FLUORESCENT PHOTOINDUCED ELECTRON-TRANSFER SENSORS - THE SIMPLE LOGIC AND ITS EXTENSIONS

The principle of photoinduced electron transfer is combined with the modular system 'Fluorophore-Spacer-Receptor' to develop the phenomenon of cation-responsive fluorescence. pH controlled 'on-off' fluorescence is demonstrated in the case of the dialkylaminoalkyl heterocyclic derivative 1a. The modular system is then extended in two directions. In the first of these, targetting/anchoring modules are added to allow the investigation of proton fields in microheterogeneous membrane media with high spatial resolution. The sensor family 2a-f is the realization of this approach. The second direction employs phosphorescent (instead of fluorescent) modules with/without protective shields to permit the development of phosphorescent pH sensing in an interference-free manner within intrinsically fluorescent environments. Sensors like 3 in aqueous beta-cyclodextrin solution illustrate the possibilities of this idea.