Discovery of anion-π interactions in the recognition mechanism of inorganic anions by 1,2,3-triazolium rings

A bis(triazolium)-based receptor designed for anion recognition is presented. NMR spectroscopic data indicate that one triazolium ring is acting as a hydrogen bond donor, whereas the second triazolium ring behaves as an anion-pi receptor. The simultaneous presence of two noncovalent interactions allows us to achieve a highly selective binding of the hydrogenpyrophosphate anion.