Supramolecular Cages Based on a Silver Complex as Adaptable Hosts for Poly‐Aromatic Hydrocarbons

Abstract In this work, an L‐shaped silver complex, AgLClO₄ (L = 2,3‐bis[3‐(pyridin‐2‐yl)‐1H‐pyrazol‐1‐yl·methyl]quinoxaline), M, is found to be adaptable enough to host a range of medium and large aromatic hydrocarbons including several polycyclic aromatic hydrocarbons (PAHs). The transformation of M from as‐synthesized closed (nonporous) crystalline to at least three types of open phase structures in the presence of different aromatic hydrocarbons enables the adaptable binding of M to these aromatics. In essence, M can rearrange its cavities to fit the different sizes and shapes of the guest molecules in the manner that is infeasible with cage compounds or coordination networks. Single‐crystal and powder X‐ray diffraction confirm the adaptable structures of the resulting host–guest complexes, M·nG (G = guest, n = 0.5 or 0.75). Detailed 1D and 2D nuclear magnetic resonance spectra, along with the fluorescence spectroscopy, reveal that the host–guest complexes feature similar chemical compositions in the solution, but are in the states of rapid exchange in and outside the cages. Such an adaptability of M provides insights into the strength of host–guest interactions and enables a new class of adsorptive molecular materials that can bind a large number of aromatics, specifically PAHs.