A generic basis for some simple light-operated mechanical molecular machines

A novel type of mechanical switch is described in which light-induced translation of a macrocycle in a [2]rotaxane quenches anthracene fluorescence. Features of the system include the remarkable 200:1 difference in fluorescence intensity between the two positional states of the molecule (∼85:1 between one isomer and the photostationary state). In principle the same concept could be used for mechanically switching virtually any property that can be influenced by functional group proximity effects. Copyright © 2004 American Chemical Society.