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.     

Multiscale Computational Study on the Adsorption and Separation of CO2/CH4 and CO2/H2 on Li+‐Doped Mixed‐Ligand Metal–Organic Framework Zn2(NDC)2(diPyNI)

The quantum mechanics (QM) method and grand canonical Monte Carlo (GCMC) simulations are used to study the effect of lithium cation doping on the adsorption and separation of CO₂, CH₄, and H₂ on a twofold interwoven metal–organic framework (MOF), Zn₂(NDC)₂(diPyNI) (NDC=2,6‐naphthalenedicarboxylate; diPyNI=N,N′‐di‐(4‐pyridyl)‐1,4,5,8‐naphthalenetetracarboxydiimide). Second‐order Moller–Plesset (MP2) calculations on the (Li⁺–diPyNI) cluster model show that the energetically most favorable lithium binding site is above the pyridine ring side at a distance of 1.817 Å from the oxygen atom. The results reveal that the adsorption capacity of Zn₂(NDC)₂(diPyNI) for carbon dioxide is higher than those of hydrogen and methane at room temperature. Furthermore, GCMC simulations on the structures obtained from QM calculations predict that the Li⁺‐doped MOF has higher adsorption capacities than the nondoped MOF, especially at low pressures. In addition, the probability density distribution plots reveal that CO₂, CH₄, and H₂ molecules accumulate close to the Li cation site. The selectivity results indicate that CO₂/H₂ selectivity values in Zn₂(NDC)₂(diPyNI) are higher than those of CO₂/CH₄. The selectivity of CO₂ over CH₄ on Li⁺‐doped Zn₂(NDC)₂(diPyNI) is improved relative to the nondoped MOF.     

The pair polarizabilities of Li+/Li+ and Cl−/Cl−

Ab initio SCF MO energies and pair polarizabilities are reported for the pairs Li⁺/Li⁺ and Cl^?/Cl^? over the ranges of internuclear separation which are of importance in molten LiCl. The shapes of the β(R) curves resemble those of inert gas diatoms. The Cl^?/Cl^? interaction is predicted to make a rather small contribution to those properties of molten LiCl which depend on $\text{α}$⁽²⁾(R), and a larger contribution to properties which depend on β(R). The Li⁺/Li⁺ interaction contributes almost nothing to the bulk polarizability.     

Regioselectivity of reactions of vinyl- and isopropenylcyclopentadienide anions with electrophilic agents. Synthesis and crystal structures of complexes [C5H4C(Me)=CH2]ZrCl3 · 2THF and [C5Me4CH=CH2]ZrCl3 · 2THF

Regioselectivity of the reactions of lithium vinyl- and isopropenylcyclopentadienides C₅H₄C(R)=CH₂ ^-Li⁺(R = H, Me) and lithium tetramethylvinylcyclopentadienide C₅Me₄CH=CH₂ ^-Li⁺ with various electrophilic agents (Me₃SiCl, Me₃SnCl, Et₂PCl, 2-chloro-1, 3-dioxaphospholane, and MeI) was studied. Two new monocyclopentadienyl zirconium complexes, [C₅H₄C(Me) = CH₂]ZrCl₃ · 2THF and [C₅Me₄CH=CH₂]ZrCl₃ · 2THF, were synthesized. Their crystal structures were established by X-ray diffraction. The results of quantum chemical calculations for the C₅H₄C(R) = CH₂ ^- (R = H, Me) and C₅Me₄CH=CH₂ ^- anions by the DFT method (RMPW1PW91) with the 6-311+G(d, p) split valence basis set are in good agreement with experimental data on the regioselectivity of their reactions with electrophilic agents.__________Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 2, pp. 390–399, February, 2005.     

Bis[μ‐P,P′‐methylenebis(diisopropyl phosphonate)‐κ3O,O′:O]bis[chlorolithium(I)]: a centrosymmetric dimer of lithium chloride with terminal chloride anions

The molecule of the title dimeric compound, [Li₂Cl₂(C₁₃­H₃₀O₆P₂)₂] or [LiCl{[(ⁱPrO)₂P(O)]₂CH₂}]₂, lies about an inversion center and features tetrahedrally coordinated Li atoms. The neutral ligands each chelate to one metal center and bridge to the other center through P=O units. Unusually for lithium chloride complexes, the Cl⁻ ions are in terminal rather than bridging positions. Principal dimensions include Li—O(four‐membered ring) = 1.959 (3) and 2.056 (3) Å, Li—O(phosphonate ring) = 1.929 (3) Å, and Li—Cl = 2.293 (3) Å.     

FTIR and quantum chemical study of LiBr solvation in acetonitrile solutions

FTIR spectroscopy and quantum chemical calculations at the RTF + MP2/6-311G** level of theory with solvation model density (SMD) corrections were used to study ion solvation and association in LiBr/acetonitrile solutions. The aim of this study was to establish the composition and geometry of the predominant ionic species solvated by acetonitrile molecules and to analyse their spectroscopic signatures. The results obtained make it possible to propose an equilibrium between Li⁺Br⁻(CH₃CN)₃, Li⁺(CH₃CN)₄, and anionic Br⁻(CH₃CN)_n complexes with an undetermined n value and bent coordination of the solvent molecules. The calculated wavenumbers and the geometric parameters of the solvated ionic species were found to be in excellent agreement with the experimental data.     

Reactivity of a Tetra(o‐tolyl)diborane(4) Dianion as a Diarylboryl Anion Equivalent

Lithium and magnesium salts of tetra(o‐tolyl)diborane(4) dianion, having B=B double bond character, were synthesized. It was clarified that the lithium salt of the dianion has a high‐lying HOMO and a narrow HOMO–LUMO gap, which were perturbed by dissociation of Li⁺ cation, as judged by UV/Vis spectroscopy and DFT calculations. The lithium salt of the dianion reacted as two equivalents of a diarylboryl anion with CH₂Cl₂ or S₈ to give boryl‐substituted products.     

Synthese und Kristallstrukturen der Nitrido‐Chloro‐Molybdate [Mg(THF)4{NMoCl4(THF)}2] · 4 CH2Cl2 und [Li(12‐Krone‐4)(NMoCl4)]2 · 2 CH2Cl2

Syntheses and Crystal Structures of the Nitrido‐chloro‐molybdates [Mg(THF)₄{NMoCl₄(THF)}₂] · 4 CH₂Cl₂ and [Li(12‐Crown‐4)(NMoCl₄)]₂ · 2 CH₂Cl₂ Both the title compounds as well as [Li(12‐crown‐4)₂]⁺MoNCl₄^– were made from MoNCl₃ and the chlorides MgCl₂ and LiCl, respectively, in dichloromethane suspensions in the presence of tetrahydrofuran and 12‐crown‐4, respectively. They form orange‐red moisture‐sensitive crystals, which were characterized by their IR spectra and partly by crystal structure analyses. [Mg(THF)₄{NMoCl₄(THF)}₂] · 4 CH₂Cl₂ ( 1 ): space group C2/m, Z = 2, lattice dimensions at –50 °C: a = 1736.6(1), b = 1194.8(1), c = 1293.5(2) pm; β = 90.87(1)°; R₁ = 0.037. In 1 the magnesium ion is coordinated octahedrally by the oxygen atoms of the four THF molecules and in trans‐position by the nitrogen atoms of the two [N≡MoCl₄(THF)]^– ions. [Li(12‐crown‐4)(NMoCl₄)]₂ · 2 CH₂Cl₂ ( 2 ): space group P 1, Z = 1, lattice dimensions at –70 °C: a = 930.4(1), b = 957.9(1), c = 1264.6(1) pm; α = 68.91(1)°, β = 81.38(1)°, γ = 63.84(1)°; R₁ = 0.0643. 2 forms a centrosymmetric ion ensemble in the dimeric cation of which, i. e. [Li(12‐crown‐4)]₂²⁺, the lithium ions on the one hand are connected to the four oxygen atoms each of the crown ether molecules in a way not yet known; and in addition, each of the lithium ions enters into a intermolecular Li–O bond with neighboring crown ether molecules under formation of a Li₂O₂ four‐membered ring. The two N≡MoCl₄^– counterions are loosely coordinated to one oxygen atom each of the crown ether molecules with Mo–O distances of 320.2 pm.     

Vibrational spectroscopic and density functional theory studies on ion solvation and ion association of lithium tetrafluoroborate in N,N-dimethylcarbamoyl chloride-based solvents

Solvation and association interactions in solutions of LiBF₄/DMCC (DMCC for N,N-dimethylcarbamoyl chloride) and LiBF₄/DMCC–DME (DME for 1,2-dimethoxyethane) have been studied as a function of concentration of lithium tetrafluoroborate by infrared and Raman spectroscopy. Strong interactions between Li⁺ and solvent molecules or BF₄⁻ anions are observed. The apparent solvation numbers of Li⁺ in LiBF₄/DMCC solutions were deduced. Band-fitting to the B–F stretching band of BF₄⁻ anion permits detailed assess of the ion pairing. Based on the calculations of density function theory, optimal structures of Li⁺(DMCC)_n (n = 1–3) were suggested. It is found that the lithium ion was preferentially solvated by DME in DMCC–DME binary solvents. This finding is supported by quantum chemistry calculations.     

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.     

Poly(triazine imide) with intercalation of lithium and chloride ions [(C3N3)2(NH(x)Li(1-x))3⋅LiCl]: a crystalline 2D carbon nitride network

Poly(triazine imide) with intercalation of lithium and chloride ions (PTI/Li⁺Cl^?) was synthesized by temperature‐induced condensation of dicyandiamide in a eutectic mixture of lithium chloride and potassium chloride as solvent. By using this ionothermal approach the well‐known problem of insufficient crystallinity of carbon nitride (CN) condensation products could be overcome. The structural characterization of PTI/Li⁺Cl^? resulted from a complementary approach using spectroscopic methods as well as different diffraction techniques. Due to the high crystallinity of PTI/Li⁺Cl^? a structure solution from both powder X‐ray and electron diffraction patterns using direct methods was possible; this yielded a triazine‐based structure model, in contrast to the proposed fully condensed heptazine‐based structure that has been reported recently. Further information from solid‐state NMR and FTIR spectroscopy as well as high‐resolution TEM investigations was used for Rietveld refinement with a goodness‐of‐fit (χ²) of 5.035 and wRp=0.05937. PTI/Li⁺Cl^? (P6₃cm (no. 185); a=846.82(10), c=675.02(9) pm) is a 2D network composed of essentially planar layers made up from imide‐bridged triazine units. Voids in these layers are stacked upon each other forming channels running parallel to [001], filled with Li⁺ and Cl^? ions. The presence of salt ions in the nanocrystallites as well as the existence of sp²‐hybridized carbon and nitrogen atoms typical of graphitic structures was confirmed by electron energy‐loss spectroscopy (EELS) measurements. Solid‐state NMR spectroscopy investigations using ¹⁵N‐labeled PTI/Li⁺Cl^? proved the absence of heptazine building blocks and NH₂ groups and corroborated the highly condensed, triazine‐based structure model.     

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.     

Enantiomer separation of rac-2,2′-dihydroxy-1,1′-binaphthyl (BNO) by inclusion complexation with racemic or achiral ammonium salts and a novel transformation of a 1:1:1 racemic complex of BNO, Me4N·Cl and MeOH into a conglomerate complex in the solid state

The complete simultaneous and mutual enantiomer resolution of 2,2′-dihydroxy-1,1′-binaphthyl (BNO) and N-(3-chloro-2-hydroxypropyl)-N,N,N-trimethylammonium chloride, Me₃N⁺CH₂CH(OH)CH₂Cl·Cl⁻ into their enantiomers by inclusion complexation between their racemates in EtOH in the presence of a chiral seed crystal is reported. The enantiomer resolution of the rac-BNO was also accomplished easily by inclusion complexation with achiral ammonium salts, N-(2-hydroxyethyl)-N,N,N-trimethylammonium chloride, Me₃N⁺CH₂CH₂OH·Cl⁻ and tetramethylammonium chloride, Me₄N⁺·Cl⁻. Inclusion complexation of the rac-BNO with Me₃N⁺ CH₂CH₂OH·Cl⁻ gave only a 1:1 conglomerate inclusion complex but not a racemic complex. Recrystallization of the rac-BNO and an equimolar amount of Me₄N⁺·Cl⁻ from MeOH (7 ml) and MeOH (15 ml) gave a 1:1:1 racemic complex, BNO·Me₄N⁺·Cl⁻·MeOH and a 1:1 conglomerate complex, BNO·Me₄N⁺·Cl⁻, respectively. Novel transformation of the former racemate into the latter conglomerate occurred by heating or by exposure to MeOH vapor in the solid state.     

Selective Lithium Adsorption of Silicon Oxide Coated Lithium Aluminum Layered Double Hydroxide Nanocrystals and Their Regeneration

Silicon oxide-coated lithium aluminum layered double hydroxide (Li_xAl₂-LDH@SiO₂) nanocrystals (NCs) are investigated to selectively separate lithium cations in aqueous lithium resources. We directly synthesized Li_xAl₂-LDH NC arrays by oxidation of aluminum foil substrate under a urea and lithium solution. Various lithium salts, including Cl⁻, CO₃²⁻, NO₃⁻, and SO₄²⁻, were applied in aqueous solution to confirm the anion effect on the captured and released lithium quantity of the Li_xAl₂-LDH NCs. In a 5% solution of sulfate ions mix with lithium chloride, the Li_xAl₂-LDH NCs separated a larger quantity of lithium than in other anion conditions. To enhance regeneration stability and lithium selectivity, thin layers of SiO₂ were coated onto the Li_xAl₂-LDH nanostructure arrays for inhibition of nanostructure destruction after desorption of lithium cations in hot water. The Li_xAl₂-LDH@SiO₂ nanostructures showed enhanced properties for lithium adsorption, including increase of stable regeneration cycles from three to five cycles, and they showed high lithium selectivity in the Mg²⁺, Na⁺, and K⁺ cation mixed aqueous resource. Our nanostructured LDH lithium adsorbents would provide a facile and efficient application for cost-efficient and large-scale lithium production.     

Kinetic and electrochemical study of nitrile adducts of tetrachloro-bis (1,2-bis(diphenylphosphine)methane)dirhenium(II)

Summary The addition of two nitrile ligands to the complex Re₂Cl₄-(dppm)₂ (dppm= 1,2-bis(diphenylphosphine)methane)in CH₂Cl₂ solution has been investigated electrochemically. Upon addition of one equivalent of nitrile NCR (R = aromatic or aliphatic group) to the CH₂Cl₂/0.1m tetra-N-butylammonium hexafluorophosphate (TBAH) solution, Re₂Cl₄(dppm)₂(NCR) is formed immediately, without dissociation of chloride; electrochemical investigation indicates this nitrile addition is reversible upon oxidation of the dirhenium complex. On addition of two or more equivalents of nitrile, a slow ligand substitution takes place with addition of a second nitrile and concomitant loss of a chloride ion to form [Re₂Cl₃-(dppm)₂(NCR)₂]⁺. The rate of addition of nitrile to Re₂Cl₄(dppm)₂(NCR) appears to depend on the electrondonating or electron-withdrawing abilities of the ligand. The change from monoadduct to diadduct was followed with differential pulse voltammetry for various concentrations of added nitrile. The addition was found to be first order in nitrile.     

Higher hydrates of lithium chloride,lithium bromide and lithium iodide

For lithium halides, LiX (X = Cl, Br and I), hydrates with a water content of 1, 2, 3 and 5 moles of water per formula unit are known as phases in aqueous solid–liquid equilibria. The crystal structures of the monohydrates of LiCl and LiBr are known, but no crystal structures have been reported so far for the higher hydrates, apart from LiI·3H₂O. In this study, the crystal structures of the di‐ and trihydrates of lithium chloride, lithium bromide and lithium iodide, and the pentahydrates of lithium chloride and lithium bromide have been determined. In each hydrate, the lithium cation is coordinated octahedrally. The dihydrates crystallize in the NaCl·2H₂O or NaI·2H₂O type structure. Surprisingly, in the tri‐ and pentahydrates of LiCl and LiBr, one water molecule per Li⁺ ion remains uncoordinated. For LiI·3H₂O, the LiClO₄·3H₂O structure type was confirmed and the H‐atom positions have been fixed. The hydrogen‐bond networks in the various structures are discussed in detail. Contrary to the monohydrates, the structures of the higher hydrates show no disorder.     

Comparative analysis of the state of lithium and sodium atoms in water clusters

Structures and energetic characteristics of Li(H₂O) _n and Li⁺(H₂O) _n clusters with n = 1–6, 19, and 27 determined in the second order of the Møller-Plesset perturbation theory with 6–31++G(d,p) basis set are analyzed. The electron density redistribution, which takes place upon the electron addition to a Li⁺(H₂O) _n cluster, is found to be provided by hydrogen-bonded water molecules: initially almost neutral molecules, which are most distant from lithium, become negatively charged. The calculated energies of the electron capture by Li⁺(H₂O) _n clusters are approximated with the appropriate electrostatic model, and estimates of the lithium ionization energy in water clusters of various sizes are found. Similar estimates obtained earlier for sodium are made more accurate.     

Radiolysis of tetrachloromethane-water two-phase systems

The radiolysis of two-phase systems CCl₄-water proceeds in kinetical regime up to dose 12 kGy. Groos radiation yields of chloride ions are the same as the radiolysis of saturated solutions in this period. A two-phase rule of additivity is valid and the partial yields for both phases were calculated; G_CCl4(Cl^- = 5.61 ± 0.10 and G_H2O(Cl^-) = 8.29 ± 0.51 molecules/100 eV, respectively.The radiolysis proceeds in diffusional regime at the absorbed dose of more than 50 kGy. The gross radiation yield of chloride ions is determined by hydrolysis of molecular chlorine which is produced with G(Cl₂) = 0.68 ± 0.14 molecules/100 eV. An additional part of chloride ions is produced by radiolysis of substrates which diffuse into both phases with value G_dif(Cl^-) = 2.38 ± 0.31 molecules/eV. This value is approximately three times less than the gross radiation yields in kinetical regime of radiolysis of two-phase systems in saturated solutions of these substrates.     

A Highly Hexane Soluble Lithium Salt and other Starting Materials of the Fluorinated Weakly Coordinating Anion [Al{OC(CF3)2(CH2SiMe3)}4]−

The lithium salt of the weakly coordinating alkoxyaluminate anion Li[Al(OC(CF₃)₂(CH₂SiMe₃))₄] ( 2 ) is soluble in polar and even in non‐polar solvents. Especially the solubility in n‐hexane confirms 2 to be an excellent candidate for Li ion catalysis. Its polymeric structure consists of a seven coordinated Li⁺ cation, coordinating a [Al(OC(CF₃)₂(CH₂SiMe₃)]^? anion that serves as hexadentate O₂F₄ ligand and a further bridging F atom of a second anion. Compound 2 reacts with ClCPh₃ giving the [CPh₃]⁺ salt which is at least stable in CD₂Cl₂ over days at 298 K, but decomposes after storage at 333 K for several days.     

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.