Anion recognition by neutral chalcogen bonding receptors: experimental and theoretical investigation.

The utilization of neutral receptors for the molecular recognition of anions based on chalcogen bonding (ChB) is an undeveloped area of host-guest chemistry. In this manuscript, the synthesis of two new families of sulfur, selenium and tellurium-based ChB binding motifs are reported. The stability of the thiophene, selenophene and tellurophene binding motifs has enabled the determination of association constants for ChB halide anion binding in the polar aprotic solvent THF by 1 H-, 77 Se- and 125 Te-NMR experiments. We have used two different aromatic cores and incorporated one or two Ch-binding motifs with the purpose to encapsulate the anion offering up to two concurrent chalcogen bonds. Theoretical calculations and NMR experiments reveal that, for S and Se receptors, hydrogen bonding interactions involving the acidic H-atom adjacent to the chalcogen atom are energetically favored over the ChB interaction. However, for the tellurophene binding motif, the σ-hole interaction is competitive and more favored than the H-bond.