Synthesis, Characterization, Computational, and Photophysical Investigation of Novel Pyran-Azo Bridged Benzothiazoles and Their Biological Studies

In this study, we reported the synthesis of novel heterocyclic azo dyes 4(a-h) by the conventional diazo-coupling reaction of 4-hydroxy-6-methyl-2-pyrone with various benzothiazole amines. The molecular structures of the target molecules were precisely assessed using different spectroscopic (FT-IR, NMR, and HRMS) studies. Through density functional theory (DFT) study, molecular geometry, frontier molecular orbitals, global reactivity parameters, and molecular electrostatic potential regions were investigated to explore the electronic properties of azo dyes. The in vitro antimycobacterial screening of target compounds was tested against M. tuberculosis, and the results showed that compounds 4b and 4e exhibited promising activity with MIC of 3.25 µg mL⁻¹. Compound 4b exhibited significant activity against S. aureus and S. mutans, with MIC values of 0.0195 and 0.625 mg mL⁻¹, respectively. Compounds 4b and 4e exhibited similar sensitivity to the tested fungal strain A. niger, with a MIC of 0.0195 mg mL⁻¹. The in silico molecular docking study was conducted against the receptor enoyl-ACP reductase to evaluate the binding affinity of the target compounds; derivatives 4b and 4e showed the highest docking scores of −9.2 and −9.1 kcal mol⁻¹, respectively. Furthermore, the active compounds 4b and 4e exhibited low cytotoxicity, and none of them posed harm to normal cells.