The Smallest Stable Fullerene, M@C28 (M = Ti, Zr, U)

Buckminster Fullerenes ("Buckyballs") have fascinated chemists since the original discovery of C₆₀, leading to the 1996 Nobel Prize in Chemistry for Curl, Kroto and Smalley. Although fullerenes of various sizes have since been observed, the theoretically smallest fullerene, C₂₈, has until now escaped detection, due to its high curvature and thus high reactivity.