Benzene Sulfonyl Linked Tetrasubstituted Thiacalix[4]arene for Selective and Sensitive Fluorometric Sensing of Sulfosulfuron along with Theoretical Studies

Herein, we designed two fluorescent tetrasubstituted benzene sulfonyl appended Thiacalix[4]arene receptors named L¹ and L², which sensitively and selectively detect Sulfosulfuron among other herbicides and pesticides. The detection limit (LOD) was found to be 0.21 ppm and 0.35 ppm, and the enhancement constant (Ks) was determined to be 7.07 X 10⁴ M^-1 and 5.55 X 10⁴ M^-1 for L¹ and L², respectively. Using the non-linear regression method, the association constant was obtained as 2.1 X 10⁴ M^-1 and 2.23 X 10⁴ M^-1 whereas, the binding ratio was found to be 1:1 for both L¹ and L², respectively. Additionally, the interference studies show the selective nature of receptors for Sulfosulfuron among its sulfonylurea family. To further confirm the interaction mechanism, ¹H-NMR spectroscopy, and a computational investigation were carried out, which validates the 1:1 binding ratio. The receptors were found to be recyclable in nature with simple acid-base treatment. This new approach of using supramolecules as fluorescent probes for sensitive and selective detection of herbicides is rare in the literature.