Synthesis of a [2]Rotaxane Incorporating a Ni(II)−Salen Moiety: Evidence of Ring-Opening-and-Closing Protocol

We have synthesized a [2]rotaxane from a crown-ether-like macrocycle that undergoes ring opening and closing through cleavage and formation
of imino bonds of a salen moiety; the self-assembly of this macrocycle and a dumbbell-shaped rodlike component, followed by addition of
nickel acetate, afforded, after counterion exchange, a [2]rotaxane that is stabilized through coordination of the Ni ion to the macrocycle's
salen moiety.