The smallest cucurbituril analogue with high affinity for Ag+

A new host, Me8TD[4], was prepared for the first time from propanediurea- formaldehyde condensation in the presence of CaCl2 as the template and it is the smallest cucurbituril analogue reported so far. Measurements of the thermodynamic quantities ( log K, Delta H, and Delta S values) of the interactions of Me8TD[4] with a series of cations by isothermal titration calorimetry indicated that Me8TD[4] binds selectively towards Ag+ with a high binding constant, K similar to 1.3 x 10(6) M-1.