Thermodynamic parameters for formation of the inclusion complexes of α-, β- and γ-cyclodextrin (α-, β- and γ-CD) with ibuprofen (BF) in Tris-HCl buffer solutions (pH=7.0) have been determined by isothermal titration calorimetry (ITC) with nanowatt sensitivity, and the inclusion structures have been investigated by using 1H-NMR spectra at 298.15 K. A theoretical study on the inclusion processes between BF and CDs has been performed with the B3LYP/6-31G*//PM3 method in order to investigate the formation mechanism of the inclusion complexes. An analysis of the thermodynamic data indicates that the stoichiometries of α-, β- and γ-CD with BF are all 1:1 and formation of the inclusion complexes α-CD⋅BF and β-CD⋅BF are driven by enthalpy and entropy, whereas formation of γ-CD⋅BF is an entropy driven process. The 1H-NMR spectra provide clear evidence for the inclusion phenomenon, and show that the isobutyl group and aromatic ring of the guest molecule are trapped inside the cavity of the CDs. Theoretical calculations suggest that the complex formed by the BF molecule entering into the cavity of the CD molecule from the wide side is more stable than that from the narrow side.
通过纳瓦灵敏度的等温滴定量热法(ITC)测定了α-、β-和γ-
环糊精(α-、β-和γ-CD)与
布洛芬(BF)在
Tris-HCl 缓冲溶液(pH=7.0)中形成包合物的热力学参数,并利用 298.15 K 下的 1H-NMR 光谱研究了包合物的结构。为了研究包合物的形成机理,我们采用 B3LYP/6-31G*//PM3 方法对 BF 和 CD 之间的包合过程进行了理论研究。对热力学数据的分析表明,α-、β- 和 γ-CD 与 BF 的
化学计量比均为 1:1,α-CD⋅BF 和 β-CD⋅BF 的形成受焓和熵的驱动,而 γ-CD⋅BF 的形成是一个熵驱动过程。1H-NMR 光谱为包合现象提供了明确的证据,并表明客体分子的异丁基和芳香环被困在 CD 的空腔内。理论计算表明,BF 分子从宽侧进入 CD 分子空腔所形成的复合物比从窄侧进入的复合物更稳定。