Buckyballs: the soccer ball-shaped molecules

The new FIFA World Cup match ball has plenty of bells and whistles, but, like most high-level footballs in the past 20 years, it lacks the classic soccer ball panel shape.

This shape, technically called a truncated icosahedron, has uses beyond the world game.

These icosahedrons create a  strong architectural structure which are often blown up to become the basis of geodesic domes.

But the football panel shape can also be shrunk – eventually it becomes so small that its points become single atoms.

Meet Buckminsterfullerenes: the football-shaped molecules.

These molecules, often called buckyballs, are named after US architect Richard Buckminster Fuller, who popularised the geodesic dome.

Buckyballs are made of pure carbon: specifically, 60 carbon atoms, with each atom connected to three others. These atoms link up in five- and six-pointed rings – both shapes that carbon readily forms into.

Buckyballs exist in nature – including in outer space – but their structure was discovered by three chemists in 1985.

Harry Kroto, a UK chemist, was investigating long chains of carbon that he and some radioastronomers identified in interstellar space.

He got in touch with Richard Smalley, a US chemist based at Rice University who operated a lab where he might be able to make these chains.

Smalley, along with another US chemist, Richard Curl, used a device called a “laser-supersonic cluster beam apparatus”.

This equipment uses high-powered lasers to vaporise just about any material into plasma at super-high temperatures, like the surfaces of stars. They mostly used it on metals, but Kroto wanted to try it on carbon.

The three of them found the long carbon chains that Kroto had been looking for, but their experiments also turned up previously-unknown carbon molecules. By far the most abundant was a molecule with 60 carbon atoms. Initially, they couldn’t tell what structure those atoms took.

After a week of puzzling, Smalley eventually landed on the truncated icosahedron – inspired in part by Kroto’s recounting of Fuller’s geodesic dome in Montreal.

The chemists built a molecular model of the structure, then phoned mathematician Bill Veech to help describe its shape.

According to the American Chemical Society, Veech’s reply was: “I could explain this to you in a number of ways, but what you’ve got there, boys, is a soccer ball”.

This entirely new form of carbon, with its symmetrical structure, delighted chemists and laypeople alike. The New York Times heralded the discovery as a “tour de force” at the time, and the three chemists won a Nobel Prize for it 11 years later.

While they spotted its significance, Kroto, Curl and Smalley probably weren’t the first chemists to make buckyballs. In fact, in 1991, the Canberran scientist Bill Burch claimed he’d made and observed buckyballs a year prior, in 1984. He told The Canberra Times in 1994 that, being a practical chemist and not a fundamental scientist, it didn’t occur to him to write to Nature.

The discovery of buckyballs, and the class of similar molecules called “fullerenes”, spurred the making of dozens of other types of carbon.

The most exciting spinoff is probably carbon nanotubes: long, thin cylinders of carbon atoms in hexagonal shapes. These strong, light, electrically conductive materials are being used in everything from ultra-powerful microscopes to extremely black paint.

So that’s the football-shaped molecule. Can we make molecules in any other ball shapes?

The 2023 FIFA ball is a tough, but not impossible, shape to crack in molecular form. Triangles are very strained shapes in the molecular world – those tight angles are not favourable for chemical bonds, so while they can form, they’re much rarer.

Aussie rules and rugby footballs are easier to create as molecules. In fact, one of the other molecules made by Kroto, Curl and Smalley’s laser experiments is a C₇₀ molecule, now often referred to as a “rugby ball” because of its oblong shape.

We’ve not seen many rugby balls with patches like that, though. German and Russian chemists tried again in 2015 with a “giant rugby ball” – but while this one has a nice divide down the middle, it has rather too many appendages to be easily kickable.

We can supply the football team, however, with some 2003 research by Stephanie Chanteau and James Tour, also from Rice University.

Chanteau and Tour made a delightful set of “NanoPutians”: molecules shaped like people, a fraction of a nanometre tall, complete with two oxygen atoms in the “head” to represent eyes.

These NanoPutians can come with a variety of different headwear, like chef hats, top hats and crowns, to help distinguish themselves – useful for denoting different teams, too. They can even hold hands.

And what’s the purpose of these little people, beyond a molecular soccer match? They’re essentially educational tools – and a nice proof that, given time, chemists could make a molecule shaped like just about anything.