Synthesis of fluorescent dicyanomethylenevinyl-1,3-dicoumarin compounds with donor-acceptor-it-donor (D-A-it-D) system and investigation of their photophysical, NLO, and chemosensor properties: Part 1

Coumarin compounds have heterocyclic core with different properties such as high quantum yields, broad Stokes shifts, and superior photophysical and biological activity. It is known that fluorescence properties increase with increased intramolecular charge transfer in systems where electron-withdrawing or donor groups are attached to different positions of the coumarin compound. When these compounds interact with analytes in the environment, the analytes in the environment can be detected by quenching or increasing fluorescence. For this purpose, dicyanomethylenevinyl-1,3-dicoumarin compounds were obtained and 1 H NMR, 13 C NMR, FT-IR, HR-MS elucidated their structures. To determine the photophysical properties of the synthesized compounds, absorption, and emission spectra were examined in solvents with different polarities, and also quantum yields and Stokes shifts were calculated. Additionally, the sensitivity/selectivity properties of the compounds towards various anions were investigated by spectrophotometric, spectrofluorometric, and 1 H NMR titration methods. The limit of detection (LOD) of the sensors to sense cyanide anion was considered based on absorption titration. The pKa value of compound that could be pH sensor candidate was determined. Thermogravimetric analysis was performed as an important parameter for compounds in electro-optical (EO) systems. Additionally, nonlinear optical (NLO) properties of the compounds were calculated experimentally and theoretically. The some experimental results were explained by Density Functional Theory (DFT) and time-dependent DFT (TDDFT) calculations.