Oxacalix[2]arene[2]triazine Derivatives with Halogen Bond Donors: Synthesis, Structure, and Halide Binding in the Solid State

By means of post-macrocyclization functionalization, a series of oxacalix[2]arene[2]triazine derivatives 3a–d, bearing mono- and dihalogen (Br, I) substituted phenyl moieties on the larger rim of the triazine rings were very efficiently synthesized with yields of 85–89%. The binding of 3a–d toward halide anions in the solid state was investigated by X-ray crystallography. For complexation of 3c (X = H, X′ = I) with chloride, a Cl–···H2O···Cl–···H2O···H2O pentagonal hydrogen bond network was found included in the cavity of the host molecule, as stabilized by cooperative anion-π interaction and halogen and hydrogen bonding. In contrast, with iodide only intermolecular halogen bonding between 3c and iodide was observed. On the other hand, 3d (X = X′ = I) forms a series of very similar chelating halogen bonding motifs with chloride, bromide, and iodide, respectively.