Cucurbituril slippage: translation is a complex motion.

The kinetics of cucurbit[6]uril slippage along a polyaminated axle are highly dependent on even minor sterical alterations of the guest. According to in silico experiments, a plausible threading mechanism includes the deprotonation of the ammoniums prior to slippage, their tunneling through the cavitand as neutral amines, and their reprotonation upon exiting cucurbit[6]uril.