AMES -- Scientists may be closer to unlocking the mystery of buckyballs – curious hollow spheres formed by 60 atoms of carbon – thanks to research being conducted by Peter Rabideau, a senior chemist at the Department of Energy’s Ames Laboratory.

Using simple solution chemistry, Rabideau has developed a process to produce gram quantities of corannulene (C₂₀H₁₀), a curved-surface, aromatic hydrocarbon. Nicknamed buckybowls, the bowl-shaped corannulene molecules represent the polar cap of the C₆₀ sphere. By making it possible to produce large quantities of these bowl segments, Rabideau hopes to eventually piece together a complete buckyball.

Buckyballs have intrigued chemists since the uniquely structured molecules were first discovered in 1985. The carbon atoms align to form a hollow structure similar to the pattern of panels found on a soccer ball. They get their name from architect/engineer/philosopher Buckminster "Bucky" Fuller, who pioneered the concept of geodesic domes.

"This shape allows one to build the largest dome without internal support because of the arrangement of six-membered and five-membered rings," says Rabideau, who also serves as dean of Iowa State University’s College of Liberal Arts and Sciences. "It turns out that geodesic stability on the molecular level is also rather remarkable. Carbon atoms like to be arranged in this particular formation and are extremely stable."

Since the structure is very stable and hollow, chemists have envisioned a whole new array of applications if they could find a way to put other atoms or compounds inside the buckyball.

Unfortunately, the only way to produce C₆₀ is to replicate the environment of interstellar space with a process that basically involves arcing carbon rods, but this reaction takes place only at high temperatures. The high temperatures make it hard to control, and therefore extremely difficult to try to make buckyballs with something inside them. So the search turned to finding a way to "build" a buckyball from scratch.

"If you took a buckyball apart, it wouldn’t be a stable entity because it would have dangling bonds," Rabideau said. "But if you took it apart and put hydrogen atoms on the dangling bonds to stabilize it, you’d have a chemical compound that we call a buckybowl."

Rabideau has focused his research on the polynuclear aromatic hydrocarbon corannulene. This compound was first synthesized in 1966 at the University of Michigan by a long and difficult 17-step process that produced quantities weighing just a few milligrams. Then in the early 90’s, another group of researchers synthesized corannulene using pyrolysis.

"The problem with this technique is that you must do it in vacuum, so by definition you’re still working with very small amounts of material," Rabideau said.

What Rabideau and fellow researcher Andrzej Sygula developed was a solution-phase synthesis using dilute sodium hydroxide in water and acetone that produces tetrabromocorannulene. This process, detailed in an article published in the Journal of the American Chemical Society, allows production of 25-gram samples, a thousand-fold increase over the pyrolysis method.

"The process is really pretty simple," Rabideau said. "In fact the final step could almost be done in your garage using household chemicals." Though it hasn’t been a particular goal of his research, Rabideau added that a feasible commercial synthesis could easily be developed.

The synthesis of tetrabromocorannulene has also had a silver lining. While the bromine atoms can easily be removed to form corannulene, it’s advantageous to leave them on and add to them.

"We now have a way of elaborating that particular molecule in a lot of different ways," Radideau said, pointing to diagrams of just eight of the many variations. "It’s better than if we’d discovered a way to go directly to corannulene because we can use the bromines to do other things, though our focus is on the fundamental chemistry involved."

Though building a buckyball is still in the distance, researchers now have an unlimited supply of bowl material to study. By unlocking the properties of these bowl-shaped compounds, Rabideau hopes to eventually discover a way to combine the bowls into a sphere.

"If we could figure out a few critical reactions, we might ultimately be able to synthesize C₆₀," Rabideau said. "That would, in principle, allow us to build C₆₀ with a hole in it so that we could trap something inside, such as an atom or metal, and then close the ball."

Rabideau’s research is being funded through the Chemical Science Program at the DOE. The Ames Laboratory is operated for the DOE by Iowa State University. The Lab conducts research into various areas of national concern, including energy resources, high-speed computer design, environmental cleanup and restoration, and the synthesis and study of new materials.

Find illustrations of a corannulene (C₂₀H₁₀) molecule at:  ftp://ftp.external.ameslab.gov/marti/bbowlcolor and

ftp://ftp.external.ameslab.gov/marti/bbowlb&w