Electrochemical fluorination: state of the art and future tendences

A brief survey of the ECF process for the preparation of perfluorinated organo-compounds is given. The yield of perfluorinated products depends on the experimental conditions and on the nature of the starting material. Some useful rules are reported in order to optimise the ECF process. An improved operational technique allowed to obtain high yield of perfluorodimorpholinepropane (PFDMP) by simultaneous fluorination of dimorpholinepropane and N-methylmorpholine.     

Structural and electronic properties of PFOS and LiPFOS

The structural and electronic properties of perfluorinated surfactants perfluorooctane sulfonate (PFOS) and lithium perfluorooctane sulfonate (LiPFOS) have been investigated theoretically by performing semi-empirical molecular orbital theory at the level of AM1 calculations. The optimized structure and the electronic properties of the molecules are obtained.     

电化学氟化的新进展

电化学氟化是利用电极反应将氟直接引入有机或无机物的一种重要方法。有机物的电化学氟化方法有两种: 一是Simons于1941年发明的, 用镍作阳极, 在无水氟化氢溶液中, 电解制备全氟化合物的方法。此方法在近年来有不少改进。另一是1970年Rozhkov提出的, 以有机溶剂(如含Et3N.3HF的MeCN)为介质, 在铂阳极上,氧化得到单氟化产物的方法。本文全面地综述了这两种方法, 并着重于最新民发展。     

单离子导体聚合硼酸锂盐的研究进展

目前商业化锂离子电池常用的锂盐LiPF6,对水极其敏感,热稳定性差,尤其是在高温条件下的应用存在着一定的安全隐患.种类多且环境友好的新型有机硼酸锂盐越来越受到人们的重视.本文综述了近年来几种锂盐的合成方法,电化学性能,各自存在的优点和不足以及本课题组在聚合硼酸锂盐方向取得的系列研究进展,并对锂盐和聚合物电解质的发展方向进行了展望.     

Novel pseudo-delocalized anions for lithium battery electrolytes

A novel anion concept of pseudo-delocalized anions, anions with distinct positive and negative charge regions, has been studied by a computer aided synthesis using DFT calculations. With the aim to find safer and better performing lithium salts for lithium battery electrolytes two factors have been evaluated: the cation-anion interaction strength via the dissociation reaction LiAn ? Li(+) + An(-) and the anion oxidative stability via a vertical ionisation from anion to radical. Based on our computational results some of these anions have shown promise to perform well as lithium salts for modern lithium batteries and should be interesting synthetic targets for future research.     

1H NMR, 13C NMR, and computational DFT studies of the structure of 2-acylcyclohexane-1,3-diones and their alkali metal salts in solution

1H and 13C NMR spectra of 2-acyl-substituted cyclohexane-1,3-diones (acyl = formyl, 1; 2-nitrobenzoyl, 2; 2-nitro-4-trifluoromethylbenzoyl, 3) and lithium sodium and potassium salts of 1 have been measured. The compound 3, known as NTBC, is a life-saving medicine applied in tyrosinemia type I. The optimum molecular structures of the investigated objects in solutions have been found using the DFT method with B3LYP functional and 6-31G** and/or 6-311G(2d,p) basis set. The theoretical values of the NMR parameters of the investigated compounds have been calculated using GIAO DFT B3LYP/6-311G(2d,p) method. The theoretical data obtained for compounds 1-3 have been exploited to interpret their experimental NMR spectra in terms of the equilibrium between different tautomers. It has been found that for these triketones an endo-tautomer prevails. The differences in NMR spectra of the salts of 1 can be rationalized taking into account the size of the cation and the degree of salt dissociation. It seems that in DMSO solution the lithium salt exists mainly as an ion pair stabilized by the chelation of a lithium cation with two oxygen atoms. The activation free energy the of formyl group rotation for this salt has been estimated to be 51.5 kJ/mol. The obtained results suggest that in all the investigated objects, including the free enolate ions, all atoms directly bonded to the carbonyl carbons lie near the same plane. Some observations concerning the chemical shift changes could indicate strong solvation of the anion of 1 by water molecules. Implications of the results obtained in this work for the inhibition mechanism of (4-hydroxyphenyl) pyruvate dioxygenase by NTBC are commented upon.     

5,6-Trimethylenethiapyrylium and 5,6,7,8-tetrahydrothiochromylium salts

5,6-Trimethylenethiapyrylium salts have been obtained for the first time. 5,6-Trimethyleneγ-thiopyrans (or 5,6,7,8-tetrahydro-γ-thiochromenes), which belong to a previously unknown series of two-ring sulfides, are formed by reaction of the 5,6-trimethylenethiapyrylium salts (or 5,6,7,8-tetrahydrothiochromylium salts) with Grignard reagents and lithium aluminum hydride.     

Quaternary ammonium salts of bis-3-azatricyclo[5,3,0,11,5]undecane

The reaction of the anhydride of exo-cis-bicyclo[3,3,0]octane-2,4-dicarboxylic acid with ammonia followed by the reduction of the resulting imide with lithium aluminum hydride has yielded 3-azatricyclo[5,3,0,1^1,5]undecane, from which a number of quaternary bisammonium salts have been obtained with dihaloalkanes. These salts have also been synthesized from the anhydride of exo-cis-bicyclo[3,3,0] octane-2,4-dicarboxylic acid and polymethylenediamines.     

Tuning and calibration in thermospray liquid chromatography/mass spectrometry using perfluorinated alkyl acids and their ammonium salts

Of the several approaches used to interface liquid chromatography with mass spectrometry, the thermospray interface has evolved as the most popular and applicable for the analysis of polar and labile organic compounds. Since a separate ion source must be used for thermospray, separate tuning and calibration are required. Unfortunately, current approaches to tuning and calibration suffer from serious shortcomings, most notably rapid contamination of the ion source. Recent reports have shown that this shortcoming can be overcome by using acetic acid-ammonia cluster ions or trifluoroacetic acid–ammonia cluster ions for tuning and calibration. In the latter approach, the tuning solution could also be used in the negative ion mode of operation but suffers from concentration of most of the ion current in one ion. The use of perfluorinated alkyl acids and their ammonium salts to generate intense high-mass negative ions for tuning and calibration to m/z 2000 is reported. Additionally, the ammonium salts of the longer chain perfluorinated acids offer an enhanced high-mass response in the positive ion mode of operation.     

Synthesis of tetra(1,4-dithiacyclohexene)porphyrazine and its metal complexes

The syntheses of tetra, 1, 4-dithiacyclohexene)porphyrazine and its lithium salt, obtained by reaction of 3,6-dithiahexene-1,2-dicarbonitrile with lithium amylate, are described. A series of metal complexes of tetra(1,4-dithiacyclohexene)porphyrazine has been synthesized starting from 3,6-dithiacyclohexene-1,2-dicarbonitrile and the salts of the corresponding metals as well as from the free ligand and metal chlorides.Translated from Khimiya Geterotsiklicheskikh Soedinenii, No. 5, pp. 603–606, May, 1986.     

Lithium Ascorbate as a Promising Neuroprotector: Fundamental and Experimental Studies of an Organic Lithium Salt

Given the observable toxicity of lithium carbonate, neuropharmacology requires effective and non-toxic lithium salts. In particular, these salts can be employed as neuroprotective agents since lithium ions demonstrate neuroprotective properties through inhibition of glycogen synthetase kinase-3β and other target proteins, increasing concentrations of endogenous neurotrofic factors. The results of theoretical and experimental studies of organic lithium salts presented here indicate their potential as neuroprotectors. Chemoreactomic modeling of lithium salts made it possible to select lithium ascorbate as a suitable candidate for further research. A neurocytological study on cerebellar granular neurons in culture under conditions of moderate glutamate stress showed that lithium ascorbate was more effective in supporting neuronal survival than chloride or carbonate, i.e., inorganic lithium salts. Biodistribution studies indicated accumulation of lithium ions in a sort of “depot”, potentially consisting of the brain, aorta, and femur. Lithium ascorbate is characterized by extremely low acute and chronic toxicity (LD50 > 5000 mg/kg) and also shows a moderate antitumor effect when used in doses studied (5 or 10 mg/kg). Studies on the model of alcohol intoxication in rats have shown that intake of lithium ascorbate in doses either 5, 10 or 30 mg/kg did not only reduced brain damage due to ischemia, but also improved the preservation of myelin sheaths of neurons.     

Phosphoryl‐Rich Flame‐Retardant Ions (FRIONs): Towards Safer Lithium‐Ion Batteries

The functionalized catecholate, tetraethyl (2,3‐dihydroxy‐1,4‐phenylene)bis(phosphonate) (H₂‐DPC), has been used to prepare a series of lithium salts Li[B(DPC)(oxalato)], Li[B(DPC)₂], Li[B(DPC)F₂], and Li[P(DPC)₃]. The phosphoryl‐rich character of these anions was designed to impart flame‐retardant properties for their use as potential flame‐retardant ions (FRIONs), additives, or replacements for other lithium salts for safer lithium‐ion batteries. The new materials were fully characterized, and the single‐crystal structures of Li[B(DPC)(oxalato)] and Li[P(DPC)₃] have been determined. Thermogravimetric analysis of the four lithium salts show that they are thermally stable up to around 200 °C. Pyrolysis combustion flow calorimetry reveals that these salts produce high char yields upon combustion.     

Unprecedented catalytic asymmetric reduction of N-H imines

[Reaction: see text] Addition of lithium bis(trimethylsilyl)amide to perfluorinated ketones 1a-j affords (E)-N-TMS-ketimines 2a-j that are reduced in situ to afford racemic perfluoromethylated amine hydrochloride salts 3a-j in 54-97% yields. Solvolysis of the N-Si bond in MeOH leads to formation of bench-stable, isolable N-H imine Z/E isomer mixtures along with a methanol adduct. Enantioselective reduction of these three-component mixtures provides the first catalytic asymmetric synthesis of trifluoromethylated amines in 72-95% yields and 75-98% ee.     

Silica-supported spinel LiMn2O4 from microemulsion-derived multicomponent gels

A preparative technique based on the gelation of a microemulsion has provided a means of homogeneously dispersing high concentrations of metal oxide precursor salts through silica gel. The microstructures and compositions of gels containing combinations of lithium and manganese nitrate, and of the multiphase materials obtained by firing to a range of temperatures up to 1000°C, have been established. Formation of the mixed metal oxide spinel phase LiMn₂O₄ within a silica support has been obtained for systems comprising from 10 to 30 wt% metal nitrate by heating to temperatures between 500 and 700°C.     

Synthesis of perfluorinated functionalized, branched ethers

We wish to report synthesis of perfluorinated functionalized, branched ethers from their hydrocarbon analogues by direct fluorination. Yields up to 90%, with high purities, have been obtained at ambient temperature and pressure. This technique will likely develop into a new general method for producing perfluorinated, hyperbranched and dendritic polymers.     

Octanuclear oxothiomolybdate(v) rings: structure and ionic-conducting properties

A family of alkali salts of octanuclear oxothiomolybdate rings has been synthesized by crystallization of the [Mo(8)S(8)O(8)(OH)(8)[HMO(5)(H(2)O)]](3-) (noted HMo(8)M(3-); M=Mo, W) and [Mo(8)S(8)O(8)(OH)(8)(C(2)O(4))](2-) (noted Mo(8)ox(2-)) anions in an aqueous solution of ACl (A=Li, Na, K, Rb). Single-crystal X-ray diffraction experiments have been performed showing that the alkali salts exhibit a similar three-dimensional structure. Disordered alkali ions form columns to which the anionic rings are anchored. Ionic-conductivity measurements on pressed pellets have revealed two different behaviors. The lithium salts of HMo(8)M(3-) (M=Mo, W) are moderately good proton conductors at room temperature (sigma=10(-5) S cm(-1)) and the profile of conductivity as a function of relative humidity shows that the conductivity is due to surface-proton motion (particle-hydrate-type mechanism). On the other hand, the lithium salt of Mo(8)ox(2-) competes with the best crystalline lithium conductors at room temperature (sigma=10(-3) S cm(-1)), and (7)Li NMR experiments confirm the mobility of the lithium ions along the one-dimensional channels of this material.     

Calculation of lithium isotope effects in extraction systems with crown ethers

Complexes of lithium salts with benzo-15-crown-5 and its derivatives have been prepared. Their structure has been established by X-ray diffraction analysis. On the basis of obtained data, the dependence of partition function ratios for isotopic forms (β factors) of these compounds on the type of extracted salt anion and other factors has been analyzed. Taking into account previously calculated value of β factor for aqua complex of lithium ion, single isotope extraction separation factors (α) for Li⁶–Li⁷ pair have been determined. Quantum chemical calculations for vibrational frequencies of isotope forms of complexes with crown ethers have been performed with the aid of Firefly (PC GAMESS) software. Lithium cation complexes with crown ethers have been calculated using RHF/6-311++G** basis set. Isotope extraction separation factors have been shown to be independent of lithium ion concentration in aqueous phase and the type of extracted salt anion but depend only on the type and size of crown ether ring.     

Tetracyanoquinodimethane Derivatives of Pentagonal Bipyramidal Complexes of Manganese(II), Iron(II), Nickel(II) and Copper(II) with 2,6-diacetylpyridinebis(semicarbazone)∶ Single Crystal Structure of dichloro[2,6-diacetylpyridinebis (semicarbazone)] Manganese(II)monohydrate

By using the donor ligand 2,6-diacetylpyridinebis(semicarbazone) (DAPSC), pentagonal bipyramidal complexes of Mn(II), Fe(II), Ni(II) and Cu(II) have been obtained. The structure of [MnCl₂(DAPSC)]·H₂O has been determined by X-ray crystallography. Further reactions of these complexes with lithium salts of 7,7',8,8'-tetracyanoquinodimethane (TCNQ) yielded their corresponding adducts.     

7Li, 31P, and 1H pulsed gradient spin-echo (PGSE) diffusion NMR spectroscopy and ion pairing: on the temperature dependence of the ion pairing in Li(CPh3), fluorenyllithium, and Li[N(SiMe3)2] amongst other salts

7Li, 31P, and 1H variable-temperature pulsed gradient spin-echo (PGSE) diffusion methods have been used to study ion pairing and aggregation states for a range of lithium salts such as lithium halides, lithium carbanions, and a lithium amide in THF solutions. For trityllithium (2) and fluorenyllithium (9), it is shown that ion pairing is favored at 299 K but the ions are well separated at 155 K. For 2-lithio-1,3-dithiane (13) and lithium hexamethyldisilazane (LiHMDS 16), low-temperature data show that the ions remain together. For the dithio anion 13, a mononuclear species has been established, whereas for the lithium amide 16, the PGSE results allow two different aggregation states to be readily recognized. For the lithium halides LiX (X = Br, Cl, I) in THF, the 7Li PGSE data show that all three salts can be described as well-separated ions at ambient temperature. The solid state structure of trityllithium (2) is described and reveals a solvent-separated ion pair formed by a [Li(thf)4]+ ion and a bare triphenylmethide anion.