Yamauchi A, Hayashita T, Kato A, Nishizawa S, Watanabe M, Teramae N
Department of Chemistry, Graduate School of Science, Tohoku University, Sendai, Japan.
Anal Chem. 2000 Dec 1;72(23):5841-6. doi: 10.1021/ac000741i.
Three fluoroionophores Cn (n = 1, 3, 5), in which the crown ether unit and pyrenyl moiety are connected by a -(CH2)n- spacer, have been used to construct supramolecular Cn/gamma-cyclodextrin (gamma-CyD) complexes for alkali metal ion sensing in water. The Cn (n = 3, 5) are found to selectively form 2:1 complexes with K+ in the presence of gamma-CyD and exhibit the pyrene dimer emission in water. Equilibrium analysis of the C3/gamma-CyD complex reveals that the observed dimer emission arises from a 2:1:1 complex of C3 with K+ and gamma-CyD. In the absence of K+, the fluorescence lifetimes for the dimer species ((C3)2CyD and (C3)2(CyD)2) and the monomer species (C3CyD and C3(CyD)2) are 13-18 and 130-180 ns, respectively. Upon addition of 0.10 M KCI, a rising component corresponding to pyrene excimer formation is observed at the dimer emission region. For the C3/gamma-CyD complex, the apparent association constant for K+ of (3.8 +/- 1.3) x 10(9) M(-2) is only slightly affected by the presence of Na+. Although the C5/gamma-CyD complex shows high sensitivity for K+, the selectivity for K+ over Na+ is lower than that of the C3/gamma-CyD complex. In contrast, fluoroionophore C1 with the shortest methylene spacer exhibits no response for alkali metal cations in the presence of gamma-CyD. These results demonstrate that the response function of supramolecular Cn/gamma-CyD complexes is strongly affected by the methylene spacer length of Cn. The highest K+ selectivity is obtained for the C3/gamma-CyD complexes in water.
三种氟离子载体Cn（n = 1、3、5），其中冠醚单元和芘基部分通过-(CH2)n-间隔基相连，已被用于构建超分子Cn/γ-环糊精（γ-CyD）配合物，用于水中碱金属离子传感。发现Cn（n = 3、5）在γ-CyD存在下与K+选择性地形成2:1配合物，并在水中表现出芘二聚体发射。对C3/γ-CyD配合物的平衡分析表明，观察到的二聚体发射源于C3与K+和γ-CyD的2:1:1配合物。在没有K+的情况下，二聚体物种（(C3)2CyD和(C3)2(CyD)2）和单体物种（C3CyD和C3(CyD)2）的荧光寿命分别为13 - 18和130 - 180 ns。加入0.10 M KCl后，在二聚体发射区域观察到对应芘激基缔合物形成的上升成分。对于C3/γ-CyD配合物，K+的表观缔合常数为(3.8 ± 1.3) x 10(9) M(-2)，仅受Na+存在的轻微影响。尽管C5/γ-CyD配合物对K+表现出高灵敏度，但对K+相对于Na+的选择性低于C3/γ-CyD配合物。相比之下，具有最短亚甲基间隔基的氟离子载体C1在γ-CyD存在下对碱金属阳离子无响应。这些结果表明，超分子Cn/γ-CyD配合物的响应功能受到Cn亚甲基间隔基长度的强烈影响。在水中，C3/γ-CyD配合物获得了最高的K+选择性。
