Assessment of chalcone-vanillin as a selective chemosensor of As(III) in aqueous solution

Chalcones are a notable group of compounds that show a wide range of pharmacological properties. However, their use in other research fields, such as material science and analytical chemistry, is increasing with chemosensor development. Because of this situation, in the current research, we synthesized chalcone-vanillin 11 using the Claisen-Schmidt reaction and assessed its application as a chemosensor for analytes of interest in biochemistry. As a result of our work, we found a high selectivity towards AsO₂⁻¹ in a short time (1 min). The titration of compound 11 with AsO₂⁻¹ showed the limit of detection (LOD) and limit of quantification (LOQ) were 0.505 µM and 1.68 µM, respectively. Likewise, using a Job graph, the stoichiometric relationship between chalcone-vanillin 11 and AsO₂⁻¹ was determined to be 2:1. Moreover, we studied this interaction using DFT and TD-DFT calculations, finding two key steps. The first step was a hydrogen atom transfer from chalcone 11 to AsO₂⁻¹ to obtain the compound 11-As(III), and the second step was a hydrogen atom transfer from the second molecule of chalcone 11 to 11-As(III), producing the dimer 11-As(III)-11. The proposed dimeric compound was confirmed by mass spectrometry, and ¹H-NMR. Furthermore, the chalcone-vanillin 11 was used to measure AsO₂⁻¹ in drinking water, obtaining good performance at low concentration of arsenite. Finally, from these results, it is plausible to develop a better chemosensor than chalcone 11, in regard to the structure and mechanism of action that is proposed in this study.