Pyrazolo[1,5-a]pyrimidinium Salts for Cyanide Sensing: A Performance and Sustainability Study of the Probes
2021
Tigreros, Alexis | Zapata-Rivera, Jhon | Portilla, Jaime
Herein, we report an efficient synthesis of two novel probes for cyanide sensing based on 7-arylpyrazolo[1,5-a]pyrimidinium salts PS (aryl = p-MeOPh) and T-PS (aryl = p-Ph₂NPh). According to theoretical analyses, T-PS was found to be an ideal probe with improved absorption and emission properties due to a better intramolecular charge transfer (ICT) process. The experimental results, such as limit of detection (LOD; PS, 0.30 and 0.34 μmol/L → T-PS, 0.15, 0.15, and 0.25 μmol/L) and outstanding selectivity demonstrated the predicted properties. DFT calculations, HRMS analysis, and ¹H NMR titration experiments were carried out to confirm the mechanism, regioselectivity, and reversibility of the CN– addition reaction in detecting the probes. These findings are especially attractive in the cyanide-sensing field. However, important repercussions on the sustainability performance, such as raw material costs and waste generation, were observed when comparing PS with T-PS. Satisfyingly, test strips fabricated using T-PS also demonstrated its practical applicability; in addition, emission in solid-state measurements of T-PS supported on silica showed its capability to detect cyanide ions in the solid state and in bitter almonds after 50 ppm. Ultimately, small amounts of CN– (0.5 μmol/L) in tap water detected by using the probe T-PS. Therefore, this work provides a sustainable and applicable approach in cyanide chemosensor preparation.
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