engleski

Spectroscopic and computational studies of protonation equlibria displayed by fluorescent pentacyclic benzimidazole derivatives

Amino substituted benzo[b]thieno[2, 3-b]pyrido[1, 2-a]benzimidazoles are presented as potential fluorescent pH sensitive probes. The general structure of these dye molecules is based on a fused and highly conjugated planar chromophore system [1]. Because of this they show excellent optical properties, including strong fluorescence in the visible spectrum (around 500 nm) as well as good photostability. In order to determine the possibility of compounds 1, 2 and 3 for analytical applications as pH sensors, the changes in their spectroscopic properties depending on the pH value were studied by UV/Vis and fluorescence spectroscopy. It has been found that the protonation-deprotonation equilibria of the dyes is associated with drastic changes in photophysical properties. For example, as shown in Fig. 2, strong increase of the fluorescence intensity of 3 occure on exposure to acidic solutions [2]. Computational analysis revealed the changes in the protonation state occurs in the range 3 < pH < 5 in accordance with experiments.

benzimidazole derivatives ; spectroscopic and computational studies ; pH sensors

nije evidentirano