engleski

Optical characterisation and immobilization of novel benzimidazole based acrylonitrile dyes

Heterocyclic molecules are able to change its photophysical properties (fluorescence or absorption) when selective recognition of an anionic/cationic substrate occurs. A great variety of heterocyclic molecules have been employed for the development of optical sensors. The benzimidazole unit is one of the most important key building block for a variety of biologically important molecules and has applications in several other areas such as optical lasers and polymer dyes in optoelectronics, fluorescent probes for detection of biological important molecules as DNA, RNA or proteins in biomedical diagnostics, efficient and selective chemosensors for cation or anion detection and as efficient ligands in metallochemistry. Thus, the study of spectral properties of benzimidazole derivatives is an important step towards the use of these compounds, and also a very interesting area of research. A number of experimental and theoretical studies of similar classes of compounds have been published, focusing on different aspects of their interesting photophysical and photochemical properties such as intramolecular charge transfer emission (ICT) and excited state intramolecular proton transfer (ESIPT). In this work the photophysical and acid-base properties of novel benzimidazole based acrylonitrile dyes has been studied. UV–Vis absorption and fluorescence spectra was recorded in several solvents with different physicochemical properties and in polymeric solid matrix. From the experimental results and the theoretical calculations, we discuss effects of pH (pK values and species distribution) and effects of solvent in ground and excited state. Depending on the structure (substituent) and H+ concentration in the solution, compounds are able to form neutral, monocation, dication and monoanion form, each with specific acid-base and spectral properties. Comparison of the obtained results in the solution and in the polymer solid matrix led to basic insights of photophisical properties and structure-property realtions.

optical sensor; benzimidazole; acrylonitrile

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