| Abstract
| - Thermodynamics on inclusion complexation of α-cyclodextrin-based molecular tube (MT) with sodiumoctyl-, decyl-, and dodecylsulfonates (C8-, C10-, and C12SO3Na) were measured by isothermal titrationcalorimetry (ITC) to evaluate the effects of alkyl chain length of CnSO3Na and temperature. It was foundthat CnSO3Na with a longer alkyl chain formed more stable inclusion complex with MT. The associationconstant of inclusion complexation between MT and C12SO3Na at 298 K was found to be on the order of105. The stoichiometric number ([host]/[guest] ratio) was found to be 0.50 ± 0.05. This result indicates thatone MT forms an inclusion complex with two CnSO3Na molecules, regardless of the alkyl chain length ofCnSO3Na. Enthalpy−entropy compensation was also observed in MT/CnSO3Na systems, and it was confirmedthat the free energy change was not affected by the change in temperature (288−308 K). From thethermodynamic parameters, it was considered that both hydrophobic interaction and van der Waalsinteraction were mainly contributed to inclusion complexation of MT with CnSO3Na. The large and negativeentropy change (TΔS) attributed to the strong binding of MT was observed. The strong TΔS dependenceon the alkyl chain length of CnSO3Na was found to be a characteristic for inclusion complexation of MT.
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