김도의 (POSTECH)

서종철 (POSTECH)

김도의 (POSTECH)

최동진 (POSTECH)

서종철 (POSTECH)

 Cucurbituril (CB) has been shown to trap alkali halide clusters during electrospray ionization, where rapid droplet evaporation promotes contact ion-pair formation and stabilizes salt clusters within the molecular cavity. Building on this concept, we expanded the system from single alkali chloride salts to mixed alkali–halide environments, including LiCl/NaI and NaCl/KI, as well as additional combinations containing Rb⁺ and Br⁻. In addition, We also conducted experiments with alkaline earth metals such as Mg, Ca, and Sr.

 Ion mobility–mass spectrometry revealed a series of doubly charged CB-bound clusters composed of multiple metal and halide ions. The observed compositions could not be explained simply as conventional 1:1 salt aggregates, indicating that mixed ionic assemblies are formed through nonclassical aggregation pathways in evaporating ESI droplets. These results suggest that, beyond the critical cluster sizes reported for individual alkali metals, additional cations and anions can be incorporated into larger mixed clusters rather than forming separate salt domains. This work demonstrates that evaporating microdroplets provide a unique environment for generating unconventional mixed metal–halide aggregates stabilized by CB.