Visible Light-Activated Organic Synthesis Techniques

Visible light-activated organic synthesis harnesses low-energy photons to initiate chemical transformations under mild conditions. Central to this approach is photoredox catalysis, in which a photosensitiser—often a transition-metal complex, organic dye or semiconductor material—absorbs visible light and reaches an excited state capable of engaging in single-electron transfer. This process generates reactive radical or radical-ion intermediates that enable bond-forming events such as C–C cross-couplings, C–H functionalisations, cyclisations and late-stage modifications of complex molecules. The mildness of visible light activation reduces the need for harsh reagents or elevated temperatures, improving functional group tolerance and minimising waste. Advances in catalyst design have led to Earth-abundant metal systems and purely organic photocatalysts, widening sustainable applications. Mechanistic elucidation via spectroscopic monitoring and computational studies has deepened understanding of excited-state redox potentials, energy-transfer pathways and radical chain processes. The convergence of homogeneous and heterogeneous platforms has further facilitated scalable flow and batch processes. Visible light-driven methods now underpin the synthesis of pharmaceutical intermediates, agrochemicals and functional materials, exemplifying a paradigm shift towards greener, more selective organic synthesis driven by readily available light sources.

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Visible Light-Activated Organic Synthesis Techniques publication trend

The graph below shows the total number of articles in visible light-activated organic synthesis techniques across all publications each year (not limited to Nature Index journals).

Technical terms

Photoredox catalysis: A process in which a photocatalyst absorbs light to reach an excited state that effects single-electron transfer, generating radical intermediates for bond formation.

Photosensitiser: A molecule or material that absorbs photons and transfers energy or electrons to substrates, initiating chemical reactions.

Hydrogen-atom transfer (HAT): A mechanistic step in which a hydrogen atom (proton plus electron) is transferred between species, often driving radical propagation.

Excited-state redox potential: The oxidation or reduction potential of a photocatalyst in its electronically excited state, determining its ability to oxidise or reduce substrates.

Semiconductor photocatalyst: A solid material with a band gap that can be excited by visible light to generate electron–hole pairs for redox chemistry on its surface.

References

1. Iodine radical mediated cascade [3 + 2] carbocyclization of ene-vinylidenecyclopropanes with thiols and selenols via photoredox catalysis. Organic Chemistry Frontiers (2024).