光谱法研究七、八元瓜环对亚甲基蓝的分子识别

利用紫外-可见吸收光谱和荧光光谱法考察了七、八元瓜环(Q7],Q8])对客体亚甲基蓝染料(g)的分子识别作用.结果表明,Q7]与g作用形成物质的量比为2:1的主客体配合物,Q8]与g作用形成的是物质的量之比为1:2的主客体配合物.吸收光谱法测得的包结常数分别为KQ7]-g=1.34×1012 L2·mol-2,KQ8]-g=5.34×1012 L2·mol-2;荧光光谱法测得的KQ7]-g=1.53×1012 L2·mol-2,KA8]-g=6.11×1012 L2·mol-2,两种方法结果一致.随着Q7或8]浓度的增加,瓜环对客体有明显的荧光增敏作用,而Q8]对客体有明显的荧光猝灭作用.从Q7]和Q8]分别与客体作用体系的紫外-可见吸光度和荧光强度随pH值改变的变化规律可以看出,体系在pH在0.5～13范围内均能观察到主客体的相互作用,且作用比例不发生变化.

Recognition of Cucurbit[7 and 8] urils Toward Methylene Blue with Spectroscopy

The molecular recognition of cucurbit［7, 8］urils toward a methylene blue dye was investigated by using electronic absorption spectroscopy and fluorescence spectroscopy. The experimental results revealed that the formation of host-guest complexes between Q［7］ and the methylene blue dye were formed with a stoichiometry of 2∶1, while the formation of host-guest complexes between Q［8］ and the methylene blue dye were formed with a stoichiometry of 1∶2. The calculated binding constants are KQ［7］-g=1.34×1012 L2·mol-2 and KQ［8］-g=5.34×1012 L2·mol-2 respectively based on the absorption spectrophotometric analysis, while the calculated binding constants are KQ［7］-g=1.53×1012 L2·mol-2 and KQ［8］-g=6.11×1012 L2·mol-2 respectively based on the fluorescence spectroscopy analysis. The values of K are reasonably consistent. The fluorescence of the guest was found to rapidly increase with the increase in the concentration of Q［7］, while the fluorescence of the guest was found to rapidly decrease with the increase in the concentration of Q［8］. Based on the variation of the absoption or fluorecence of the host-guest complexes of Q［7］ or Q［8］-methylene blue dye with the variation of pH, the interaction of the Q［7］ or Q［8］ and the methylene blue dye with an unchangeable ratio can be observed in the range of pH between 0.5 and 13.