Fluorescence is an optical phenomenon when the substance absorbs light at a shorter wavelength with higher energy and then emits it at a longer wavelength with less energy. Fluorophores are components that play the central role in fluorescence. The main characteristic of organic fluorophores is that in their structure there are several conjugated double bonds and/or an aromatic structure. Synthetic fluorophores have many applications in different fields, and many are also used in science. Due to their widespread use, new fluorophores are developing all the time. During the master’s thesis, Andraž Bevk isolated a new fluorophore that belongs into the cyanine / polymethine group, but with a completely new skeleton through a novel synthesis path.
In our master’s thesis we researched the reaction mechanism and conditions in which the above mentioned fluorophore is formed. In the first part we synthetized fluorophores that are structural analogues of the mentioned fluorophore, where we tried different reactants and conditions for the formation of the desired dye. From our experiments it has been found that for the formation of fluorophores, a heteroaromatic ring containing a pyridine-type nitrogen is essential. As a donor of the methine group, dimethylformamide (DMF) is needed, and it is also used as a solvent. To obtain the desired product, acidic conditions are required which was achieved with 4,0 M HBr in acetic acid (AcOH) or 2,0 M HCl. Also, a higher temperature is required for the desired reaction, we found that 60 ° C is the optimum, since higher temperatures did not show a significantly better reaction efficiency.
In the second part of the master's thesis, the effect of different reaction conditions on the yield of the reaction was determined with ultra-high performance liquid chromatography (UHPLC). In the analysis, compounds 2, 4, 5, and 7 were used. First, we had to prepare solutions for the analysis with the UHPLC system, which proved quite difficult, since the isolated compounds were very insoluble. Then, for each compound, a chromatographic method was developed. The analysis followed, where we examined the effect of different temperatures and acids on the yield of the reaction. We found that the best yields were obtained at a temperature of 60 ° C and with acids 4,0 M HBr in AcOH and 2,0 M HCl.
?Finally, all the absorption and emission spectrums of isolated compounds were measured and we established that our compounds emit light in the green color part of the visible spectrum.
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