We have demonstrated that guanidinium ions can thread through the cavity of BPX26C6 to form [2]pseudorotaxane-like complexes in low-polarity solvents. A [2]rotaxane derived from this new recognition system functions as a molecular switch, in which translational movement of macrocyclic component can be controlled two ways: through changes in solovent polarity and through exchanges of the counter anions.
