Sodium Salts of 6-Hydroxy-Azolo[1,5-a]pyrimidine-5-Сarbonitriles as Red-Emissive Fluorescent Chemosensors for Picric Acid

Victor Fedotov; Semen Aminov; Dmitry Kopchuk; Ekaterina Kudryashova; Yulia Sayfutdinova; Timofey Moseev; Mikhail Varaksin; Anton Tsmokalyuk; Grigoriy Zyryanov; Vladimir Rusinov

doi:10.15826/chimtech.9537

Sodium Salts of 6-Hydroxy-Azolo[1,5-a]pyrimidine-5-Сarbonitriles as Red-Emissive Fluorescent Chemosensors for Picric Acid

Victor Fedotov, Semen Aminov, Dmitry Kopchuk, Ekaterina Kudryashova, Yulia Sayfutdinova, Timofey Moseev, Mikhail Varaksin, Anton Tsmokalyuk, Grigoriy Zyryanov, Vladimir Rusinov

Abstract

This paper deals with the synthesis and a comprehensive study of the photophysical and sensing properties of sodium salts of 6-hydroxy-azolo[1,5-a]pyrimidine-5-carbonitriles. The target compounds were obtained in good to high yields (81–95%) via the reaction of the corresponding 6-hydroxy-azolopyrimidines with sodium hydroxide in an aqueous ethanol. Study of the optical characteristics revealed that the synthesized compounds could be considered as red fluorophores exhibiting an intense fluorescence with emission maxima in the range of 567–597 nm with up to 55% PLQYs. The sensing properties of the obtained fluorophores were examined towards a series of nitroaromatic compounds (NACs), namely picric acid (PA), 2,4-dinitrotoluene, and 2,4,6-trinitrotoluene. The compounds exhibited a pronounced and selective fluorescence response to PA in DMSO solution, whereas no sensory effect was observed in the presence of 2,4-dinitrotoluene or 2,4,6-trinitrotoluene. As a result, a well-pronounced and selective fluorescence “turn-off” response towards PA in DMSO solution was observed with Stern-Volmer constant values of up to 5.77 × 10⁶ М^-1, whereas no sensory effect was observed for 2,4-dinitrotoluene (DNT) or 2,4,6-trinitrotoluene (TNT). Furthermore, the reversibility of the fluorescence response to acidic analytes was demonstrated using trifluoroacetic acid as a model compound.

Keywords

Azolo[1,5-a]pyrimidines; fluorophores; Fluorescent chemosensors; Nitroaromatics; Picric acid detection

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DOI: https://doi.org/10.15826/chimtech.9537

Copyright (c) 2026 Semen Aminov, Victor Fedotov, Dmitry Kopchuk, Ekaterina Kudryashova, Yulia Sayfutdinova, Timofey Moseev, Mikhail Varaksin, Anton Tsmokalyuk, Grigoriy Zyryanov, Vladimir Rusinov

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