New Colorimetric and Fluorometric Fluoride Ion Probe Based on Anthra[1,9-cd]pyrazol-6(2H)-one

Current Advances in Diazoles-based Chemosensors for CN- and FDetection

Advances in molecular probes have recently intensified because they are valuable tools in studying species of interest for human health, the environment, and industry. Among these species, cyanide (CN-) and fluoride (F-) stand out as hazardous and toxic ions in trace amounts. Thus, there is a significant interest in probes design for their detection with diverse diazoles (pyrazole and imidazole) used for this purpose. These diazole derivatives are known as functional molecules because of their known synthetic versatility and applicability, as they exhibit essential photophysical properties with helpful recognition centers. This review provides an overview of the recent progress (2017-2021) in diazole-based sensors for CN- and F- detection, using the azolic ring as a signaling or recognition unit. The discussion focuses on the mechanism of the action described for recognizing the anion, the structure of the probes with the best synthetic simplicity, detection limits (LODs), application, and selectivity. In this context, the analysis involves probes for cyanide sensing first, then probes for fluoride sensing, and ultimately, dual probes that allow both species recognition.

Quinoline based thiosemicarbazones as colorimetric chemosensors for fluoride and cyanide ions and DFT studies

High toxicity and extensive accessibility of fluoride and cyanide ions in diverse environmental media encouraged attention for scheming well-organized probes for their detection. Keeping in mind we have designed and synthesized thiosemicarbazone-based chemosensors RB-1, RB-2 and RB-3 for the detection of fluoride and cyanide ions. The structural elucidation of the synthesized chemosensors is done by employing different analytical techniques including nuclear magnetic resonance and electronic absorption specrtoscopies. Admirable detection limit, binding constant and fast response time (2 s) to F⁻ and CN⁻ ions enlarged the applications of these chemosensors. Additional confirmation of the sensing ability of these chemosensors is derived from DFT and TDDFT calculations with M06/6-311G(d,p) method by performing FMO, UV–Vis, QTAIM and global reactivity parameters elucidation. Overall results point out that investigated chemosensors are suitable candidates for sensing the F⁻ ions. These chemosensors were successfully applied to detect F⁻ ions in a commercial toothpaste sample.

Recent progress in chemosensors based on pyrazole derivatives

Colorimetric and fluorescent probes based on small organic molecules have become important tools in modern biology because they provide dynamic information concerning the localization and quantity of the molecules and ions of interest without the need for genetic engineering of the sample. In the past five years, these probes for ions and molecules have attracted great attention because of their biological, environmental and industrial significance combined with the simplicity and high sensitivity of absorption and fluorescence techniques. Moreover, pyrazole derivatives display a number of remarkable photophysical properties and wide synthetic versatility superior to those of other broadly used scaffolds. This review provides an overview of the recent (2016-2020) findings on chemosensors containing pyrazole derivatives (pyrazoles, pyrazolines and fused pyrazoles). The discussion focuses on the design and physicochemical properties of chemosensors in order to realize their full potential for practical applications in environmental and biological monitoring (sensing of metal ions, anions, explosives, and biomolecules). We also present our conclusions and outlook for the future.

A phenolphthalein-based fluorescent probe for the sequential sensing of Al3+ and F- ions in aqueous medium and live cells

A novel fluorescent probe, phenolphthalein‑dialdehyde‑(2‑pyridyl) hydrazone (L), for sequentially detecting Al³⁺ and F^- in almost 100% aqueous medium was successfully designed and synthesized. The probe offers two binding pockets for Al³⁺ to form a 1: 2 ligand/metal complex, leading to a significant fluorescence enhancement at 465 nm. Further, the in-situ formed L-Al complex acts as a secondary fluorescent chemosensor for F^- by quenching the fluorescence of the complex with high selectivity. The detection limit for Al³⁺ and F^- sensing is 2.28 nM and 0.13 μM, respectively, which are far below the World Health Organization (WHO) acceptable limits (7.41 μM for Al³⁺ ion and 79 μM for F^-) in drinking water. The probe L was successfully applied to the detection of Al³⁺ and F^- in cells using fluorescence microscopy.