Xing Hang, Lin Shrong-Shi, Yan Peng, Xiao Jin-Xin, Chen Yong-Ming
Beijing National Laboratory for Molecular Sciences, College of Chemistry and Molecular Engineering, Peking University, Beijing 100871, China.
J Phys Chem B. 2007 Jul 19;111(28):8089-95. doi: 10.1021/jp070198a. Epub 2007 Jun 27.
The interactions between beta-cyclodextrin (beta-CD) and the equimolar/nonequimolar mixtures of sodium perfluorooctanoate (C(7)F(15)COONa, SPFO) and sodium alkyl sulfate (C(n)H(2n+1)SO(4)Na, C(n)SO(4), n = 8, 10, 12) were investigated by 1H and 19F NMR. It showed that beta-CD preferentially included the fluorinated surfactant when exposed to mixtures of hydrogenated (C(n)SO(4)) and fluorinated (SPFO) surfactants, notwithstanding whether the hydrogenated surfactant C(n)SO(4) was more or less hydrophobic than the SPFO. Such preferential inclusion of the fluorinated surfactant continued to a certain concentration of beta-CD at which time the C(n)SO(4) was then observed to be included. The longer the hydrocarbon chain of C(n)SO(4) the lower the concentration of beta-CD at which the hydrogenated surfactants began to show inclusion. The inclusion process can be qualitatively divided into three stages: first, formation of 1:1 beta-CD/SPFO complexes; second, formation of 1:1 beta-CD/C(n)SO(4) complexes; and finally, formation of 2:1 beta-CD/SPFO complexes upon further increase of beta-CD concentration. In the concentration range studied, during the last stage of inclusion both 2:1 beta-CD/C(12)SO(4) and 2:1 beta-CD/SPFO complexes appear to be simultaneously formed in the system of beta-CD/SPFO/C(12)SO(4) but not in either the systems of beta-CD/SPFO/C(8)SO(4) or beta-CD/SPFO/C(10)SO(4). The selective inclusion of the shorter fluorocarbon chain surfactant might be attributed to the greater rigidity and size of the fluorocarbon chains, compared to those of the hydrocarbon chains, which provide for a tighter fit and better interaction between the host and guest. This latter effect appears to dominate the increase in hydrophobic character as the carbon chain length increases in the hydrogenated series.
通过氢核磁共振（1H NMR）和氟核磁共振（19F NMR）研究了β-环糊精（β-CD）与全氟辛酸钠（C(7)F(15)COONa，SPFO）和烷基硫酸钠（C(n)H(2n + 1)SO(4)Na，C(n)SO(4)，n = 8、10、12）等摩尔/非等摩尔混合物之间的相互作用。结果表明，当β-环糊精与氢化（C(n)SO(4)）和氟化（SPFO）表面活性剂的混合物接触时，无论氢化表面活性剂C(n)SO(4)的疏水性比SPFO强还是弱，β-环糊精都优先包合氟化表面活性剂。这种对氟化表面活性剂的优先包合作用会持续到一定浓度的β-环糊精，此时才观察到C(n)SO(4)被包合。C(n)SO(4)的碳氢链越长，氢化表面活性剂开始显示被包合时β-环糊精的浓度越低。包合过程可定性地分为三个阶段：第一，形成1:1的β-CD/SPFO复合物；第二，形成1:1的β-CD/C(n)SO(4)复合物；最后，随着β-环糊精浓度的进一步增加，形成2:1的β-CD/SPFO复合物。在所研究的浓度范围内，在包合的最后阶段，在β-CD/SPFO/C(12)SO(4)体系中似乎同时形成了2:1的β-CD/C(12)SO(4)和2:1的β-CD/SPFO复合物，但在β-CD/SPFO/C(8)SO(4)或β-CD/SPFO/C(10)SO(4)体系中则没有。较短碳氟链表面活性剂的选择性包合可能归因于碳氟链比碳氢链具有更大的刚性和尺寸，这使得主体与客体之间的配合更紧密，相互作用更好。随着氢化系列中碳链长度的增加，后一种效应似乎主导了疏水性的增加。
