Key Laboratory of Macrocyclic and Supramolecular Chemistry of Guizhou Province, Guizhou University, Guiyang 550025, China.
Key Laboratory of Guizhou High Performance Computational Chemistry of Guizhou Province, Guizhou University, Guiyang 550025, China.
Spectrochim Acta A Mol Biomol Spectrosc. 2021 Jun 5;254:119656. doi: 10.1016/j.saa.2021.119656. Epub 2021 Mar 9.
In the present work, we have investigated the effect of pH and mercury ions on the host-guest complex formed between cucurbit[7]uril (Q[7]) and Hoechst 33342 (H33342). H NMR, UV-vis and fluorescence spectroscopy revealed that acid/base stimulation could change the binding stoichiometry between Q[7] and H33342. The results suggest that two complexation equilibria (1:1 and 2:1) may exist between H33342 and Q[7] at pH 2.0 and 4.5, respectively. However, a 1:1 host-guest complex was formed between H33342 and Q[7] at pH 7.0 and 10.0. Q[7] shows differential affinities for the protonated and neutral forms of H33342 dye. Moreover, the switching between H33342∙2H@2Q7 at pH 4.5 and H33342∙H@Q7 at pH 7.0 was reversible. Furthermore, as a metal stimulus, Hg ions could push (i) Q[7] from the piperazine ring to the benzimidazole position with a 1:1 guest-host ratio and (ii) a second Q[7] onto the ethyl position with a 1:2 guest-host stoichiometry. This stimulus response system will have potential applications in the field of molecular switch design.
在本工作中，我们研究了 pH 值和汞离子对葫芦[7]脲（Q[7]）与 Hoechst 33342（H33342）形成的主客体配合物的影响。1H NMR、UV-vis 和荧光光谱表明，酸碱刺激可以改变 Q[7]和 H33342 之间的结合化学计量比。结果表明，在 pH 2.0 和 4.5 时，H33342 和 Q[7]之间可能存在两种配合平衡（1:1 和 2:1）。然而，在 pH 7.0 和 10.0 时，H33342 和 Q[7]之间形成了 1:1 的主客体配合物。Q[7]对 H33342 染料的质子化和中性形式表现出不同的亲和力。此外，在 pH 4.5 时 H33342∙2H@2Q7 和在 pH 7.0 时 H33342∙H@Q7之间的转换是可逆的。此外，作为一种金属刺激物，Hg 离子可以将（i）Q[7]从哌嗪环推到苯并咪唑位置，形成 1:1 的客体-主体比例，和（ii）第二个 Q[7]推到乙基位置，形成 1:2 的客体-主体化学计量比。这种刺激-响应体系将在分子开关设计领域具有潜在的应用价值。
