Supramolecular Luminescent Lanthanide Dimers for Fluoride Sequestering and Sensing

Lanthanide complexes (Ln=Eu, Tb, and Yb) that are based on a C₂‐symmetric cyclen scaffold were prepared and characterized. The addition of fluoride anions to aqueous solutions of the complexes resulted in the formation of dinuclear supramolecular compounds in which the anion is confined into the cavity that is formed by the two complexes. The supramolecular assembly process was monitored by UV/Vis absorption, luminescence, and NMR spectroscopy and high‐resolution mass spectrometry. The X‐ray crystal structure of the europium dimer revealed that the architecture of the scaffold is stabilized by synergistic effects of the Eu? F? Eu bridging motive, π stacking interactions, and a four‐component hydrogen‐bonding network, which control the assembly of the two [EuL] entities around the fluoride ion. The strong association in water allowed for the luminescence sensing of fluoride down to a detection limit of 24 nM .     

Fluoride anion sensing mechanism of a BODIPY‐linked hydrogen‐bonding probe

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.     

“Grafting” of Coordination Complex Modified Polyoxometalate on Ethylenediamine Planted Polyvinylidene Fluoride: Superhydrophilic Composite Membrane for Oxytetracycline Treatment

Under the guide of chemical bonding, a composite membrane had been fabricated successfully through grafting of a coordination complex modified polyoxometalate to an ethylenediamine planted polyvinylidene fluoride. Compared with neat polyvinylidene fluoride membrane, the oxytetracycline adsorption capacity of the polyoxometalate grafted composite membrane has been improved to a great extent. In addition, this polyoxometalate grafted composite membrane also exhibits excellent hydrophilicity, which leads to a clear enhancement in its antifouling properties. Besides oxytetracycline, its performances in the removal of other tetracycline‐type antibiotics, such as tetracycline and doxycycline, also looks outstanding. Furthermore, after successive adsorption and desorption experiments, the pollutant removal activity and antifouling property of this composite membrane are well retained, which suggests it is stable for removing tetracycline‐type antibiotics in waste water treatment processes.     

环境水中低含量氟化物的离子色谱分析

建立了离子色谱仪测定环境水中氟离子的方法.优化了试验条件,即淋洗液选1.8 mmol/L Na_2CO_3-1.7mmol/L NaHCO_3,流速0.8 m L/min.试验选择了活性炭作为固体吸附剂,采用固相萃取消除环境水中有可能存在的痕量乙酸对检测F~-的干扰.方法的检出限为0.022 2 mg/L,回收率为97.6%~98.9%,相对标准偏差小于2%.结果表明方法处理简单、准确度高,可用于环境水中低含量氟化物的测定.     

A Borinic Acid Polymer with Fluoride Ion‐ and Thermo‐responsive Properties that are Tunable over a Wide Temperature Range

A new type of smart borinic acid polymer with luminescence and multiple stimuli‐responsive properties is reported. In DMSO with small amounts of water, the homopolymer PBA shows a tunable upper critical solution temperature (UCST). As the amount of water increases from 0 to 2.5 % (v/v), the UCST rises linearly from 20 °C to 100 °C (boiling point of water). Thus, the thermal responsive behavior can be tuned over a wide temperature range. Furthermore, polymer solutions in DMSO show a reversible response to fluoride ions, which can be correlated to the presence of the Lewis acidic borinic acid groups. Upon addition of fluoride, the polymer becomes soluble because the functional R₂BOH groups are converted into ionic [R₂BF₂]^? groups, but turns insoluble again upon addition of H₂O, which reverses this process.     

Release of the Water Molecule Encapsulated Inside an Open‐Cage Fullerene through Hydrogen Bonding Mediated by Hydrogen Fluoride

A reversible wetting/dewetting procedure is reported for an open‐cage fullerene with an 18‐membered orifice. In a homogeneous mixture of H₂O/EtOH/CHCl₃, water was encapsulated into the cavity of the open‐cage compound quantitatively at 80 °C. Addition of aqueous hydrogen fluoride into the water‐encapsulated complex removed the encapsulated water completely at room temperature. H‐bonding between the trapped water and fluoride is shown to play a key role for the water release process.     

On the Nature of Fluoride Ion Hydration

Hydration of aqueous fluoride ions has been studied by theoretical ab initiocalculations in an attempt to understand the experimental Raman spectrum.Calculations for hydrated fluoride, F^– (H₂O)_n where n = 1–10, have been performedat the RHF/6-31 + G^* level. A relatively stable geometry exists for n = 6; abovethis number, additional waters hydrogen bond to water of the hydrated fluoride.On the long time scale of the ab initio calculation or experimental diffractionstudies, the average coordination of fluoride is 6. However, it has been possibleto interpret the low-frequency Raman spectrum on the basis of a singlehydrogen-bonded water molecule, F^– ... HOH. To rationalize these results, it is proposedthat the average coordination of fluoride is 6, but on the time scale of the Ramanexperiment the fluoride is symmetrically bonded to only one hydrogen of onewater molecule.Chairman and Organizer of the Symposium dedicated to Donald Irish. Unfortunately Murray died during the preparation of this special issue     

α-芳基-α-羟基酮(酯)与全氟烷基磺酰氟/甲基三乙氧基硅烷/碱体系不期望的氧化反应

研究了全氟烷基磺酰氟/甲基三乙氧基硅烷/碱体系与α-芳基-α-羟基酮(酯)化合物不期望的氧化反应, 以中等到优良的收率生成了相应的1,2-二酮(α-酮酸酯)产物. 所用全氟烷基磺酰氟为全氟正丁基磺酰氟或全氟正辛基磺酰氟; 碱为1,8-二氮杂二环[5.4.0]十一碳-7-烯(DBU). 提出了一种可能的反应机理. 为制备芳基取代的1,2-二酮(或α-酮酸酯)化合物提供了一种新方法.     

Access to Heteroleptic Fluorido‐Cyanido Complexes with a Large Magnetic Anisotropy by Fluoride Abstraction

Silicon‐mediated fluoride abstraction is demonstrated as a means of generating the first fluorido‐cyanido transition metal complexes. This new synthetic approach is exemplified by the synthesis and characterization of the heteroleptic complexes, trans‐[M^IVF₄(CN)₂]^2? (M=Re, Os), obtained from their homoleptic [M^IVF₆]^2? parents. As shown by combined high‐field electron paramagnetic resonance spectroscopy and magnetization measurements, the partial substitution of fluoride by cyanide ligands leads to a marked increase in the magnetic anisotropy of trans‐[ReF₄(CN)₂]^2? as compared to [ReF₆]^2?, reflecting the severe departure from an ideal octahedral (O_h point group) ligand field. This methodology paves the way toward the realization of new heteroleptic transition metal complexes that may be used as highly anisotropic building‐blocks for the design of high‐performance molecule‐based magnetic materials.     

Enantioselective Palladium(II)‐Catalyzed Oxidative Aminofluorination of Unactivated Alkenes with Et4NF⋅3 HF as a Fluoride Source

The first asymmetric Pd^II‐catalyzed aminofluorination of unactivated alkenes using chiral quinoline‐oxazolines (Quox) as ligands has been developed. This reaction provides easy access to a wide array of enantiomerically enriched β‐fluoropiperidines in good yields and with excellent enantioselectivity. Notably, Et₄NF?3 HF as a readily accessible nucleophilic fluoride source was found to play an essential role in the enantioselective control, and CsOCF₃ also acts a key additive to improve the excellent ee value of products.     

Fluoride optical nanoceramics

The methods for preparation of highly transparent optical ceramics based on simple and complex fluoride compounds of elements of the first, second, and third Group in the Periodical system are considered. The use of precursors as nanopowders and processes of their self-assembling on heating results in maximally homogeneous, transparent, and mechanically strong ceramics. The resulting calcium fluoride ceramics possess optical losses of 10⁻²–10⁻³ cm⁻¹ at 1.06 μm and shock resistance characterized by the fracture toughness K _1C = 4.7±0.3 MPa m^1/2 (for comparison, for a calcium fluoride single crystal K _1C = 1.5±0.15 MPa m^1/2). Regularities of the chemistry of fluoride nanopowders were considered in comparison with the oxide nanopowders: the fluorides are prone to hydrolysis, and powder nanoparticles precipitated from aqueous solutions have complex and heterogeneous (over the volume) chemical composition. The spectral luminescence properties of the ceramics activated by rare-earth metals (Ce³⁺, Nd³⁺, Er³⁺, Yb³⁺) or containing active color centers are presented. The generation properties of the lithium fluoride ceramics with the color centers and the ternary Ca-Sr-Yb fluoride during diode laser pumping are describe Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 863–872, May, 2008.     

Influence of Surface Coating on Fluoride Removal by Magnetite

Al(OH)₃- and ZrO(OH)₂-coated magnetites were prepared and used for fluoride removal from aqueous samples. The influence of pH, sorbent mass, and ions such as chloride, sulfate, and phosphate on the removal of fluoride was characterized. The sorption process was highly pH dependent, and the optimal sorption was obtained from pH 4 to 5 for ZrO(OH)₂- and pH 4 to 7 for Al(OH)₃-coated magnetites. The sorption isotherm was well described by the Langmuir equation for the sorbents. The maximum adsorption capacity of ZrO(OH)₂-coated magnetite (57.47?mg-F?g^?1-sorbent) was higher than for Al(OH)₃-coated magnetite (23.87?mg-F?g^?1-sorbent). The ion-exchange reaction occurred in 5?min and more than 99% of fluoride was removed from solution. When the ZrO(OH)₂-coated magnetite was used, the presence of foreign ions negatively affected the fluoride removal. The prepared sorbents showed an excellent performance for the removal of fluoride in water samples.     

离子选择电极法测定生活饮用水中氟化物

采用离子选择电极法对生活饮用水中氟化物浓度进行了测定。讨论了水样中pH值、温度、响应时间对测定结果的影响。在最佳条件下,方法的线性范围为0．10～3．0mg／L,相关系数为0．9999,检出限为0．05mg／L,实际水样加标回收率为97％～106％,相对标准偏差（n=5）为0．04％～0．65％。方法简单快速,干扰小,重现性好,加标回收率令人满意,能进行生活饮用水中氟化物浓度的有效测定。     

Stoichiometrically Controlled Revocable Self‐Assembled “Spiro” versus Quadruple‐Stranded “Double‐Decker” Type Coordination Cages

The simple combination of Pd^II with the tris‐monodentate ligand bis(pyridin‐3‐ylmethyl) pyridine‐3,5‐dicarboxylate, L , at ratios of 1:2 and 3:4 demonstrated the stoichiometrically controlled exclusive formation of the “spiro‐type” Pd₁L₂ macrocycle, 1 , and the quadruple‐stranded Pd₃L₄ cage, 2 , respectively. The architecture of 2 is elaborated with two compartments that can accommodate two units of fluoride, chloride, or bromide ions, one in each of the enclosures. However, the entry of iodide is altogether restricted. Complexes 1 and 2 are interconvertible under suitable conditions.     

On the Aqueous Chemistry of the UIV–DOTA Complex

The 1,4,7,10-tetrazacyclodecane-1,4,7,10-tetraacetic acid (DOTA) aqueous complex of U^IV with H₂O, OH⁻, and F⁻ as axial ligands was studied by using UV/Vis spectrophotometry, ESI-MS, NMR spectroscopy, X-ray crystallography, and electrochemistry. The U^IV–DOTA complex with either water or fluoride as axial ligands was found to be inert to oxidation by molecular oxygen, whereas the complex with hydroxide as an axial ligand slowly hydrolyzed and was oxidized by dioxygen to a diuranate precipitate. The combined data set acquired shows that, although axial substitution of fluoride and hydroxide ligands instead of water does not seem to significantly change the aqueous DOTA complex structure, it has an important effect on the electronic configuration of the complex. The U^IV/U^III redox couple was found to be quasi-reversible for the complex with both axially bonded H₂O and hydroxide, but irreversible for the complex with axially bonded fluoride. Intriguingly, binding of the axial fluoride renders the irreversible one-electron U^V/U^IV oxidation of the [U^IV(DOTA)(H₂O)] complex quasi-reversible, which suggests the formation of the short-lived pentavalent form of the complex, an aqueous non-uranyl chelated U^V cation.     

含氟体系中高性能T型分子筛膜的合成

含氟体系中,在负载晶种的大孔莫来石支撑体表面快速合成了高性能且取向生长的T型分子筛膜。采用XRD、SEM和MASNMR等手段对分子筛膜层和粉末进行表征。讨论了添加物、氟硅比、合成温度和合成时间等条件对膜生长与分离性能的影响,并阐述了含氟体系中T型分子筛膜快速晶化的机理。碱金属氟盐的加入促进了T型分子筛晶体层的晶化速率,并对晶体层形貌产生了一定的影响。膜应用于75℃、水/异丙醇（10：90,w/w）体系的平均渗透通量和分离因子分别为（4.91±0.18）kg·m^-2·h^-1和7060±1130。     

Fluoride adsorption enhancement of Calcined-Kaolin/Hydroxyapatite composite

The use of waste or natural resources is an interesting approach to preparing adsorbent materials. Most adsorption materials are powder-based, making them impractical for a variety of applications. In this work, the natural kaolin clay and hydroxyapatite synthesized from biogenic waste were studied as defluoridation materials. The point of zero charge (pH_PZC), the fluoride adsorption capability and the adsorption isotherm of calcined kaolin and mixed calcined kaolin/hydroxyapatite in both powdered and moulded forms were investigated. The hardness of the moulded (post-formed) samples was tested before and after in immersion in a fluoride solution. The maximum hardness was 15.8 kilo-pounds for the post-formed calcined kaolin sample. Sample hardness values slightly decreased after immersion in a fluoride solution due to the formation of micro-cracks. Most samples presented high pH_PZC values, implying that these materials are suitable for the capture of fluoride anions. The adsorption properties varied with the ratio of calcined kaolin to hydroxyapatite. These properties for post-formed samples were different from those in powdered form. Post-formed samples showed higher fluoride adsorption. The maximum fluoride adsorption capacity and efficiency of the post-formed samples (calcined kaolin) at pH 3 were 1.74 F^? mg/g and 87%, respectively. The sorption of fluoride of hydroxyapatite and mixed calcined kaolin/hydroxyapatite powders was found to have the form of the Langmuir isotherm, which indicates a monolayer adsorption on the adsorbent surface. Isotherms of calcined kaolin powder, post-formed calcined kaolin and mixed calcined kaolin/hydroxyapatite samples followed the Freundlich isotherm, which indicates multilayer adsorption on a heterogenous adsorbent surface.     

Fluorometric Determination of Trace Amounts of Fluoride Ion Using an Expanded Porphyrin

A highly selective and sensitive method of fluorometry is described for determination of the fluoride ion at the parts per billion level via the ion-pair complex formation of the fluoride ion with an expanded prophyrin [2,23-diethyl-8,17-bis(2-ethoxycarbonylethyl)-3,7,12,13,18,22-hexamethylsapphyrin (H₃sap)]. The ion-pair complex gives out an enhanced fluorescence intensity at 680 nm on excitation at 450 nm. Since the present method is based on a direct reaction of the fluoride ion with the sappyrin, a 200-fold amount of the aluminum (III) ion [10⁻⁴M (M = mol dm⁻³)] and a 2000-fold amount of the iron(III) ion (10⁻³M) over the fluoride ion did not interfere with determination of the fluoride ion at concentrations as low as 5 × 10⁻⁷M in the presence of 1,2-diaminocyclohexane-N,N,N′,N′-teraacetic acid. The proposed method was applied to determination of the fluoride ion in various water samples (tap water, river water, rain water, underground water, and hot spring water) and satisfactory results were obtained.     

Aluminum(III) Porphyrins as Ionophores for Fluoride Selective Polymeric Membrane Electrodes

Aluminum(III) porphyrins are examined as potential fluoride selective ionophores in polymeric membrane type ion‐selective electrodes. Membranes formulated with Al(III) tetraphenyl (TPP) or octaethyl (OEP) porphyrins are shown to exhibit enhanced potentiometric selectivity for fluoride over more lipophilic anions, including perchlorate and thiocyanate. However, such membrane electrodes display undesirable super‐Nernstian behavior, with concomitant slow response and recovery times. By employing a sterically hindered Al(III) picket fence porphyrin (PFP) complex as the membrane active species, fully reversible and Nernstian response toward fluoride is achieved. This finding suggests that the super‐Nernstian behavior observed with the nonpicket fence metalloporphyrins is due to the formation of aggregate porphyrin species (likely dimers) within the membrane phase. The steric hindrance of the PFP ligand structure eliminates such chemistry, thus leading to theoretical response slopes toward fluoride. Addition of lipophilic anionic sites into the organic membranes enhances response and selectivity, indicating that the Al(III) porphyrin ionophores function as charged carrier type ionophores. Optimized membranes formulated with Al(III)‐PFP in an o‐nitrophenyloctyl ether plasticized PVC film exhibit fast response to fluoride down to 40 μM, with very high selectivity over SCN^?, ClO₄^?, Cl^?, Br^? and NO₃^? (k^pot<10^?3 for all anions tested). With further refinements in the membrane chemistry, it is anticipated that Al(III) porphyrin‐based membrane electrodes can exhibit potentiometric fluoride response and selectivity that approaches that of the classical solid‐state LaF₃ crystal‐based fluoride sensor.