Nobel Prize in Chemistry 2016: Molecular Machines and Their Three Inventors

This note covers the Nobel Prize in Chemistry 2016: who won it, what molecular machines are, how catenanes, rotaxanes and molecular motors work, how the discovery unfolded from 1983 to 2016, why it matters and quick facts for exams.

What was the Nobel Prize in Chemistry 2016 awarded for?

The Royal Swedish Academy of Sciences gave the prize to three chemists with the citation: "for the design and synthesis of molecular machines".

In plain words, the three laureates built molecules whose parts can move relative to one another in a controlled way when energy is supplied, just as the moving parts of an everyday machine do.

A molecular machine is a group of connected molecules designed so that, when given energy such as light or heat, they perform a task-like movement.

The laureates showed that chemists could design and make such machines on purpose, not just stumble on them. The official name of this award is the Nobel Prize in Chemistry, and it was announced on 5 October 2016.

Who are the laureates?

Jean-Pierre Sauvage

Sauvage was born on 21 October 1944 in Paris, France. He earned his doctoral degree in 1971 at the Université Louis-Pasteur in Strasbourg, where his supervisor was Jean-Marie Lehn, who later became a Nobel laureate himself.

At the time of the 2016 award Sauvage was affiliated with the University of Strasbourg, France, where he was Professor Emeritus, and he was also Director of Research Emeritus at the National Center for Scientific Research (CNRS).

He received one third of the prize. In 1983 his research group was the first to link two ring-shaped molecules into a chain, called a catenane, using a copper ion as a template.

This was the first practical step toward a molecular machine. Sauvage's original research area was photochemistry, the study of molecules that capture light energy to drive chemical reactions, and it was while building a model of one such light-absorbing complex that he noticed its resemblance to two intertwined molecules, which redirected his work toward interlocked molecules.

Sir J. Fraser Stoddart

Stoddart was born on 24 May 1942 in Edinburgh, United Kingdom, and died on 30 December 2024.

He grew up on a farm without electricity and received his PhD from the University of Edinburgh in 1966, after which he worked at Queens' University in Canada, the University of Sheffield, the ICI Corporate Laboratory and the University of Birmingham, before moving to the University of California, Los Angeles and then to Northwestern University, in the United States.

At the time of the award he worked at Northwestern University, Evanston, Illinois, USA, as Board of Trustees Professor of Chemistry.

He also received one third of the prize. In 1991 his group built a rotaxane, a ring-shaped molecule threaded onto a molecular axle, and later used this design to build a molecular lift, an artificial muscle and a molecule-based computer chip memory.

As a child, Stoddart's fondness for jigsaw puzzles is said to have trained the same skill for recognising shapes and linking them together that he later relied on as a chemist.

Bernard L. Feringa

Feringa was born on 18 May 1951 in Barger-Compascuum, the Netherlands, where his family kept a farm.

He received his PhD from the University of Groningen in 1978, then spent several years at the Shell oil company in the Netherlands and Great Britain before returning to academic research.

At the time of the award he was Professor of Organic Chemistry at the University of Groningen, the Netherlands, and received the final one third of the prize.

In 1999 his group built the first molecular motor by making a tiny rotor blade spin continuously in one direction when pulsed with light.

Feringa once described his motivation in an interview, saying that the power of chemistry lies not only in understanding but also in creating and making molecules and materials that never existed before.

What problem were the laureates trying to solve?

By the mid-20th century chemists already knew how to join atoms into molecules using strong covalent bonds, where atoms share electrons. But a true machine needs parts that can move relative to each other, not a single rigid structure.

The challenge was to make molecules that were linked without being chemically welded together, so the pieces stayed connected yet could slide or rotate.

In 1959 the physicist Richard Feynman, speaking at a meeting of the American Physical Society, raised the possibility of building machines out of atoms and discussed the challenges of working at that tiny scale, an idea later connected to the birth of nanotechnology.

In a further lecture in 1984 Feynman returned to the same theme, asking the audience how small machinery could be made and pointing to nature's own molecular machines, such as the corkscrew-shaped flagella that bacteria spin to swim forward, as proof that tiny moving machinery was already possible.

Feynman also sketched two possible routes to tiny machines: building ever-smaller mechanical hands that could assemble still smaller hands, which he admitted had been tried without great success, or building machinery from the bottom up by depositing and removing layers of atoms on a surface, a method closer to how silicon chips are later made.

He closed his talk by telling the audience to experiment with redesigning familiar machinery at tiny scale, predicting that within 25 to 30 years some practical use would emerge, though he admitted he did not know what it would be.

Chemists in the 1950s and 1960s tried to make interlocked rings of molecules but could only produce tiny, impractical amounts using complicated methods, so the field was seen more as a curiosity than useful chemistry, and after repeated setbacks many researchers lost interest by the early 1980s.

The task that the 2016 laureates solved was to invent a reliable method of making such interlocked and moving molecular structures in useful quantities.

Their shared solution rests on a key idea: a mechanical bond, in which the parts of a molecule are trapped together by shape rather than by shared electrons, leaving them free to move relative to each other while still being inseparable.

How does a catenane work?

A catenane is two or more interlocked rings of molecules, like links of a chain, held together by a mechanical bond rather than a covalent one.

Sauvage's breakthrough in 1983 was to use an ordinary copper ion as a temporary scaffold that pulled two molecule fragments into the right shape before they were chemically closed into rings.

1. A ring-shaped molecule and a crescent-shaped molecule are each designed to be attracted to a copper ion.
2. The two pieces gather around the copper ion, which acts as a cohesive force holding them in the correct interlocking arrangement.
3. The crescent-shaped piece is chemically joined with a third molecule fragment, closing it into a second ring around the first.
4. The copper ion, having done its job as a template, is removed, leaving two mechanically interlocked rings, the catenane.

Before this method, researchers achieved yields of only a few per cent when trying to link rings;

Sauvage's templated approach reached about 42 per cent, which the Nobel committee's popular science article called progress that turned the chain from a curiosity into something researchers could actually work with.

In 1994 Sauvage's group also made a catenane in which one ring could be made to rotate a full turn around the other when energy was added, an early working molecular machine.

This copper-ion method reinvigorated an entire branch of chemistry known as topological chemistry, in which chemists interlock molecules into increasingly complex shapes, often using metal ions as scaffolds.

Building on their techniques, Sauvage's and Stoddart's groups went on to make molecular versions of culturally significant knot shapes, including a trefoil knot, a Solomon's knot and a structure called Borromean rings, each built from interlocked loops rather than welded joints.

These knotted molecules were themselves a side branch rather than machines, but they showed how far the interlocking method could be pushed.

Draw a central dot labelled "Cu ion", with a ring-shaped molecule and a crescent-shaped molecule both curving around it. Then draw a second picture showing the crescent closed into a full ring and the copper ion removed, leaving two mechanically interlocked rings.

How do rotaxanes and molecular motors work?

A rotaxane, developed by Stoddart in 1991, is a ring-shaped molecule threaded onto a thin molecular "axle", with bulky stopper groups at each end so the ring cannot slide off.

The ring in Stoddart's rotaxane could shuttle back and forth between two electron-rich points on the axle, and by 1994 he could control this movement completely rather than leaving it to chance.

Building on this, his group later made a molecular lift that could raise itself about 0.7 nanometres, an artificial muscle built from rotaxanes that bend a gold strip, and a rotaxane-based computer chip memory.

Feringa's contribution, the molecular motor, used a different trick. His molecule had two flat "rotor blade" sections joined by a double bond between two carbon atoms, with small chemical groups acting like ratchets that forced rotation to continue in one direction only, rather than randomly both ways as molecules usually move.

1. A pulse of ultraviolet light makes one rotor blade jump 180 degrees around the central double bond.
2. The ratchet-like groups on the blades then click into a new stable position, blocking the blade from swinging back.
3. A further light pulse pushes the blade another 180 degrees, continuing the rotation in the same direction.
4. Repeating these light pulses keeps the motor spinning round and round, always the same way.

Feringa's group later optimised this design so it span at 12 million revolutions per second, used it to rotate a glass cylinder 10,000 times larger than the motor itself, and in 2011 built a four-wheeled "nanocar" whose wheels were four of these molecular motors.

The glass-cylinder experiment is a useful illustration of how a molecular-scale effect can act on something visible.

Feringa's group mixed a small amount of molecular motors, only about one per cent of the mixture, into a liquid crystal, a fluid whose molecules line up in an orderly, crystal-like way.

When the motors were switched on by light, their spinning gradually twisted the surrounding liquid crystal structure, and a glass cylinder placed on top, roughly 28 micrometres long and about 10,000 times bigger than a single motor molecule, was made to rotate by the collective effect of countless tiny motors working together.

Draw a straight line (the axle) with two bulky stoppers at each end and two marked stations along its length; draw a ring around the axle and show it moving between the two stations with arrows.

How did the discovery unfold?

Why does it matter?

The Nobel committee's press release compared the molecular motor's stage of development to the electric motor in the 1830s, when scientists displayed spinning cranks and wheels without knowing these would one day power washing machines and fans.

In the same way, the press release said these molecular machines "will most likely be used in the development of things such as new materials, sensors and energy storage systems", though their full future uses are not yet known.

The laureates' work created a toolbox other researchers could build on. One example mentioned in the popular science background is a molecular robot, built in 2013 on a rotaxane foundation, able to grasp and connect amino acids.

Another is a material where molecular motors wind up long polymer chains when exposed to light, storing light energy in the molecule's structure and shrinking the material, which researchers hoped could lead to new sensors or batteries if the stored energy could be retrieved.

A broader idea the committee highlighted is that these machines work by being pushed away from chemical equilibrium, the stable low-energy resting state that chemical systems naturally settle into.

Living cells do something similar: when we eat, the energy from food pushes our body's molecules away from equilibrium so they can do useful work; a body in full chemical equilibrium would be dead.

The laureates showed that artificial molecular systems can be driven the same way, using light or other energy sources to perform controlled tasks instead of random motion.

The scientific background also noted that the field remains in its infancy compared with the machines that followed the industrial revolution, and that just as early steam engines and electric motors once puzzled onlookers before their uses became clear, the long-term applications of molecular machinery are still being discovered rather than already settled.

How does this connect to what you study?

This prize links directly to chemical bonding, a topic in school chemistry. Students usually learn about covalent bonds, where atoms share electrons to form molecules.

The laureates' key innovation, the mechanical bond, is a different kind of connection entirely: it holds molecular parts together through shape and entanglement rather than shared electrons, which is why the interlocked rings or threaded rings can still move relative to each other.

The idea of a chemical system being pushed away from equilibrium by an energy input, as described in the Nobel committee's background material, also connects to basic ideas about energy and chemical reactions taught in school science, including why living organisms need a constant supply of energy from food to keep functioning rather than settling into a low-energy resting state.

What toolbox did these inventions create for other scientists?

Once Sauvage, Stoddart and Feringa had shown that molecular machines could be designed and built reliably, their methods became a kind of toolbox that other research groups around the world used to build further, more advanced devices.

One example highlighted in the popular science background is a molecular robot, built in 2013 on a rotaxane foundation, which was able to grasp individual amino acids and connect them together, showing that mechanically interlocked parts could be made to carry out a multi-step task rather than a single repetitive movement.

Other researchers connected molecular motors to long polymer chains, forming a tangled web-like material. When these motors were exposed to light, they wound the polymer chains up into a messy bundle, storing the light's energy in the twisted structure of the material itself.

The material also shrank as it tangled, a property the scientific background suggested could be useful for building sensors that react to light, and researchers hoped that if a way were found to release the stored energy again, the same principle could lead to new kinds of batteries.

Stoddart's rotaxanes were also developed into molecular-scale electronic devices. By mounting rotaxanes between electrodes, his group and collaborators built a memory device that could be switched between open and closed states by applying a small voltage, and read back without disturbing the stored state, giving a working memory built from a dense array of rotaxane molecules.

Sauvage's group, meanwhile, used two threaded, looped rotaxane units to build an elastic structure in 2000 that could stretch and contract in a controlled way, described as resembling the filaments found in a human muscle, extending the mechanical-bond idea from simple rings into a device that mimicked a biological function.

Taken together, these follow-on inventions show why the Nobel committee described the three laureates' work as a foundation rather than an endpoint: each basic structure, the catenane, the rotaxane and the molecular motor, became a building block that other chemists adapted for new purposes.

Quick facts for exams

The Nobel Prize in Chemistry 2016 was awarded jointly to Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa "for the design and synthesis of molecular machines".

It was announced on 5 October 2016 by the Royal Swedish Academy of Sciences, which awards the Chemistry prize each year. Sauvage, working in France, discovered the catenane in 1983;

Stoddart, working in the UK and later the USA, invented the rotaxane in 1991; and Feringa, working in the Netherlands, built the first molecular motor in 1999. The three laureates shared the prize money equally, each receiving one third.

Note: Source. The prize facts in this note are from the Nobel Prize's official site, nobelprize.org.

Glossary

• Molecular machine — an assembly of molecules designed to perform machine-like movement when given energy such as light or heat.
• Covalent bond — a chemical bond in which atoms are held together by sharing electrons.
• Mechanical bond — a connection between molecular parts that holds them together by shape and entanglement rather than by shared electrons.
• Catenane — two or more ring-shaped molecules interlocked together like links of a chain.
• Rotaxane — a ring-shaped molecule threaded onto a molecular axle and held there by bulky stopper groups.
• Template synthesis — a method of using a temporary scaffold, such as a metal ion, to hold molecular pieces in the right shape before joining them.
• Molecular motor — a molecule engineered to rotate continuously in one chosen direction when supplied with energy.
• Yield — the percentage of starting molecules that successfully form the desired target molecule in a reaction.
• Equilibrium (chemical) — the stable, lowest-energy resting state that a chemical system naturally tends towards.
• Nanocar — a molecule-sized construction with a chassis and wheel-like motor units that moves across a surface.
• Trefoil knot — a knot-shaped molecular structure made using the same interlocking chemistry as catenanes.

Common errors and misconceptions

• Misconception: The prize was for inventing nanotechnology in general. Correct: It was specifically for the design and synthesis of molecular machines, built using mechanical bonds and unidirectional rotation.
• Misconception: A catenane's rings are joined by a normal chemical bond. Correct: The rings are mechanically interlocked and not directly bonded by shared electrons.
• Misconception: All three laureates worked together on one invention. Correct: Each laureate made a separate, distinct contribution, the catenane, the rotaxane and the molecular motor, though their work built on shared ideas.
• Misconception: Molecular motors can already power real-world devices. Correct: The committee compared them to electric motors in the 1830s, meaning practical large-scale uses were not yet developed at the time of the award.
• Misconception: The copper ion in Sauvage's catenane synthesis becomes a permanent part of the final molecule. Correct: The copper ion is a template that is removed once the rings are formed.
• Misconception: Feringa's first motor was already fast. Correct: The first version was slow; his group later optimised it to reach 12 million revolutions per second by 2014.

Exam-style questions with model answers

Q1. What was the official citation for the Nobel Prize in Chemistry 2016? [2 marks]

1. The citation was "for the design and synthesis of molecular machines", awarded jointly to Sauvage, Stoddart and Feringa.

Q2. Define a catenane and a rotaxane. [3 marks]

1. A catenane is two or more ring-shaped molecules interlocked together like chain links, held by a mechanical bond rather than a covalent one.
2. A rotaxane is a ring-shaped molecule threaded onto a molecular axle, with bulky stopper groups at each end that stop the ring sliding off.
3. Both structures allow their parts to move freely relative to each other while remaining permanently connected.

Q3. Explain how Jean-Pierre Sauvage's group made the first catenane in 1983. [4 marks]

1. A ring-shaped molecule and a crescent-shaped molecule were designed to be attracted to a copper ion.
2. The copper ion acted as a template, pulling the two pieces into the correct interlocking shape.
3. The crescent-shaped piece was then chemically joined with a third molecule fragment to close it into a full ring around the first one.
4. The copper ion was finally removed, leaving two interlocked rings connected only by a mechanical bond, with a yield of about 42 per cent.

Q4. Describe how Bernard Feringa's molecular motor achieves continuous rotation in one direction. [5 marks]

1. The motor molecule has two rotor-blade-like sections joined by a double bond between two carbon atoms.
2. Small chemical groups on the blades act like ratchets that block backward rotation.
3. A pulse of ultraviolet light makes one blade jump 180 degrees around the double bond.
4. The ratchet groups then click into a new stable position, preventing the blade from swinging back the way it came.
5. Repeated light pulses keep pushing the rotation in the same direction, and later versions of the motor were optimised to spin at 12 million revolutions per second.

Q5. Discuss why the Nobel committee compared molecular machines to the electric motor of the 1830s, and give two possible future uses mentioned for molecular machines. [6 marks]

1. The committee said that in the 1830s scientists displayed spinning electric cranks and wheels, not realising this invention would later power washing machines, fans and food processors.
2. Similarly, the committee said molecular machines in 2016 were at an early stage of development, with their most useful applications still unknown.
3. The comparison highlighted that early-stage inventions can seem like curiosities before later generations find major practical uses for them.
4. The press release stated that molecular machines "will most likely be used in the development of things such as new materials, sensors and energy storage systems".
5. The popular science background also mentioned a molecular robot able to grasp and connect amino acids, built on a rotaxane foundation in 2013.
6. It also described a material in which light-driven molecular motors wind up polymer chains, storing energy and shrinking the material, which researchers thought might lead to new batteries or light-sensitive sensors.

Q6. Who received the 2016 Nobel Prize in Chemistry and in what shares? [2 marks]

1. Jean-Pierre Sauvage, Sir J. Fraser Stoddart and Bernard L. Feringa received the prize, each getting one third of the award.

Q7. What is a mechanical bond and how does it differ from a covalent bond? [4 marks]

1. A covalent bond holds atoms together because they share electrons directly.
2. A mechanical bond instead holds molecular parts together through shape and entanglement, without the atoms interacting directly.
3. Parts connected by a mechanical bond, such as the two rings of a catenane, can move freely relative to each other.
4. This freedom to move is essential for building molecules that behave like machines with moving parts.

Key takeaways

• The Nobel Prize in Chemistry 2016 honoured the design and synthesis of molecular machines, molecules whose parts can move in a controlled way.
• Jean-Pierre Sauvage built the first catenane in 1983 using a copper ion as a template to interlock two rings.
• Sir J. Fraser Stoddart built the first rotaxane in 1991, a ring threaded onto a molecular axle.
• Bernard Feringa built the first molecular motor in 1999, using ratchet-like groups to force one-direction rotation.
• Mechanical bonds hold molecular parts together by shape, unlike covalent bonds, which hold atoms together by shared electrons.
• The laureates' inventions led to further devices such as molecular lifts, muscles, a nanocar and a computer chip memory.
• The committee compared molecular machines in 2016 to electric motors in the 1830s, suggesting major future uses are still to be discovered.
• Possible future uses mentioned include new materials, sensors and energy storage systems.

Test yourself

What does the term "molecular machine" mean?

It means an assembly of molecules designed so its parts move in a controlled way when supplied with energy such as light.

Where was Jean-Pierre Sauvage affiliated at the time of the award?

Jean-Pierre Sauvage was affiliated with the University of Strasbourg in France at the time of the award.

What did Sir J. Fraser Stoddart invent in 1991?

Sir J. Fraser Stoddart invented the rotaxane in 1991, a ring-shaped molecule threaded onto a molecular axle.

What made Bernard Feringa's 1999 motor special?

It was the first molecular motor to spin continuously in one chosen direction, using light pulses and ratchet-like chemical groups.

What is a catenane?

A catenane is two or more ring-shaped molecules interlocked together like chain links, connected by a mechanical bond.

What speed did Feringa's optimised molecular motor reach by 2014?

By 2014 Feringa's group had optimised the motor to spin at 12 million revolutions per second.

What playful device did Feringa's group build using four molecular motors?

In 2011 Feringa's group built a four-wheel-drive nanocar whose wheels were four molecular motors that moved it across a surface.