engleski

The influence of the nitrogen position on the spectroscopic properties of regioisomers based on imidazo[4,5-b]pyridine

Nitrogen-containing heterocycles are, besides their well-known biological features, recognized as an interesting class of organic fluorescent sensors present in a wide range of biological, environmental and chemical processes. Owing to their excellent spectroscopic properties, as well as pronounced and diverse spectral responses, such derivatives offer promising applications in optoelectronics as optical lasers, fluorescence probes, organic luminophores or fluorescent dyes.[1] This work presents the synthesis and spectroscopic characterization of regioisomers based on imidazo[4, 5-b]pyridine. Potential application as pH sensors was explored. Due to condensation of 2-cyanomethylimidazo[4, 5-b]pyridine with 2-chlorobenzoyl chloride, acyclic precursor was prepared. Chloro-substituted tetracyclic precursors were prepared in 2 step procedure including termic cyclization. Amino substituted regioisomers were prepared by uncatalyzed microwave assisted amination.[2] Structures of newly prepared compounds were confirmed by means of 1H i 13C NMR, as well as MS spectrometry. Structure of regioisomers was determined by 2D NMR spectroscopy. Spectroscopic characterization of regioisomers was performed by using UV/Vis and fluorimetric spectroscopy in 11 organic solvents of varying polarities. Studied regioisomers showed interesting spectroscopic characteristics which are significantly dependant on the used solvent and are different for each regioisomer. pH spectroscopic titrations were performed in order to determine possible application as pH sensors in solutions followed by determination of pKa values experimentally as well as by computational approaches.

imidazo[4, 5-b]pyridine ; pH sensors ; regioisomers

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