Pyrrole-Based Anion Sensors, Part I: Colorimetric Sensors

Regioselective synthetic approach for key precursors of 6-aryl benzo[c]phenanthridin-10-ol derivatives: A useful compound for selective chromogenic recognition of fluoride

A regioselective synthetic strategy for 6-aryl-8,9-dihydro-benzo[c]phenanthridine-10(7H)-ones (4) is accomplished using a one-pot four-component reaction by fine-tuning of reaction temperature. DMSO is excellently used as a reactant-cum-solvent to introduce carbonyl functionality...

Colorimetric anion sensors based on positional effect of nitro group for recognition of biologically relevant anions in organic and aqueous medium, insight real-life application and DFT studies

A new six colorimetric receptors A1-A6 were designed and synthesized, characterized by typical common spectroscopic techniques like FT-IR, UV-Visible, ¹H NMR, ¹³C NMR and ESI-MS. The receptor A1 and A2 exhibit a significant naked-eye response towards F^- and AcO^- ions in DMSO. Due to presences of the NO₂ group at para and ortho position with extended π-conjugation of naphthyl group carrying OH as a binding site. Compared to receptor A2, A1 is extremely capable of detecting F^- and AcO^- ions present in the form of sodium salts in an aqueous medium. This is owed to the occurrence of NO₂ group at para position induced in increasing the acidity of OH proton. Consequently, it easily gets deprotonated in aqueous media. The detection limit of receptor A1 was turned out to be 0.40 and 0.35ppm for F^- and AcO^- ions which is beneath WHO permission level (1.0ppm). Receptor A1 shows a solitary property of solvatochromism in different aprotic solvents in presence of AcO^- ion. Receptor A1 depicts high selectivity towards AcO^- ion in DMSO: HEPES buffer (9:1, v/v). Receptor A1 proved itself for real life application by detecting anion in solution and solid state. The binding mechanism of receptor A1 with AcO^- and F^- ions was monitored from ¹HNMR titration and DFT study.

Colorimetric detection of fluoride ions by anthraimidazoledione based sensors in the presence of Cu(ii) ions

A thioimidazole bearing anthraimidazoledione detects fluoride selectively in the presence of Cu²⁺with a detection limit of 0.04 ppm. The results show that the change of thioimidazole to imidazole leads to no detection.

Lewis acidic stiborafluorenes for the fluorescence turn-on sensing of fluoride in drinking water at ppm concentrations

Lewis acidic organoantimony(v) derivatives have been developed for the fluorescence turn-on sensing of fluoride in biphasic water–CH₂Cl₂mixtures at sub-ppm concentrations.

Intra- and intermolecular hydrogen bonds in pyrrolylindandione derivatives and their interaction with fluoride and acetate: possible anion sensing properties

The series of push-pull compounds containing the pyrrole ring as a donor and the 1,3-indandione derived moieties as the acceptor unit were synthesized, and strong intramolecular hydrogen bonding in their molecules was studied. In the presence of fluoride and acetate anions their solutions undergo color changes. It was shown by NMR, UV-vis, and quantum chemical calculations including AIM analysis that all these compounds undergo solvent-assisted rupture of the intramolecular hydrogen bond followed by the formation of a strong intermolecular hydrogen bond with fluoride and acetate anions which finally abstract a proton from the pyrrole ring. The insensitivity of the studied compounds to other anions (Cl, Br, HSO4, PF6) is consequence of the instability of the corresponding hydrogen-bonded complexes.