A Switchable Palladium-Complexed Molecular Shuttle and Its Metastable Positional Isomers

We report the design, synthesis, characterization, and operation of a [2]rotaxane in which a
palladium-complexed macrocycle can be translocated between 4-dimethylaminopyridine and pyridine
monodentate ligand sites via reversible protonation, the metal remaining coordinated to the macrocycle
throughout. The substitution pattern of the ligands and the kinetic stability of the Pd−N bond means that
changing the chemical state of the thread does not automatically cause a change in the macrocycle's
position in the absence of an additional input (heat and/or coordinating solvent/anion). Accordingly, under
ambient conditions any of the four sets of protonated and neutral, stable, and metastable co-conformers
of the [2]rotaxane can be selected, manipulated, isolated, and characterized.