Synthesis, Characterization, Biological Properties, and Sensor Applications of Novel Thiosemicarbazone Derivatives

In this study, novel thiosemicarbazone derivative molecules (5a-j) were synthesized. The characterization of the synthesized molecules was carried out using ¹H-, ¹³C-NMR, FT-IR, and Q-TOF spectroscopic techniques. Then, the inhibitory effect of these compounds was examined for human carbonic anhydrase I and II (hCA I, and II) and acetylcholinesterase (AChE). The hCA I II, and AChE were efficiently inhibited by synthesized thiosemicarbazone derivatives, with Ki values in the range of 0.293-1.666 µM for hCA I, 0.298-1.332 µM for hCA II, and 52.51-138.63 µM for AChE, respectively. Finally, the sensor properties of the synthesized thiosemicarbazone derivatives were investigated. The newly synthesized thiosemicarbazone derivative molecules exhibited high selectivity towards Pb²⁺ ions. The sensor prepared with 5a from these molecules had a Nernstian behavior of 28.8 ± 1.5 mV/decade and a low detection limit of 2.86 × 10^-6 M in a wide concentration range of 1.0 × 10^-1-1.0 × 10^-5 M. The newly proposed sensor also had a wide pH working range (5.0-10.0), a very fast response time (5 s), and good reproducibility. The newly fabricated sensors were used as indicator electrodes for the potentiometric titration of Pb²⁺ ions with ethylenediaminetetraacetic acid (EDTA) and were successfully applied for the determination of Pb²⁺ ion content in different water samples.