A pH‐ and Metal‐Actuated Molecular Shuttle in Water
Amine Kriat, Simon Pascal, Brice Kauffmann, Yann Ferrand, David Bergé‐Lefranc, Didier Gigmès, Olivier Siri, Anthony Kermagoret, David Bardelang
Abstract
Abstract The structure of the Viologen‐Phenylene‐Imidazole ( VPI ) guest, previously shown to be bound by cucurbit[7]uril (CB[7]) with binding modes depending on pH and silver ions, has been extended by adding hydrophobic groups on the two extremities of VPI before investigations of CB[7] binding by NMR, ITC, X‐ray diffraction, UV‐vis and fluorescence spectroscopies. With an imidazole station extended by a naphthalene group ( VPI‐N ), binding modes of CB[7] are similar to those previously observed. However, with the viologen extended by a tolyl group ( T‐VPI ), CB[7] preferentially sits on station T , shuttling between the T and P stations at acid pH or after Ag + addition. The CB[7] ⋅ T‐VPI complex thus behaves as a metal‐actuated thermodynamic stop‐and‐go molecular shuttle featured by fast and autonomous ring translocation between two stations and a continuum for fractional station occupancy solely and easily controlled by Ag + concentration.