OrtHo-hydroxybenzaldehyde derivatives

This observation has led to many other cases in which a large red shift is found, and where ESIPT is invoked to explain this. Since absorption and emission wavelengths can be modified by substituents at various places in the ring system, and there is a considerable dependence on the solvent or other environment (protein, membranes), many reporter systems have been designed on the basis of this idea. Salicylic acid and the related ortHo-hydroxybenzaldehyde derivatives have attracted most attention in the literature for fundamental research, but there are a few other groups of ESIPT molecules that have attracted attention as well. 

The most extensively investigated class of molecules is the ortho-hydroxybenzaldehyde derivatives (Figure 1.13). Almost every conceivable technique has been used to probe its properties in the gas phase as well as in a large variety of solvents and solvent mixtures. Starting with the work of Weller, both steady-state and time-resolved fluorescence remain the most commonly used techniques [96]. Femtosecond spectroscopy gives details of proton transfer... 

Among the oldest kinetic studies on tautomerization reactions, [5] is the enolization of compounds like acetaldehyde, depicted in Figure 9.2. A second group of compounds that have been the topic of numerous studies are ortho-hydroxybenzaldehyde (o-HBA) derivatives, shown in Figure 9.3. 

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