Aski Sahar Nikkhou, Kowalewski Jozef
Department of Physical, Inorganic and Structural Chemistry, Arrhenius Laboratory, Stockholm University, S-106 91 Stockholm, Sweden.
Magn Reson Chem. 2008 Mar;46(3):261-7. doi: 10.1002/mrc.2180.
The stability of an inclusion complex of quinuclidine with alpha-cyclodextrin in solution was investigated by NMR measurements of the translational diffusion coefficient. A 1:1 stoichiometry model yielded an association constant of 35 +/- 3 M(-1). The guest molecules exchange rapidly between the host cavity and the bulk solution. The reorientational dynamics of the guest and host molecules was studied using carbon-13 NMR relaxation at two magnetic fields. The relaxation of the host nuclei showed very little dependence on the guest-host concentration ratio, while the 13C spins in quinuclidine were sensitive to the solution composition. Using mole-fraction data, it was possible to extract the relaxation parameters for the bound and free form of quinuclidine. Relaxation rates of the guest molecule, free in solution, were best described by an axially symmetric model, while the data of the complex species were analyzed using the Lipari-Szabo method. Applying the axially symmetric model to the complexed quinuclidine indicated that the anisotropy of its reorientation in the bound form was increased.
通过对平移扩散系数的核磁共振测量，研究了奎宁环与α-环糊精在溶液中的包合物稳定性。1:1化学计量模型得出的缔合常数为35±3 M⁻¹。客体分子在主体空腔和本体溶液之间快速交换。利用两个磁场下的碳-13核磁共振弛豫研究了客体和主体分子的重取向动力学。主体核的弛豫对客体-主体浓度比的依赖性很小，而奎宁环中的¹³C自旋对溶液组成敏感。利用摩尔分数数据，可以提取奎宁环结合态和游离态的弛豫参数。溶液中游离的客体分子的弛豫速率最好用轴对称模型描述，而配合物物种的数据则用Lipari-Szabo方法分析。将轴对称模型应用于络合的奎宁环表明，其结合形式的重取向各向异性增加。
