Assembly of an electronically switchable rotaxane on the surface of a titanium dioxide nanoparticle.

This paper describes the self-assembly of a heterosupramolecular system consisting of a tripodal [2]rotaxane adsorbed at the surface of a titanium dioxide nanoparticle. The tripodal [2]rotaxane consists of a dumbbell-shaped molecule, incorporating two electron-poor viologens, threading an electron-rich crown ether. The [2]rotaxane also incorporates a bulky tripodal linker group at one end and a bulky stopper group at the other end. The [2]rotaxane is adsorbed, via the tripodal linker group, at the surface of a titanium dioxide nanoparticle. The structure and function of the resulting hetero[2]rotaxane have been studied in detail by (1)H NMR spectroscopy and cyclic voltammetry. A key finding is that it is possible to electronically address and switch the above hetero[2]rotaxane.