Noble gas binding and bonding with gold-substituted cyclopropenyl cation

Abstract

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.