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A Cucurbit[8]uril2:2 Complex with a Negative pKa Shift
Hang Yin1; Qian Cheng1; Roselyne Rosas2; StØphane Viel2,3; ValØrie Monnier2; Laurence Charles2,3; Didier Siri2,3; Didier Gigmes2,3; Olivier Ouari2,3; Ruibing Wang1; Anthony Kermagoret2,3; David Bardelang2,3

A viologen derivative carrying a benzimidazole group (V‐P‐I2+; viologen–phenylene–imidazole V‐P‐I) can be dimerized in water using cucurbit[8]uril (CB[8]) in the form of a 2:2 complex resulting in a negative shift of the guest pKa, by more than 1 pH unit, contrasting with the positive pKa shift usually observed for CB‐based complexes. Whereas 2:2 complex protonation is unclear by NMR, silver cations have been used for probing the accessibility of the imidazole groups of the 2:2 complexes. The protonation capacity of the buried imidazole groups is reduced, suggesting that CB[8] could trigger proton release upon 2:2 complex formation. The addition of CB[8] to a solution containing V‐P‐I3+ indeed released protons as monitored by pH‐metry and visualized by a coloured indicator. This property was used to induce a host/guest swapping, accompanied by a proton transfer, between V‐P‐I3+CB[7] and a CB[8] complex of 1‐methyl‐4‐(4‐pyridyl)pyridinium. The origin of this negative pKa shift is proposed to stand in an ideal charge state, and in the position of the two pH‐responsive fragments inside the two CB[8] which, alike residues engulfed in proteins, favour the deprotonated form of the guest molecules. Such proton release triggered by a recognition event is reminiscent of several biological processes and may open new avenues toward bioinspired enzyme mimics catalyzing proton transfer or chemical reactions.

Keyword2:2complexes Cucurbituril Host–guestsystems Imidazoles Viologen
Indexed BySCIE
WOS Research AreaChemistry
WOS SubjectChemistry, Multidisciplinary
WOS IDWOS:000481075600001
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Cited Times [WOS]:8   [WOS Record]     [Related Records in WOS]
Document TypeJournal article
CollectionUniversity of Macau
Corresponding AuthorRuibing Wang; Anthony Kermagoret
Affiliation1.State Key Laboratory of Quality Research in Chinese Medicine Institute of Chinese Medical Sciences, University of Macau Avenidada Universidade,Taipa, Macau(P.R.China)
2.Aix Marseille Univ,CNRS,Spectropole, FR 1739,Marseille (France)
3.Institut Universitaire de France, Paris(France)
First Author AffilicationInstitute of Chinese Medical Sciences
Corresponding Author AffilicationInstitute of Chinese Medical Sciences
Recommended Citation
GB/T 7714
Hang Yin,Qian Cheng,Roselyne Rosas,et al. A Cucurbit[8]uril2:2 Complex with a Negative pKa Shift[J]. CHEMISTRY-A EUROPEAN JOURNAL,2019,25(54):12552-12559.
APA Hang Yin,Qian Cheng,Roselyne Rosas,StØphane Viel,ValØrie Monnier,Laurence Charles,Didier Siri,Didier Gigmes,Olivier Ouari,Ruibing Wang,Anthony Kermagoret,&David Bardelang.(2019).A Cucurbit[8]uril2:2 Complex with a Negative pKa Shift.CHEMISTRY-A EUROPEAN JOURNAL,25(54),12552-12559.
MLA Hang Yin,et al."A Cucurbit[8]uril2:2 Complex with a Negative pKa Shift".CHEMISTRY-A EUROPEAN JOURNAL 25.54(2019):12552-12559.
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