Fluoride Ion Source Research Articles

Potassium fluoride for one-pot desilylation and the Sonogashira coupling of ethynylsilanes and buta-1,3-diynylsilanes

Opportunities were outlined for application of available KF as a source of fluoride ions and a base in desilylation/the Sonogashira coupling reactions under conditions of a one-pot process.

The Effect of Sodium Fluoride on Cell Apoptosis and the Mechanism of Human Lung BEAS-2B Cells In Vitro.

Sodium fluoride (NaF) is a source of fluoride ions used in many applications. Previous studies found that NaF suppressed the proliferation of osteoblast MC3T3 E1 cells and induced the apoptosis of chondrocytes. However, little is known about the effects of NaF on human lung BEAS-2B cells. Therefore, we investigated the mode of cell death induced by NaF and its underlying molecular mechanisms. BEAS-2B cells were treated with NaF at concentrations of 0, 0.25, 0.5, 1.0, 2.0, and 4.0mmol/L. Cell viability decreased and apoptotic cells significantly increased as concentrations of NaF increased over specific periods of time. The IC50 of NaF was 1.9 and 0.9mM after 24 and 48h, respectively. The rates of apoptosis increased from 4.8 to 37.7% after NaF exposure. HE staining, electron microscopy, and single cell gel electrophoresis revealed that morphological changes of apoptosis increased with exposure concentrations. RT-PCR and Western blotting were used to detect the apoptotic pathways. The expressions of bax, caspase-3, caspase-9, p53, and the cytoplasmic CytC of the NaF groups increased, while bcl-2 and mitochondrial CytC decreased compared with that of the control group (P<0.05). Further, the fluorescence intensities of ROS in the NaF groups were higher than those in the control group, and the membrane potential of mitochondria in the NaF group was significantly lower than that of the control group (P<0.05). These findings suggested that NaF induced apoptosis in the BEAS-2B cells through mitochondria-mediated signal pathways. Our study provides the theoretical foundation and experimental basis for exploring the mechanisms of human lung epithelial cell damage and cytotoxicity induced by fluorine.

The first nucleophilic C-H perfluoroalkylation of aromatic compounds via (arene)tricarbonylchromium complexes.

The first nucleophilic perfluoroalkylation of arenes is based on the arene π-system activation via (η6-arene)tricarbonylchromium complexes. Perfluoroalkyl anions generated from Me3SiRF and a fluoride ion source [Me4N]F exclusively attack the arene ligand under mild conditions. The formed negatively charged analogs of Meisenheimer adducts readily undergo a one-pot oxidation to perfluoroalkyl arenes.

Nanocrystalline rare earth fluorides doped with Pr3+ ions

Praseodymium(III) doped CeF3, CeF3:Gd, LaF3, GdF3 and YF3 inorganic fluorides were precipitated in an aqueous, surfactant-free solution, using NH4F as a source of fluoride ions. The as-prepared products were subjected to a hydrothermal treatment, which led to the formation of crystalline nanoluminophores, composed of spherical (≈30 nm) and elongated (≈40–200 nm) nanostructures. Due to the presence of Pr3+ ions, the synthesized nanomaterials showed yellow luminescence under a blue light irradiation. The nanoluminophore based on the YF3 host revealed the most promising spectroscopic properties, i.e., bright and intensive emission, hence it was investigated in detail. The photophysical properties of the nanomaterials obtained were studied by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and spectrofluorometry, i.e., measurements of excitation/emission spectra and luminescence decay curves.

Synthesis of high performance mordenite membranes from fluoride-containing dilute solution under microwave-assisted heating

High performance mordenite membranes were successfully prepared in a short synthesis time from fluoride-containing dilute solution without organic template under microwave-assisted heating. The effects of crystallization temperature, fluoride ion and aluminum source on the membrane morphology and separation performance for dehydration of acetic acid by pervaporation were systematically investigated. High performance mordenite membranes with a thickness about 5µm could be prepared from dilute solution with composition of SiO2: 0.06Al2O3:0.24Na2O:0.3NaF:120H2O at 165°C for 4h using various aluminum sources. These mordenite membranes exhibited high fluxes of 0.87±0.06kgm−2h−1 and excellent selectivities, that is only pure water was detected in the permeate side for dehydration of 90wt% acetic acid aqueous mixtures at 75°C. The reproducibility of mordenite membranes was high, using the fluoride-containing dilute solution under microwave-assisted heating, which forebodes a promising prospect for industrial applications in preferential separation of water from acetic acid aqueous solutions.

The influence of fluoride ions on the equilibrium between titanium ions and titanium metal in fused alkali chloride melts.

KF is employed as a source of fluoride ions added to the melt to disclose the influence of fluoride on the disproportionation reactions of titanium ions, 3Ti(2+) = 2Ti(3+) + Ti, and 4Ti(3+) = 3Ti(4+) + Ti. The results reveal that the equilibrium transferred to the right direction for the first reaction and the apparent equilibrium constant increased sharply, mainly because of the formation of coordination compounds: TiFi(3-i). The accurate values of the equilibrium constants referring to the formation reactions of Ti(3+) + iF(-) = TiFi(3-i) (i = 1-6) in NaCl-KCl melt at 1023 K were evaluated with a best fit least squares method. It is also revealed that the stable states of the coordination compounds are TiF(2+), TiF2(+), TiF4(-) and TiF6(3-). Moreover, the Gibbs free energies for complex formation were estimated. Ti(2+) was undetectable when the concentration of fluoride ion was high enough. The equilibrium constant for the formation reaction, Ti(4-) + 6F(-) = TiF6(2-), was evaluated. The equilibrium constant, Kc2, for the disproportionation reaction 4Ti(3+) = 3Ti(4+) + Ti, in chloride melt was determined as 0.015.

Fluorination of α-bromomethyl aryl ketones with fluorohydrogenate-based ionic liquids

Abstract Fluorination of α-bromomethyl aryl ketones using fluorohydrogenate-based ionic liquids as fluorinating reagent is described. Reaction of various α-bromomethyl aryl ketones (1a-g) with fluorohydrogenate-based ionic liquids such as EMIMF·(HF)2.3, PYR13F·(HF)2.3 or PYR14F·(HF)2.3 as a fluoride ion source in anhydrous THF led to the formation of the corresponding α-fluoromethyl aryl ketones (2a–g) in very good yield. Compared to alternative fluorinating agents for this reaction, fluorohydrogenate-based ionic liquids are safer to handle and have the potential to be less expensive and more selective.

Fluoride-mediated polycondensation for the synthesis of polymers of intrinsic microporosity

A fluoride-mediated double SNAr polycondensation method was successfully developed to prepare high-molecular weight polymers of intrinsic microporosity (PIMs). The polymerization was conducted between a t-butyldimethylsilyl (TBS)-protected biscatechol monomer (2) and a widely used tetrafluoro monomer (3) in the presence of fluoride ion with excellent to quantitative yields. Three fluoride ion sources (i.e. KF, TBAF and CsF) were investigated, and all of them were effective as catalysts to give high-molecular weight linear products with good film forming property. Therefore, this method warrants its synthetic utility for PIM synthesis.

Ion release from, and fluoride recharge of a composite with a fluoride-containing bioactive glass

ObjectivesMaterials that are capable of releasing ions such as calcium and fluoride, that are necessary for remineralization of dentin and enamel, have been the topic of intensive research for many years. The source of calcium has most often been some form of calcium phosphate, and that for fluoride has been one of several metal fluoride or hexafluorophosphate salts. Fluoride-containing bioactive glass (BAG) prepared by the sol–gel method acts as a single source of both calcium and fluoride ions in aqueous solutions. The objective of this investigation was to determine if BAG, when added to a composite formulation, can be used as a single source for calcium and fluoride ion release over an extended time period, and to determine if the BAG-containing composite can be recharged upon exposure to a solution of 5000ppm fluoride. MethodsBAG 61 (61% Si; 31% Ca; 4% P; 3% F; 1% B) and BAG 81 (81% Si; 11% Ca; 4% P; 3% F; 1% B) were synthesized by the sol–gel method. The composite used was composed of 50/50 Bis-GMA/TEGDMA, 0.8% EDMAB, 0.4% CQ, and 0.05% BHT, combined with a mixture of BAG (15%) and strontium glass (85%) to a total filler load of 72% by weight. Disks were prepared, allowed to age for 24h, abraded, then placed into DI water. Calcium and fluoride release was measured by atomic absorption spectroscopy and fluoride ion selective electrode methods, respectively, after 2, 22, and 222h. The composite samples were then soaked for 5min in an aqueous 5000ppm fluoride solution, after which calcium and fluoride release was again measured at 2, 22, and 222h time points. ResultsPrior to fluoride recharge, release of fluoride ions was similar for the BAG 61 and BAG 81 composites after 2h, and also similar after 22h. At the four subsequent time points, one prior to, and three following fluoride recharge, the BAG 81 composite released significantly more fluoride ions (p<0.05). Both composites were recharged by exposure to 5000ppm fluoride, although the BAG 81 composite was recharged more than the BAG 61 composite. The BAG 61 composite released substantially more calcium ions prior to fluoride recharge during each of the 2 and 22h time periods. Thereafter, the release of calcium at the four subsequent time points was not significantly different (p>0.05) for the two composites. SignificanceThese results show that, when added to a composite formulation, fluoride-containing bioactive glass made by the sol–gel route can function as a single source for both calcium and fluoride ions, and that the composite can be readily recharged with fluoride.

Rechargeable batteries with high energy storage activated by in-situ induced fluorination of carbon nanotube cathode.

High performance rechargeable batteries are urgently demanded for future energy storage systems. Here, we adopted a lithium-carbon battery configuration. Instead of using carbon materials as the surface provider for lithium-ion adsorption and desorption, we realized induced fluorination of carbon nanotube array (CNTA) paper cathodes, with the source of fluoride ions from electrolytes, by an in-situ electrochemical induction process. The induced fluorination of CNTA papers activated the reversible fluorination/defluorination reactions and lithium-ion storage/release at the CNTA paper cathodes, resulting in a dual-storage mechanism. The rechargeable battery with this dual-storage mechanism demonstrated a maximum discharging capacity of 2174 mAh gcarbon−1 and a specific energy of 4113 Wh kgcarbon−1 with good cycling performance.

Fluoride Ion Sensing and Caging by a Preformed Molecular D4R Zinc Phosphate Heterocubane

Double-4-ring (D4R) zinc phosphate [Zn(dipp)(DMSO)]4 (1, dipp = 2,6-di-iso-propylphenylphosphate, DMSO = dimethyl sulfoxide), on treatment with a free fluoride ion source, exhibited ability to sense and capture fluoride ions from a variety of sources, as evidenced by extensive solution (31)P and (19)F NMR spectral titration studies. The fluoride ion-encapsulated cage [(n)Bu4N][F@{Zn(dipp)(DMSO)}4] (2) was isolated in good yield from an equimolar reaction between 1 and (n)Bu4NF in methanol and characterized by analytical and spectroscopic methods. When 1-methyl-4,4'-bipyridin-1-ium fluoride (MeQ-F) was used as the fluoride ion source a zwitterionic cage [F@{Zn4(dipp)4(MeQ)(DMSO)3}] (3) was isolated. Crystal structure determination for 3 confirmed not only fluoride incorporation inside the D4R cage but also a weak interaction of the central fluoride ion with all four zinc centers of the cubane, resulting in a trigonal bipyramidal geometry around the zinc centers. To establish the selectivity, cubane 1 was treated with 2 equiv of MeQ-X (X = various anions) under similar conditions to isolate [F@{Zn4(dipp)4(MeQ)2(MeOH)2}][X] (X = I 4; BF4 5; PF6 6) in good yields. The crystal structure determination of 4 and 5 showed that the iodide and tetrafluoroborate anions are found outside the cage while fluoride ion has entered the cavity. The final fluoride encapsulated D4R cage is anionic in 2, neutral in 3, and cationic in 4-6, showing the versatility of the cubane framework to stabilize fluoride ions in all three forms. NMR titrations showed that 1 can sense even 1 ppm level of fluoride ions and sequester them from fluoridated water and toothpaste extract.

The cariostatic mechanisms of fluoride

This article discusses the possible cariostatic mechanisms of the action of fluoride. In the past, fluoride inhibition of caries was ascribed to reduced solubility of enamel due to incorporation of fluoride (F-) into the enamel minerals. The present evidence from clinical and laboratory studies suggests that the caries-preventive mode of action of fluoride is mainly topical. There is convincing evidence that fluoride has a major effect on demineralisation and remineralisation of dental hard tissue. The source of this fluoride could either be fluorapatite (formed due to the incorporation of fluoride into enamel) or calcium fluoride (CaF2)-like precipitates, which are formed on the enamel and in the plaque after application of topical fluoride. Calcium fluoride deposits are protected from rapid dissolution by a phosphate -protein coating of salivary origin. At lower pH, the coating is lost and an increased dissolution rate of calcium fluoride occurs. The CaF2, therefore, act as an efficient source of free fluoride ions during the cariogenic challenge. The current evidence indicates that fluoride has a direct and indirect effect on bacterial cells, although the in vivo implications of this are still not clear. A better understanding of the mechanisms of the action of fluoride is very important for caries prevention and control. The effectiveness of fluoride as a cariostatic agent depends on the availability of free fluoride in plaque during cariogenic challenge, i.e. during acid production. Thus, a constant supply of low levels of fluoride in biofilm/saliva/dental interference is considered the most beneficial in preventing dental caries.

Structural, morphological and spectroscopic properties of Eu3+-doped rare earth fluorides synthesized by the hydrothermalmethod

Rare earth fluorides (REF3, RE=Y, La, Gd or Yb) doped with 5% of Eu3+ ions were synthesized via the hydrothermal method and their physicochemical properties were compared. The synthesis was carried out in an aqueous medium at elevated pressure and temperature. The reaction was performed in situ, with use of NaBF4 as a source of fluoride ions. Structural and morphological properties of obtained nanophosphors were characterized with the use of powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and Raman spectroscopy. Synthesized products were nanocrystalline with hexagonal or orthorhombic crystal structures. They showed different morphology, from nanoplates to nanorings, depending on the used REF3 fluoride as the host for the Eu3+ ions. The elemental composition was confirmed by the energy-dispersive X-ray spectroscopy (EDX) results. Spectroscopic properties were investigated by measuring the excitation and emission spectra. Also luminescence lifetimes were determined. The synthesized materials showed bright red luminescence, due to the presence of Eu3+ ions in their structure.

Sodium fluoride induces apoptosis in mouse embryonic stem cells through ROS-dependent and caspase- and JNK-mediated pathways

Sodium fluoride (NaF) is used as a source of fluoride ions in diverse applications. Fluoride salt is an effective prophylactic for dental caries and is an essential element required for bone health. However, fluoride is known to cause cytotoxicity in a concentration-dependent manner. Further, no information is available on the effects of NaF on mouse embryonic stem cells (mESCs). We investigated the mode of cell death induced by NaF and the mechanisms involved. NaF treatment greater than 1mM reduced viability and DNA synthesis in mESCs and induced cell cycle arrest in the G2/M phase. The addition of NaF induced cell death mainly by apoptosis rather than necrosis. Catalase (CAT) treatment significantly inhibited the NaF-mediated cell death and also suppressed the NaF-mediated increase in phospho-c-Jun N-terminal kinase (p-JNK) levels. Pre-treatment with SP600125 or z-VAD-fmk significantly attenuated the NaF-mediated reduction in cell viability. In contrast, intracellular free calcium chelator, but not of sodium or calcium ion channel blockers, facilitated NaF-induced toxicity in the cells. A JNK specific inhibitor (SP600125) prevented the NaF-induced increase in growth arrest and the DNA damage-inducible protein 45α. Further, NaF-mediated loss of mitochondrial membrane potential was apparently inhibited by pifithrin-α or CAT inhibitor. These findings suggest that NaF affects viability of mESCs in a concentration-dependent manner, where more than 1mM NaF causes apoptosis through hydroxyl radical-dependent and caspase- and JNK-mediated pathways.

New data on the reaction of hexafluorothioacetone with styrenes

Hexafluorothioacetone, generated in situ from its cyclic dimer ( 1) in the presence of CsF catalyst was shown to react with styrene or 4-alkyl-styrenes (alkyl = c-hexyl, Me, t-Bu) forming the corresponding 2:1 Diels–Alder cycloadducts as major products. All cycloadducts were isolated, and the structure of two of them was established by single crystal X-ray diffraction. While 2-vinylnaphthalene, 4-CF 3- and 4-Cl-styrenes in the presence of CsF catalyst react with 1 producing the corresponding 1:1 Diels–Alder cycloadducts, 4-alkoxy styrenes were found to produce preferentially the corresponding thietanes. The reaction of styrenes with 1 was also found to be sensitive to the source of fluoride ion and the solvent.

ChemInform Abstract: Palladium-Mediated Reaction Between Aryl Iodides and Stereodefined 2- Arylethenyldimethylphenylsilanes or 2-Arylethynyldimethylphenylsilanes, in the Presence of a Fluoride Ion Source.

ChemInform Abstract: Palladium-Mediated Reaction Between Aryl Iodides and Stereodefined 2- Arylethenyldimethylphenylsilanes or 2-Arylethynyldimethylphenylsilanes, in the Presence of a Fluoride Ion Source.

Synthesis of 2H-Indazoles via [3+2]-Dipolar Cycloaddition

Reported is an efficient and selective method for the synthesis of 2H-indazoles 3 generated by fluoride-mediated fragmentation of 1 and easily obtained sydnones 2 (see also: D. Azarifar, H. Ghasemnejad-Borsa Synthesis 2006, 1123). The sequence consists of [3+2]-­dipolar cycloaddition-decarboxylation. The optimized conditions involve use of an excess of TBAF instead of CsF, which is usually the most widely used fluoride ion source for generating benzynes. The scope of this reaction was investigated with symmetrical and unsymmetrical aryne precursors as well as a variety of C3-substituted N-phenylsydnones (R = aromatics with EDGs and EWGs, alkynyl, alkyl, vinyl, and heterocycles) providing the 2H-indazoles 3 in moderate to good yields. The use of an unsymmetrical benzyne precursor afforded a regioisomeric mixture.

A General Method for the Synthesis of 2,2-[60]Fullerenoalkanals: The Reaction of [60]Fullerene with 2-Bromoenol Silyl Ethers

Five kinds of 2,2-[60]fullerenoalkanals were synthesized by the fluoride ion-mediated reaction of [60]fullerene with 2-bromoenol silyl ethers, which were easily prepared by 2-bromination of the corresponding enol silyl ethers. The reactivity differed significantly depending on the stability of the 2-bromoenol silyl ethers. High yield and selectivity were achieved for the reaction of 2-bromoenol trimethylsilyl ethers under mild conditions (KF/18-crown-6-ether). The reaction of stable 2-bromoenol tert-butyldimethylsilyl ethers, on the other hand, required the use of more reactive tetra­butylammonium fluoride as a fluoride ion source.

Mechanical and Physicochemical Properties of Some Originally Made Composite Materials for Dental Fillings

This work presents results of research on compressive strength, microhardness, polymerization shrinkage and water sorption of some specially developed composite materials for dental fillings. The investigated powder fillers were divided into two groups: fluorine-based fillers, such as fluoridated glass, strontium fluoride, ytterbium fluoride and additives of improved mechanical characteristics such as nanosilica and polyethylene. The influence of fluoride ion source on the properties of the composite materials was evaluated. Tests were performed just after the material polymerization and, additionally, after seven, thirty and sixty days. Some small differences between composites were observed.

Regioselective electrophilic substitution of 2,3-aziridino-γ-lactones: preliminary studies aimed at the synthesis of α,α-disubstituted α- or β-amino acids

2,3-Aziridino-γ-lactones are versatile synthons for the preparation of polysubstituted α- or β-amino acids. With the intention of preparing α,α-disubstituted α- or β-amino acids, regioselective electrophilic substitution of aziridino-γ-lactones at C2 was realized using two different methods. In the first, the anion was generated at C2 with LDA in the presence of the electrophilic agent. In the second method, the anion was trapped with TMS. Subsequent treatment of the C2 silylated product with a fluoride ion source regenerated the anion, which then reacted in situ with various electrophiles. Intramolecular aziridine opening of the C2 benzyl derivative prepared by the first method allowed access to a novel furan derivative, a direct precursor of an α,α-disubstituted β-amino acid.