Evolution of manganese low-energy photoredox catalysis from high-energy visible light photocatalysis

Turning Down the Light, Keeping the Chemistry

Chemists often use bright, high‑energy light—like intense blue or ultraviolet lamps—to drive reactions that build complex molecules. But this “hard” light can waste energy, damage delicate parts of molecules, and is difficult to use deep inside tissues or large reactors. This study shows how simple, inexpensive manganese salts can be assembled directly in the reaction flask to work with much softer red and near‑infrared light, while still performing powerful bond‑forming chemistry that is valuable for drug discovery and materials science.

Why Gentler Light Matters

High‑energy light is a bit like using a blowtorch to light a candle: it gets the job done, but it can also scorch everything nearby. In chemical reactions, this can lead to over‑reaction, destruction of sensitive groups, and poor control. Softer light—especially red and near‑infrared, which carry less energy—penetrates deeper through liquids and even biological tissues and is generally more compatible with complex, fragile molecules. The challenge is that most existing light‑driven catalysts are tuned to absorb higher‑energy light, and redesigning them usually requires long, complex synthesis. The authors set out to lower the “photon budget” of such reactions without having to rebuild the catalysts from scratch.

Building the Catalyst on the Spot

Instead of making elaborate metal complexes in advance, the team used an in‑situ strategy: they simply mixed off‑the‑shelf manganese salts with a small helper molecule (a ligand) and an azide source directly in the reaction mixture. This self‑assembly created a light‑absorbing system based on manganese. With a manganese(II) salt, the mixture strongly absorbed blue light and could generate short‑lived “azido radicals” from a common reagent called TMSN3. These reactive fragments then added across simple carbon‑carbon double bonds (alkenes), placing an azide group (N₃) at the less substituted end of the double bond—a pattern known as anti‑Markovnikov addition. Remarkably, plain water served as the hydrogen source, making the process both simple and atom‑efficient.

Shifting from Blue to Deep Red

The researchers then asked whether a closely related manganese system could work with much lower‑energy light, in the deep red and near‑infrared region. By moving from manganese(II) to manganese(III) and fine‑tuning the reaction medium, they created a new mixture that absorbed light all the way out to about 850 nanometers—well into the near‑infrared. Under this gentle light, the manganese(III) complex still produced azido radicals, but now in the presence of air (as a source of oxygen) and a simple alcohol, the reaction installed both an azide and an alcohol group across the alkene in one step. The result is a b2‑azido alcohol, a particularly useful building block because it contains two highly versatile handles—N₃ and OH—on neighboring carbon atoms.

From Simple Alkenes to Complex Drug‑Like Molecules

With both the blue‑light and low‑energy light systems in hand, the team tested a wide variety of alkenes. They converted many different starting materials into alkyl azides or b2‑azido alcohols in moderate to high yields, even when the molecules carried groups that typically interfere with metal catalysts, such as unprotected amines, alcohols, sulfur‑containing groups, and complex ring systems. They also demonstrated “late‑stage functionalization” by modifying advanced drug‑like molecules, turning existing pharmaceuticals into new derivatives with azide and, in some cases, alcohol groups added. These new functions can later be transformed into other nitrogen‑rich structures or clicked onto biological targets, expanding the toolbox for medicinal chemistry.

Energy‑Saving Chemistry with Real‑World Promise

The work shows that it is possible to “evolve” a high‑energy blue‑light reaction into a low‑energy near‑infrared process simply by changing how a common metal salt is assembled in solution. The in‑situ‑built manganese systems avoid time‑consuming catalyst synthesis, use abundant and relatively non‑toxic metal, and can even be powered by natural sunlight. For non‑specialists, the key message is that we do not always need harsher light or expensive rare metals to do demanding chemistry. By designing catalysts that form themselves from simple pieces and that respond to gentler light, this approach points toward more energy‑efficient, scalable, and biologically friendly ways to make the complex molecules on which modern medicine and materials depend.

Citation: Yang, W., Song, Y., Yu, X. et al. Evolution of manganese low-energy photoredox catalysis from high-energy visible light photocatalysis. Nat Commun 17, 2062 (2026). https://doi.org/10.1038/s41467-026-68837-y

Keywords: photoredox catalysis, manganese catalysis, low-energy light, alkene functionalization, azido radicals