Ring around the osmium

By constructing an aromatic hydrocarbon framework around an osmium ion, chemists have created a new class of organometallic compound . The in-plane metallo-annulenes are essentially carbon clusters embedded with transition metals. The molecules could have applications in high-performance electronics or could be used to make graphene doped with metal ( Nature 2025, DOI: 10.1038/s41586-025-08841-2). Organometallic compounds tend to marry metals with aromatic hydrocarbons so that the metal sits above or below the carbon-based group’s flat plane and interacts with the hydrocarbon’s p orbitals. The archetypal example is ferrocene, in which two cyclopentadiene ions make a sandwich with an iron ion in the center. The new, in-plane metallo-annulenes differ in that the metal sits within the plane of the aromatic hydrocarbon, and it participates in the molecule’s π conjugation and aromaticity. The molecules are reminiscent of porphyrins—flat, aromatic rings containing nitrogens that bind metal ions, such as iron in heme. Southern