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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). 1H 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+@2Q[7](1:2) at pH 4.5 and H33342∙H+@Q[7](1:1) at pH 7.0 was reversible. Furthermore, as a metal stimulus, Hg2+ 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. Copyright © 2021 Elsevier B.V. All rights reserved.


Qin Wang, Li-Bing Lü, Zhu Tao, Tao Sun, Qing Tang, Ying Huang. The pH and mercury ion stimuli-responsive supramolecular assemblies of cucurbit[7]uril and Hoechst 33342. Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy. 2021 Jun 05;254:119656

PMID: 33744695

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