Photosynthesis is nature’s way of turning sunlight into chemical energy.

Plants use a green pigment called chlorophyll to absorb sunlight, using this solar energy to convert carbon dioxide from the air and water from the soil into glucose, which they use as a food source. This process also produces oxygen, which is released into the atmosphere.

Flowers in a sunny field — Photosynthesis is an elegant solution to the challenge of capturing and storing solar energy. Picture: Getty Images

This transformation, however, does not happen in a single step. Instead, plants absorb four photons (particles of light) in a carefully choreographed sequence, gradually accumulating the energy required to split water molecules and release oxygen.

This multi-photon process is a remarkably elegant solution to the challenge of capturing and storing solar energy.

For decades, we chemists have looked to photosynthesis for inspiration, seeking ways to harness visible light to drive important chemical transformations.

Yet a major challenge has been that most synthetic light-absorbing chemicals – known as photocatalysts – can only absorb one photon at a time. So they don’t produce enough energy to power complex reactions.

As a result, many energy-demanding chemical processes, like building intricate pharmaceuticals or advanced materials, have remained beyond the reach of being powered by visible light alone.

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Mimicking nature’s multi-photon mastery

In the Polyzos research group at the School of Chemistry, we have developed a new class of photocatalysts that, like plants, can absorb energy from multiple photons.

This breakthrough allows us to harness light energy more effectively, driving challenging and energy-demanding chemical reactions.

We have applied this technology to generate carbanions – negatively charged carbon atoms that serve as crucial building blocks in the creation, or synthesis, of carbon- and hydrogen-rich chemicals known as organic chemicals.

Carbanions are vital in making drugs, polymers and many other important materials. However, traditional methods to produce carbanions often require lots of energy and dangerous reagents, and generate significant chemical waste, posing environmental and safety challenges.

These reagents are most commonly organolithium reagents or Grignard reagents that require extremely cold temperatures to control their reactivity.

Chambers with different coloured lights and glowing liquids — Using light to turn alkenes into highly reactive carbanions is greener and safer than other common methods. Picture: Supplied

Our new method offers a greener, safer alternative.

By using visible light and renewable starting materials, and a photocatalyst system that mimics the energy-accumulating multiple photon steps of photosynthesis, the technology generates carbanions under mild, environmentally friendly conditions.

Unlocking the hidden potential of alkenes

Alkenes – simple molecules with strong, carbon-carbon double bonds – are among the most abundant and versatile building blocks in chemistry.

Yet, turning them into highly reactive carbanions has been a long-standing challenge.

Using our multi-photon photocatalytic system, we transform alkenes into carbanions and then rapidly convert these into complex molecules.

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This approach is a significant departure from classical methods. Instead of relying on toxic metals or other harsh reagents, the reaction proceeds under gentle conditions, is scalable, and generates less waste.

From lab-scale to industrial-scale

Beyond the scientific novelty of designing this process, our method has practical impact.

We’ve used it to synthesise important drug molecules, including antihistamines, in a single step using simple, cheap and commonly available ‘commodity chemicals’ – amines and alkenes.

And importantly, the reaction scales well in commercial-scale continuous flow reactors, highlighting its potential for industrial applications.

By using light to break alkenes into carbanions, we can then add different chemical groups stepwise in a controlled way – building complex molecules like amino acids and pharmaceuticals with greater efficiency.

Woman standing next to a device with blue light glowing inside it — Dr Milena Czyz uses an EPR (Electron Paramagnetic Resonance) spectrometer to catch fleeting reaction intermediates created by exposure to blue light. Picture: Supplied

Man in laboratory clothes working under an eerie green light — Dr Anastasios Polyzos harnesses intense green light to drive photochemical reactions and build complex molecules. Picture: Supplied

Toward a sustainable, light-driven future

Our discovery reframes how chemists approach alkenes, showing they can serve as sources of highly reactive carbanions accessed through visible light under mild conditions.

The strategy aligns with nature’s own principles of efficiency and sustainability, promising new routes for constructing complex organic molecules without reliance on heavy metals or harsh reagents.

Looking ahead, the team plans to expand this light-driven chemistry to include more diverse carbon–carbon bond-forming reactions and combine it with enzyme catalysis.

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Enzymes, nature’s precise molecular machines, offer unmatched selectivity and could, together with our photocatalysts, enable the synthesis of complex three-dimensional molecules crucial for discovering new medicines.

By learning from the subtle mastery of photosynthesis, our research group is forging a new paradigm for chemical manufacturing – one where sunlight powers sustainable and elegant solutions for the molecules that shape our world.

Visit the Polyzos Laboratory during a behind-the-scenes tour of the Chemistry building on Tuesday, 12 August 2015, part of the University of Melbourne's Science Festival.

This article was first published on Pursuit. Read the original article.

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Milena Czyz

Postdoc Fellow - ARC ITTC - Chemical Industry

School of Chemistry

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Milena Czyz

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