New dicationic piperidinium hexafluorophosphate ILs,synthesis, characterization and dielectric measurements

A new class of dicationic ionic liquids (ILs) were synthesized for electrochemical applications at high temperatures. The syntheses are based on a dialkylation reaction of N-alkylpiperidine followed by anion exchange. The structures of ILs, based on piperidinium combined with hexafluorophosphate anion, were identified by using ¹H, ¹³C, ¹⁹F, ³¹P NMR and FT-IR spectroscopy. ILs’ thermal properties were investigated in the temperature range from −50 to 350 °C by using differential scanning calorimetry (DSC). In the frequency of 10⁻²–10⁶ Hz range, dielectric measurements were performed on ILs’ samples at various temperatures from −80 to 20 °C, i.e. around the glass transition temperature. The peak relaxation was observed near to this temperature. Also, the conductivity was investigated and the energy activation determined. The temperature dependence of the relaxation times was shown to be governed by the Arrhenius equation.     

离子液体[BDMIM]PF_6修饰碳糊电极的制备及其电化学性能

以离子液体1,2-二甲基-3-丁基咪唑六氟磷酸盐（[BDMIM]PF6）代替传统液态石蜡为粘合剂与石墨粉相混合,制备了一种新型的离子液体修饰碳糊电极（IL/CPE）。采用扫描电子显微镜分别对其表面形貌和石蜡碳糊电极（CPE）表面形貌进行了表征。以亚铁氰化钾为电化学探针对IL/CPE的电化学行为进行了研究,并与CPE进行了比较。结果表明,[BDMIM]PF6由于具有较高的导电性,使IL/CPE比CPE具有更高的导电效率,铁氰化钾在电极上的可逆性变好,ΔEP值变小,峰电流响应增加10倍,电极过程由CPE上的吸附控制变为扩散控制,根据计时库仑法求解出铁氰化钾的扩散系数为5.52×10^-6cm2/s（25℃）。电化学交流阻抗图亦表明与不导电的液态石蜡油相比,离子液体的存在加快了电子传递。     

Hexafluorophosphate salts of bis and tetrakis(2,2′-bipyridine)lead(II) complexes

Both bis- and tetrakis-substituted 2,2′-bipyridine complexes of lead(II), [Pb(bpy)₂](PF₆)₂ and [Pb(bpy)₄](PF₆)₂ · bpy, respectively, have been characterized by X-ray crystallography as hexafluorophosphate salts when three equivalents of bipyridine is combined with Pb(NO₃)₂ in aqueous solution prior to metathesis. The tetrakis-substituted product, [Pb(bpy)₄](PF₆)₂ · bpy, shows an unusual combination of intramolecular and intermolecular π-stacking of two of the bipyridine ligands throughout the crystal. Incomplete metathesis also produces a catenated, mixed-anion complex, [Pb(bpy)₂(µ-NO₃)](PF₆), where the nitrate bridges lead(II) metal centers to form a 1-D coordination polymer. If metathesis is carried out using perchlorate, a known [Pb(bpy)₂](ClO₄)₂ analog is produced along with [bpyH](ClO₄), which has not been previously characterized by X-ray crystallography.     

A Reference Electrode for Electrochemical and Cryoelectrochemical Use in Tetrahydrofuran Solvent

We report a reference electrode for direct use in tetrahydrofuran (THF) at low temperatures. A reference solution containing equimolar amounts of ferrocene/ferrocenium hexafluorophosphate (Fc/Fc⁺) are prepared to give a 4 mM solution in THF that contains tetrabutylammonium hexafluorophosphate (TBAF) supporting electrolyte thus, minimizing liquid junction potentials. The reference solution is added to a sealed glass tube with a porous frit at one end, and a platinum wire is inserted into the tube. The reference electrode assembly is then inserted into a THF test solution. Potentiometric measurements show that the system responds in the expected Nernstian fashion over the concentration and temperature ranges, 4 mM to 40 μM and 20 °C to ?45 °C respectively. In addition, it is shown by steady–state cyclic voltammetry at a platinum microelectrode that the chemical reactivity of ferrocenium hexafluorophosphate (Fc⁺) otherwise seen in THF is suppressed by ion‐pairing with PF using tetrabutylammonium hexafluorophosphate (TBAF) as the supporting electrolyte.     

离子色谱法同时测定氟、磷酸根和六氟磷酸根离子

氟、磷酸根和六氟磷酸根离子在流速为0．25ml.min^-1,淋洗液为0．001mol.l^-1Na2CO3和0．005mol.L^-1NaOH溶液,在离子色谱仪上能较好地分离。氟,磷酸根和六氟磷酸根离子的检出限分别为7．29,70．5和295ng.ml^-1,该方法具有良好的线性,测定结果有较好的重现性,样品测定结果满意。     

Ion chromatographic determination of hydrolysis products of hexafluorophosphate salts in aqueous solution

In this work, hydrolysis of three different hexafluorophosphate salts in purified water was investigated. Aqueous samples of lithium hexafluorophosphate (LiPF₆), sodium hexafluorophosphate (NaPF₆) and potassium hexafluorophosphate (KPF₆) were prepared and stored for different times. Ion chromatography (IC) with UV as well as non-suppressed and suppressed conductivity detection was used for the analysis of the reaction products. For the detection and identification of the formed decomposition products, an IC method using IonPac AS14A 250 mm × 4.0 mm i.d. column and 2.5 mM KHCO₃–2.5 mM K₂CO₃ eluent was established. Besides hexafluorophosphate, four other anionic species were detected in fresh and matured aqueous solutions. The hydrolysis products fluoride (F⁻), monofluorophosphate (HPO₃F⁻), phosphate (HPO₄²⁻) and difluorophosphate (PO₂F₂⁻) were found and were unambiguously identified by means of standards or electrospray ionization mass spectrometry (ESI-MS). It was shown that stability of hexafluorophosphate solutions depends on the nature of the counter ion and decreases in the order potassium > sodium > lithium.     

Binding of fluorine containing anions by new cationic Co(III) complex: Competitive interaction of chloride and hexafluorophosphate with [Co(phen)(H2biim)2]

A new mixed ligand cobalt(III) complex salt [Co(phen)(H₂biim)₂]Cl₃ (1) (where phen = 1,10-phenanthroline, H₂biim = 2,2′-biimidazole) has been synthesized for the first time. In an effort to explore this new cationic complex [Co(phen)(H₂biim)₂]³⁺ as binding agent for fluoroanions, complex salt [Co(phen)(H₂biim)₂](PF₆)₂Cl·2H₂O(2) has been synthesized and characterized. Single crystal X-ray structure determination has revealed that complex salt 2 crystallizes in monoclinic crystal system with space group P2₁/c and consist of one complex cation, one chloride, two hexafluorophosphate anions and two water molecules of crystallization. The packing analyses revealed that the complex cations are arranged in such a way that N-H groups of biimidazole moiety are involved in N-H?Cl interaction with chloride ion while C-H groups of phen/H₂biim are involved in C-H?F interaction with hexafluorophosphate to keep these groups in close proximity. A strong network of hydrogen bond interactions C-H?F, N-H?O, N-H?Cl, C-H?O (water) and O-H?O (water) are responsible for the stabilization of 3D supramolecular architecture. To the best of our knowledge, this is the first crystal structure of any salt containing the cation [Co(phen)(H₂biim)₂]³⁺.     

Extraction of Metal Ions from Aqueous Solutions Using Imidazolium Based Ionic Liquids

This article represents a step towards how to choose an ionic liquid as the solvent to improve metal ion (Ag⁺ and Pb²⁺) extraction. The liquid-liquid solvent extraction is proposed with the following imidazolium ionic liquids (ILs): 1-ethyl-3-ethylimidazolium, or 1-butyl-3-ethylimidazolium, or 1-hexyl-3-ethylimidazolium bis{(trifluoromethyl)sylfonyl}imide [EEIM][NTf₂], or [BEIM][NTf₂], or [HEIM][NTf₂], or 1-butyl-3-ethylimidazolium hexafluorophosphate [BEIM][PF₆], or 1-hexyl-3-ethylimidazolium hexafluorophosphate [HEIM][PF₆] and the popular 1-butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF₆] for comparison. The effect of anion type (NTf₂⁻ versus PF₆⁻) and the effect of structural components of an ionic liquid including alkyl chain length at the cation and the ethyl substituent instead methyl at the cation, on the extraction and re-extraction processes by using dithizone as a metal chelator, were studied at 296 K. Dithizone was employed to form neutral metal-dithizone complexes with heavy metal ions to extract them from aqueous solution into the ILs. Electronic Supplementary Material  The online version of this article () contains supplementary material, which is available to authorized users. Presented at the 236th ACS National Meeting, August 17–21, Philadelphia, USA.     

Synthesis,Characterization, and Physicochemical Properties of Hydrophobic Pyridinium‐based Ionic Liquids with N‐Propyl and N‐Isopropyl

Synthesis and physicochemical properties of four pyridinium‐based ionic liquids (ILs), N‐propylpyridinium bromide [N‐propylPyr]⁺[Br]^–, N‐isopropylpyridinium bromide [N‐isopropylPyr]⁺[Br]^–, N‐propylpyridinium hexafluorophosphate [N‐propylPyr]⁺[PF₆]^–, and N‐isopropylpyridinium hexafluorophosphate [N‐isopropylPyr]⁺[PF₆]^– are reported. The molecular structures of these compounds were characterized by FT‐IR, ¹H, ¹⁹F, and ³¹P NMR, spectroscopy. The thermal properties, conductivity, and solubility of these ionic liquids were also investigated. The effects of propyl and isopropyl alkyl lateral chain at the N‐position of pyridinium cation on the thermal stability, conductivity, and solubility of ionic liquids are discussed. The results obtained confirmed that the ionic liquids based on pyridinium cations exhibit higher decomposition temperature, low melting points, immiscible with water, and their conductivities are mainly influenced by mobility of ions.     

直接进样-电感耦合等离子体发射光谱（ICP-OES）法测定六氟磷酸锂电解液中17种杂质元素

电解液,被称为锂电池的血液,对锂离子电池的主要性能起着决定作用。六氟磷酸锂(LiPF₆)是生产电解液的核心材料,电解液中的杂质离子会对电池性能造成极大的负面影响。因此,掌握锂离子六氟磷酸锂电解液中杂质元素的检测方法显得格外重要。传统的消解后测试的方法会造成部分元素损失,会引入新的污染,对低含量的元素难以准确定量,标准推荐的稀释剂需要用到电子级碳酸甲乙酯,成本较高。采用30%(V/V)乙醇水溶液稀释六氟磷酸锂电解液后直接进样,搭配电感耦合等离子体发射光谱(ICP-OES)有机进样系统,采用标准曲线法,测定了六氟磷酸锂电解液中的铝、砷、钙、镉、钴、铬、铜、铁、汞、钾、镁、钼、镍、钠、铅、硫、锌共17种杂质元素含量。实验中对ICP-OES最佳工作条件(包括雾化室温度、雾化气流量、雾化器、蠕动泵转速、电源功率、氧气流量)进行了优化,结果表明,雾化室温度在5℃,雾化气流量在0.6 L/min,使用的雾化器为OneNeb雾化器,蠕动泵转速为50 r/min,电源功率为1 150 W,氧气流量为50 mL/min时,各元素的灵敏度、试液的消耗、耗材的磨损能达到最佳效果。结果表明...