A rotaxane exciplex.

The creation of molecular-scale photonic devices requires supramolecular logic elements.1-3 Although the study of supramolecular photochemistry is still in its infancy, it is clear that it offers much greater diversity than single-molecule systems. These components may permit access to complex photophysical processes, such as vectorial energy transfer, energy migration, and optical switching.4 Fundamental studies of supramolecular photochemistry are also relevant to biological studies of vision and photosynthesis.5,6 Intramolecular exciplexes formed between tethered donor and acceptor moieties have been investigated extensively.7,8 These studies are important for understanding energy transport and molecular dynmaics, as well as designing new chemical sensors. Luminescent intramolecular exciplexes between molecular components that are not covalently bound to one another have not been developed.9,10 Herein, we report the observation of an emissive exciplex formed between two components of a rotaxane, an unusual optical phenomenon. Making use of methods developed by Sauvage,11 rotaxane 3 was prepared in 81% yield from a Cu(I)-templated esterification of tris(p-tert-butylphenyl)(4-hydroxyphenyl)-methane with 5,5′-