Fluorescent sensors that undergo

Our aim is to design fluorescent sensors that undergo photophysical changes (extinction coefficient, fluorescence intensity, shifts in absorption and emission spectra) as marked as possible upon cation binding. Special attention is of course paid to selectivity and complex stability. With this in mind, two types of systems are being investigated in our laboratory fluoroionophores and complexing bifluorophores. 

Depending on the photophysical properties the pH fluorescent sensors can be divided into three classes (1) chemosensors that undergo photoinduced proton transfer, (2) chemosensors that undergo photoinduced electron transfer, and (3) those sensors that undergo neither proton nor electron transfer. 

It was found, however, that metallo-complexes that contain transition metal centers are especially convenient for fluorescence sensors as they undergo fast and kinetically uncomplicated one-electron redox changes (Bergonzi et al. 1998). Moreover, transition metals tend to participate in luminescence quenching of both the electron transfer, eT, and energy transfer, ET, varieties (see Fig. 10.5). Finally, the potential of the metal-centered redox couple can be modulated by varying the nature of the hosting... 

In contrast to the amino-rich dansyl monolayer MD-1, it is instead the amido-rich coumarin monolayer MC-2 that exhibits the largest fluorescence response toward Pb2+, undergoing 80% quenching. The amino-terminated coumarin monolayer MC-1 shows unique behavior within the library, with a 20% increase in fluorescence in the presence of Zn2+. This enhancement is important for sensor development because it would reduce the likelihood of false-positive signals. 

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