Separated Ion Pairs Research Articles

Solvation structures in weakly solvating solvents lead to hybrid vehicular/structural ion transport

Despite the reported benefits of weakly solvating electrolytes (WSEs), investigations on the solvation structures and ion transport mechanisms present in WSEs are limited. This is particularly the case for electrolytes containing the weakly solvating 1,2-diethoxyethane (DEE), which has shown great promise recently. It is for this purpose, we employ molecular dynamics simulations and quantum mechanical calculations to investigate the solvation structure and Li+ transport for lithium bis(fluorosulfonyl)imide (LiFSI) in DEE. From the results reported herein, it was found that at lower concentrations, solvent separated ion pairs are particularly stable, primarily due to the presence of FSI– in the second solvation shell of Li+. As the salt concentration increases, cation–anion complexes appear and form large aggregates. The presence of these large aggregates promotes a hybrid/structural diffusion mechanism at high concentrations, where Li+ ions readily exchange ligands with FSI– anions but remains coordinated with DEE molecules. Hence, the results reported herein investigate how the solvation structure influences transport properties in weakly solvating solvents and provides insights that can be used to optimize electrolytes for energy storage applications.

Propylene carbonate activated electrochemical performances of in situ polymerized ionogel electrolytes

Ionogel electrolytes show great potential in solid-state batteries attributed to their outstanding characteristics. However, because of the strong ionic nature of ionic liquids, ionogel electrolytes generally exhibit low lithium-ion transference number and poor inferior interfacial contact, limiting their practical applications. In present research, propylene carbonate (PC) is added to form solvation separated ion pair with lithium ions in the conventional pyrrolidinium ionogel electrolytes, which comprehensively improves electrochemical properties of ionogels in lithium metal batteries. An astonished improvement is observed in an abrupt increase of the lithium-ion transference number from 0.1 to 0.41, thereby elevating ionic conductivities from 4.7 × 10−4 S/cm to 1.72 × 10−3 S/cm and reducing the activation energies of ion transport from 0.036eV to 0.018eV. As a result, PC highly activates electrochemical performances in assembled LiFePO4|Li batteries, exhibiting high discharging specific capacities: 134 mAh/g (1C), while that of PC free ionogel is 5 mAh/g (1C), respectively. The PC assisted LiFePO4|Li cell could retain 90 % of its initial specific capacity after 200 cycles and could work at a wide temperature range from 0 °C to 100 °C. The results demonstrate a new strategy to improve lithium-ion transference number in ionogel electrolytes for achieving improved performance in solid-state lithium metal batteries.

Synthesis and characterization of alkali metal iminophosphoranomethanide complexes

Herein we report the synthesis of three sets of alkali metal complexes with the iminophosphoranomethanide ligands {CH(SiMe3)P(Ph)2NSiMe3}− (TMSNPC-H) and {CH(SiMe2tBu)P(Ph)2NSiMe3}− (TBDMSNPC-H), the latter of which is first reported here. The compounds of general formula [M(RNPC-H)] (3-M and 4-M; M = Li, Na, K) were obtained via a protonolysis reaction between an alkyl reagent (n-butyllithium, benzylsodium, or benzylpotassium) and the proligand. All resulting compounds were characterized by multinuclear NMR, IR spectroscopy, elemental analysis and single crystal X-ray diffraction. We also attempted to prepare the separated ion pairs of [M(TMSNPC-H)] with the matched crown ethers, and obtained the ‘ate’ complexes [Li(12-crown-4)2]+[Li(TMSNPC-H)2]− (5-Li) and [Na(15-crown-5)2]+[Na(TMSNPC-H)2]− (5-Na), the coordination polymer [{K(18-crown-6)2}{K(TMSNPC-H)(18-crown-6)}(TMSNPC-H)]∞ (6) and separate ion pair complex [K(15-crown-5)2]+[TMSNPC-H]− (7). 5-Li is an unusual lithium-lithiate crown ether species, whilst 5-Na represents the first example of a sodium-sodiate crown-ether complex.

Reversed-phase ion-pair high performance liquid chromatography with electrochemical detection for simultaneous quantification of neurotransmitters in mice brain tissues

An analytical method for the simultaneous quantification of neurotransmitters has been developed using reversed-phase ion-pair high performance liquid chromatography (RPIP-HPLC) coupled with electrochemical detection (ECD). As a strategy to simultaneously analyze acetylcholine, glutamate, and γ-aminobutyric acid, which were previously difficult to analyze in ECD, along with serotonin and dopamine, the ion pair separation technique was optimized, and electroactivity was induced by eluting with strong alkaline solution. This method achieved improved sensitivity, showing limits of quantification of 0.02 to 0.1 μg/mL and linear regression coefficients of determination of 0.9938–0.9994 through the use of an 8% acetonitrile solution containing 15 mM H3PO4 and 0.4 mM sodium 1-octanesulfonate as the mobile phase and 200 mM NaOH as the post-column eluent, detected at the gold electrode. All inter- and intra-day precision were below 4.10%, and the average recoveries were 97.43–103.69%. In an application comparing cerebral cortical tissues and hippocampal tissues between a control group and a scopolamine-treated group, the levels of the five components showed a clear difference. As a result of evaluating the eco-friendliness of this method, the Analytical GREEnness metric was determined as 0.47. Our method is expected to be useful in screening for neurotransmitters in various biological and clinical samples.

Paradigm Shift: Major Role of Ion-Pairing-Dependent Size Exclusion Effects in Bottom-Up Proteomics Reversed-Phase Peptide Separations.

Can reversed-phase peptide retention be the same for C8 and C18 columns? or increase for otherwise identical columns with a smaller surface area? Can replacing trifluoroacetic acid (TFA) with formic acid (FA) improve the peak shape? According to our common understanding of peptide chromatography, absolutely not. Surprisingly, a thorough comparison of the peptide separation selectivity of 100 and 120 Å fully porous C18 sorbents to maximize the performance of our in-house proteomics LC-MS/MS setup revealed an unexpectedly higher peptide retentivity for a wider pore packing material, despite it having a smaller surface area. Concurrently, the observed increase in peptide retention─which drives variation in separation selectivity between 100 and 120 Å pore size materials─was more pronounced for smaller peptides. These findings contradict the central dogmas that underlie the development of all peptide RP-HPLC applications: (i) a larger surface area leads to higher retention and (ii) increasing the pore size should benefit the retention of larger analytes. Based on our intriguing findings, we compared reversed-phase high-performance liquid chromatography peptide retention for a total of 20 columns with pore sizes between 60 and 300 Å using FA- and TFA-based eluents. Our results unequivocally attest that the larger size of ion pairs in FA- vs TFA-based eluents leads to the observed impact on selectivity and peptide retention. For FA, peptide retention peaks at 200 Å pore size, compared to between 120 and 200 Å for TFA. However, the decrease in retention for narrow-pore particles is more profound in FA. Our findings suggest that common assumptions about analyte size and accessible surface area should be revisited for ion-pair RP separation of small peptides, typical for proteomic applications that are predominantly applying FA eluents. Hybrid silica-based materials with pore sizes of 130-200 Å should be specifically targeted for bottom-up proteomic applications to obtain both superior peak shape and peptide retentivity. This challenging task of attaining the best RPLC column for proteomics calls for closer collaboration between LC column manufacturers and proteomic LC specialists.

Redox-Active Triazole-Derived Mesoionic Imines with Ferrocenyl Substituents and their Metal Complexes: Directed Hydrogen-Bonding, Unusual C-H Activation and Ion-Pair Formation.

We present herein the synthesis, characterization and complexation of ferrocenyl-substituted MIIs (mesoionic imines) and their metal complexes. In the free MIIs, strong hydrogen bonding interactions are observed between the imine-N and the C-H bonds of the ferrocenyl substituents both in the solid state and in solution. The influence of this hydrogen bonding is so strong that complexation of the MIIs with [IrCp*Cl2]2 yields unique six-membered iridacycles via C-H-activation of the corresponding C-H-site at the Fc-substituent and not the Ph-substituent. This result is in contrast to previous reports in which always a preferential C-H activation at the phenyl substituent is observed in competitive reactions in the presence of ferrocenyl substituents. The corresponding Ir complexes formed after in-situ halide exchange reaction exist in either [Ir-I] contact or as [Ir]+I- solvent separated ion-pairs depending on the solvent polarity. The iodide coordinated and solvent separated ion-pairs display drastically different physical properties. The TEP (Tolman-electronic-parameter) of these ligands was determined and lines up with previously reported MII-ligands. The redox properties were investigated by a combination of electrochemical and spectroelectrochemical methods. We show here how non-covalent interactions can have a drastic influence on the physical and chemical properties of these new class of compounds.

F-Element Zintl Chemistry: Actinide-Mediated Dehydrocoupling of H2Sb1- Affords the Trithorium and Triuranium Undeca-Antimontriide Zintl Clusters [{An(TrenTIPS)}3(μ3-Sb11)] (An = Th, U; TrenTIPS = {N(CH2CH2NSiiPr3)3}3-).

Reaction of the cesium antimonide complex [Cs(18C6)2][SbH2] (1, 18C6 = 18-crown-6 ether) with the triamidoamine actinide separated ion pairs [An(TrenTIPS)(L)][BPh4] (TrenTIPS = {N(CH2CH2NSiiPr3)3}3-; An/L = Th/DME (2Th); U/THF (2U)) affords the triactinide undeca-antimontriide Zintl clusters [{An(TrenTIPS)}3(μ3-Sb11)] (An = Th (3Th), U (3U)) by dehydrocoupling. Clusters 3Th and 3U provide two new examples of the Sb113- Zintl trianion and are unprecedented examples of molecular Sb113- being coordinated to anything since all previous reports featured isolated Sb113- Zintl trianions in separated ion quadruple formulations with noncoordinating cations. Quantum chemical calculations describe dominant ionic An-Sb interactions in 3Th and 3U, though the data suggest that the latter exhibits slightly more covalent An-Sb linkages than the former. Complexes 3Th and 3U have been characterized by single crystal X-ray diffraction, NMR, IR, and UV/vis/NIR spectroscopies, elemental analysis, and quantum chemical calculations.

Synthesis of Superbulky Amide Ligands by Addition of Polar Reagents to Sila-Imine.

The chemistry of extremely bulky amide ligands is troubled by difficulties in deprotonation of the parent amine. As an alternative route to superbulky amide reagents, the addition of polar reagents to a sila-imine has been investigated. Attempts to synthesize the superbulky amide anion (tBu3Si)2N- by addition of tBuLi to tBu2Si=N(SitBu3) failed and gave tBu3Si(tBu2HSi)NLi and isobutene. Reaction of the sila-imine with KOtBu successfully led to tBu3Si[tBu2(tBuO)Si]NK which crystallized as a separated ion-pair. Reaction with the slightly bulkier KOAd (Ad=1-adamantyl) led in presence of THF to ether ring-opening. Reaction with tBuOH gave tBu3Si[tBu2(tBuO)Si]NH but this amine cannot be easily deprotonated. Reaction with (BDI*)MgnBu in presence of THF gave (BDI*)Mg+ ⋅ (THF)2 and the non-coordinating anion tBu3Si[tBu2(nBu)Si]N-; BDI*=ß-diketiminate ligand HC[C(tBu)N-DIPP]2, DIPP=2,6-diisopropylphenyl. Reaction of Mg(nBu)2 with tBu2Si=N(SitBu3) led to a Mg complex with one amide ligand: tBu3Si[tBu2(nBu)Si]N-. The other superbulky amide anion isomerized by internal deprotonation of a tBu-substituent to give a primary carbanion that is also coordinated to Mg. Although the amide-to-carbanion isomerization is highly contrathermodynamic, it allows for coordination of both anions to a single Mg center. The new bulky amides are rare cases of halogen-free weakly coordinating anions.

Insight into the solvation and dynamic behaviors of lithium salt in water-in-bisalt electrolytes

Through a combination of molecular dynamics simulations and experimental approaches, the solvation structure and diffusion behavior of Li+ was investigated in water-in-bisalt electrolytes formed by introducing a second lithium salt (LiBF4, LiNO3, LiOAc) into the LiTFSI aqueous electrolyte. The calculation and experimental results indicate that nanostructures of water-in-bisalt electrolytes include “water-rich” and “anion-rich” domains. When LiBF4 is added, Li+ is mostly located in the water-rich domain, effectively increasing the diffusion coefficient of Li+. This electrolyte exhibits a higher conductivity and a much lower price compared to mono-LiTFSI electrolytes, On the contrary, with the addition of LiOAc, OAc− will strongly coordinate with Li+ to change the solvation structure of solvent separated ion pairs (Li+(H2O)4) to aggregates, which results in the decrease of Li+ diffusion coefficient. These fundamental insights highlight the correlation of microstructural and dynamic heterogeneities of water-in-bisalt electrolytes, which are expected to trigger rational design of solvation and dynamic behaviors of advanced aqueous electrolytes.

Zinc(ii)-mediated stereoselective construction of 1,2-cis 2-azido-2-deoxy glycosidic linkage: assembly of Acinetobacter baumannii K48 capsular pentasaccharide derivative.

The capsular polysaccharide (CPS) is a major virulence factor of the pathogenic Acinetobacter baumannii and a promising target for vaccine development. However, the synthesis of the 1,2-cis-2-amino-2-deoxyglycoside core of CPS remains challenging to date. Here we develop a highly α-selective ZnI2-mediated 1,2-cis 2-azido-2-deoxy chemical glycosylation strategy using 2-azido-2-deoxy glucosyl donors equipped with various 4,6-O-tethered groups. Among them the tetraisopropyldisiloxane (TIPDS)-protected 2-azido-2-deoxy-d-glucosyl donor afforded predominantly α-glycoside (α : β = >20 : 1) in maximum yield. This novel approach applies to a wide acceptor substrate scope, including various aliphatic alcohols, sugar alcohols, and natural products. We demonstrated the versatility and effectiveness of this strategy by the synthesis of A. baumannii K48 capsular pentasaccharide repeating fragments, employing the developed reaction as the key step for constructing the 1,2-cis 2-azido-2-deoxy glycosidic linkage. The reaction mechanism was explored with combined experimental variable-temperature NMR (VT-NMR) studies and mass spectroscopy (MS) analysis, and theoretical density functional theory calculations, which suggested the formation of covalent α-C1GlcN-iodide intermediate in equilibrium with separated oxocarbenium-counter ion pair, followed by an SN1-like α-nucleophilic attack most likely from separated ion pairs by the ZnI2-activated acceptor complex under the influence of the 2-azido gauche effect.

Reactivity of Mg(AlMe4)2 towards neutral tris(pyrazolyl)alkanes.

Various new tris(pyrazolyl)alkanes of the class R'CTp3-R (R' = Me, Et, nPr, iBu; R = Et, cyPr, Cy, p-tBuPh, Ph; cyPr = cyclopropyl, Cy = cyclohexyl, p-tBuPh = para-tert-butylphenyl) were synthesised and their reactivity towards Mg(AlMe4)2 was examined. Along with new examples of recurring structural motifs, such as separated ion pairs and "metal in a box" complexes, e.g., [(MeCTp3-Et)2Mg][AlMe4]2, several magnesium complexes with new structural features/compositions were obtained. Treatment of the "metal in a box" species [(MeCTp3-R)Mg][AlMe4]2 with THF donor gave the terminal methyl complex [(MeCTp3-cyPr)MgMe(thf)2][AlMe4]. Variation of the backbone alkyl substituent R' in the tris(pyrazolyl)alkane R'CTp3-Ph gave ionic liquids (R' = Et, nPr) and the methyl-bridged dimagnesium complex [({iBuCTp3-Ph}Mg{AlMe4})2(μ-Me)][AlMe4]. The bulky Cy and p-tBuPh moieties at the pyrazolyl 3 position gave the new structural motif [MeCTp3-RMg(ηn-AlMe4)][AlMe4] (η3, R = Cy; η2, R = p-tBuPh), stabilising a "[Mg(AlMe4)]+" entity. The AlMe3 group can be reversibly displaced under reduced pressure affording the new separated ion pair [(MeCTp3-p-tBuPh)MgMe][AlMe4] with a terminal "[MgMe]+" moiety. Moderate thermal treatment of both [(MeCTp3-p-tBuPh)MgMe][AlMe4] and [(MeCTp3-p-tBuPh)Mg(η2-AlMe4)][AlMe4] resulted in selective C-H-bond activation in the 5 position of one of the pyrazolyl moieties and the formation of an AlMe3-modified anionic tris(pyrazolyl)alkane and hence the neutral complex [MeC(pz3-p-tBuPh)2(pz3-p-tBuPh,5-AlMe3)]MgMe.

S-Block metal complexes of superbulky (tBu3Si)2N-: a new weakly coordinating anion?

Sterically hindered amide anions have found widespread application as deprotonation agents or as ligands to stabilize metals in unusual coordination geometries or oxidation states. The use of bulky amides has also been advantageous in catalyst design. Herein we present s-block metal chemistry with one of the bulkiest known amide ligands: (tBu3Si)2N- (abbreviated: tBuN-). The parent amine (tBuNH), introduced earlier by Wiberg, is extremely resistant to deprotonation (even with nBuLi/KOtBu superbases) but can be deprotonated slowly with a blue Cs+/e- electride formed by addition of Cs0 to THF. (tBuN)Cs crystallized as a separated ion-pair, even without cocrystallized solvent. As salt-metathesis reactions with (tBuN)Cs are sluggish and incomplete, it has only limited use as an amide transfer reagent. However, ball-milling with LiI led to quantitative formation of (tBuN)Li and CsI. Structural characterization shows that (tBuN)Li is a monomeric contact ion-pair with a relatively short N-Li bond, an unusual T-shaped coordination geometry around N and extremely short Li⋯Me anagostic interactions. Crystal structures are compared with Li and Cs complexes of less bulky amide ligands (iPr3Si)2N- (iPrN-) and (Me3Si)2N- (MeN-). DFT calculations show trends in the geometries and electron distributions of amide ligands of increasing steric bulk (MeN- < iPrN- < tBuN-) and confirm that tBuN- is a rare example of a halogen-free weakly coordinating anion.

AtomAccess: A Predictive Tool for Molecular Design and Its Application to the Targeted Synthesis of Dysprosium Single-Molecule Magnets.

Isolated dysprosocenium cations, [Dy(CpR)2]+ (CpR = substituted cyclopentadienyl), have recently been shown to exhibit superior single-molecule magnet (SMM) properties over closely related complexes with equatorially bound ligands. However, gauging the crossover point at which the CpR substituents are large enough to prevent equatorial ligand binding, but small enough to approach the metal closely and generate strong crystal field splitting has required laborious synthetic optimization. We therefore created the computer program AtomAccess to predict the accessibility of a metal binding site and its ability to accommodate additional ligands. Here, we apply AtomAccess to identify the crossover point for equatorial coordination in [Dy(CpR)2]+ cations in silico and hence predict a cation that is at the cusp of stability without equatorial interactions, viz., [Dy(Cpttt)(Cp*)]+ (Cpttt = C5H2tBu3-1,2,4, Cp* = C5Me5). Upon synthesizing this cation, we found that it crystallizes as either a contact ion-pair, [Dy(Cpttt)(Cp*){Al[OC(CF3)3]4-κ-F}], or separated ion-pair polymorph, [Dy(Cpttt)(Cp*)][Al{OC(CF3)3}4]·C6H6. Upon characterizing these complexes, together with their precursors, yttrium and yttrium-doped analogues, we find that the contact ion-pair shows inferior SMM properties to the separated ion-pair, as expected, due to faster Raman and quantum tunneling of magnetization relaxation processes, while the Orbach region is relatively unaffected. The experimental verification of the predicted crossover point for equatorial coordination in this work tests the limitations of the use of AtomAccess as a predictive tool and also indicates that the application of this type of program shows considerable potential to boost efficiency in exploratory synthetic chemistry.

Three‐Dimensional Printing of High‐Performance Moisture Power Generators

AbstractWater‐enabled electricity generation technologies that are highly accessible and fundamentally clean are promising for next‐generation green energy. However, the challenge of scalability in both material processing and device fabrication greatly limits their practical applications. A high‐performance polyelectrolyte moist‐electric generator (MEG), which can be directly 3D printed for massive production and efficient integration, is reported. The printed MEG (p‐MEG) generates a high open‐circuit voltage of 0.8 V and a short‐circuit‐current density of 0.12 mA cm−2 by actively harvesting moisture from humid conditions. The synergistic effects of moisture gradient, ionic concentration gradient, and ion diffusion gradient, which remarkably enhance the driving force to separate ion pairs and notably facilitate the directional ion transport, are responsible for the high power generation performance of p‐MEG, as further backed up by in situ ion dynamics investigations and molecular simulations. When connected in serial and parallel, hundreds of p‐MEGs can deliver a high voltage of more than 180 V and a current of more than 1 mA. A constructed “moisture‐powered cup lamp” that lights up for hours further demonstrates the practicability of p‐MEG. This work provides a feasible and scalable 3D printing approach for the next‐generation environment‐adaptive self‐powered system.

Revealing Local Structure and Dynamics in Li-Salt Electrolytes Using Dielectric Relaxation Spectroscopy

Understanding the interplay between local structure and dynamics is critical for establishing design rules for advanced ion-conducting electrolytes. In this work, a set of Li-salt in liquid electrolytes is studied using dielectric relaxation spectroscopy (DRS) to examine correlations between several electrolyte properties, including conductivity, dielectric relaxation time and strength, ionicity, and viscosity. These properties were evaluated by changing ion concentration, solvent type, and anion type. DRS was used to identify relaxation processes associated with the solvent and different ion-solvent coordinating structures, and the dielectric properties are reported for the first time for a majority of these systems. The behavior of viscosity and conductivity were shown to change similarly with concentration when accounting for the local coordinating environment, regardless of the salt or solvent type. τα, the dielectric relaxation time of the solvent-ion complexes, is shown to be independent of ion content at low salt concentrations, when solvent separated ion pairs are the dominant ion-solvent complex. However, at high ion concentrations, a new relationship, a power-law dependence, was identified between molar conductivity and τα, as well as viscosity and τα, demonstrating that the dependence of molar conductivity or viscosity on τα is controlled in part by the solvent type, due to variation in shielding between contact ion pairs and aggregates. In contrast, there was not a clear change in the dependence of molar conductivity or viscosity on τα with changing anion. Furthermore, the effective dipole moments of the ion-solvent complexes were determined, and found to decrease with increasing ion concentration, as contact ion pairs and aggregates form. This systematic analysis of the wide range of Li-salts and solvents, and discussion of relations between different local structures and dynamic processes that contribute to conductivity, helps lay a foundation for the design of new liquid electrolytes.

Revisiting the Schlenk dimerisation reaction of 1,1-diphenylethene

The reaction between 1,1-diphenylethene and two equivalents of lithium in THF gave the complex [(Ph2CCH2CH2CPh2)Li2(THF)4] (3), which crystallised from Et2O/THF as the dialkyllithate salt [Li(THF)4][(Ph2CCH2CH2CPh2)Li(THF)] (3a). A similar reaction between 1,1-diphenylethene and sodium metal in THF gave [(Ph2CCH2CH2CPh2)Na2(THF)1.5] (4), which crystallised from THF as the polymer [(Ph2CCH2CH2CPh2)Na2(THF)3]∞ (4a). In contrast, reactions between 1,1-diphenylethene and potassium under the same conditions gave intractable mixtures of products. However, treatment of 3 with two equivalents of KOtBu in THF yielded the complex [(Ph2CCH2CH2CPh2)K2(THF)0.5] (5) as a deep red powder; treatment of 5 with two equivalents of 12-crown-4, followed by crystallisation from methylcyclohexane/THF, gave the adduct [(Ph2CCH2CH2CPh2)K2(THF)2(12-crown-4)2] (5a). A similar reaction between 3 and 12-crown-4 gave the separated ion pair [Li(THF)(12-crown-4)][Li(THF)0.5(OEt2)0.5(12-crown-4)](Ph2CCH2CH2CPh2) (3b), which contains the free 1,1,4,4-tetraphenyl-1,4-butanediide dicarbanion. X-ray crystallography revealed that the C3C centres of the ligands adopt a near planar geometry, irrespective of whether a metal cation is in close contact.

Lithium Nitrate as Salt Additive for Solid Electrolyte Interphase Formation in Dual‐Ion Battery

AbstractTuning the solid electrolyte interphase (SEI) formation in dual‐ion batteries is important for improving their long‐term stability. In this context, salt additives have gained importance which can sacrificially undergo reduction thereby protecting the working salt. Herein, we have considered dual salt electrolyte models of LiNO3 additive with LiPF6 and LiFSI salt to carry out ab initio molecular dynamics (AIMD) simulations and witness the evolution of SEI layer. Various contact ion pair and solvent separated ion pair models of the dual salt electrolytes have been considered to further understand the role played by solvation shells of the ions. The small size and quicker diffusion of anions through the electrolyte results in its decomposition at the electrode surface irrespective of the anion being in contact ion pair or solvated by solvent molecules. Overall, along with underlining the role of salt additives in SEI formation, this detailed study also provides insights regarding the factors beyond solvation characteristics of salt that determines the SEI growth process.

Separation of Anionic Chlorinated Dyes from Polluted Aqueous Streams Using Ionic Liquids and Their Subsequent Recycling.

The effect of ionic liquids on the separation of chlorinated anionic dyes such as Mordant Blue 9 (MB9) or Acid Yellow 17 (AY17) via ion exchange has been investigated in model aqueous solutions that simulate wastewater from the textile dyeing industry. The effect of ionic liquids chemical nature on the separation efficiency of mentioned dyes has been compared. It was found that especially ionic liquid based on quaternary ammonium salts comprising two or three long alkyl chains bound to the quaternary ammonium nitrogen (typically benzalkonium chloride or Aliquat 336) are very effective for the separation of both studied MB9 and AY17 from aqueous solution. In addition, the innovative technique has been developed for the reactivation of spent ionic liquids which is based on the chemical reduction of the formed ion pairs using NaBH4/NiSO4, NaBH4/Na2S2O5 or Raney Al-Ni alloy/NaOH. Thus, only NaBH4/NiSO4 in co-action with Al-Ni alloy enables both effective reduction of the azo bond and subsequent hydrodechlorination of emerging chlorinated aromatic amines. The efficiency of tested dyes separation or regeneration of ion pairs was evaluated by determination of the absorbance at wavelength of the maximum absorbance, of the Chemical Oxidation Demand (COD), and of the Adsorbables Organically bound Halogens (AOX). The formation of ion pairs or products of reduction and hydrodechlorination of these ion pairs has been studied using the 1H NMR and LC-MS techniques.

Breaking the tert-Butyllithium Contact Ion Pair: A Gateway to Alternate Selectivity in Lithiation Reactions.

The effects of Lewis basic phosphoramides on the aggregate structure of t-BuLi have been investigated in detail by NMR and DFT methods. It was determined that hexamethylphosphoramide (HMPA) can shift the equilibrium of t-BuLi to include the triple ion pair (t-Bu-Li-t-Bu)-/HMPA4Li+ which serves as a reservoir for the highly reactive separated ion pair t-Bu-/HMPA4Li+. Because the Li-atom's valences are saturated in this ion pair, the Lewis acidity is significantly decreased; in turn, the basicity is maximized which allowed for the typical directing effects within oxygen heterocycles to be overridden and for remote sp3 C-H bonds to be deprotonated. Furthermore, these newly accessed lithium aggregation states were leveraged to develop a simple γ-lithiation and capture protocol of chromane heterocycles with a variety of alkyl halide electrophiles in good yields.

Regulating the solvation chemistry of non-flammable high voltage electrolyte through salt-solvent ratio modulation

Boosting the energy density and safety issue of lithium-ion batteries has become ever more important to satisfy the diverse applications such as energy storage and mobile electronic devices. Herein, we present a new high voltage polyether-based electrolyte (HVPEE) by solvation structure design that can endure high-voltage operations and also possess non-flammable features. Especially, HVPEEs show better compatibility and stability with electrode than conventional electrolyte. We find that the solvent separated ion pair (SSIP) and contact ion pair (CIP) dominate the ion–solvent structure of HVPEEs, rather than the free solvent and ions. In this way, the oxidative decomposition of HVPEE on the cathode interface can be suppressed significantly due to the reduced highest occupied molecular orbital of SSIP complex structure than that of free TFSI-. As a result, the oxidation voltage can achieve as high as 5.35 V when the ether group/Li is optimized at 10/1 in the HVPEE, enabling the LiFePO4//Li full cells deliver a capacity of 165 mA h g−1 with a capacity retention of 98 % after 200 cycles. Moreover, when the cut-off voltage is 4.5 V, the discharge capacity of the LiNi0.6Mn0.2Co0.2O2//Li full cell can reach 170 mA h g−1.