2-[4-(Dimethylamino)phenyl]-3-hydroxy-4H-chromene-4-one: A H-bond-sensitive fluorescent probe for investigating binary mixtures of organic solvents

Molecules of electronically excited 2-[4-(dimethylamino)phenyl]-3-hydroxy-4H-chromene-4-one (a fluorescent probe) co-exist in the normal (N^*) and tautomeric (T^*) forms and emit radiation in different spectral regions. The positions (expressed in wave numbers, ν) and intensities (I) of the emission bands are strongly affected by the ability of the medium's molecules to participate in hydrogen bonding with the probe. In such cases, I_N*, I_N*/I_T*, ν_N*, ν_N* + ν_T* or ν_N* − ν_T*, depend on the concentration (over a certain range) or its base-10 logarithm (log) of the component interacting with the probe. These relationships form the basis for a quantitative assay of such compounds in binary mixtures. On the other hand, the log(I_N*/I_T*) versus ν_N* + ν_T* or ν_N* − ν_T* relationships demonstrate unique features that can be used to distinguish components (alcohols) interacting with the probe and to quantify their contents. The prospects for the analytical application of these findings are outlined briefly.