Endohedral Tubular [X©Ae6X6]2- Dianions: A Class of Highly Stable Superchalcogens

Superchalcogens have emerged as an important class of multiply charged anions with significant potential as building blocks for novel materials, analogous to the roles of superalkalis and superhalogens in forming superatomic salts with unique properties. Herein, we design a series of tubular [X©Ae6X6]2- (X = O-Te; Ae = Be-Ba) clusters, in which a central chalcogen atom is encapsulated inside two staggered Ae3X3 rings. Comprehensive exploration of the potential energy surfaces identifies seven members of this series as global minima, exhibiting high thermodynamic, kinetic, and electronic stability. Pronounced charge transfer from Ae to X atoms gives rise to strong electrostatic stabilization, while additional dative interactions from the chalcogen atoms to vacant Ae orbitals generate a highly polarized multicenter bonding framework. These combined interactions underpin the remarkable stability of the dianions. This work introduces a viable strategy for the design of new superchalcogens and provides promising gas-phase targets for future experimental realization, thereby expanding the scope of superatomic chemistry and functional materials design.