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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. The prospects for the practical application of the investigated materials in the fiber optics sensing devices were outlined.
During the last decades, biologically and medically oriented analysis was directed towards the miniaturization of both the studied objects and the sensing instruments. Fluorescence spectroscopy was often applied in line with such tendency because of its high sensitivity and ability to obtain analytical signal from the very low analytical volume.A great number of multi-purpose fluorescent compounds have been developed [1]. Among these compounds, the pH and metal cations sensitive compounds are of particular interest because of their high potential for the practical application in the biological and medical analysis. Several classes of organic compounds are suitable for this purpose, for example cyanines [2,3] Protolytic interactions in the series of prospective fluorescent ratiometric wide-range pH indicators -structurally rigid analogs of 2,6-distyrylpyridine -(3E,5E)-3, 5-dibenzylidene-8-phenyl-1,2,3,5,6,7-hexahydrodicyclopentano[b,e]pyridine -were investigated. The pyridine nitrogen atom basicity in these compounds is significantly lower in comparison with that of unsubstituted heterocycle and 2,6-distyrylpyridine. The photochemical E→Z photoisomerization and the side benzene rings substituents influence on the acid-base equilibria were studied. The complex multi-stage mechanism of the acid-base interactions of the polysubstituted compounds was elucidated. The most significant spectral effects were typical to the N,N-dialkylamino substituted compounds of the investigated series. The widest pH sensitivity interval covering nearly the full range of 0-14 units was demonstrated for compounds with both proton donor and proton acceptor substituents.
A series of novel aryl derivatives of 2-pyrazoline bearing 2-benzimidazolyl moiety was synthesized via condensation of corresponding chalcones with phenyl hydrazine. Pyrazoles on their background were obtained by the optimized oxidation procedure with manganese dioxide in benzene. Fluorescent characteristics of the title compounds were determined for their solutions in acetonitrile. Quantum-chemical modeling of molecular structure, UV/Vis spectra, electron density redistribution and structural relaxation at electronic excitation resulting in high fluorescence Stokes shifts were conducted as well.
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