Host-guest Interaction of Thiophene Viologen with Cucurbit6uril and its Cyclohexano-substituted Derivatives

Taking thiophene viologen as the guest, four kinds of melon rings, namely, six membered melon ring (Q6), symmetrical cyclohexyl six membered melon ring (Cy2Q6), four substituted cyclohexyl six membered melon ring (Cy4Q6) and all substituted cyclohexyl six membered melon ring (Cy6Q6) were taken as the host. The binding interactions of hosts Q6, Cy2Q6, Cy4Q6 and Cy6Q6 with guest thiophene viologen in aqueous solution were studied with the methods of ¹H NMR spectroscopy, UV-visible spectroscopy and isothermal titration calorimetry. The results show that the guest molecule forms stable inclusion complexes with four kinds of hosts, and the inclusion complexes with the inclusion ratio of 2:1 are formed between the four host molecules and the guest molecules, respectively. The interaction of Q6, Cy4Q6, Cy2Q6 and Cy6Q6 with thiophene viologen is enthalpy driven.