Progress in appended calix[4]arene-based receptors for selective recognition of copper ions.

In the past two decades, there has been significant progress in the design and development of synthetic receptors for molecular recognition as they find application in the field of chemical, biological, medical, and environmental sciences. Synthetic receptors based on calix systems appended with fluorogenic and chromogenic groups have gained considerable attention for sensing and recognition of ions and molecules. Copper (Cu2+) is an essential element required in trace amounts in all living organisms to carry out various biological processes. The aim of this review is to summarize advancement in π-conjugated fluorogenic and chromogenic groups appended to calix[4]arene motifs for detection and quantitation of Cu2+ ion. The focus is to present a comprehensive account of extended calix[4]arene systems with different linkers and highlight the unique design and binding characteristics for the recognition and sensing of Cu2+ ions.

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.