14502-43-3Relevant articles and documents
A new pH-switchable dimannosyl[c2]daisy chain molecular machine
Coutrot, Frederic,Romuald, Camille,Busseron, Eric
, p. 3741 - 3744 (2008)
(Figure Presented) The preparation of a dimannosyl[c2]daisy chain molecular machine containing an ammonium and a triazolium station is described. The both stretched and contracted states of the molecular machine can be obtained by variation of the pH, thus localizing the mannosyl stoppers closer or farther away.
Very contracted to extended co -conformations with or without oscillations in two- and three-station ['2]daisy chains
Romuald, Camille,Busseron, Eric,Coutrot, Frederic
supporting information; experimental part, p. 6516 - 6531 (2010/12/24)
The syntheses of various two- and three-station mannosyl [c2]daisy chains, based on a dibenzo-24-crown-8 macrocyclic moiety and an ammonium, a triazolium, and a mono- or disubstituted pyridinium amide station, are reported. The ability of these molecules to act as molecular machine based mimetics has been further studied by 1H NMR studies. In all the protonated ammonium states, the interwoven rotaxane dimers adopt an extended co-conformation. However, carbamoylation of the ammonium station led to many different other [c2]daisy chain co-conformations, depending on the other molecular stations belonging to the axle. In the two-station [c2]daisy chains containing an ammonium and a mono- or disubstituted pyridinium amide station, two large-amplitude relative movements of the interwoven components were noticed and afforded either an extended and a contracted or very contracted state with, in the latter case, an impressive chairlike conformational flipping of the mannopyranose from 1C4 to 4C1. In the case of the three-station-based [c2]daisy chains containing an ammonium, a triazolium, and disubstituted pyridinium amide, an extended and a half-contracted molecular state could be obtained because of the stronger affinity of the dibenzo-24-crown-8 part for, respectively, the ammonium, the triazolium, and the disubstituted pyridinium amide. Eventually, with axles comprising an ammonium, a triazolium, and a monosubstituted pyridinium amide, an extended conformation was noticed in the protonated state whereas a continuous oscillation between half-contracted and contracted states, in fast-exchange on the NMR time scale, was triggered by carbamoylation. Variations of the solvent or the temperature allow the modification of the population of each co-conformer. Thermodynamic data provided a small free Gibbs energy δG of 2.1 kJ·mol -1 between the two translational isomers at 298 K.
