Thermally Driven Reorganization of Aurophilic AIE Aggregates in Microheterogeneous Acetonitrile/Water Media

Abstract

We report a combined spectroscopic, kinetic, and computational study of aggregation-induced emission (AIE) in tetranuclear Au(I)/Ag(I) complexes in microheterogeneous acetonitrile/water mixtures. Time-resolved UV–vis spectroscopy and multivariate analysis reveal that once AIE aggregates are formed, a further aggregation process proceeds via a continuous, cooperative reorganization pathway rather than classical nucleation–growth. The process follows compressed-exponential kinetics and exhibits a well-defined activation barrier (Ea = 86 kJ·mol–1). Dynamic light scattering confirms a hierarchical growth from nanometric aggregates to micron-scale species leading to precipitation. DFT calculations show that interunit interactions (116 kJ·mol–1), dominated by aurophilic and π-stacking forces, govern aggregate stability and are mechanistically linked to the kinetic barrier arising from their partial reorganization. Conductor-like Screening Model (COSMO) analysis further indicates weak solvation, rationalizing the dominance of intermolecular interactions.