Tetramidocavitand: strong anion receptor by well-organized four –(CO)N–H⋯X− interactions

Resorcin[4]arene-based tetramidocavitands containing four secondary amide groups on their upper rim showed strong RSO 3 - (R = methyl or ethyl) binding properties. The caviplex formation through hydrogen bonds of –(CO)N–H⋯X− was supported by 1H NMR and crystal structure analyses. In a mixture of C2D2Cl4/DMSO/D2O = 5:15:2 at 25 °C, the thermodynamic parameters for caviplex CH 3 SO 3 - @1, ΔG (kcal mol−1), ΔH (kcal mol−1), and ΔS (cal K−1 mol−1), are −3.7, −8.6, and −16.7, respectively.