Dual influence of lithium chloride on the reactivity of polystyryllithium in ethereal solvents

Addition of LiCl to ethereal solutions of polystyryllithium retards propagation of the polymerization at low polymer concentration, but accelerates it at higher polymer concentrations. This phenomenon is accounted for by the dual action of LiCl. Its dissociation yielding free common Li⁺ ions which diminish the concentration of the reactive free polystyryl anions dominates at low electrolyte concentrations. However, at their higher concentrations the Li⁺ scavenging action of LiCl, resulting in the formation of LiClLi⁺ triple ions, becomes important, it reduces the concentration of the free Li⁺ ions and increases, therefore, the proportion of the reactive free polystyryl anions.     

Non-ergodic effect of LiCl on the anionic polymerization of styrene in ether-solvents. Specific solvation of Li+ ions in THF solution and prevention of this effect by LiCl

In this work conductance measurements were performed on polystyryllithium PStLi in tetrahydrofuran (THF) in the concentration range of 10⁻³ mol dm⁻³ at various temperatures between −60°C and 20°C. The comparison with the other alkali salts shows that in these solutions Li⁺ gives specific interactions with partial electronic charge transfer from the solvent molecules, presumably of the formula LiS₄⁺. A quantitative treatment shows that at 25°C the extrapolated stabilization factor K_S is larger than 50000 but rapidly drops for the heavier alkali ions: 3000 for Na⁺, 200 for K⁺ and negligible for C_s⁺. Surprisingly, such a stabilization is not observed for LiCl, although the ionic radii of the anions are quite comparable. The conductances κ at given concentration C of the electrolyte are 100 times smaller. Furthermore the curves of κ² versus C exhibit in this case an important curvature whereas they are practically linear for PStLi. The absence of specific solvation for LiCl seems thus to be accompanied by the formation of triple ions. Due to the symmetry of the electrolyte the formation of both triple anions ClLiCl⁻ and cations LiClLi⁺ has to be considered. Moreover, the concentrations of these ions is then always much smaller than that of the neutral dimer LiClLiCl, even if the extent of dimerization of LiCl remains small. The triple ions therefore appear as related to the dissociation of the dimer. This means that through the intermediate formation of the neutral dimer the couples triple ion - counterfoil perpetually exchange an LiCl entity in the course of time: Li⁺ + ClLiCl⁻⇋ LiClLiCl ⇋ LiClLi⁺ + Cl⁻. Only in the dimer the central LiCl is in possession of the (negative) energy of the insertion bond. In the solution this bond can be attributed neither to ClLiCl⁻ nor to LiClLi⁺. These entities have to be considered as transient ones during the life-time of which the energy of the insertion bond is transferred to the medium or vice-versa and which possess the energy of the insertion bond only during half of their life-time. The energy of such entities is thus not unambiguously defined in the ensemble at a given time and the ergodic principle does not hold. Such transient species cannot be specifically solvated by the solvent molecules because this would prevent the necessary passage through the dimer form. It is therefore the dimerization of LiCl which opposes itself to the formation of LiS₄⁺ in the THF solutions. Quantitatively the problem can be treated by a thermodynamics based not on ensemble fractions but on time fractions. One considers that a given LiCl can only give solvated ions during a fraction ξ_C° of the time and that during the remaining fraction it participates in a dissociation process which passes through the formation of non-ergodic triple ions and neutral dimers. (1-ξ_C°)/ξ_C° is equal to K^aC^3/2/[(1 + K_S)K^do]^½ where K^a is the non-ergodic equilibrium constant governing the formation of dimers and higher aggregates and K^do the dissociation constant of LiCl in non-solvated ions. This non-ergodic treatment also allows to describe quantitatively the strange conductometric behaviour of ternary solutions of LiCl and PStLi in THF. The addition of amounts of LiCl in a mole ratio of 7/1 to a given solution of PStLi increases unexpectedly in a very spectacular way the conductivity and provokes the appearance of a non-linear term in the κ² versus concentration function. In fact this behaviour is due to the replacement of a LiCl entity in the dimers by a PStLi molecule, yielding mixed dimers LiClLiStP. The displaced LiCl molecules are again susceptible of ergodic dissociation and specific solvation of the Li⁺ ions which originate from this dissociation. Thus for the LiCl entities the time fraction ξ_C increases. Moreover, at higher concentrations the dissociation of the mixed dimers leads to an important formation of non-ergodic triple anions: Li⁺ + ClLiStP⁻ ⇋ LiClLiStP ⇋ LiClLi⁺ + StP⁻ where the entity LiCl constantly jumps in the course of time from an StP⁻ to an Li⁺ and vice-versa.     

Cellobiose as a model compound for cellulose to study the interactions in cellulose/lithium chloride/<Emphasis Type="Italic">N</Emphasis>-methyl-2-pyrrolidone systems

To investigate the solvent/solute interactions that take place during the dissolution of cellulose, cellobiose was employed as a model of the longer-chain cellulose molecule in a dissolution study of the cellobiose/LiCl/N-methyl-2-pyrrolidone (NMP) system, conducted using attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR), ¹³C, ³⁵Cl, and ⁷Li NMR spectroscopy, and conductivity measurements. For the LiCl/NMP system, FTIR and ¹³C NMR analyses of the NMP carbonyl moiety showed a strong dependence on the LiCl concentration, which suggested an association between the Li⁺ cations and the carbonyl groups of NMP. As the cellobiose molecules are dissolved in the LiCl/NMP solvent, the Li⁺–Cl^? ion-pairs in LiCl/NMP are dissociated. Strong hydrogen bonds are then formed between the hydroxyl groups of cellobiose and the Cl^? anions, resulting in breakage of the intermolecular hydrogen bonds of cellobiose. Meanwhile, the Li⁺ cations are further associated with the extra free NMP molecules. However, the NMP molecules do not directly interact with the dissolved cellobiose. Based on these results, we propose that our study is conducive to a more in-depth comprehension of the dissolution mechanism of cellulose in LiCl/NMP.     

Vibrational Spectroscopic Study on Ion Solvation and Ion Association of Lithium Tetrafluoroborate in 4‐Ethoxymethyl‐ethylene Carbonate

应用红外及拉曼光谱研究了不同浓度的四氟硼酸锂在4-乙氧甲基-碳酸乙烯酯溶剂中的离子溶剂化和离子缔合现象。环形变谱带和羰基伸缩振动谱带的分裂,以及骨架环振动谱带的迁移和分裂表明,锂离子与溶剂分子间存在着较强的相互作用,这种相互作用是通过溶剂羰基氧原子实现的。利用光谱拟合技术定量计算了表观溶剂化数。随着电解质锂盐浓度的增加,溶剂化数逐渐由4.32降至1.26。此外,四氟硼酸根v1谱带的分裂表明在高浓度溶液中存在着光谱自由的四氟硼酸根、直接接触离子对和离子对二聚体。     

Polymérisation anionique des diènes. III. Etude thermodynamique de la propagation du butadiène et de i'isoprène par les organo-alcalins

The present work is concerned with the influence of the polymerization temperature on the propagation mechanisms of polyisoprenyl- and polybutadienyl-alkali metals. The thermodynamic parameters of the contact ion pairs and free ions propagations have been calculated. With Li⁺ in dioxane solvent, the vinyl propagation is stereospecific (for isoprene, the propagation is mainly 4–3). In comparison with benzene, the vinyl propagation of the polydienyl-Li contact ions pairs should be due to complexation of Li⁺ by dioxane, an electron donor having a weak dielectric constant. In general, the stereospecificity of the propagation of contact ion pairs decreases with increasing counterion size; little difference has been observed with K⁺ and Cs⁺ ion pairs in dioxane and benzene media. For isoprene, the methyl substituant should have chiefly a steric effect in the propagation of free ions, whereas it should confer a polar character to the isoprene molecule in the presence of ions pairs.     

Synthesis and Photocatalytic Activity of Poly(triazine imide)

Poly(triazine imide) was synthesized with incorporation of Li⁺ and Cl^? ions (PTI/Li⁺Cl^?) to form a carbon nitride derivative. The synthesis of this material by the temperature‐induced condensation of dicyandiamide was examined both in a eutectic mixture of LiCl–KCl and without KCl. On the basis of X‐ray diffraction measurements of the synthesized materials, we suggest that a stoichiometric amount of LiCl is necessary to obtain the PTI/Li⁺Cl^? phase without requiring the presence of KCl at 873 K. PTI/Li⁺Cl^? with modification by either Pt or CoO_x as cocatalyst photocatalytically produced H₂ or O₂, respectively, from water. The production of H₂ or O₂ from water indicates that the valence and conduction bands of PTI/Li⁺Cl^? were properly located to achieve overall water splitting. The treatment of PTI/Li⁺Cl^? with [Pt(NH₃)₄]²⁺ cations enabled the deposition of Pt through ion exchange, demonstrating photocatalytic activity for H₂ evolution, while treatment with [PtCl₆]^2? anions resulted in no Pt deposition. This was most likely because of the preferential exchange between Li⁺ ions and [Pt(NH₃)₄]²⁺ cations.     

Low‐energy collision‐induced dissociation (low‐energy CID), collision‐induced dissociation (CID), and higher energy collision dissociation (HCD) mass spectrometry for structural elucidation of saccharides and clarification of their dissolution mechanism in DMAc/LiCl

The dissolution mechanism of oligosaccharides in N,N‐dimethylacetamide/lithium chloride (DMAc/LiCl), a solvent used for cellulose dissolution, and the capabilities of low‐energy collision‐induced dissociation (low‐energy CID), collision‐induced dissociation (CID), and higher energy collision dissociation (HCD) for structural analysis of carbohydrates were investigated. Comparing the spectra obtained using 3 techniques shows that, generally, when working with monolithiated sugars, CID spectra provide more structurally informative fragments, and glycosidic bond cleavage is the main pathway. However, when working with dilithiated sugars, HCD spectra can be more informative providing predominately cross‐ring cleavage fragments. This is because HCD is a nonresonant activation technique, and it allows a higher amount of energy to be deposited in a short time, giving access to more endothermic decomposition pathways as well as consecutive fragmentations. The difference in preferred dissociation pathways of monolithiated and dilithiated sugars indicates that the presence of the second lithium strongly influences the relative rate constants for cross‐ring cleavages vs glycosidic bond cleavages, and disfavors the latter. Regarding the dissolution mechanism of sugars in DMAc/LiCl, CID and HCD experiments on dilithiated and trilithiated sugars reveal that intensities of product ions containing 2 Li⁺ or 3 Li⁺, respectively, are higher than those bearing only 1 Li⁺. In addition, comparing the fragmentation spectra (both HCD and CID) of LiCl‐adducted lithiated sugar and NaCl‐adducted sodiated sugar shows that while, in the latter case, loss of NaCl is dominant, in the former case, loss of HCl occurs preferentially. The compiled evidence implies that there is a strong and direct interaction between lithium and the saccharide during the dissolution process in the DMAc/LiCl solvent system.     

The flash-photolysis of sodium pyrenide in tetrahydrofuran. On the photo-oxidation process and on the existence of sodium atoms NaO

Evidence is given that the yields of photo-oxidation for free pyrene anions (Π^?) and for anions associated with sodium cations (Π^?Na⁺) in liquid THF and THP are connected to the effective threshold values for the photo- ionization of free and associated pyrene anions. Our experimental results indicate that the phenomena observed by Fisher and Rämme after flash-photolysis of sodium pyrenide in THF which have led to the postulation of transient; sodium atoms Na⁰ may be interpreted as being caused by benzene or toluene negative ions.     

Effect of alkali cations,halides and thiocyanate on the Mn(Hg)/Mn(II) electrode reactions

The title subject has been studied by galvanostatic single-pulse, chronopotentiometric and equilibrium measurements on the Mn(Hg)/Mn(II) electrode (mainly saturated managanese amalgams) in one molar alkali chloride (LiCl, KCl and CsCl) and potassium iodide and thiocyanate solutions of pH 4 to 5 at 25°C. The Mn(Hg)/Mn(II) reactions are found to occur in two consecutive steps with monovalent ions as intermediate in all these solutions. The rates of both the ion-transfer step Mn(Hg)/Mn(I) and the electron-transfer step Mn(I)/Mn(II) appear independent of the cations Li⁺ and K⁺ and of the anions Cl^?, I^? and SCN^?, when differences in bulk activities of electroactive species are corrected for. The Cs⁺ ion, however, seems to retard the reactions more than expected from bulk activity changes, and this can be explained by Cs⁺ specific adsorption or by variations in the properties of the inner layer with the cation.     

Structure formation features of water and concentrated aqueous lithium halide solutions at low temperatures from the data of integral equation method

The structure of water and the influence of halide ions on the structure formation of concentrated LiX : H₂O (1 : 5; X = Cl, Br, I) solutions at low temperatures were studied by the method of integral equations. Based on the results obtained, supercooling of pure water is expected to significantly enhance the tetrahedral ordering of its molecules, strengthen hydrogen bonding in the system, and decrease the number of the nearest-neighbor water molecules. The effects for the solutions on lowering the temperature include a partial restoration of the tetrahedral network of H-bonds of the solvent molecules, insignificant increase in the number of the nearest-neighbor water molecules, enhancement of the coordination ability of Li⁺ cation, strengthening of hydrogen bonding between anions and water molecules in the first hydration shell, increase in the number of solvent-separated ion pairs, and weakening of the temperature effect on these structural parameters in the following order of solutions: LiCl > LiBr > LiI. The probability of contact ion pair formation in the systems studied should appreciably decrease. The temperature should to a greater extent influence the associative ability of larger anions.     

Cation,solvent, and substituent effects on the decay kinetics of alkali metal salts of diaryl disulfide radical anions in nonaqueous solutions

The transient diaryl disulfide radical anions (RSSR^?) were produced in nonaqueous solutions at room temperature by the flash photolysis of a solution of arylthiolate ion pair in the presence of the excess corresponding disulfide. The transient spectra were almost identical with those obtained from γ-radiolysis of the disulfides in 77 K 2-methyl-tetrahydrofuran (MTHF) glassy matrix. The spectra of disulfide radical anions in nonaqueous solutions were changed by cations, solvents, and para-substituents depending on the ion pair properties. The tighter ion pairs showed a shift of absorption band to the shorter wavelength. The disulfide radical anions decay by a unimolecular dissociation reaction to yield thiolate anion and thiyl radical. The decay kinetics were first-order in the initial time region. The rate constants obtained were changed by the counter cations in the order Na⁺ > K⁺ > Cs⁺ > Li⁺, and by solvents. The tighter ion pairs of the disulfide radical anions showed faster dissociation reaction. This is due to stabilization of a transition state with the counter cation.     

Understanding Structural and Transport Properties of Dissolved Li2S8 in Ionic Liquid Electrolytes through Molecular Dynamics Simulations

Lithium-sulfur batteries with high energy density are considered as one of the most promising future energy storage devices. However, the parasitic lithium polysulfides shuttle phenomenon severely hinders the commercialization of such batteries. Ionic liquids have been found to suppress the lithium polysulfides solubility, diminishing the shuttle effect effectively. Herein, we performed classical molecular dynamics simulations to explore the microscopic mechanism and transport behaviors of typical Li₂S₈ species in ionic liquids and ionic liquid-based electrolyte systems. We found that the trifluoromethanesulfonate anions ([OTf]⁻) exhibit higher coordination strength with lithium ions compared with bis(trifluoromethanesulfonyl)imide anions ([TFSI]⁻) in static microstructures. However, the dynamical characteristics indicate that the presence of the [OTf]⁻ anions in ionic liquid electrolytes bring faster Li⁺ exchange rate and easier dissociation of Li⁺ solvation structures. Our simulation models offer a significant guidance to future studies on designing ionic liquid electrolytes for lithium-sulfur batteries.     

Transferring Lithium Ions in Nanochannels: A PEO/Li+ Solid Polymer Electrolyte Design

A new category of crystalline polymer electrolyte prepared by the supramolecular self‐assembly of polyethylene oxide (PEO), α‐cyclodextrin (α‐CD), and LiAsF₆ is reported. The polymer electrolyte consists of the nanochannels formed by α‐CDs in which the PEO/Li⁺ complexes are confined. The nanochannels formed by α‐CD provide the pathway for the directional motion of Li⁺ ions and at the same time prevent the access of the anions by size exclusion, resulting in good separation of the Li⁺ ions and the anions. The conductivity of the reported material is 30 times higher than that of the comparable PEO/Li⁺ complex crystal at room temperature. By using state‐of‐art solid‐state NMR spectroscopy, the structure and dynamics of the material were investigated in detail. The dynamics of the Li⁺ ions was studied and correlated to the ionic conductivity of the material.     

Features of Cation Hydration in Concentrated Aqueous Solutions of MeCl (Me = Li, Na, K, Rb): A Study by the Method of Integral Equations

The structural features of concentrated aqueous solutions of MeCl (Me = Li, Na, K, Rb; molar ratio [salt] : [water] = 1 : 15) at 293 K and 0.1 MPa were studied by the method of integral equations. The calculation results show that the disordering effect of the cation on the solvent structure grows in the order NaCl < KCl < RbCl (the number of free water molecules grows, and the content of tetrahedrally ordered molecules decreases). With LiCl, the changes in these parameters are maximal. In the systems containing Li⁺ and Na⁺ ions, the association parameter is lower than in pure water, whereas in the solutions with the K⁺ and Rb⁺ ions it is higher, in agreement with the concept of positive and negative hydration. It was suggested that, with increasing cationic radius, formation of hydrogen bonds between bulk water molecules becomes more preferential, and interactions between the anion and solvent molecules are weakened. On the contrary, the coordination number of the cation increases with its radius. In the examined series of solutions, the probability of formation of contact ion pairs grows considerably, and that of formation of hydration-separated ion pairs decreases.     

Raman spectra in the libration region of concentrated aqueous solutions of lithium-6 and lithium-7 halides. Evidence for tetrahedral Li(OH2) 4 +

The Raman spectra of saturated solutions of⁶LiCl and⁷LiCl have been decomposed into Gaussian components, one of which is a polarized band that occurs at 360 cm^–1 when the ion is⁶Li⁺ and shifts to 335 cm^–1 when the ion is⁷Li⁺. Equivalent bands occur in the spectra of saturated solutions of⁶LiBr and⁷LiBr at 343 and 320 cm^–1, respectively. These bands are assigned to solvent-separated ion aggregates. The Raman spectra of 8.0 and 3.5 m solutions of the isotopic lithium chlorides have been decomposed into five Gaussian components, three of which are assigned to water librations. In addition, there is a polarized band at 440 cm^–1 independent of the lithium isotope used, and a depolarized band which occurs at 385 cm^–1 in the⁶LiCl solutions and 360 cm^–1 in the⁷LiCl solutions. We interpret these two additional bands as theA ₁ andF ₂ stretching modes of Li⁺ tetrahedrally solvated by water molecules.     

Copolymerization reactivities and conductivities of some living polymers of p-substituted styrenes

A kinetic study in tetrahydrofuran of the addition of 1,1-diphenylethylene on para-substituted styrylcarbanions (with Cs⁺ as counterion) has given the reactivities of free ions and ion-pairs. For both species, the addition rate constant increased in the following sequence for the substituent of the phenyl ring: pH < p-CH₃ <p-CH₃O. It was also shown that in the same solvent, the dissociation constants of the polystyryl ion-pairs decreased with the electron-donating power of the substituent.     

Ion formation in fast atom bombardment mass spectrometry: a divided probe investigation of gas-phase reactions

Some ion-formation processes during fast atom bombardment (FAB) are discussed, especially the possibility of reactions in the gas phase. Divided (two halves) FAB probe tips were used for introducing two different samples into the source at the same time. Our results showed [M + A]⁺ ions (where M = crown ethers and A = alkali metal ions), can be produced, at least in part, in the gas phase when crown ethers and sources of alkali metal ion are placed on two halves of the FAB probe tip. The extent of this ion formation depends on the volatility of the crown ether and on steric factors. Cluster ions such as (M + LiCl)Li⁺, (2M + LiCl)Li⁺, [2M + K]⁺ and [2M + Na]⁺ are also observed to form in the gas phase. Unimolecular decompositions contribute to some ions detected in FAB. When the alkali ion salt and the crown ether are mixed together the probability of [M + A]⁺ ion formation increases significantly, regardless of the volatility of the crown ether.     

A lithium-selective glass electrode

We pioneered the study of the electrode properties of glasses containing 80 and 85 wt % LiF and 20 and 15 wt % A1(PO₃)₃. LiF-80-based glass electrodes functioned as lithium-selective electrodes in 1-0.0001 M LiCl solutions. Contrary to aliminosilicate glasses, these glasses responded to the Li⁺ ion better than to the Na⁺ ion and were nonselective to the Hi⁺ ion. This made them promising for the development of sensors for Li⁺ ions in different solutions. Forward and reverse transitions of these glasses from the hydrogen to the lithium function and from the lithium to the sodium function are described by the equation of the simple Nikol’skii theory. Presented at the V All-Russian Conference with the Participation of CIS Countries on Electrochemical Methods of Analysis (EMA-99), Moscow, December 6–8, 1999.     

Density Functional Theory Study of Selectivity of Crown Ethers to Li+ in Spent Lithium-Ion Batteries Leaching Solutions

It is a challenge to recover lithium from the leaching solution of spent lithium-ion batteries, and crown ethers are potential extractants due to their selectivity to alkali metal ions. The theoretical calculations for the selectivity of crown ethers with different structures to Li ions in aqueous solutions were carried out based on the density functional theory. The calculated results of geometries, binding energies, and thermodynamic parameters show that 15C5 has the strongest selectivity to Li ions in the three crown ethers of 12C4, 15C5, and 18C6. B15C5 has a smaller binding energy but more negative free energy than 15C5 when combined with Li⁺, leading to that the lithium ions in aqueous solutions will combine with B15C5 rather than 15C5. The exchange reactions between B15C5 and hydrated Li⁺, Co²⁺, and Ni²⁺ were analyzed and the results show that B15C5 is more likely to capture Li⁺ from the hydrated ions in an aqueous solution containing Li⁺, Co²⁺, and Ni²⁺. This study indicates that it is feasible to extract Li ions selectively using B15C5 as an extractant from the leaching solution of spent lithium-ion batteries.     

Enthalpy changes of salting processes of hen-egg white lysozyme in various electrolyte solutions

The enthalpy changes of salting process of hen-egg white lysozyme in buffer acetate solutions (pH=4.25) as a function of concentration of following electrolytes: LiCl, KCl, K₂SO₄, Li₂ SO₄ and (NH₄)₂SO₄ are determined. Obtained data according to McMillan and Mayer’s approach, has been analyzed in the terms of the enthalpic pairwise interaction coefficients: lysozyme – lysozyme h_xx, and lysozyme – salt h_xy. The ability of cations to precipitate lysozyme solution in relation to the concentration of cations can be seen from the series as follows: Li⁺> Na⁺>K⁺>NH₄+⁺