Chemists have created a stable fullerene molecule made entirely of metal atoms. In the cage-shaped cluster (shown), 12 gold atoms and 20 antimony atoms surround a single potassium ion, giving it the formula [K@Au12Sb20]5−. The inorganic fullerene could guide chemists as they try to make other precisely engineered nanostructures.
Fullerenes have fascinated chemists for decades—with the discoverers of the all-carbon version C60 even nabbing the 1996 Nobel Prize in Chemistry. Chemists have also tried to make these cagey compounds from non-carbon elements, but they’ve had to use external ligands to stabilize them—until now.
A team led by Nankai University’s Zhong-Ming Sun synthesized [K@Au12 Sb20 ]5− using a solution-based process. X-ray crystallography revealed that the molecule is a dodecahedral cage of Sb atoms combined with an icosahedron of Au atoms. Each Au sits at the center of an Sb pentagonal plane. The Au atoms stretch the cage so that it’s approximately the same size as C60, even though it has only 32 atoms (Science 2023, DOI: 10.1126/science.adj6491).
“What amazed us most was the ability of such a large heavy metal spherical cluster, supported only by a single potassium atom internally and devoid of any external ligand protection, to exist independently and be isolated,” Sun says in an email.
Andreas Schnepf, who studies metal clusters at the University of Tübingen and was not involved in the work, says the molecule has interesting bonding properties in the solid phase. But he is curious about the molecule’s behavior in solution, where he suggests these clusters could have interesting reactivity and applications.
“Initially we didn’t set out with the intention of creating such a unique molecular structure,” Sun tells C&EN. “During our research journey, we often encounter many interesting discoveries, which frequently come as surprises to us. It’s like reaching into a box of chocolates—it’s hard to predict the appearance or flavor of the next piece you’ll pick out.”