Noble gas binding and bonding with gold-substituted cyclopropenyl cation

The electrophilic character of gold atoms in aromatic systems presents a unique opportunity for noble gas (Ng) bond formation. This computational study investigates the formation of noble gas (Ng) complexes with the aromatic C₃Au₃⁺ cation, yielding C₃Au₃Ng_n⁺ (n = 1-3; Ng = He-Rn). Thermodynamic analyses at the DFT and MP2 levels confirm that complexes from Ar to Rn are stable at 298 K, with dissociation energies increasing with Ng polarizability, while He/Ne binding is exergonic but feasible at low temperatures. The Au-Ng bond is characterized by dominant dative covalent character, as revealed by Natural Bond Orbital Theory and Natural Energy Decomposition Analysis, with charge transfer from Ng to Au constituting 66-78% of the attractive interactions. Furthermore, noble gas coordination enhances the electronic delocalization in the ring, leading to a measurable increase in aromaticity (via ring current strength) and a larger HOMO-LUMO gap, thereby reducing the system's reactivity compared to bare C₃Au₃⁺. This work establishes aurocarbocations as promising motifs for noble gas chemistry and underscores the interplay between bonding and electronic stability in these unique complexes.