Fluorescent Switches Based on Photochromic Compounds

The photochemical transformations associated with photochromic compounds can be exploited to switch the emission of complementary flourophores under the influence of optical stimulations. Specifically, fluorescent. and photochromic components can be integrated within the same molecular or supramolecular assembly and the significant changes in the stereoelectronic properties associated with the photoinduced interconversion of one component can be designed to modulate the emission intensity and/or wavelength of the other. In particular, the modifications in absorption properties, conjugation, dipole moment, redox potentials and shape of a photochrome can all be transduced effectively into reversible alterations of the emissive behavior of a fluorophore. Furthermore, some of these ingenious mechanisms for fluorescence modulation can be extended from relatively small molecular and supramolecular assemblies to large macromolecular, nanostructured and biomolecular constructs. In fact, a diversity of chemical systems with photoswitchable luminescence have already emerged on the basis of these operating principles and choice of functional components. Ultimately, these fundamental studies on the photochemical and photophysical signature of multicomponent assemblies might well lead to a new generation of photonic materials With unique properties for possible applications in biomedical imaging and sensing as well as in information processing and storage.