Monitoring Fluoride Binding in DMSO: Why is a Singular Binding Behavior Observed?

Abstract

Fluoride recognition by molecular receptors is attracting much interest in the scientific community and a variety of approaches are used to achieve recognition with high affinity and selectivity. Most of the synthetic systems reported have been extensively studied in organic solvents by using tetrabutylammonium fluoride (TBAF) as the source of fluoride. In many cases, titration behaviors are observed that cannot be ascribed to a classical 1:1 binding isotherm. By using UV/Vis, 19F NMR, and 1H NMR spectroscopy we have been able to highlight that the equilibrium between the fluoride and the corresponding bihalide ion, HF2, which is inevitably generated in situ due to trace amounts of water, can be at the origin of this singular behavior. Our results highlight that when undertaking titrations with fluoride in DMSO, the data can be affected by the fluoridebihalide equilibrium and that the latter species can even be the dominating species at low TBAF concentrations

Fluoride binding in water with the use of micellar nanodevices based on salophen complexes

“…Receptors 1 and 2 were available from previous investigations. 49,50 Solutions of surfactants were prepared by dissolving the surfactant in H 2 O, for UV-vis spectroscopy, or D 2 O, for NMR experiments. For the DLS experiments, surfactant solutions were prepared by dissolving the surfactant in 100 mM KCl solutions in H 2 O for CTACl and in 50 mM KBr solutions for CTABr.…”

Colorimetric and fluorescence “turn-on” recognition of fluoride by a maleonitrile-based uranyl salen-complex

“…The development of simple and effective fluorescent and/or colorimetric sensors for the fluoride anion is thus the object of reports in the literature [9]. Studies have been undertaken with receptors exploiting different binding paradigms such as boron−fluoride interactions [10], hydrogen bonding with the NH protons of amides [11], indoles [12], pyrroles [13], urea or thiourea [14], Lewis acid coordination [15][16][17] or anion-π interactions [18]. The visual detection of fluoride has also been obtained by taking advantage of fluoride-promoted cleavage reactions [19].…”

Highly Selective Fluoride Recognition by a Small Tris-Urea Covalent Cage

“…Indeed, the 1 H and 19 F NMR-monitored complexation of fluoride at 3 (Figures S7 and S8) did not reveal any formation of additional species such as protonated forms of F – (bifluoride anion HF 2 – e.g.) . Finally, ESI-HRMS analysis clearly supports the formation of [ 3 ·F – ] in a 1:1 stoichiometry (Figure S9).…”