A fluorescent “off–on–off” proton switch derived from natural products and further studies of first-generation fluorescent photoinduced electron transfer (PET) systems

Abstract

Two new second generation fluorescent switches that are based on the chromophore–spacer–receptor architecture are reported in this paper. The fluorescence modulation of these switches is a result of quenching or initiating photoinduced electron transfer (PET) between the chromophore and the receptors due to cation binding. These two molecules utilize an alkaloid, anabasine, as the proton receptor, and function as fluorescent off–on–off switches with decreasing pH. One of these molecules also utilizes a coumarin as the chromophore, making it the first rationally designed fluorescent PET system based on natural products. Further studies of two well-known first generation fluorescent switches to achieve more complex fluorescence modulation are also reported in this paper.