(Li ₆ Si ₅ ) _2–5: The Smallest Cluster-Assembled Materials Based on Aromatic Si ₅ ⁶⁻ Rings

Extensive explorations of their potential energy surfaces, combined with high-level quantum chemical computations, strikingly show that the lowest energy structures of the (Li ₆ Si ₅ ) _2–5 systems consist of 2–5 Si ₅ ⁶⁻ aromatic units, surrounded by Li ⁺ counterions, respectively. These viable gas-phase compounds are the pioneering reported cases of oligomers made by planar aromatic silicon rings. Based on the key evidence that these oligomers are energetically favored, and that their silicon rings aromaticity is thoroughly preserved, the Li ₆ Si ₅ cluster is proposed as a potential assembly unit to build silicon-lithium nanostructures, thus opening new paths to design Zintl compounds at the nanoscale level.