The first all-carbon ring that’s stable at room temperature

For the first time, researchers have created an all-carbon molecular ring that is stable in solution at room temperature, with a bit of supramolecular support (Science 2025, DOI: 10.1126/science.ady6054). Cyclocarbons are unusual and extremely reactive cyclic carbon allotropes first detected in the gas phase in the 1950s. “Until not that long ago, we didn't really think it would be possible to study them by normal spectroscopic techniques in solution at room temperature,” says Harry L. Anderson of the University of Oxford, who has been working on cyclocarbons with his group for over a decade.Anderson’s team, alongside researchers at IBM, previously managed to make cyclo[18]carbon and cyclo[16]carbon on solid surfaces at supercold temperatures using a scanning tunneling microscope to manipulate the atoms. But to capture a cyclocarbon in solution, they needed to think outside the box—and inside a supramolecular assembly.The researchers took inspiration from studies from the 1990s that show that putting unstable molecules inside a cage-like structure can tame them enough to characterize them in solution. They started off by making linear polyyne chains, each threaded through a stabilizing macrocyclic ring and bearing a cobalt complex at each end to keep the ring in place. They published the synthesis of those structures at the end of 2023 (Nat. Chem., DOI: 10.1038/s41557-023-01374-z). Now they took it to the next step by linking three of these linear building blocks into a loop. Finally, the researchers removed the cobalt groups to reveal the final cyclo[48]carbon catenane product: a 48-carbon hoop bearing three supporting