Confining Cu(i) ions within an Ir(iii)-based twin-cavity cage for photo-triggered dioxygen activation toward C(sp3)–H oxidation

Abstract

Efficient activation of dioxygen (O₂) under mild and environmentally friendly conditions remains a challenging yet crucial area of research in chemistry. In this study, we present a simple yet effective approach for O₂ activation under 450 nm light irradiation by rationally modulating the coordination environment of Cu(I) ions and incorporating a photoactive Ir(III) module into a supramolecular system, leading to efficient C(sp³)−H photo-oxidation of N-aryl tetrahydroisoquinolines. The hexaformyl end-capped fac-Ir(ppy)₃ module (1), the Ir(III)-based twin-cavity cage (2), and the supramolecular Cu₂@2 entity—where two Cu(I) ions are coordinated within cage 2—were comprehensively characterized using NMR, HR-MS, and X-ray crystallography. The confined cavities of 2 effectively trap Cu(I) ions, protecting them from oxidation by O₂. Mechanistic studies reveal that photoinduced singlet oxygen (¹O₂), generated by the fac-Ir(ppy)₃ module, activates Cu(I) to generate superoxide radical (O₂˙⁻) species. Importantly, the Cu(I) redox-active state is regenerated through electron transfer from the photoexcited *Ir(III) state to the resulting Cu(II) ions. This study introduces a gradual and controlled energy/electron delivery mechanism from Ir(III) module to O₂ and the Cu centres, offering an advanced supramolecular strategy for photo-induced O₂ activation in oxidation reactions.