Synthesis, photophysical and antioxidant properties of carbazole-based bis-thiosemicarbazones

Utilizing Schiff base condensation of the 9-ethylcarbazole-3,6-dicarbaldehyde and thiosemicarbazides, four new N -ethylcarbazole-based bis-thiosemicarbazone compounds 4a–d were successfully synthesized in high yields. The photophysical properties of the targeted compounds 4a–d were investigated using UV–vis absorption and fluorescence emission spectroscopy. The antioxidant properties of targeted compounds 4a–d were determined by DPPH radical scavenging, ABTS Cation Radical Decolarization and CUPRAC Cupric Reducing Antioxidant Capacity assay methods. Moreover, the anti-cholinesterase properties of designated compounds were investigated by the Acetylcholinesterase (Ach) and Butyrylcholinesterase (BCh) enzyme inhibition assays. The compound 4a was determined as a valuable candidate to be a potent antioxidant agent for the DPPH and ABTS assays. The compound 4d was found to be a target compound for the kinetic measurements to identify the mechanism of action in the area of anticholinesterase activity assay.