A study of anion binding behaviour of 1,3-alternate thiacalixarene-based receptors bearing urea moieties†
Three novel thiacalixarene receptors 4a–c each with a 1,3-alternate conformation and possessing two urea moieties linking various phenyl groups substituted with either para electron-donating or -withdrawing groups have been synthesized. The binding properties of these receptors were investigated by means of 1H NMR spectroscopy and UV-vis absorption titration experiments using various anions. The structures and complexation energies were also studied by density functional theory (DFT) methods. The results suggested that receptor 4c, which possesses two p-(trifluoromethyl)phenyl ureido moieties, can complex most efficiently in the urea cavity and exhibits high selectivity towards F− and AcO− ions.