Photocatalysis in the Dark: Near-Infrared Light Driven Photoredox Catalysis by an Upconversion Nanoparticle/Photocatalyst System

Herein, we present a novel upconversion nanoparticle/photocatalyst system for infrared-light-initiated photoredox catalysis. A tailor-made, metal-based photoredox catalyst was immobilized by ligand exchange to stabilize NaYF4 upconversion nanoparticles. The absorption properties of the immobilized photoredox catalyst were only negligibly changed and the particles could excite the photoredox catalyst by energy transfer, determined by extensive luminescence spectroscopy and excited-state lifetime measurements using a 980 nm near-infrared laser excitation source. The system successfully catalyzed a [Ru(bpy)(3)](2+) promoted oxidation reaction, normally performed with visible light, by using 980 nm near-infrared light. Neither the complex nor the particle without immobilized complex was active in this reaction. The presented system enables potential in vivo application of photoredox catalysis, utilizing the biological window of tissues for near-infrared light by combining the mildness of photoredox catalysis and near-infrared light.