Equilibrating Dynamic [2]Rotaxanes

Upon mixing and dehydration, 2,6-diformylpyridine and 2,2‘-oxybis(ethylamine) form a dynamic
combinatorial library of at least nine members. Through hydrogen bonding and other intermolecular
interactions, templating dumbbell molecules select one macrocyclic member of the library, at the expense
of all the others, to create [2]rotaxanes. These rotaxanes, however, retain the dynamic character of the
library, since a diformylpyridine analogue can exchange with the macrocyclic component in solution. In
addition, crystallization of the mixture surprisingly furnishes only the [24]crown-8-like macrocycle on
its ownevidence of a kinetic selection process occurring between phase transitions.