Enhanced Macroanion Recognition of Superchaotropic Keggin Clusters Achieved by Synergy of Anion‐π Interaction and Anion‐Cation Interaction

Keggin clusters are the most widely used polyoxomatales building blocks for construction advanced materials, while effective methods of precisely recognizing the isostructural analogues of Keggins are still limited. Here we applied zwitterionic molecule 4,4'-dipyridyl-N,N'-dioxide (dpdo) as a recognition receptor to specifically bind with the three Keggin analogues, PW12O403-, PMo12O403- and SiW12O404-, which co-assembled into three groups of spherical charged colloids with different sizes, separately. The recognition phenomena were further confirmed by electrochemistry study and crystallization behaviors. Compared with sole anion-cation interaction driven systems, the synergism from anion-π adsorption between the superchaotropic Keggins and the electro-deficient pyridine rings is believed to enhance the recognition phenomenon. The observation is intriguing as the long-range solution assembly of Keggins is mainly driven by the short-range anion-π interaction. Our results show that the little-noticed hydration shell of Keggins was significantly influenced by the superchaotropic effect, leading to differentiated binding affinity to the receptors and more obvious recognition phenomena between W/Mo Keggin analogues.