葫芦[8]脲主客体包合物特性及对金属离子键合常数测定

Characteristics of Cucurbit[8]uril Host-guest Inclusion Complexes and Determination of the Binding Constants of Metal Ions with Cucurbit[8]uril

利用核磁共振、紫外-可见光谱、荧光发射光谱等检测手段,研究了葫芦[8]脲与一种双咪唑盐(C1)客体的包合模式。并以包合物为荧光探针测定了几种金属离子与葫芦[8]脲的键合常数。结果显示葫芦[8]脲与双咪唑盐C1以3∶1的比例形成包合物。核磁和紫外检测结果显示葫芦[8]脲优先结合双咪唑盐C1上新铜试剂基团,当其摩尔浓度超过C1后,葫芦[8]脲逐渐结合蒽基团。荧光滴定实验表明,葫芦[8]脲的加入显著增强了双咪唑盐C1的荧光强度。当葫芦[8]脲摩尔浓度为C1的4倍时,客体C1的荧光增强幅度达5倍。进一步的研究发现,金属离子与双咪唑盐C1竞争结合葫芦[8]脲造成葫芦[8]脲-C1包合物的荧光猝灭。Job’s plot曲线确定了金属离子与葫芦[8]脲的结合模式为1∶1和1∶2共存。通过荧光滴定,测定了Na^+、K^+、Ca^(2+)、Mg^(2+)、Cu^(2+)、Mn^(2+)、Cd^(2+)、Fe^(3+)8种金属离子与葫芦[8]脲的键合常数,其中Fe^(3+)与葫芦[8]脲的键合常数高达4.3×10~8(mol/L)^(-2)。

The host-guest interaction between a bisimidazolium salt(C1)and cucurbit[8]uril(CB[8])was investigated in aqueous solution by UV-Vis,fluorescence spectroscopic techniques,and 1H NMR.The results showed that CB[8]formed a 3∶1(3CB[8]·C1)inclusion complex with C1.NMR and UV-Vis results showed that CB[8]firstly bound the neocuproine group,and gradually bound the anthracene group.When more than 1.0equivalent,the addition of CB[8]could significantly enhance the fluorescence intensity of C1.When the concentration of CB[8]was 4times of C1,the fluorescence intensity of C1increased by 5times.Further investigation displayed that C1could not bind metal ions in aqueous solution.However,the inclusion complex of C1with CB[8]could be used as a fluorescent probe since metal ions compete with C1to bind with CB[8],causing the fluorescence quenching of C1.Eight metal ions(Na+,K+,Ca2+,Mg2+,Cu2+,Mn2+,Cd2+,Fe3+)were selected to check their binding with CB[8]and Fe3+showed the strongest binding affinity with CB[8](K=4.3×108(mol/L)-2).