Host-guest interaction of cucurbit[7]uril with <i>para-</i>nitrophenol: A weakly binding inclusion complex

Abstract

Host-guest interaction between water soluble rigid molecular container cucurbit[7]uril (CB[7]) and a water soluble organic guest <i>para</i>-nitrophenol (PNP) has been investigated using ¹H NMR spectroscopy and isothermal titration calorimetry. The stoichiometry, binding constant and other thermodynamic parameters of complexation have been obtained which show the formation of weakly binding 1:1 inclusion complex resulting from enthalpy-entropy compensation. Cyclic voltammetry study of PNP-CB[7] complex in acidic pH reveals a large cathodic shift in the reduction potentials of PNP, indicating either stabilization of PNP or destabilization of the electro-reduced product inside CB[7] cavity.