Fluoride Anion Research Articles

Pyrrolic Type N Directed Borylation Route to BN-PAHs: Tuning the Photophysical Properties by Varying the Conjugation Shape and Size

Two series of BN-cyclopenta[a]phenalenes have been synthesized through an indole/pyrrole oriented borylation reaction. A total of five compounds are obtained and fully characterized; one of them is unambiguously confirmed by single X-ray crystal structure. Their photophysical properties could be finely tuned through varying the conjugation size and shape of the bottom PAHs applied. Moreover, their response toward fluoride anions was also investigated.

Zeta potentials of fluoride anion result in the instability of DNA hairpin

High dose intake of fluoride results in fluorosis and our previous experiments at single-molecule level using magnetic tweezers have proved that fluoride anions destabilize DNA hairpin and its equilibrium critical force decreases with increasing concentration of fluoride anions. One possible mechanism is that a fluoride anion competes with a DNA base and forms a hydrogen bond with its complementary base. The Isothermal Titration Calorimetry experiments suggest that the fluoride anion does not form a hydrogen bond with a DNA base. With increasing concentration of fluoride anions, decreasing Zeta potentials for different oligonucleotides enhance the electrostatic repulsion between complementary oligonucleotides, which accounts for the decreasing association constant and destabilization of DNA hairpin. Molecule dynamics simulation was further performed to determine the ion distribution around the oligonucleotide, radial distribution functions (RDFs) indicate that the fluoride anion distributes far from the oligonucleotide in comparison with the chloride anion, which is the possible mechanism that decreases Zeta potentials with the increasing concentration of fluoride anions.

Optical Anion Receptors with Urea/Thiourea Subunits on a TentaGel Support.

Two simple chemosensors with urea (L1) and thiourea (L2) groups were synthesized and studied by different spectroscopic techniques. Both receptors can sense acetate (Ac–), dihydrogen phosphate (H2PO4–), and fluoride (F–) anions, accompanied by changes in UV–vis and 1H NMR spectra, and an optical response is observed as a color change of the solutions due to deprotonation and hydrogen-bonding processes. Also, L1 and L2 were supported on TentaGel resins (R1 and R2), and their fluoride-sensing properties in DMSO and water solutions were studied. Interestingly, R2 can sense fluoride ions in sample solutions of 100% water.

Nd5OF5Se4 and Sm5OF5Se4: New layered oxide fluoride selenides of the lanthanoids

The formula Ln5OF5Se4 (Ln = Nd and Sm) represents a new composition for lanthanoid(III) oxide fluoride selenides. Nd5OF5Se4 could be seen as aristotype of this system, crystallizing in the tetragonal crystal system with space group I4/mmm and the lattice parameters a = 404.53(2) pm and c = 3400.02(18) pm (c/a = 8.4, Z = 2). In contrast to the aristotype, Sm5OF5Se4 exhibtis a symmetry reduction and adopts space group Ccce with lattice parameters of a = 564.85(3) pm, b = 3391.79(18) pm, c = 564.83(3) pm (b/c ≈ b/a = 6.0, Z = 4). Both compounds can be described by a layered arrangement of sheets, which are formed by the coordination polyhedra surrounding the three crystallographically independent Ln3+ cations in eight- and ninefold coordination of anions. For reasons of electroneutrality one light-anion position has to be mixed-occupied with oxide (O2−) and fluoride (F−) anions for both compounds. Ln5OF5Se4, with edge-sharing [FLn4]11+ and [(O,F)Ln4]10.75+ tetrahedra linked to single and double layers separated by Se2− slabs, shows strong structural analogies to Er3OF3S2. In the case for Sm5OF5Se4 the absence of Sm2+ has been well supported by bond-valence calculations and XANES spectroscopy, while recorded DRS measurements were ambiguous owing to the red color of the substance.

A naked-eye visible colorimetric and ratiometric chemosensor based on Schiff base for fluoride anion detection

A dual-platform colorimetric and ratiometric chemosensor, namely 6-(2-hydroxynaphthalen)-N-n-butyl-naphthalimide (HNA), based on Schiff base constructed from N-n-butyl-4-amino-1,8-naphthalimide and 2-hydroxy-1-naphthaldehyde has been designed and fabricated for detecting fluoride anion (F−) in DMSO solution. HNA is a colorimetic and ratiometric probe with superior selectivity and sensitivity. The color changes of HNA from yellow to purple was observed by the naked eyes in the presence of F−. The absorbance in the UV-Vis spectra of HNA was decreasing in 422 nm, while gradually increasing in 583 nm by adding F−. The limit of detection (LOD) of HNA for detecting F− is low to 0.61 μM and the binding model of HNA and F− is in 3:2 stoichiometry. Meanwhile, HNA can be used to detect F− in real samples. Finally, the mechanism of HNA for the detection of F− was investigated. The present work indicated that HNA would be a superior potential chemosensor in monitoring F− selectively and sensitively.

Release and Recharge of Fluoride Ions from Acrylic Resin Modified with Bioactive Glass.

Background: Oral hygiene is essential for maintaining residual dentition of partial denture wearers. The dental material should positively affect the oral environment. Fluoride-releasing dental materials help to inhibit microbial colonization and formation of plaque as well as to initiate the remineralization process in the early cavity area. Aim: To evaluate fluoride ion release and recharge capacity, sorption, and solubility of polymethyl methacrylate (PMMA) dental resin modified with bioactive glass addition. Materials and methods: Two bioactive glass materials (5 wt% Kavitan, 10 wt% Kavitan, and 10 wt% Fritex) and pure 10 wt% NaF were added to dental acrylic resin. After polymerization of the modified resins, the release levels of fluoride anions were measured based on color complex formation by using a spectrophotometer after 7, 14, 28, and 35 days of storage in distilled water at 37 °C. Subsequently, specimens were brushed with a fluoride-containing tooth paste on each side for 30 s, and the fluoride recharge and release potential was investigated after 1, 7, and 14 days. Sorption and solubility after 7 days of storage in distilled water was also investigated. Results: The acrylic resins with addition of 10% bioactive glass materials released fluoride ions for over 4 weeks (from 0.14 to 2.27 µg/cm2). The amount of fluoride ions released from the PMMA resin with addition of 10 wt% Fritex glass was higher than that from the resin with addition of 10 wt% Kavitan. The acrylic resin containing 10 wt% NaF released a high amount of ions over a period of 1 week (1.58 µg/cm2), but the amount of released ions decreased rapidly after 14 days of storage. For specimens containing 5 wt% Kavitan glass, the ion-releasing capacity also lasted only for 14 days. Fluoride ion rechargeable properties were observed for the PMMA resin modified with addition of 10 wt% Fritex glass. The ion release levels after recharge ranged from 0.32 to 0.48 µg/cm2. Sorption values ranged from 10.23 μm/mm3 for unmodified PMMA resin to 12.11 μm/mm3 for specimens modified with 10 wt% Kavitan glass. No significant differences were found regarding solubility levels after 7 days. Conclusions: The addition of 10 wt% Fritex and 10 wt% Kavitan bioactive glass materials to heat-cured acrylic resin may improve its material properties, with bioactive fluoride ion release ability lasting for over 4 weeks. The resin modified with 10 wt% Fritex glass could absorb fluoride ions from the toothpaste solution and then effectively release them. Addition of fluoride releasing fillers have a small effect on sorption and solubility increase of the modified PMMA resin. Clinical significance: The addition of bioactive glass may be promising in the development of the novel bioactive heat-cured denture base resin.

Textile-based wearable solid-contact flexible fluoride sensor: Toward biodetection of G-type nerve agents

Rising global concerns posed by chemical and biological threat agents highlight the critical need to develop reliable strategies for the real-time detection of such threats. While wearable sensing technology is well suited to fulfill this task, the use of on-body devices for rapid and selective field identification of chemical agents is relatively a new area. This work describes a flexible printed textile-based solid-contact potentiometric sensor for the selective detection of fluoride anions liberated by the biocatalytic hydrolysis of fluorine-containing G-type nerve agents (such as sarin or soman). The newly developed solid-contact textile fluoride sensor relies on a fluoride-selective bis(fluorodioctylstannyl)methane ionophore to provide attractive analytical performance with near-Nernstian sensitivity and effective discrimination against common anions, along with excellent reversibility and repeatability for dynamically changing fluoride concentrations. By using stress-enduring printed inks and serpentine structures along with stretchable textile substrates, the resulting textile-based fluoride sensor exhibits robust mechanical resiliency under severe mechanical strains. Such realization of an effective textile-based fluoride-selective electrode allowed biosensing of the nerve-agent simulant diisopropyl fluorophosphate (DFP), in connection to immobilized organophosphorus acid anhydrolylase (OPAA) or organophosphorus hydrolase (OPH) enzymes. A user-friendly portable electronic module transmits data from the new textile-based potentiometric biosensor wirelessly to a nearby smartphone for alerting the wearer instantaneously about potential chemical threats. While expanding the scope of wearable solid-contact anion sensors, such a textile-based potentiometric fluoride electrode transducer offers particular promise for effective discrimination of G-type neurotoxins from organophosphate (OP) pesticides, toward specific field detection of these agents in diverse defense settings.

A molecular design for a turn-off NIR fluoride chemosensor

We designed a turn-off near-infrared fluorescent fluoride chemosensor NIR-BODIPY-Si through the density functional theory/time-dependent functional theory calculations. In the designed sensor, the tert-butyldimethylsilyloxy moiety responses to the fluoride-triggered desilylation process, and the BODIPY dye serves as fluorophore. The molecular design firstly showed that the possibility of photoinduced electron transfer is low/high in NIR-BODIPY-Si/NIR-BODIPY-O (the desilylation product), thus referring that the fluorescence sensing mechanism is a photoinduced electron transfer mechanism that quenched the sensor's fluorescence after detection of fluoride anions. Absorption and emission spectra further demonstrated that the designed sensor is a near-infrared chemosensor. The largest binding energy between NIR-BODIPY-Si and F- suggests that the sensor has an excellent selectivity to F- and the low barrier of the desilylation reaction accounts for the sensor's rapid response speed to F-. We also provided the synthetic routine for the molecule sensor, with the expectation that this molecular design can shed some light on the experimentally based design procedure.

RuII tris-bipyridine-modified electrode as a sensor for battery electrolyte

Functionalization of a carbon electrode through the electrochemical reduction of ruthenium tris-bipyridine diazonium salts prepared in situ allows determination of the nature of the anions often present in commonly used lithium and sodium battery electrolyte (i.e. PF6− and ClO4−) and also the presence of fluoride anions arising from PF6− degradation. Surprisingly, although these “battery” anions are supposed to exhibit poor coordination ability, their interaction with the electrogenerated RuIII complex is sufficiently strong and reversible to selectively discriminate between the anions ClO4− and PF6− through the observed shift in E°. This study examined the impact of any fluoride present and found a linear relationship between the current response and the F− concentration. This has been applied to ageing LP30 battery electrolyte, confirming the low solubility of LiF in battery electrolyte. This overall behavior could help in the analysis of electrolytes from the recycling sector.

Ion transport mechanism in gramicidin A channels formed in floating bilayer lipid membranes supported on gold electrodes

The ion channel properties of gramicidin A (gA) in a model floating bilayer lipid membrane were studied by electrochemical impedance spectroscopy (EIS) and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS). To determine if the transport of Na+ across the membrane is coupled with the transport of the counterion, fluoride and perchlorate anions were explored due to their large differences in hydration energy. The combined EIS and IR experiments demonstrated that in contrast to valinomycin, the mechanism of Na+ transfer through the gA channel is independent of the accompanying anion present in the supporting electrolyte. These studies also demonstrated that the conductivity of the gA sodium channel depends on the transmembrane potential and the IR measurements indicated that more gA molecules insert into the bilayer with the decrease of the transmembrane potential. The results of this present study demonstrate that the fBLM system is a suitable model bilayer for the in situ investigations of membrane-active peptides.

Extra-Large Pore Titanosilicate Synthesized via Reversible 3D–2D–3D Structural Transformation as Highly Active Catalyst for Cycloalkene Epoxidation

Titanosilicates with extra-large pores or cages are expected to effectively release the diffusion constraints suffered by the bulky substrates in the hydrogen peroxide-involved liquid-phase selective oxidation reactions. A reversible 3D–2D–3D structural transformation was developed to fabricate a highly active IWV-type titanosilicate (Ti-IWV) with a two-dimensional intersecting 12-membered ring (MR) channel system and extra-large 14-MR supercages. The IWV germanosilicate was readily disassembled into a layered 2D material (Hydro-IWV) in HNO3 aqueous solution, which was reconstructed to Ti-IWV with various Ti contents (Si/Ti ratio of 40–∞) through the (NH4)2TiF6-assisted isomorphous substitution of Ti and structure repair. The fluoride anions were critical to recover the interlayer double-four-ring (d4r) units, which were destroyed in the hydrolysis process. Ti-IWV was extremely active in the liquid-phase epoxidation reaction of cycloalkenes, especially showing a much higher conversion (99%) for cyclooctene than conventional titanosilicates. Rather than diffusion rate, the high capacity for the adsorption of bulky alkene molecules of extra-large 14-MR cages contributed to the outstanding activity of Ti-IWV.

The Fluoride Anion-Catalyzed Sulfurization of Thioketones with Elemental Sulfur Leading to Sulfur-Rich Heterocycles: First Sulfurization of Thiochalcones.

Fluoride anion was demonstrated as a superior activator of elemental sulfur (S8) to perform sulfurization of thioketones leading to diverse sulfur-rich heterocycles. Due to solubility problems, reactions must be carried out either in THF using tetrabutylammonium fluoride (TBAF) or in DMF using cesium fluoride (CsF), respectively. The reactive sulfurizing reagents are in situ generated, nucleophilic fluoropolysulfide anions FS(8−x)−, which react with the C=S bond according to the carbophilic addition mode. Dithiiranes formed thereby, existing in an equilibrium with the ring-opened form (diradicals/zwitterions) are key-intermediates, which undergo either a step-wise dimerization to afford 1,2,4,5-tetrathianes or an intramolecular insertion, leading in the case of thioxo derivatives of 2,2,4,4-tetramethylcyclobutane-1,3-dione to ring enlarged products. In reactions catalyzed by TBAF, water bounded to fluoride anion via H-bridges and forming thereby its stable hydrates is involved in secondary reactions leading, e.g., in the case of 2,2,4,4-tetramethyl-3-thioxocyclobutanone to the formation of some unexpected products such as the ring enlarged dithiolactone and ring-opened dithiocarboxylate. In contrast to thioketones, the fluoride anion catalyzed sulfurization of their α,β-unsaturated analogues, i.e., thiochalcones is slow and inefficient. However, an alternative protocol with triphenylphosphine (PPh3) applied as a catalyst, offers an attractive approach to the synthesis of 3H-1,2-dithioles via 1,5-dipolar electrocyclization of the in situ-generated α,β-unsaturated thiocabonyl S-sulfides. All reactions occur under mild conditions and can be considered as attractive methods for the preparation of sulfur rich heterocycles with diverse ring-size.

On the Structures of Thorium Fluoride and Oxyfluoride Anions in Molten FLiBe and FLiNaK.

The structures of thorium fluoride and oxyfluoride ions in molten FLiBe-ThF4 and FLiNaK-ThF4 were investigated by Raman spectroscopy and density functional theory calculations. Thorium fluorides are present in the form of ThF62- (Oh) and ThF73- (C2v) in molten FLiNaK-ThF4. Similar speciation was identified in FLiBe-ThF4, and the thorium fluoride anions are in equilibrium with free F- ions and beryllium fluoride anions, which are responsible for the red shift of the beryllium fluoride bands in the Raman spectra. With the addition of Li2O into the FLiNaK-ThF4 and FLiBe-ThF4 melts, the Th2OF104- anion with a linear Th-O-Th geometry was formed at the expense of thorium fluoride anions. The beryllium fluoride bands in the Raman spectra of FLiBe-ThF4 exhibit a blue shift upon Th2OF104- formation, which results from the release of free F- ions that can further react with beryllium fluoride. Insoluble thorium oxides were found in the FLiNaK and FLiBe melts at a Li2O concentration of 15 mol %, and the Th2OF104- anion is, therefore, a bridge connecting the soluble thorium fluorides and insoluble thorium oxides in molten fluorides.

Molecular structures of heteroligand ScIII complexes with porphyrazine, its dibenzo and tetrabenzo derivatives, and fluoride anion, as determined from DFT calculations

Molecular structures of heteroligand ScIII complexes with porphyrazine, its dibenzo and tetrabenzo derivatives, and fluoride anion, as determined from DFT calculations

Molecular Structures of Heteroligand Macrotetracyclic Complexes of 3d Ions with Phthalocyanine and Fluoride Anion Studied by Density Functional Theory

Molecular Structures of Heteroligand Macrotetracyclic Complexes of 3d Ions with Phthalocyanine and Fluoride Anion Studied by Density Functional Theory

Selective fluoride chemosensors based on coumarin semicarbazones

Twelve (five new) colorimetric anion sensors based on coumarin semicarbazone were studied for selective sensing of fluoride anion. The distinct colour change (by 44–125 nm) under ambient light observed in the Vis region makes the present sensors suitable for naked eye detection of fluoride anion, with detection limit (LOD) 6.6–8.6 ppm for the most sensitive ones. Whereas significant colorimetric changes are observed in the presence of fluoride anion in Me2SO, the commonly competing AcO−, Cl−, Br−, HSO4−, NO2− or NO3− ions induce none or relatively negligible changes. Deprotonation of the semicarbazone NH group is responsible for the sensing event, albeit the mechanism depends on electron density distribution in the coumarin moiety. Quantum chemical calculations suggest several possible geometries for the semicarbazones; the geometry with a hydrogen bond between the hydrazone nitrogen and the NH hydrogen of all of the aniline, cyclohexylamine and aminopyridine fragments, however, results in the most stable structures.

A DFT-based analysis of adsorption properties of fluoride anion on intrinsic, B-doped, and Al-doped graphene.

Fluorine emission from domestic wastewater is a major cause of severe environmental issues. In this paper, the density functional theory has been used to reveal the adsorption properties of F- ions and HF molecules on intrinsic graphene, B-doped graphene, and Al-doped graphene. Throughout the analysis of band structure, geometric structure, adsorption energy, charge transfer, charge density, density of states, and frontier orbital, we can find that the adsorption of F- ions and HF molecules on intrinsic graphene and HF molecules on B-doped graphene is weak, and it is only physical adsorption. When F- ions and HF molecules are adsorbed on Al-doped graphene and F- ions adsorbed on B-doped graphene, the adsorption energy, charge transfer, and charge density greatly increase, and the adsorption distance significantly decreases, and there exist obvious hybridizations by analyzing the charge density and density of states. We can also find that Al-doped graphene is more sensitive to F- ions after comparing the variation of band gap. The work conducted in this research provides a theoretical guidance for the application of fluorine sensors based on graphene.

Smartphone-based colorimetric determination of fluoride anions using polymethacrylate optode

We developed a new transparent polymer optode based on polymethacrylate with Zr(IV) and alizarin red complex immobilized into it for digital colorimetric and solid-phase spectrophotometric determination of fluoride anions. The matrix changes its colour from purple to yellow after it contacts fluoride anion. We developed a processing algorithm for coloured images which helps calculate mean value for the RGB colour-coordinate system in a selected optode image and translates it into a fluoride concentration value. The analytical signal of the suggested method has a linearity range of 0.1–30 mg⋅L−1 with the detection limit 0.03 mg⋅L−1. Compared to other methods, the modified polymethacrylate matrix is actually a ready-to-use colorimetric system offering rapid results for drinking water quality control.

Synthesis of gelation-induced emissive, o-phenylazonaphthol-based organogel and its responsiveness to fluoride anion

Abstract Type your Abstract text here An organogelator based on o-phenylazonaphthol (o-AN) was synthesized to achieve gelation-induced emission using the resultant organogel. Although the o-AN-containing organogelator did not fluoresce in solution, its resulting organogel became red fluorescent. The fluorescence originated from the aggregation-induced emissive property of o-AN. The structural planarization, required for gelation was induced by the intramolecular hydrogen bond of the o-AN in the organogelator, leading to an intermolecular π-π interaction. The gelation was also facilitated by the non-covalent interaction of the van der Waals force. The gelation was investigated in terms of a molecular packing model and the organogel fluorescence. The organogel collapsed upon exposure to the fluoride anion, because the hydroxyl group of the o-AN was deprotonated, resulting in a weakened hydrogen bond and, finally, the disappearance of fluorescence. The organogel is potentially promising for applications such as ion sensing and stimuli-responsiveness-related fields.

Distiboranes based on ortho-phenylene backbones as bidentate Lewis acids for fluoride anion chelation.

As part of our efforts in the chemistry of main group platforms that support anion sensing and transport, we are now reporting the synthesis of anitmony-based bidentate Lewis acids featuring the o-C6F4 backbone. These compounds can be easily accessed by reaction of the newly synthesized o-C6F4(SbPh2)2 (5) with o-chloranil or octafluorophenanthra-9,10-quinone, affording the corresponding distiboranes 6 and 7 of general formula o-C6F4(SbPh2(diolate))2 with diolate = tetrachlorocatecholate for 6 and octafluorophenanthrene-9,10-diolate for 7, respectively. While 6 is very poorly soluble, its octafluorophenanthrene-9,10-diolate analog 7 readily dissolves in CH2Cl2 and undergoes swift conversion into the corresponding fluoride chelate complex [7-μ2-F]- which has been isolated as a [nBu4N]+ salt. The o-C6H4 analog of 7, referred to as 8, has also been prepared. Although less Lewis acidic than 7, 8 also forms a very stable fluoride chelate complex ([8-μ2-F]-). Altogether, our experiental results, coupled with computational analyses and fluoride anion affinity calculations, show that 7 and 8 are some of the strongest antimony-based fluoride anion chelators prepared to date. Another notable aspect of this work concerns the use of the octafluorophenanthrene-9,10-diolate ligand and its ablity to impart advantageous solubility and Lewis acidity properties.