Fluoride Anion Research Articles

Radiation-Induced Transformations of 2-Fluoroethanol in Aqueous Solutions

Steady-state radiolysis has been used to study the radiation-induced transformations of 2-fluoroethanol in dilute aqueous solutions as a model system for examining the autoradiolytic dehalogenation of the radiopharmaceutical drug 2-[18F]fluorodeoxyglucose ([18F]FDG). A derivatization–gas chromatography procedure for determining the fluoride anion in the presence of organofluorine compounds has been developed. It has been established that •OH and H• induced the dehalogenation of 2-fluoroethanol in aqueous solutions. Unlike bromo- and chlorohydrins, 2-fluoroethanol does not interact with $${\text{e}}_{{{\text{aq}}}}^{ - }$$ according to the dissociative attachment mechanism. It has been shown that О2 halved the radiation-chemical yield of fluoride due to the oxidation of hydroxyl-containing carbon-centered radicals of 2-fluoroethanol. The constant of unimolecular dehalogenation of the 2-fluoroethanol radical is 3.9 × 106 s−1, as calculated using the method of competing reactions.

Fluorescent Fluoride Sensor Based on Indolizine Core Skeleton for Bioimaging

Schematic representation of fluoride anion sensing with Silyl-KIz in live cell

IDTI Dyes for Fluoride Anion Chemosensors.

Fluoride anions play a key role in human health and chemical engineering, such as in organic synthesis and biological processes. The development of high-sensitivity naked-eye detection sensors for fluoride anions in organic solutions is crucial and challenging. In this study, (3Z,3′Z)-3,3′-[4,4,9,9-tetrakis(4-hexylphenyl)-4,9-dihydro-s-indaceno(1,2-b:5,6-b′)dithiophene]-2,7-diylbis(methan-1-yl-1-ylidene) bis(6-bromo-indolin-2-one) (IDTI) was designed and used as a fluoride chemosensor for the first time. IDTI is a highly sensitive fluoride sensor with a detection limit of as low as 1 × 10−7 M. In addition, upon the reaction of IDTI with fluoride anions in a tetrahydrofuran (THF) solution, color changes from red to yellow under ambient light and from purple to green under UV light were detectable by the naked eye. These studies indicate that IDTI is a promising fluoride chemosensor.

Synthesis and properties of supramolecular gels based on tetrathiafulvalene and cyanobiphenyl units

ABSTRACT For the development of self-assembly donor-σ-acceptor (D-σ-A) molecules, a series of D-σ-A low-molecular mass organogelators, consisting of tetrathiafulvalene (D) and cyanobiphenyl (A) connected by a thioalkanoyloxy spacer of varying lengths modified with hydrophobic chains incorporating amide groups on the side, was designed and readily synthesized. Their gelation properties were studied. The results showed that the gelation capability of these compounds was highly dependent on the alkyl chain length in the spacer group and the TTF and cyanobiphenyl units. Derivative 1a with short alkyl chain (n = 4) efficiently gelated in some aromatic solvents, forming opaque organogels. These gelators reacted with F4TCNQ to form stable charge-transfer complex gels in ethanol. Clear evidence of self-assembled micro/nanoflower, fibrous, or tubular morphologies in gelation state was obtained by scanning electron microscopy. It was found that the molecules adopted lamellar and rectangular columnar molecular packing models in the gel phase by X-ray diffraction. The native gels underwent a reversible gel-sol phase transition upon exposure to external stimuli. The gel-sol transition of the organogel was stimulated by the addition of fluoride anions. Interestingly, all gels showed an irreversible gel-sol transition triggered by TFA and TEA. The formation of flower-like morphologies of TTF-based derivatives in the gel state was observed.

A theoretical study describing the sensing mechanism of the novel triarylborane substituted naphthalimide molecule

Theoretical methods (DFT/TD-DFT) were applied to study the sensing mechanism of triarylborane naphthalimide. The free-energy and binding-energy change revealed more feasibility and binding affinity of fluoride in comparison to cyanide anion. FMO revealed the absence of the intramolecular charge transfer (ICT) character in the molecular receptor 3; however, the anion added products (3CN and 3F) showed the presence of ICT that is responsible for inducing the fluorescence quenching. Furthermore, the electrophilic nature of the boron atom has been explained via natural population analysis, which indicates that the boron site is active for the nucleophilic addition of cyanide and fluoride anions.

About Lanthanoid Fluoride Selenide Oxoselenotantalates with the Composition Ln3F2Se2TaO4 (Ln = La – Nd)

After solid‐state reactions of the light lanthanoid metals, their oxides and fluorides as well as selenium in sealed tantalum ampoules with sodium chloride as a fluxing agent at 850 °C for 8 days needle‐shaped single crystals of Ln3F2Se2TaO4 (Ln = La – Nd) were obtained. They crystallize in the orthorhombic space group Pnma analogous to La3F2Se2NbO4 with a = 1133–1120 pm, b = 400–393 pm and c = 1812–1778 pm (Ln = La – Nd) for Z = 4 as the first known quinary lanthanoid(III) oxoselenotantalates(V) with fluoride and selenide anions. The three crystallographically different Ln3+ cations are all surrounded by nine anions (O2–, F– and Se2–) each. Tantalum resides in an octahedral chalcogen coordination by forming trans‐vertex oxygen‐connected [TaO5Se]7– polyhedra, which build up chains 1∞{[TaOV2/2Ot3/1Set1/1]5–} along [010]. The sites of the four crystallographically different oxygen atoms and the two distinct fluoride anions were established by bond‐valence calculations. One fluorine and three oxygen atoms are surrounded tetrahedrally by cations, while another fluoride and oxide anion exhibit just triangular non‐planar coordination spheres. The two independent Se2– anions have five or six cationic neighbors.

Sensing mechanism of fluorogenic urea with fluoride in solvent media: A new fluorescence quenching mechanism.

The interaction of 1-Phenyl-3-(pyren-1-yl) urea (LH) and fluoride anion (F-) with a unique ON1-OFF-ON2 fluorescent response has been investigated by the density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The hydrogen-bonding dynamics and photophysical properties of the complex LH-F, as well as its isolated receptor LH and anion form L-H1, have been studied in detail. We demonstrate that the intermolecular hydrogen bond (N-H…F) of the complex LH-F is greatly enhanced in the electronically excited state. The nonradiative deactivation via electron transfer and internal conversion rather than excited-state intramolecular proton transfer (ESIPT) can be facilitated by the excited state hydrogen bond strengthening. The results have been cross-validated by molecular structure, electronic spectra, frontier molecular orbitals, and infrared spectra as well as hydrogen bond binding energy. These results indicate that the current calculations completely reproduce the experimental results and provide compelling evidence for the sensing mechanism of LH for F-.

Isatin-3-thiosemicarbazone as Chromogenic Sensor for the Selective Detection of Fluoride Anion

Abstract In this study, we describe the anion recognition ability of isatin-3-thiosemicarbazone 2, which contains two different anion recognition units i.e. isatin NH and the thiourea moiety. Both have the ability to act as proton donors. Most importantly, a significant colour change of 2 was observed (from light yellow to reddish orange) in organic medium only after the addition of the F– anion. No such colour change could be observed for any other anions including Cl–, Br–, I–, H 2 PO 4 − , ${{\text{H}}_{2}}\text{P}{{\text{O}}_{4}}^{-},$ NO 2 − , $\text{N}{{\text{O}}_{\text{2}}}^{-},$ PF 4 − $\text{P}{{\text{F}}_{4}}^{-}$ etc. The UV-Vis spectroscopic studies also indicate the potential of this compound for selective detection of fluoride anions. 1H-NMR titrations clearly indicate the formation of the 2.F– anionic complex. The Density-functional theory (DFT) calculations are also performed to get further insights on the formation of 2.F– complex.

Colorimetric and fluorimetric chemosensor based on upper rim-functionalized calix[4]arene for selective detection of fluoride ion

A new colorimetric and fluorescent chemosensor for fluoride anion based on calix [4]arene bearing four sulfonamide-fluorenone subunits on the upper rim was conveniently synthesized. It showed a remarkable color change as well as the fluorescence quenching upon addition of F- even in the presence of a wide range of anions in DMSO. The binding property of L with F- was studied by a combination of various spectroscopic techniques, such as absorption and emission titration, Job's plot and 1H NMR titration. It is anticipated that this design with functional group attached to upper rim of calix[4]arene platform can provide a new approach for the development of F- chemosensor.

Water‐Soluble Organotin Compounds – Syntheses, Structures and Reactivity towards Fluoride Anions in Water

Herein, we report the syntheses of the water‐soluble organotin compounds [{Me2(H)N(CH2)3}2SnX2]Y2 (1, X = Cl, Y = ClO4; 2, X = F, Y = ClO4) and {Me2(H)N(CH2)3}2SnX4 (3, X = Cl; 4, X = F). The compounds were characterized by elemental analysis, electrospray mass spectrometry, 1H, 13C, 19F, and 119Sn NMR spectroscopy, and in the case of compounds 1, 3 and 4, by single‐crystal X‐ray diffraction analysis. The reaction of compound 2 with fluoride anions in water was investigated by NMR spectroscopy. DFT calculations accompany the experimental work.

Poly(N,N-bis(2-methoxyethyl)acrylamide), a thermoresponsive non-ionic polymer combining the amide and the ethyleneglycolether motifs

Poly(N,N-bis(2-methoxyethyl)acrylamide) (PbMOEAm) featuring two classical chemical motifs from non-ionic water-soluble polymers, namely, the amide and ethyleneglycolether moieties, was synthesized by reversible addition fragmentation transfer (RAFT) polymerization. This tertiary polyacrylamide is thermoresponsive exhibiting a lower critical solution temperature (LCST)–type phase transition. A series of homo- and block copolymers with varying molar masses but low dispersities and different end groups were prepared. Their thermoresponsive behavior in aqueous solution was analyzed via turbidimetry and dynamic light scattering (DLS). The cloud points (CP) increased with increasing molar masses, converging to 46 °C for 1 wt% solutions. This rise is attributed to the polymers’ hydrophobic end groups incorporated via the RAFT agents. When a surfactant-like strongly hydrophobic end group was attached using a functional RAFT agent, CP was lowered to 42 °C, i.e., closer to human body temperature. Also, the effect of added salts, in particular, the role of the Hofmeister series, on the phase transition of PbMOEAm was investigated, exemplified for the kosmotropic fluoride, intermediate chloride, and chaotropic thiocyanate anions. A pronounced shift of the cloud point of about 10 °C to lower or higher temperatures was observed for 0.2 M fluoride and thiocyanate, respectively. When PbMOEAm was attached to a long hydrophilic block of poly(N,N-dimethylacrylamide) (PDMAm), the cloud points of these block copolymers were strongly shifted towards higher temperatures. While no phase transition was observed for PDMAm-b-pbMOEAm with short thermoresponsive blocks, block copolymers with about equally sized PbMOEAm and PDMAm blocks underwent the coil-to-globule transition around 60 °C.

In Silico Design of Cylindrophanes: The Role of Functional Groups in a Fluoride Selective Host.

Molecular recognition is the key driver in the formation of supramolecular complexes, enabling the selective encapsulation of specific guests. Here, we explore the delicate balance between different energetic terms in the formation of an efficient host for fluoride anions based on a cylindrophane structure, which can be achieved by the incorporation of ligand sites into a cyanuric acid based cyclophane framework, resulting a close proximity between the ammonium hydrogens and the anion. This study describes the character and contribution of different energetic and repulsive terms that favor the efficient inclusion of fluoride. Our findings are useful for further rational design and synthesis of efficient and highly selective fluoride hosts, which have been generally less well described than complexing agents for other halides.

Layered double hydroxides intercalated with fluoride and methacrylate anions as multifunctional filler of acrylic resins for dental composites

ZnAl layered double hydroxides (LDH) was selected as fluorinated filler of photoactivated Bis-GMA/Bis-EMA/TEGDMA resin. The ability of LDH to intercalate fluoride anions and to release them over the time, made this material a good filler to prepare acrylic resin composites with the potential of preventing dental caries. Moreover, LDH in fluoride form was functionalized on the surface by methacrylate anions (MA) which are able to participate to the polymerization process of the resin. This strategy allowed to improve the polymer/filler interactions and subsequently the mechanical properties of the final composite. LDH containing both fluoride and methacrylate anions were prepared with different methods. The best samples, selected on the basis of mechanical properties, were obtained starting from LDH intercalated with fluoride and then exposed to a partial exchange of the fluoride with methacrylate anions (LDH-F/MA). The effect of the presence of the fillers, which were LDH-F/MA and LDH intercalated with MA (LDH-MA), on the resin degree of conversion (DC) and on mechanical properties was investigated. Composites with DC of 75% showed an improvement in the mechanical properties in comparison with those of the pure resin. Moreover, the composites were able to release fluoride anions and to recapture them when contacted with fluoride solution.

Application of NMR Crystallography to Highly Disordered Templated Materials: Extensive Local Structural Disorder in the Gallophosphate GaPO-34A.

We present an NMR crystallographic investigation of two as-made forms of the recently characterized gallophosphate GaPO-34A, which has an unusual framework composition with a Ga:P ratio of 7:6 and contains both hydroxide and fluoride anions and either 1-methylimidazolium or pyridinium as the structure-directing agent. We combine previously reported X-ray crystallographic data with solid-state NMR spectroscopy and periodic density functional theory (DFT) calculations to show that the structure contains at least three distinct types of disorder (occupational, compositional, and dynamic). The occupational disorder arises from the presence of six anion sites per unit cell, but a total occupancy of five of these, leading to full occupancy of four sites and partial occupancy of the fifth and sixth (which are related by symmetry). The mixture of OH and F present leads to compositional disorder on the occupied anion sites, although the occupancy of some sites by F is calculated to be energetically unfavorable and signals relating to F on these sites are not observed by NMR spectroscopy, confirming that the compositional disorder is not random. Finally, a combination of high-field 71Ga NMR spectroscopy and variable-temperature 13C and 31P NMR experiments shows that the structure directing agents are dynamic on the microsecond time scale, which can be supported by averaging the 31P chemical shifts calculated with the SDA in different orientations. This demonstrates the value of an NMR crystallographic approach, particularly in the case of highly disordered crystalline materials, where the growth of large single crystals for conventional structure determination may not be possible owing to the extent of disorder present.

Fluoride anion sensing mechanism of 2‐(quinolin‐2‐yl)‐3‐hydroxy‐4H‐chromen‐4‐one chemosensor based on inhibition of excited state intramolecular ultrafast proton transfer

AbstractThe excited state hydrogen bonding interactions and intramolecular proton transfer (ESIPT) process for 2‐(quinolin‐2‐yl)‐3‐hydroxy‐4H‐chromen‐4‐one (Qu3HC) system has been theoretically studied via density functional theory (DFT) and time‐dependent DFT (TDDFT) methods. We confirmed that the reversible tuning of intramolecular hydrogen bonding direction is impossible for Qu3HC system. Then, we have studied the S0‐state and S1‐state hydrogen bonding dynamical behaviors of Qu3HC structure and confirmed that the strengthening of intramolecular hydrogen bond in the S1 state could facilitate ESIPT reaction. Given photo‐induced excitation, we find that the charge redistribution around hydroxyl moiety plays important roles in providing driving force for ESIPT. Our constructed potential energy curves further verify that the ESIPT process of Qu3HC should be ultrafast due to low potential barrier. With the addition of fluoride anions, the exothermal deprotonation process occurs spontaneously along with the intermolecular hydrogen bond O–H···F, which reveals the uniqueness of detecting fluoride anion using Qu3HC molecule. As a whole, the fluoride anion inhibits the initial ESIPT process of Qu3HC, which results in different fluorescence behaviors.

Turn-on fluorescence sensor for selective detection of fluoride ion and its molecular logic gates behavior

Loutonin based emissive probe (L) for the dual sensing of fluoride (F−) and bisulphate (HSO4−) anions in aqueous media. The development is based on reports that the interaction between fluoride and loutonin based fluorescent probe exhibits rapid and remarkable color changes in both colorimetrically as well as fluorimetrically. More amusingly, on the introduction of bisulphate ion into the medium containing loutonin fluoride ion complex (L-F−) which shows both the color and fluorescence has been recovered. The limit of detection for fluoride ions by the probe was determined as 8.62 × 10−7 M by fluorescence titrations. Further the probe L can be employed for the removal of fluoride ions. The need for a dual anion detection system with such an outstanding reversible and reproducible process characteristics led us to consider loutonin as a feasible nominee for the construction of molecular keypad lock and molecular logic circuits. The fluorescence change of loutonin after appendage of fluoride ions is mainly due to the hydrogen bonding interaction. Further, the probe could be potentially incorporated into the test strips and silica gel plates, with better selectivity for fluoride and bisulphate anions in aqueous media.

Raman Spectroscopic and Theoretical Study of Scandium Fluoride and Oxyfluoride Anions in Molten FLiNaK.

The speciation in the FLiNaK-ScF3 and FLiNaK-ScF3-Li2O melts above 873 K was investigated by Raman spectroscopy and density functional theory (DFT) calculations. Binary scandium fluoride anions in the form of ScF52- and ScF63- were identified in molten FLiNaK containing 20 mol % ScF3, which were not affected by either temperature or alkali cations in molten fluoride. With the addition of Li2O into the FLiNaK-ScF3 (20 mol %) melt, ternary scandium oxyfluoride anion Sc2OF62- was formed and dominated the spectrum, and it was characterized to possess a linear Sc-O-Sc geometry with two ScF3 moieties bridged by a single oxygen atom. Further increase in Li2O content to 40 mol % resulted in the formation of the second oxyfluoride anion Sc2O2F64- containing a rhombic Sc2O2 ring, while the Raman bands due to Sc2OF62- disappeared. When the Li2O concentration went beyond 40 mol %, the sample was no longer homogeneous due to the appearance of insoluble scandium oxide on the surface of the melt, suggesting that scandium oxide is formed via the reactions of ScF52- and ScF63- with O2- in molten FLiNaK mediated by Sc2OF62- and Sc2O2F64-.

Silver ion-assisted substitutive fluorination of chlorofullerenes

Treatment of the skew-pentagonal-pyramid (SPP) isomer of C60Cl6 with silver(I) fluoride affords displacement of chlorine addends to give mixed C60Cl6–nFn compounds with n = 1–5 and pure C60Fn fluorides with n = 2, 4, and 6. Likewise, treatment of Cs-C70Cl10 produces C70Fn fluorides with n = 2–10 and a series of mixed chloro-fluoro derivatives. Several of the newly synthesized substances, SPP-C60Cl5F, SPP-C60ClF5 (two isomers), SPP-C60F6, and non-symmetric C60F4 and C60F6, have been isolated, and spectroscopically characterized. Their structures have been established on the basis of the 19F NMR data supplemented with DFT calculations. Our experimental data and theoretical considerations suggest that the reaction likely proceeds via Ag+-mediated elimination of chloride anion from the fullerene cage followed by fluoride anion attachment to the site thus vacated.

Solid-phase chemiluminescent reaction of Eu2(SO4)3 with XeF2 as a possible source of the Eu(IV) highest oxidation state

The highly exothermic solid-phase interaction of anhydrous europium (III) sulfate polycrystalline powder with xenon difluoride was found to be a potential source of the highest oxidation state (HOS) of europium, Eu4+. The reaction is accompanied by chemiluminescence (CL) in the visible spectral region and proceeds spontaneously at room temperature for ​~ ​20 ​h. Several photon emitters are established and identified, namely, atomic Xe and single-ionized xenon Xe+, emitting in the wavelength range 420–700 ​nm, as well as the electronically excited ion Eu3+ (590–700 ​nm). Absorption with a maximum of ~340 ​nm is registered in the diffuse reflectance spectrum of the reaction mixture during first few minutes of the reaction. This signal is tentatively assigned to the HOS of europium (+4). The reaction mechanism is proposed which includes a) Eu3+-assisted decomposition of xenon difluoride leading to atomic fluorine as well as highly reactive intermediates XeF+ and Xe+; b) oxidation of Eu3+ ion to the HOS by the latter; c) generation of excited species in the reduction stages followed by CL: Xe2+(Xe+) → Xe0 (blue-green emission) and Eu4+ → Eu3+ (red emission), sulfate environment is considered as the reductant; d) the F• ​+ ​SO4•- interaction and partial replacement of sulfate ligands with fluoride and fluorosulfate anions in the coordination sphere of the europium ion. Theoretical calculations using composite methods suggest the proposed mechanism and demonstrate the thermodynamic probability of ozone formation in the studied reaction, which was detected by the characteristic UV absorption band.

Bi3(SeO3)3(Se2O5)F: A Polar Bismuth Selenite Fluoride with Polyhedra of Highly Distortive Lone Pair Cations and Strong Second-Harmonic Generation Response

A polar bismuth selenite fluoride, Bi3(SeO3)3(Se2O5)F, consisting of extremely distortive lone pair cations as well as a very electronegative fluoride anion has been synthesized in high yield via a...