Rotaxane
Appearance
A rotaxane is a molecular structure in two parts which do not chemically interact: a ring, and an axis with end bumps which prevent the ring from leaving the axis.
Rotaxanes, like catenanes, are of interest for their potential role in the future of molecular electronics as logic switching elements.
External links
http://website.lineone.net/~matthew.carroll/research/crest/rotaxane.gif