C─N bond formation at semiconductor surfaces and position metal-halide perovskites as tunable and recyclable platforms for N-centered radical chemistry under mild conditions.