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.