A pH‐ and Metal‐Actuated Molecular Shuttle in Water

Abstract

AbstractThe 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 ofVPIbefore 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 stationT, shuttling between theTandPstations at acid pH or after Ag+addition. The CB[7] ⋅ T‐VPIcomplex thus behaves as a metal‐actuated thermodynamicstop‐and‐gomolecular 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.