Search

Due to their high electron density, fluoride anions can be considered the most effective halogen bond (HaB) acceptors among the halides. However, under common experimental conditions, F− uncommonly acts as HaB acceptor, expectedly as it is present in hydrated form. Herein we report that under specific crystallization conditions a hydrogen bond‐free F− functioning as donor of electron density can be obtained, with the formed HaBs constituting the driving force of the observed crystal packings. Computations confirm the strength of these HaBs compared to analogous interactions involving other halides. [ABSTRACT FROM AUTHOR]

By using quantum mechanical calculations, the most probable structure of the anionic complex species dodecabenzylbambus[6]uril–F− was derived. In this "asymmetrical" complex, the fluoride anion F−, included in the macrocyclic cavity, is bound by six weak C–H⋯F− hydrogen bonds between methine hydrogen atoms on the convex face of glycoluril units and the F− ion. The interaction energy, E(int), of the resulting anionic complex was found to be − 427.8 kJ mol−1, confirming also the formation of this complex species. [ABSTRACT FROM AUTHOR]

One tetra-imidazolium salt (2) based on quinoxaline was prepared and characterized, and the detection of anions by compound 2 as a chemosensor was researched through fluorescence spectra, UV/Vis spectra, 1H NMR titrations, MS and IR spectra. The experimental results displayed that sensor 2 can selectively recognize F− through the instrument or the naked eyes (the color changed from colorless to brown in visible light). The high K value (6.4 × 104 M−1) for 2 F− indicated that 2 had strong bonding force to F−. The low detection limit (1.84 × 10−7 mol/L) indicated that the detection of F− by 2 was sensitive. One tetra-imidazolium salt was prepared, and its selective recognition for F- was investigated. [Display omitted] • A new tetra-imidazolium salt based on quinoxaline (2) was prepared and characterized. • The selective recognition of 2 to fluoride ion was investigated. • Compound 2 had high sensitivity for the detection of F− with the detection limit of 1.84 × 10−7 M mol/L. • The association constant of 2 F− was 6.4 × 104 M−1, which indicated that 2 had strong bonding force to F−. [ABSTRACT FROM AUTHOR]

Fluoride detection has been playing an important role in chemical, biological, and medicinal field, especially for keeping physical health and resisting environmental pollution. Herein, a urolithin B fluorescent probe has been successfully developed with good sensitivity, selectivity, anti-interference ability. The low limit of detection (LOD) refers to 0.156 μM, and the instant response time to F− is less than 1 s. The probe is suitable for quantitatively and qualitatively ratiometric detection for F− in solution with two distinct emission bands at 425 (blue) and 566 nm (orange), with the coordinate change of CIE from (0.38, 0.41) to (0.22, 0.11). Urolithin B displayed a remarkable ratiometric fluorescence response towards F−. The detection mechanistic was further proposed by NMR and electronic spectroscopic experiments combining with time-dependent density functional theoretical calculation. [Display omitted] • A Ratiometric fluorescent probe was developed. • The photochemical properties and LOD of UB to F− were investigated. • Mechanism of UB sensing toward F− was confirmed by 1H NMR, DFT and TD-DFT calculation. • Response time less than second could be applied as an instant detection. • Coordination ratio for UB and F− was determined according to Job's plot. [ABSTRACT FROM AUTHOR]

Abstract The work discusses about the synthesis of indium-alizarin red S complex followed by its application toward the sensing of F¯ ion. At first, the interaction between indium and alizarin red S dye was studied at three different pH medium, pH 4, 7 and 9, of which pH 7 gave the best result. The indium-alizarin red S complex so obtained was then utilized for the ratiometric sensing of fluoride ion using absorption spectroscopy with variation of temperature. The lowest limit of detection (0.040 mM) was obtained at 313 K. The mechanism for the sensing of F¯ ion was then investigated using isothermal titration calorimetry. The endothermic nature of the interaction between F¯ ion with indium-alizarin red S complex shows temperature dependence on the sensing experiment. At the end, the utility of the technique toward natural sample was also examined. The present work reports a simple, rapid and efficient detection of fluoride anion in environmental water samples.

In the current work, we studied the sensing process of the sensor (E)-2-((quinolin-8ylimino) methyl) phenol (QP) for fluoride anion (F–) with a "turn on" fluorescent response by density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The proton transfer process and the twisted intramolecular charge transfer (TICT) process of QP have been explored by using potential energy curves as functions of the distance of N-H and dihedral angle C-N=C-C both in the ground and the excited states. According to the calculated results, the fluorescence quenching mechanism of QP and the fluorescent response for F– have been fully explored. These results indicate that the current calculations completely reproduce the experimental results and provide compelling evidence for the sensing mechanism of QP for F–. [ABSTRACT FROM AUTHOR]

Excessive fluoride anions in drinking water are toxic to the health of human beings. In this article, an effective fluoride removal adsorbent on the basis of amino-functionalized porous polydivinylbenzene (PDVB) was prepared through low cost processes, which included solvothermal preparation of porous PDVB and subsequent surface amino-functionalization. The obtained amino-functionalized porous PDVB (A-PDVB) has high surface area of 443 m2 g−1 and high adsorption capacity towards fluoride anion up to 105.9 mg g−1. Considering adsorbents surface area, the adsorption capacity per unit surface area of A-PDVB is 0.24 mg m−2 which is more than 4 times of porous PDVB (0.058 mg m−2). The enhanced adsorption performance of A-PDVB was due to amino groups electrostatic interaction coupled with hydrogen bond binding with fluoride anions. In addition, the amino-functionalized porous PDVB could be regenerated in high efficiency under alkaline conditions. This work not only exhibits the possibility of A-PDVB for application as an environment-friendly adsorbent for fluoride removal but also gives an insight into understanding mechanism of the fluoride anions adsorption onto amino-functionalized porous PDVB.

The electroreduction of SF6 is shown at ambient temperature in acetonitrile using an array of platinum microelectrodes to improve the electrical detection. Its half reduction potential occurs at −2.17 V vs Fc+/Fc. The exact number of electrons for the full consumption of sulfur hexafluoride was determined and this gas further quantitatively transformed into environmentally benign fluoride anion and sulfur by electrochemical reduction.

The work discusses about the synthesis of indium-alizarin red S complex followed by its application toward the sensing of F¯ ion. At first, the interaction between indium and alizarin red S dye was studied at three different pH medium, pH 4, 7 and 9, of which pH 7 gave the best result. The indium-alizarin red S complex so obtained was then utilized for the ratiometric sensing of fluoride ion using absorption spectroscopy with variation of temperature. The lowest limit of detection (0.040 mM) was obtained at 313 K. The mechanism for the sensing of F¯ ion was then investigated using isothermal titration calorimetry. The endothermic nature of the interaction between F¯ ion with indium-alizarin red S complex shows temperature dependence on the sensing experiment. At the end, the utility of the technique toward natural sample was also examined. The present work reports a simple, rapid and efficient detection of fluoride anion in environmental water samples. [ABSTRACT FROM AUTHOR]

In this work, we have designed and synthesized the fluorescent probe 1, which was capable to selectively detect fluoride anion (F−). More importantly, the probe 1 possessed near-infrared excitation and emission wavelengths (excitation at 650 nm and emission at 695), and the probe solution had changed dramatically from yellow to cyan with the addition of F–. In addition, the fluorescence intensity exhibited perfectly positive correlation with concentration of F− concentration from 0 to 40 μM (R2 = 0.9972), which offered the important condition for quantitative analysis. The probe 1 owned detection limit of 46 nM. Therefore, this near-infrared probe can be of great benefit for detecting F− in practical application.

Molecular structure calculations of heteroligand macrotetracyclic complexes of 3d elements MIV (M = Ti, V, Cr, Mn, Fe, Co, Ni, Cu) with phthalocyanine as the (NNNN) donor-atom ligand and two fluoride anions were carried out in terms of the density functional theory with the OPBE functional and the TZVP basis set. The key bond lengths, bond angles, and non-bond angles in the complexes are presented. The standard enthalpies, entropies, and Gibbs energies of formation of the compounds are calculated. According to calculations, all complexes have tetragonal bipyramidal or similar structures. The complex-forming agent MIV lies in the plane formed by the donor nitrogen atoms of the phthalocyanine ligand. The M-N bond lengths as well as the M-F bond lengths are equal to one another. All six-membered metal chelate rings in the complexes are identical to one another both in terms of the sum and the set of the bond angles. The same holds for the five-membered rings containing nitrogen atoms. [ABSTRACT FROM AUTHOR]

In the current work, we studied the sensing process of the sensor (E)-2-((quinolin-8ylimino) methyl) phenol (QP) for fluoride anion (F–) with a “turn on” fluorescent response by density functional theory (DFT) and time-dependent density functional theory (TDDFT) calculations. The proton transfer process and the twisted intramolecular charge transfer (TICT) process of QP have been explored by using potential energy curves as functions of the distance of N-H and dihedral angle C-N=C-C both in the ground and the excited states. According to the calculated results, the fluorescence quenching mechanism of QP and the fluorescent response for F– have been fully explored. These results indicate that the current calculations completely reproduce the experimental results and provide compelling evidence for the sensing mechanism of QP for F–.

Molecular structure calculations of macrotetracyclic metal complexes containing a scan-dium(III) ion, a macrocyclic (N,N,N,N)-donor ligand (porphyrazine, trans-dibenzoporphyrazine, tetrabenzoporphyrazine), and a F− anion were carried out at the OPBE/TZVP level of the density functional theory. The most important bond lengths, bond angles, and non-bond angles in these heteroligand metal complexes were determined. All complexes have distorted tetragonal-pyramidal structures where the complex-forming agent ScIII is above the basal plane formed by the donor nitrogen atoms. The distance between the ScIII atom and the basal plane somewhat decreases in the order porphyrazine—trans-dibenzoporphyrazine—tetrabenzopor-phyrazine. Although all six-membered metal chelate rings in each complex are identical to one another, none of them is planar; on the contrary, all five-membered rings are planar. The standard enthalpies, entropies, and Gibbs energies of formation of the metal complexes in question were determined. Different metal complexes are characterized by different numerical values of the same thermodynamic parameters. [ABSTRACT FROM AUTHOR]

The molecular structures of the (6666) macrotetracyclic heteroligand chelates of M(III) (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu) with the (NNNN)-donor-atom ligand phthalocyanine and fluoride anion were calculated using the density functional theory (DFT) in the OPBE/TZVP version. All these metal complexes have the structure of a slightly distorted tetragonal pyramid, where the M(III) complexing agent lies over its base consisting of nitrogen donor atoms. The values ​​of the most important bond lengths and bond and non-bond angles in these complexes were given. All the six-membered metal chelate cycles in eight of these nine metal chelates are identical both in the sum of their bond angles and assortment; the only exception is the Mn(III) complex, in which these metallocycles are equal only in pairs. Pronounced electron density delocalization takes place over the entire macrocycle in each of these coordination compounds. The standard enthalpy, entropy, and Gibbs energy of formation of these compounds were also calculated. [ABSTRACT FROM AUTHOR]

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.

High selectivity and sensitivity detection of fluoride anions (F−) in an organic solution by the naked eye has always been a challenge. In this investigation, a simple compound based on aminobenzodifuranone (ABDF) was designed and synthesized. Deprotonation of the amino moiety caused by F− is responsible for a color change from dark blue to various colors (colorless, yellow, orange, and red) in different common organic solvents due to a blue shift over 200 nm in the UV/Vis spectrum. The color change is quite visible to the naked eye under ambient light. The detection limit for F− can reach a concentration of as low as 5.0 × 10−7 M with high selectivity, even in a solution containing multiple anions.

BODIPY dyes have received great attention in the last few years as optical chemosensors since they can recognize metal ions in solutions through optical signals (colorimetric and/or fluorimetric). In this context, our research group reports the synthesis of a carbazolyl-BODIPY derivative and its respective characterization by 1H NMR spectroscopy and mass spectrometry. Furthermore, a preliminary study of the chemosensory capacity of this BODIPY derivative was carried out in acetonitrile solution in the presence of several anions and a highly selective fluorimetric response was obtained for F-.

Molecular structure calculations of heteroligand (6666)macrotetracyclic metal (MIV) chelates (M = Fe, Co, Ni, Cu) with trans-di[benzo]porphyrazine as the (N,N,N,N)-donor ligand and two F− anions were carried out at the OPBE/TZVP level of density functional theory. The key bond lengths, bond angles, and non-bond angles in the complexes were determined and corresponding standard enthalpies, entropies, and Gibbs energies of formation were calculated. All complexes have slightly distorted tetrahedral structures. The complex-forming agent MIV lies in the plane formed by the donor nitrogen atoms. The metal—nitrogen bonds are usually pair-wise equal. The six-membered metal chelate rings in the complexes are identical to one another from the standpoint of both the sum and set of the bond angles. [ABSTRACT FROM AUTHOR]

A novel naked eye fluorescence sensor (ANI) based on naphthalimide and imidazolium moieties for fluoride detection has been designed and synthesized by multiple step synthesis. The fluorescence response of ANI sensor was significantly quenched in the presence of fluoride ion upon the interaction between an acidic amide proton and acidic C2 proton (-C(2)H-) of imidazolium compound. The binding behavior of ANI and F− ion was extensively explored by using NMR titration. Comparison of binding ability of ANI and AN sensors addressed the dominant electrostatic and hydrogen bonding interaction with F− ion. Consequently, ANI sensor highlights a strong binding with F− ions with a high selectivity over AN. Interestingly, ANI demonstrated a naked-eye response with colorimetric and fluorometric assay. [ABSTRACT FROM AUTHOR]

In this study we found that appropriate introduction of OH groups as the proton donor and amine as the electron donors to the perylene bisimide core can result in hydrogen‐bonded structures that facilitate tunable intramolecular charge transfer. Addition of F− anions can disrupt the intramolecular hydrogen bonds, therefore facilitate intracomplex proton transfer from O−H to F−, excess fluoride promotes deprotonation of the ground‐state complex. Therefore multiple fluorescence emission can be provided by this system. We used NMR, UV‐Vis‐NIR, and fluorescence spectroscopy to characterize these processes. The corresponding pronounced changes in photophysical properties (including color changes from green to blue to red) suggest new opportunities for creating novel functional supramolecular systems, such as multistate fluorescent switches. [ABSTRACT FROM AUTHOR]

It is well known that ions play important roles in our life sciences, and the detection of ions has attracted more and more attention. In this work, we focus on the sensing response mechanism of a novel fluoride chemosensor, 4‐((tert‐butyldiphenylsilyl)oxy)isophthalaldehyde (BIPA). Based on density functional theory and time‐dependent density functional theory methods, we clarify that fluoride anions could trigger the cleavage reaction of the Si‐O bond of BIPA in the ground state. And, the potential energy curve of desilylation process reveals the rapid response to fluoride anions. Comparing the binding energies between fluoride anions and other anions, we confirm that only the fluoride anions could be detected using the BIPA chemosensor in ethanol solvent. Considering the photo‐excitation process, we find the strong intramolecular charge transfer process for the S0 → S1 transition could explain the red shift of the absorption spectra of the BIPA system. This work not only clarifies the specific fluoride‐sensing mechanism, but also plays a role in facilitating designing and synthesizing of novel fluorescent sensors in future. [ABSTRACT FROM AUTHOR]

Fluoride ion plays a pivotal role in a range of biological and chemical applications however excessive exposure can cause severe kidney and gastric problems. A simple and selective molecular sensor, 4,5-di(thien-2-yl)-2-(4-(1,2,2-triphenylvinyl)-phenyl)-1H-imidazole, DTITPE, has been synthesized for the detection of fluoride ions, with detection limits of 1.37 × 10−7 M and 2.67 × 10−13 M, determined by UV-vis. and fluorescence spectroscopy, respectively. The variation in the optical properties of the molecular sensor in the presence of fluoride ions was explained by an intermolecular charge transfer (ICT) process between the bis(thienyl) and tetraphenylethylene (TPE) moieties upon the formation of a N-H---F− hydrogen bond of the imidazole proton. The sensing mechanism exhibited by DTITPE for fluoride ions was confirmed by 1H NMR spectroscopic studies and density functional theory (DFT) calculations. Test strips coated with the molecular sensor can detect fluoride ions in THF, undergoing a color change from white to yellow, which can be observed with the naked eye, showcasing their potential real-world application.

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.

In this study, we have designed and synthesized a novel 'AND' logic based fluorescence probe,1-(3′,6′-bis((tert-butyldiphenylsilyl)oxy)-3-oxospiro (isoindoline-1,9′-xanthen)-2-yl)-3-phenylthiourea (FPSi), for the rapid (3 min) simultaneous detection of F− and Hg2+ in DMSO/H 2 O solution (7:3, v/v). The FPSi probe, synthesized over three steps starting from commercially available fluorescein, was constructed by attaching tert-butyldiphenylsilyl and thiosemicarbazide (as the specific identification groups for F− and Hg2+) to the skeleton of fluorescein, respectively. FPSi produced no fluorescence response towards the addition of F− or Hg2+ separately. However, when the probe was exposed to a solution containing both F− and Hg2+, there was a significant yellow-green fluorescence. FPSi demonstrated an excellent selectivity towards both F− and Hg2+ in the presence of interfering substances. The results of TOF-MS-EI analysis indicated that the response of FPSi towards F− and Hg2+ was mainly aroused by the F− promoted cleavage of Si–O bond, and Hg2+ triggered an irreversible desulfurization reaction leading to the spiral ring opening. Furthermore, the FPSi probe has been successfully used to detect F− and Hg2+ ions in tap water and cropland soil. Image 1 • A fluorescein-based chemosensor was synthesized. • The sensor is an efficient AND-logic probe for detecting Hg2+ and F−. • It can turn on the fluorescence in the coexisting solution of Hg2+ and F−. • The response of the probe towards Hg2+ and F− is rapid. [ABSTRACT FROM AUTHOR]

Abstract A novel supramolecular organic framework gel (PQPA) has been constructed by a novel bilateral 8-hydroxyquinoline modified pillar[5]arene host (P5Q) and a bilateral bromohexyl functionalized pillar[5]arene guest (P5C6). Interestingly, the gel PQPA shows special selective and ultrasensitive sensing property for Fe3+. The limit of lowest detection (LOD) of gel PQPA for Fe3+ is 0.102 nM. Meanwhile, by adding Fe3+ into the gel PQPA , a no fluorescence Fe3+ coordinated metallogel (PQPA-Fe) could be constructed. Due to the competitive coordination of F−, fluorescent "turn-on" ultrasensitive response of the Fe3+ coordinated metallogel (PQPA-Fe) for F− is achieved. The limit of lowest detection of the Fe3+ coordinated metallogel (PQPA-Fe) for F− is 9.79 nM. In addition, the xerogel of the supramolecular organic framework gel (PQPA) is capable for removing Fe3+ in a lower concentration aqueous solution at an adsorption rate of 99.9%. More importantly, the supramolecular organic framework gel (PQPA) could be used to detect Fe3+ in the Yellow River Water samples. The supramolecular organic framework gel (PQPA) and Fe3+ coordinated metallogel (PQPA-Fe) could act as ultrasensitive reversible fluorescent chemosensor, test kits and fluorescent display materials for Fe3+ and F−. Graphical abstract Novel supramolecular organic framework gel PQPA was constructed by functionalized pillar[5]arenes. Interestingly, the SOF gel PQPA could continuously and ultrasensitively detect Fe3+ and F− in water. Unlabelled Image Highlights • Novel pillar[5]arene-based SOF gel (PQPA) was successfully constructed. • PQPA could carry out ultrasensitive detection of Fe3+ in water (LOD = 0.102 nM). • PQPA-Fe could ultrasensitively detect F− in water (LOD = 9.79 nM). • Fe3+ could be adsorbed by PQPA from water (adsorption rate of 99.9%). • Test kits for Fe3+ and F− were prepared. [ABSTRACT FROM AUTHOR]

Abstract A highly selective and sensitive colorimetric sensor based on aggregation-induced color change of 4-mercaptophenylboronic modified gold nanoparticles was designed for the determination of fluoride anion. The 4-mercaptophenylboronic modified gold nanoparticles were synthesized by a simple one-pot reaction. The aggregation process occurred when interaction between fluoride anion and 4-mercaptophenylboronic on the surface of gold nanoparticles took place; as a result, fluoroborate anions were formed coupled with changes in the electronic properties of the AuNPs. The change can be measured by UV–Vis absorption spectra. The sensor shows good selectivity and sensitivity for fluoride anion. The linear range is 10.0–30.0 μM for fluoride and the detection limit of fluoride is 3.45 × 10−7 M according to IUPAC criteria (3σ rule). Furthermore, the sensor has been used for the detection of fluoride anion in tap water, ground water and human serum samples, the recovery can achieve 94.0%–103.3%, 94.7%–101.0% and 89.8–100.9%, respectively. The excellent performance of colorimetric sensor in the detection of the fluoride anion demonstrated the potential application in the detecting fluoride anion present in the complex environmental and biological samples. Graphical abstract Unlabelled Image Highlights • A colorimetric sensor for fluoride detection by naked eyes. • The fluoride resulted in aggregation-induced color change of gold nanoparticles. • The linear range is 10.0–30.0 μM for fluoride. • The detection limit of fluoride is 3.45 × 10−7 M. • The fluoride detection in the environmental and biological samples. [ABSTRACT FROM AUTHOR]

Abstract Fluoride anion plays an important role in dental health and the treatment of osteoporosis. On the other hand, over exposure to fluoride may lead to severely diseases. Therefore, quantitative analysis of fluoride ions with high specificity and sensitivity by facile and rapid method is in urgent demand. In this paper, an amino-group functionalized MOFs NH 2 -UiO-66 is synthesized by treating Zr4+ ions and 2-aminaterephthalic acid under hydrothermal condition. A drastic fluorescence enhancement of NH 2 -UiO-66 at 455 nm induced by fluoride ions is demonstrated. Using NH 2 -UiO-66 as a receptor, a high selective and sensitive fluorescent detection of F- ions in aqueous solution is achieved. This detection is free from interferences of the co-existing anions and cations, such as Cl-, Br- and I-, NO 3 -, SO 4 2-, PO 4 3-, CO 3 2-, metal ions and humic acid, etc, for which the allowed amount is up to 1.0 g L−1. The detection limit of F- anion is 0.229 mg L−1. The F- anion-enhanced fluorescent sensing mechanism can be ascribed to the formation of hydrogen bonds between the guest F- anions and the free amino groups in NH 2 -UiO-66, which result in incremental electron transfer from organic ligands to Zr-oxo clusters. These studies indicate that the luminescent MOF material of NH 2 -UiO-66 as fluorescent probes may hold promising application in highly selective and sensitive detection of F- anions together with facile receptor fabrication and regeneration. [ABSTRACT FROM AUTHOR]

Abstract Two new benzimidazolium salts with the same cationic moiety and different anions 3-(2′-((8″-hydroxy-9″,10″-dioxo-9″,10″-dihydroanthracen-1″-yl)oxy)ethyl)-1-(pyridin-2‴-ylmethyl)-1H-benzo[ d ]imidazol-3-ium bromide and 3-(2′-((8″-hydroxy-9″,10″-dioxo-9″,10″-dihydroanthracen-1″-yl)oxy)ethyl)-1-(pyridin-2‴-ylmethyl)-1H-benzo[ d ]imidazol-3-ium hexafluorophosphate were prepared and characterized. The single crystal structure of 3-(2′-((8″-hydroxy-9″,10″-dioxo-9″,10″-dihydroanthracen-1″-yl)oxy)ethyl)-1-(pyridin-2‴-ylmethyl)-1H-benzo[ d ]imidazol-3-ium bromide was determined by X-ray single crystal diffraction. Particularly, anion recognition using 3-(2′-((8″-hydroxy-9″,10″-dioxo-9″,10″-dihydroanthracen-1″-yl)oxy)ethyl)-1-(pyridin-2‴-ylmethyl)-1H-benzo[ d ]imidazol-3-ium hexafluorophosphate as a chemosensor was carried out via fluorescence and ultraviolet spectroscopy, 1H NMR titrations, HRMS and IR spectra. The response of this chemosensor to fluoride anion can be observed through both remarkable fluorescence quenching and color change under visible light (from orange to purple). The results indicated that this chemosensor can distinguish fluoride anion from other anions via the instrument and naked eyes, and this is greatly convenient in practical operation. Graphical abstract Benzimidazolium salts 2 and 3 were synthesized and characterized, and the recognition of 3 for F− was studied via fluorescence and ultraviolet spectroscopy. Image 1 [ABSTRACT FROM AUTHOR]

• One pot, multi-step reaction. • Activation of S 8 with the fluoride anion leading to fluoropolysulfide anion. • Mild reaction conditions and excellent to satisfactory yields. • The fluoride anion assistant rearrangement of 1,2-diarylcyclopropenethiones. • A new pathway to get to desaurines. Elemental sulfur, upon treatment with tetrabutylammonium fluoride (TBAF, 20 mol%) in THF solution at room temperature, undergoes activation via ring opening, leading to in situ-generation of the red colored, highly reactive fluoropolysulfide anion FS x ‒. The latter easily reacts with sterically congested 2,3-diarylcyclopropenethiones and five membered 3 H -1,2-dithiole-3-thiones are formed selectively as single products in good to excellent yields. The analogous course of sulfurization via ring expansion was observed in the case of 2,3-bis(4-chlorophenyl)cyclopropenone and in this case the expected 3 H -1,2-dithiol-3-one derivative was isolated in 83% yield. The elaborated protocol can replace the already reported, less convenient procedure, based on application of DMF as a solvent and potassium fluoride as an activator. Treatment of 2,3-diphenylcyclopropenethione with TBAF in the absence of sulfur resulted in the unexpected formation of the (E,Z)- and (Z,Z)-isomers of the dimeric α-benzoylthioketene (desaurines), and a tentative mechanism involving participation of the initially formed, reactive (α-thioketene)phenylmethylene (a carbene species) as a key intermediate, is postulated. [Display omitted] [ABSTRACT FROM AUTHOR]

The sensing mechanism of a fluoride‐anion probe BODIPY‐amidothiourea (1c) has been elucidated through the density functional theory (DFT) and time‐dependent density functional theory (TDDFT) calculations. The theoretical study indicates that in the DMSO/water mixtures the fluorescent sensing has been regulated by the fluoride complex that formed between the probe 1c/two water molecules and the fluoride anion, and the excited‐state intermolecular hydrogen bond (H‐B) plays an important role in the fluoride sensing mechanism. In the first excited state, the H‐Bs of the fluoride complex 1cFH2 are overall strengthened, which induces the weak fluorescence emission. In addition, molecular orbital analysis demonstrates that 1cFH2 has more obvious intramolecular charge transfer (ICT) character in the S1 state than 1cH2 formed between the probe 1c and two water molecules, which also gives reason to the weaker fluorescence intensity of 1cFH2. Further, our calculated UV‐vis absorbance and fluorescence spectra are in accordance with the experimental measurements. © 2018 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

A series of colorimetric and reversible receptors for fluoride anions based on diketopyrrolopyrrole (DPP) were designed and synthesized successfully. The position of nitro substituent on the phenylhydrazide affected the alteration of photophysical properties to varying degrees. While the photoluminescence intensity of receptor 1 was weaker than that of receptor 2 and receptor 3 on account of the formation of intramolecular hydrogen bond deriving from oxygen atom of nitro substituent and hydrogen atom of hydrazide. The receptor 2 was a preferable chemosensor for responding fluoride anions. The fluorescence was quenched in the presence of fluoride anion resulted from the photo-induced electron transfer (PET) effect from the amide. The formation of deprotonation species, which produced by hydrazide N H moiety and F − was answerable for the spectral changes. Especially, the spectral and color responses of receptors could be switched back and forth successively by adding F − and HSO 4 − anions in DMSO solution. These receptors could response fluoride anion sensitively, visually and selectively in a manner of reversible with a low determination. [ABSTRACT FROM AUTHOR]

The reaction of cyclopentenylsilane derivatives with n -Bu 4 NF in THF at rt was shown to proceed with the regio- and stereoselective formation of the corresponding bicyclo[3.1.0]hex-2-ene derivatives. [ABSTRACT FROM AUTHOR]

A novel silicon-oxygen aurone derivative TBDPSA was synthesized and used for the detection of fluoride anions in aqueous solution based on a specifically F − -triggered silicon-oxygen cleavage. Even though the compound has shown high selectivity, obvious absorption and fluorescence response for fluoride anions in aqueous solution, but it also is suffered from many limits, such as low detection sensitivity and long response time. Here the compound was successfully assembled on the graphene oxide (GO) surface by π-π stacking. GO improves recognition sensitivity and shortens response time of TBDPSA for fluoride anions by taking advantage of the nanocarrier GO. Compared with TBDPSA , the response time of GO / TBDPSA is shortened greatly from 1 h to < 5 s and the detection limit is lowered about four times with fluorescence as detected signal. Generally speaking, GO is an excellent promoter for accelerate recognition. [ABSTRACT FROM AUTHOR]

A novel siloxane-aurone compound, 4′-cyano-4- tert -butyldiphenylsiloxane-aurone (named as TBDCN ), was synthesized. The compound exhibits high sensitivity, fast response rate and high selectivity for fluoride anions recognition with obvious absorption and fluorescence response in aqueous solution, which is more sensitive than the traditionally type of chemodosimeters based on F − -triggered cleavage. The detection limits of TBDCN for F − are determined to be 1.9 μM and 0.0017 μM with absorption and fluorescence as detected signal, respectively, which satisfy the requirement from U.S. Environmental Protection Agency. The recognition mechanism is the F − -promoted dissociation of silicon-oxygen bond based on in situ mass spectra and 1 H NMR spectra analysis. [ABSTRACT FROM AUTHOR]

A novel coumarin-based compound 1 featuring thiosemicarbazone as binding unit, was reported as a colorimetric and fluorescent probe for the detection of fluoride anion. The addition of F − to a solution of probe 1 in tetrahydrofuran resulted in evident naked-eye color change from green-yellow to orange-red under daylight and obvious fluorescence quenching within 3 s. And the detection limit toward F − was calculated to be as low as 2.16 × 10 −7 mol/L. 1 H NMR titrations proved that the interaction between 1 and fluoride ion: hydrogen bond at low fluoride ion concentration, deprotonation at high fluoride ion concentration. Besides, it exhibited highly sensitivity and selectivity for F − over other examined ions (Cl − , Br − , I − , AcO − , NO 3 − , HSO 4 − , H 2 PO 4 − ) in tetrahydrofuran solution. [ABSTRACT FROM AUTHOR]

Sulfurization of selected thiiranes such as 2-phenylthiirane (styrene sulfide), 2,3-tetramethylenethiirane (cyclohexene sulfide) and 2-(α-thienyl)thiirane was carried out, leading to sulfur-rich polymers. The activation of the S 8 molecule was initiated by the fluoride anion (F−) delivered by tetrabutylammonium fluoride (TBAF) dissolved in tetrahydrofuran (THF). The opening of the thiirane ring, followed by the copolymerization process, was initiated by the fluoropolysulfide anions (FS x −) generated in situ. The anionic copolymerizations were carried out under mild conditions, below the floor temperature of S 8 (159 °C), and a variable ratio of monomers (thiirane/sulfur) was applied to obtain polysulfides with a diversified sulfur content. Polysulfides were characterized using analytical (elemental analysis, gel permeation chromatography), spectroscopic (Raman spectroscopy, FTIR), and thermal (thermogravimetry (TGA), differential scanning calorimetry (DSC)) methods. Mechanistic interpretation of sulfur transfer in the anionic copolymerization of thiiranes with S 8 , in the presence of the fluoride anion, has been discussed. [Display omitted] • A series of polysulfides derived from thiiranes and elemental sulfur were synthesized. • Polymers with sulfur rank controlled by thiirane/sulfur ratio were obtained. • Structure of obtained copolymers was confirmed by vibrational spectroscopy. • Influence of sulfur rank on thermal stability and phase structure was shown. • Protocol for efficient sulfur waste management was elaborated. [ABSTRACT FROM AUTHOR]