I once had an old brass padlock on a shed, and a keyring of fifteen nearly identical keys. Whenever I stood in the cold trying to examine the microscopic ridges under a torch to pick the “right” key, I’d waste ten minutes getting nowhere.
Eventually, I stopped overthinking it and learned a much faster trick: jam and twist every key down the line as fast as possible. Fourteen keys wouldn’t turn at all — they instantly slipped back out without doing anything. But the moment key number fifteen caught the internal tumblers, the lock clicked open and stayed open.
It turns out that researchers at the University of Wisconsin–Madison, Colorado State University, and the University of Colorado Boulder just used a remarkably similar trick to shatter a decades-old rule of chemistry.
The Old Rule: The Easy Target Wins
Chemistry has rules. Some are fundamental laws of nature, while others are reliable principles that chemists use to predict what happens when molecules meet.
One of those core principles concerns electrons.
Imagine placing two different molecules in front of an available electron. One molecule desperately wants it. The other is much more reluctant to accept it.
For decades, chemists have designed single-electron-transfer reactions around one obvious assumption: the molecule that is easier to reduce will normally receive the electron first.
That sounds sensible. But what happens when the molecule you actually want to react is the stubborn one?
When two molecules compete for an electron, their reduction potentials help predict which one accepts it. That preference is incredibly useful for controlling reactions, but it creates a massive brick wall when your desired target is hard to reduce while an easier target sits right next to it in the same mixture. The electron naturally favours the easier target every time.
The Unconventional Fix: Stop Choosing the Target
The research team, led by Wisconsin chemist Zachary Wickens alongside Robert Paton (CSU) and Niels Damrauer (CU Boulder), tried an approach that sounds completely backwards on paper.
Instead of building a catalyst that carefully hand-delivers an electron to the stubborn molecule, they made the electron donor so overwhelming that it ejects electrons directly into the surrounding liquid.
This creates a solvated electron — an excess electron floating free in the solvent, stabilised temporarily by surrounding liquid molecules rather than attached to any single atom. Because it exists on its own, a solvated electron is an extraordinarily powerful reducing agent looking for anything to react with.
The team’s electrochemically generated photocatalyst uses light energy to launch these wild-card electrons into solution.
At first, this sounds like a terrible strategy. Chemists normally want more precision, not less. If your catalyst throws high-energy particles at everything in sight, shouldn’t that just create a chaotic chemical mess?
Surprisingly, no — because the real selection happens after the collision.
The Keyring Trick: Selection After the Transfer
Published in Nature under the title “Selectivity Emerges from Indiscriminate Photoreduction,” the team demonstrated their concept using a reaction between cyclopropyl ketones and alkenes.
Under normal rules, the alkene is easier to reduce than the ketone. That is inconvenient, because the researchers specifically needed to activate the harder-to-reduce ketone to build their target product.
The new solvated-electron system transfers electrons to both molecules indiscriminately. But what happens next determines the winner:
- The Easy Target (Alkene): Receives an electron, but nothing permanent happens. The process rapidly reverses, and the electron travels right back to the catalyst via back electron transfer. The alkene resets completely unharmed.
- The Stubborn Target (Cyclopropyl Ketone): Receives an electron, and its strained three-membered molecular ring instantly snaps open. Once that structural change occurs, the molecule cannot give the electron back. It is trapped in a new reactive state that continues forward to form the final product.
Easy-to-reduce molecule → Receives electron → Instantly gives it back (Reset) Hard-to-reduce molecule → Receives electron → Structural ring snaps open → Trapped! (Product)
Just like trying fifteen keys on a ring, the system doesn’t win by choosing the right target on the first try. It wins because wrong choices reset harmlessly, while the right choice locks in permanently.
How Big Was the Mismatch?
This wasn’t a subtle loophole. The researchers reported that their system could successfully drive the desired reaction even when the stubborn target was disadvantaged by as much as one volt.
In the world of electrochemistry, a one-volt mismatch is a massive thermodynamic canyon. Under normal conditions, that gap would lead chemists to dismiss the reaction as impossible.
Instead of forcing the electron to obey thermodynamic preferences, the system shifts the deciding factor to reaction kinetics — what the molecule physically does after it gets the electron.
Why This Matters for Medicine and Materials
Single-electron transfer is one of the most powerful tools in organic chemistry because adding a single electron briefly turns a stable molecule into a highly reactive radical capable of forming new bonds.
Expanding which molecules can be activated means expanding the library of complex structures chemists can build. If this strategy applies broadly beyond cyclopropyl ketones, it could help synthesise:
- Next-generation pharmaceutical candidates
- Advanced polymers and electronic materials
- Specialised agricultural chemicals
- Complex environmental clean-up catalysts
The Limitations
While exciting, this is not a universal magic trick.
The strategy relies on specific photoreducing conditions combining light and electrochemistry. Most importantly, the stubborn target must have a fast, irreversible structural pathway (like ring-opening) to trap the electron. If receiving an electron doesn’t cause a fast structural change, back electron transfer will simply reset both molecules, and no product will form.
Breaking Rules to Make Rules
The broader lesson of this breakthrough is deeply counterintuitive: sometimes, to get extreme precision, you first have to embrace complete chaos.
For decades, chemists treated reduction potentials as an unyielding rulebook for which molecule gets an electron first. This research shows that you don’t always have to obey the rulebook — you can simply go around it.
By releasing wild electrons into solution, letting molecules compete freely, and relying on kinetic traps to filter out the wrong outcomes, scientists have unlocked a new path forward. Molecules once written off as too ‘stubborn’ to react might finally get their chance.
Frequently Asked Questions
What is a solvated electron?
A solvated electron is a free electron released directly into a liquid solvent and stabilised by surrounding solvent molecules rather than being bound to a specific atom or molecule. It acts as an exceptionally strong reducing agent.
What traditional chemistry assumption did this research challenge?
It challenged the belief that differences in reduction potential must dictate reaction selectivity. The researchers showed that a harder-to-reduce molecule can react selectively even in the presence of an easier-to-reduce competitor.
Who led this study?
The research was conducted by teams across the University of Wisconsin–Madison, Colorado State University, and the University of Colorado Boulder, led by researchers including Zachary Wickens, Robert S. Paton, and Niels H. Damrauer.
When was this research published?
The paper “Selectivity Emerges from Indiscriminate Photoreduction” was published online in Nature in July 2026.