Heterogeneous wide range pH-sensing materials allowing ratiometric fluorescence detection based on structurally rigid analogs of 2,6-distyrylpyridine.

The new sensing materials based on the microsized silica gel powder with non-covalently immobilized structurally rigid analogs of 2,6-distyrylpyrydine ((3E,5E)-3,5-dibenzylidene-8-phenyl-1,2,3,5,6,7-hexahydrodicyclopenta[b,e]pyridines) were developed and tested. Most of the investigated compositions demonstrate linear ratiometric fluorescence response on pH in the physiologically important interval (pH 6-9). The compound with the greatest number of protolytic centers within the studied series demonstrated the widest pH sensitivity range, however in this case the analytical signal was the lowest.

Radiationless deactivation of the excited phototautomer form and molecular structure of ESIPT-compounds.

Correlation between the character of electronic density redistribution in the excited normal and phototautomer forms, which are involved in the excited state intramolecular proton transfer (ESIPT) reaction, and the rates of primary photoprocesses--proton phototransfer and radiationless deactivation of the phototautomer form--was analysed on the qualitative level. It was revealed that noticeable improvement of fluorescence properties of ESIPT molecules could be achieved by directed modification of their chemical structure, most importantly by the introduction of electron withdrawing substituents into their proton donor moieties. Several facts are presented in favour of the last statement.