Buckyball Research : The Magic Molecule
Popular Science, August 1991, by Edward Edelson May 2, 2016
"It's the starting material for making a whole new family of organic compounds."
A FULLERENE FAMILY PORTRAIT
(Left) A C-60 molecule has a spherical shape; C-70 looks more like a rugby ball.
(Right) The first visual evidence for the existence of the fullerenes came from a team of scientists at IBM’s Almaden Research Center in San Jose, Calif., adept at using a special instrument that can image minute features. Called the scanning tunneling microscope, it works by dragging a tungsten or diamond tip, just one atom in width, across a surface and detecting the current that is generated when electrons “tunnel” between the tip and the surface [“Seeing Atoms,” April ’89].
Robert J. Wilson and colleague Donald Bethune, scientists at the IBM research center, first deposited a thin layer of sooty material they believed contained fullerenes on a nonreactive gold surface, then cooled the rapidly spinning molecules with liquid nitrogen to slow them down enough so that they could be imaged. The resulting photo gives the first direct evidence of the proposed shapes of C-60—spherical, like a soccer ball—and C-70—like an oblong rugby ball (drawings, top). The elongated, taller C-70 structures appear lighter because they jut higher than the gold surface. The image area is about 0.6 millionths of an inch on a side; the C-60 molecules are spaced about 44 billionths of an inch apart and are arranged in a hexagonal pattern typical of spheres that are packed tightly together. The fullerenes seen here are magnified about 12 million times.
Only the overall shapes of the C-60 and C-70 molecules can be seen, not the internal arrangement of their carbon atoms. Proof of buckyball’s geodesic structure had to wait until other scientists found a way to “freeze” the molecule.
Popular Science, August 1991
The Buckyball Lives
In the spring of 1991, chemists were able for the first time to take a picture of the buckyball molecule that shows exactly how the 60 carbon atoms are arranged. The result was to remove all doubt that the molecule’s geometry was indeed that of a hollow soccer ball, an elegant structure of hexagons and pentagons closely resembling one of Buckminster Fuller’s geodesic domes. That geometry had been originally proposed six years earlier. ‘This molecule is just as marvelous as we thought,” exults Joel Hawkins, who led the team of research chemists who made the image at the University of California at Berkeley.
Delineating the actual positions of carbon atoms inside the molecule was possible only by latching onto it long enough to stop its whirligig spin—a billion times a second. The Berkeley chemists were able to do this by attaching an osmium-based chemical handle—the “rabbit ears” in the picture—to the C-60 molecule. They were then able to make this computer-generated X-ray image of the resulting crystal structure.
In the picture, carbon atoms are purple; oxygen, red; nitrogen, green; and osmium, yellow.
The large, raspberry-shaped ball is the C-60 molecule. The yellow osmium atom is attached to it by two red oxygen atoms, and two structures called pyridine ligands, which look like rabbit ears, are attached to the osmium by the green nitrogen atoms.
Hawkins, Robin, & Loren