Valence-Delocalized Trithorium Nanocluster Superatoms with Open-Shell Exalted Diamagnetism

Quantum confined nanoclusters can be described by the jellium model, which emphasizes closed-shell electron configurations, but an open-shell variation with jellium aromaticity has been proposed. Such clusters are termed superatoms because they behave like an atom, and they exhibit unusual properties. Superatoms feature metal-metal bonding, hence since their discovery forty years ago superatoms have exclusively involved main group or transition metals, with actinides only considered computationally as dopants due to actinide-actinide bonding being exceedingly rare. Here, we report trithorium nanoclusters exhibiting three-centre-one-electron actinide-actinide bonding. Experimental and computational analysis demonstrates Robin-Day Class III 6d-orbital valence-delocalization in these clusters. These S = 1/2 clusters are paramagnetic, but in external applied magnetic fields they exhibit exalted diamagnetism, evidencing actinide open-shell jellium aromaticity superatom character. Exalted diamagnetism is not normally associated with a single unpaired electron, but with a 1S1 magic number the valence-delocalization enables exalted diamagnetism, which is aromaticity, via superatom ring-currents.