Microwave-enhanced and conventional procedures for the synthesis of coumarin-thiophene amides, sulfonamide, and urea derivatives: Synthesis, photophysical activities, and multiple anions signalling via different mechanisms

Abstract Herein, two synthetic protocols (i.e. conventional and microwave-enhanced irradiation) have been designed and employed successfully for the synthesis of five chemosensors 3a-e. All the prepared compounds were obtained in excellent yields (90–98%). The anion interaction mechanisms, the effect of substitution on the absorption spectra, and the spectral characteristics of the prepared chemosensors (three amides, a disulfonamide, and a urea) have been investigated. The novel coumarin-thiophene appended dyes offer peculiar features in their ability to signal different anions under different types of mechanisms in the varying spectral range. These mechanisms were investigated and then confirmed using DFT and 1H NMR. The optical properties of the novel chemosensors for anions were found to base on H-bonding, deprotonation, and nucleophilic attack and these were assessed and confirmed using 1H NMR titration analysis. Again, theoretical calculations have employed to support the experimental results. All the probes have been found to be thermostable and applicable as optical dyes.