Photoredoxenabled

Photoredox-enabled refers to chemical transformations that rely on photoredox catalysis, a mode of catalysis in which light-activated catalysts mediate single-electron transfer events to generate reactive radical or ionic species under mild conditions. The term highlights the central role of visible-light excitation in enabling new reactivity that is often difficult to achieve with traditional methods.

Most photoredox catalysts are metal complexes based on ruthenium or iridium or certain organic dyes. Common examples include Ru(bpy)3^2+, Ir(ppy)3, organic dyes such as eosin Y, and organic photoredox catalysts like 4CzIPN. These catalysts absorb visible light, typically from blue LEDs, to reach strong excited states with either oxidizing or reducing power. The excited-state catalyst then engages substrates via single-electron transfer or energy-transfer processes, generating radical intermediates that propagate the reaction and are regenerated to complete the catalytic cycle.

Applications of photoredox-enabled chemistry span carbon–carbon and carbon–heteroatom bond formation, including decarboxylative couplings, hydrofunctionalizations, and cross-electrophile couplings often in combination with transition-metal catalysis such as nickel. It also enables radical additions, cyclizations, and functional-group-tolerant transformations under mild, often ambient, conditions.

Advantages of photoredox-enabled strategies include broad functional-group tolerance, operational simplicity, and the use of visible light as a sustainable energy source. Limitations encompass issues with light penetration in larger batches, oxygen sensitivity, the cost or availability of some catalysts, and the need for specialized equipment, though flow processes and scalable reactor designs mitigate many practical concerns. The field has significantly influenced modern organic synthesis and medicinal chemistry by expanding the accessible reaction space under gentle conditions.