Experimental and Theoretical Aspects of Anion Complexes with a Thiophene-Based Cryptand

Selective recognition of anions has received a tremendous amount of attention in recent years because of their significant importance in biology and environment. This article highlights our recent research on a thiophene-based azacryptand that has been shown to effectively bind anions, including iodide, bromide, chloride, nitrate, and sulfate. Structural studies indicate that the ligand forms inclusion complexes with chloride and iodide. On the other hand, it forms cleft-like complexes with nitrate and sulfate, where three anions are bound between the cyclic arms. The ligand binds each anion with a 1:1 binding mode in water, exhibiting strong selectivity for sulfate, which is further supported by ESI-MS and DFT calculations.