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The ethynyl-expanded cubane 2 is examined at the B3LYP/6-31G* level for its structure, ring-strain energy, deprotonation energy, and affinity toward lithium and sodium cation. The estimate of the ring-strain energy of 2 is 48.3 kcal mol-1. Its free energy of deprotonation is 325 kcal mol-1. Lithium cation coordinates to the face of 2, while sodium coordinates to the cage center. These properties are compared with those of simple acyclic alkynes and cyclododeca-1,4,7,10-tetrayne, the analogue of the face of 2.

The trilithium triamide [HC{SiMe2NLi(2-FC6H4)}3] (2) was obtained by treatment of HC{SiMe2NH(2-FC6H4)}3 (1) with 3 M equivalents of n-butyllithium in n-pentane. Upon reaction of 2 with 1 M equivalent of SnCl2 in toluene at elevated temperature, the amidostannate [HC{SiMe2N(2-FC6H4)}3 SnLi] (3) was formed for which an X-ray diffraction study established the intramolecular coordination of the lithium cation by two of the peripheral ortho-fluoro groups. The mean LiF bond distances found in 3 are 1.986(8) and 1.982(9) A for the two independent molecules in the asymmetric unit. This exposed position of the lithium, bonded to two amido N atoms and the two fluorine atoms, leads to a very close contact with the adjacent methyl-group [d(Li1C3)=2.545 and 2.516 A for the two independent molecules in the unit cell] which effectively occupies a vacant coordination site of the lithium centre. This disposition of the alkyl group at close proximity of the Li centre is probably due to the unusual cation coordination geometry (distorted square-planar instead of tetrahedral) imposed by the rigid caged structure of the triamidoatannate(II).

Novel thermoplastic polyurethanes with chelating groups were synthesized from 4,4′-diphenylmethane diisocyanate (MDI), poly(ethylene glycol) (PEG), and EP-IDA. Differential scanning calorimetry (DSC), fourier transform infrared spectroscopy (FT-IR), and impedance spectroscopy (IS) were used to monitor changes in the morphology of these polyurethanes with the concentration of lithium perchlorate (LiClO4) dopants. Adding the salt significantly changes the FTIR spectrum of the polyurethane, indicating an interaction between the lithium cation within the urethane group and the chelating group. The soft segment Tg increases with LiClO4 concentration, as determined by DSC, indicating that solubility of the lithium cation in the host polyurethane increases with the chelating groups. IS shows that the bulk conductivity reaches a maximum as the salt concentration is increased. One of the investigated polyurethane electrolytes has an ionic conductivity as high as ∼10−6 S cm−1 at room temperature.

The lithium cation binding energies of 15 of the common amino acids were determined via the kinetic method in a quadrupole ion trap mass spectrometer. Values were obtained in two ways. First, a ladder of relative lithium cation binding energies was developed from pairwise comparisons of the amino acids. Second, values were determined by comparison to a pair of simple reference compounds, dimethoxyethane and diethoxyethane. The values from the two approaches are in good accord. The scale from glycine to glutamic acid spans a range from 41.6 to 52.9 kcal/mol. The present values for lithium cations have been compared to those obtained by others previously for sodium, copper, and silver cations. These comparisons suggest that the alkali metals have exalted binding energies for amino acids with side chains that include oxygen-bearing functional groups (i.e., alcohols and carboxylic acids) whereas the transition metals have enhanced binding energies for amino acids with side chains that include sulfur-bearing or aromatic functional groups. This analysis is in accord with the principles of hard-soft acid/base behavior.

The lithium cation coordination to the 1,2,3-Triazole-4,5-dicarbonitrile (TADC) anion was studied using Raman spectroscopy and ab initio SCF-MO Hartree-Fock (HF) calculations. Three stable 1:1 ion pair complex geometries were found, one transition state (TS) and two local minima, all of which having comparable lithium binding energies. The binding energies were further evaluated using single point calculations with larger basis sets and electron correlation: HF/6-311+G*//HF/6-31G* and LMP2/6-31G*//HF/6-31G*. By comparing theoretical spectra with both polarised and depolarised Raman spectra of the pure lithium salt of TADC and salt solutions, a preference for bi-dentate lithium ion coordination to the nitrogen atoms in the planar five-member ring was revealed. Finally, comparisons with other previously calculated coordination strengths for lithium ion–anion 1:1 systems were made.

This work has demonstrated that the incorporation of benzimidazole derivatives, 2,2′-p-phenylene-bisindole (PPBI), enhances the ionic conductivity of a poly(ethylene oxide) (PEO)–based electrolyte by 20 times more than the plain system. Specific interactions among amino group, ethyl oxide, and lithium cation were investigated using differential scanning calorimetry (DSC), FTIR, and alternating current impedance. The DSC characterization confirms that the initial addition of PPBI is able to enhance the PEO crystallinity attributed to the interaction between the negative charge from the amino group and the lithium cation. Three types of complexes are present: complex I is present in the PEO phase, complex II resides at interphase, and complex III is located within the PPBI domain. Complex II plays the key role in stabilizing these two microstructure phases. FTIR spectra confirm that because of the presence of PPBI one is able to dissolve lithium salts more easily than in the plain electrolyte system and thus increase the fraction of free ions. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 719–725, 2004

A mixture of magnesium thiolate or selenolate, β-substituted-α,β-unsaturated ester and aldehyde affords a Michael/aldol tandem adduct, α-phenylthio- or α-phenylselenoalkyl-β-hydroxyester, in a good yield. The reaction proceeded in anti-aldol selective manner, which is contrast to the products from a similar reaction in the presence of lithium cation. An NMR study and an experiment for trapping the reaction intermediates suggest that magnesium thiolate, which forms precipitate in the reaction mixture, first attacks the aldehyde, not the unsaturated ester, to give α-alkoxysulfide.

7Li, 51V solid-state nuclear magnetic resonance (NMR) and electron paramagnetic resonance (EPR) measurements have been performed upon chemically lithiated LixV2O5 aerogels, with compositions of 1.00

The gas-phase lithium-cation basicities of a series of monosubstituted benzene derivatives, namely C 6 H 5 X (X=H, Me, CHCH 2 , OH, OMe, SH, Cl, Br) have been measured by means of Fourier transform ion cyclotron resonance (FT-ICR) mass spectrometry. The structures of the corresponding complexes and their relative stabilities were investigated with B3LYP/6-311+G(3df,2p)//B3LYP/6-31G(d) density functional theory calculations. In all cases, the π-complexes are favored with respect to those in which the metal monocation interacts with the substituent. These latter kind of complexes, which are entropically favored with respect to the π-complexes, are found to be chelated species, in which Li + bridges the heteroatom of the substituent and the ipso carbon atom. The Li + basicity of the benzene derivatives investigated reflects the electron-donor ability of the aromatic moiety as a function of the substituent. Consistently, there is a linear correlation between the Li + basicity and the frequency of the vertical displacement of Li + with respect to the aromatic ring.

This work has demonstrated that the addition of an optimum content of dimethyldioctadecylammonium chloride (DDAC)-modified montmorillonite clay (Dclay) enhances the ionic conductivity of the plasticized poly(methyl methacrylate)-based electrolyte by nearly 40 times higher than the plain system. Specific interactions among silicate layer, carbonyl group (CO) and lithium cation have been investigated using Fourier-transform infrared (FTIR), solid-state NMR, alternating current impedance. The FTIR characterization confirms that both of the relative fractions of ‘complexed’ CO sites and ‘free’ anions increase with the increase of the Dclay content, indicating that strong interaction exists between the CO group and the lithium salt. In addition, the solid-state NMR demonstrates that the interaction between the PMMA and the clay mineral is insignificant. The addition of clay mineral promotes the dissociation of the lithium salt and thus, the specific interaction can be enhanced between the CO and the free lithium cation. However, the balanced attractive forces among silicate layers, CO groups, lithium cations and anions is critical to result in the higher ionic conductivity.

This work has demonstrated that the addition of specific amount of poly(oxypropylene) diamine (d2000) and mineral clay in the PEO-based electrolyte system can form the high conductivity film at room temperature. Specific interactions among silicate layer, d2000, ether oxygen, and lithium cation have been investigated using differential scanning calorimetry (DSC), alternating current impedance (AC impedance) and Fourier-transform infrared (FT-IR). The DSC characterization confirms that the addition of 25 wt[percnt] d2000 is able to produce low Tg and fully amorphous (PEO)8LiClO4/d2000 electrolyte system which produce the good environment for ionic transfer. Additionally, the incorporation of the mineral clay into the (PEO)8LiClO4/d2000 electrolyte system can sustain the polymeric mechanical property by its huge surface area and enhance the conductivity due to the specific interaction between silicate layers and lithium cation. FT-IR spectra confirm that the incorporation of the clay is able to dissolve the lithium salts more effectively and resulting to the higher fraction of free anions due to the strong interaction between negative charges of the silicate layers and lithium cations of the lithium salt.

A quantum chemical study of the binding of Li+ cation to polyalkyloxides has been carried out. The lithium cation interaction with three polyalkyloxides (polyethylene oxide (PEO), polytrimethylene oxide (PTMO), and polypropylene oxide (PPO)) has been investigated using ab initio molecular orbital theory at the HF/6-31G∗ level with molecular models for the polymers. Coordination by one to six oxygens was considered. In addition, higher level calculations were carried out using G3(MP2) theory for coordination of Li+ by one oxygen. For coordination of lithium by one oxygen, the binding energy ordering is PTMO>PPO>PEO, with PTMO having the largest lithium cation affinity. The same ordering is found for larger coordination numbers with the exception of coordination by six oxygens, where the ordering changes due to the steric interactions.

Anions usually have been shown to play a dominant role in the interactions between starches and electrolytes prepared from various salts of metals from the first non-transition group. Except for lithium, the salts, at least their cations, did not penetrate starch granules and retarded granule swelling. Because the lithium cation has specific colligative properties and coordination ability it is distinctly different from the other salts of this group and formed complexes with starch. However, it was not equivalent to the formation of starch lithium salt and hydrochloric acid. The results of this study explain the acidity of starch and all other phenomena thus far interpreted with the argument that salt cations formed metal salts of starch. Our arguments are collected from the studies, which involved dynamic rheometry, crossed polarized–non-polarized light beam microscopy (CLBM), powder X-ray diffraction, energy dispersion spectroscopy (EDS), 19 F, 23 Na, and 35 Cl NMR, AFM and SEM of sliced starch granules, and CD/ORD. Irreversibility of swelling of granules was shown by CLBM.

Using a refined Gaussian-3 (G3) protocol, the highest level of ab initio calculations reported so far, we have established the Li+ cation binding enthalpy (affinity) at 0 K (in kJ mol−1) for formamide (195.7), N-methylformamide (209.2), N,N′-dimethylformamide (220.0), acetamide (211.7), N-methylacetamide (222.5), and N,N′-dimethylacetamide (230.1), with an estimated maximum uncertainty of ±8 kJ mol−1. With these six theoretical lithium cation binding affinities as reference values, the absolute Li+ affinities of imidazole and dimethoxyethane were determined by the extended kinetic method, and by adopting the statistical data treatment protocol recently proposed by Armentrout. The Li+ affinities obtained for these two ligands are in good agreement (within 6 kJ mol−1) with recent values determined by the threshold collision-induced dissociation method, and consistent with the Li+ basicity values first reported by Taft and co-workers in 1990. Our study confirms that the previously suggested, and recently implemented, downward revision of Taft's original basicity scale by 10.9 kJ mol−1 is justified for ligands with revised basicities less than 151 kJ mol−1. However, for selected ligands with Li+ basicities greater than 151 kJ mol−1, including some of the six amides studied in this work, the reported discrepancy between theoretical and experimental estimates in the revised Li+ basicity scale of Burk et al. is likely to arise from experimental uncertainties. Copyright © 2002 John Wiley & Sons, Ltd.

In oxidation of 1,3-dinitro- and 1,3,5-trinitrobenzene acetonate σ adducts (Yanovskii complexes) with sodium, potassium, and tetrabutylammonium cations in acetonitrile and tetrahydrofuran (290-313 K), ion pairs are less reactive than free ions, which is explained by charge redistribution in the ring of the σ adducts, decreasing the electron-donor power of the associated anion. Separation of the apparent rate constants into ionic and ion-pair contributions showed that the reactivity of the ion pairs depends on the radius of their cation. The revealed kinetic regularities are interpreted on the basis of AM1 semiempirical quantum-chemical calculations of the ions and ion pairs with lithium cation.

Transport properties and crystallochemical features of lithium-containing lanthanum metaniobates La2/3 – xLi3x□4/3 – 2xNb2O6 with the structure of fault perovskite are studied. The materials studied have high conductivity by lithium ions. A correlation between the conductivity magnitude, chemical composition, and crystallographic parameters is found.

A novel mixture cations templated indium phosphates, Li(C 2 N 2 H 10 )[In 2 (HPO 4 ) 3 (PO 4 )], has been synthesized under mild hydrothermal conditions and characterized by elemental analysis and FT-IR spectrum. The crystal structure of title compound was determined by single crystal X-ray diffraction data. It belongs to monoclinic, space group P 2/ n with unit cell dimension a = 9.4692(13) A, b = 9.1622(12) A, c = 9.7063(14) A, β = 117.5620(10)°. Its structure is characterized as a three-dimensional open-framework with 8-membered ring channels along a axis, where the inorganic lithium cation and organic double-protonated ethylenediamine cation are located and interact with the framework both electrostatically and via hydrogen bonds of N–H⋯O.

Confining ionic liquids (ILs) with added lithium salt within silica host networks enhances their fragility and improves their conductivity. Overall, conductivity measurements, Raman spectroscopy of the TFSI anion and NMR spectroscopy of the lithium cation show segregative interaction of lithium ions with the SiO2 host matrix. This implies at IL/SiO2 interfaces a breakdown of aggregated regions that are found systematically in bulk ILs. Such destructuration due to the interface effect determines the fragility and thus results locally at the interface in short relaxation times, low viscosity, and good ionic conductivity. The “destructuration” of ion pairs or domains makes ILs within ionogels a competitive alternative to existing solid ionic conductors in all-solid devices, such as lithium batteries and supercapacitors.

The reaction of 1,1,3,3-tetraphenyl-1,3-disiloxandiol (LH2) with n-butyllithium and CrCl2 results in a mononuclear chromium(II) complex (1) that further reacts with O2 at low temperatures to yield a mononuclear chromium(III) superoxide complex [L2CrO2(THF)][Li2(THF)3] (2). The crystal structure revealed that the chromium superoxido entity is stabilized by the coordination to an adjacent lithium cation. Complex 2 thus contains an unprecedented heterobimetallic [Cr(III)(μ-O2)Li(+)] core; beyond this it is the first chromium superoxide for which a temperature-dependent magnetic characterization could be achieved, and the first structurally characterized representative with chromium in an exclusive O-donor environment.

Three novel metal complexes [(acac)2Cu2(NtBu)4S] (), [Li(thf)4]2[I4Cd2(NtBu)4S] () and [(thf)2Li{(SiMe3)2N}Zn(NtBu)4S] () are prepared from the intended transmetalation of the dilithium complex of N,N',N'',N'''-tetrakis(tert-butyl)tetraimidosulfate [(thf)4Li2(NtBu)4S] (). The two lithium cations are replaced by either the cationic (acac)Cu(ii) moiety, the neutral I2Cd(ii) residue or only a single lithium cation is substituted by the cationic (Me3Si)2NZn(ii) fragment. The complexes show two main results: first the S(NtBu)4(2-) tetrahedron can serve as a ligand to transition metals from the soft Cu(ii) to the harder Zn(ii) at opposite sides and second the S-N bond distances vary only marginally in response to the various metals and the four distances constantly sum up to 6.38(2) Å. Hence the electropositive sulfur atom responds by internal shift to the metal-polarized negative charge at the outside of the S(NR)4(2-) tetrahedron. peerReviewed

An unusual lithium lithiate [Li(diglyme)2 ][(diglyme)Li2 (C4 H3 S)3 ], made up from three carbanions, two lithium cations, and a single donor base molecule in the anion and a single lithium cation, coordinated by two donor base molecules, is investigated in a combined study including X-ray diffraction, NMR spectroscopy and computational approaches in solution and the solid state. While the multicomponent lithiate is the only species present in the solid state, solution NMR spectroscopy and computational methods were employed to identify a second species in solution. The dimer [(diglyme)Li(C4 H3 S)]2 coexists with the lithiate in solution in a 1:1 ratio, the more the higher the polarity of the solvent is. Only the combination of this multitude of methods provides a firm picture of the whole.

The crystal structure of Li4P2O7 is refined by high temperature neutron diffraction at 300—1050 K.

A series of 1,4-disubstituted ruthenium-vinyl complexes, (E,E)-[{(PMe3)3(CO)ClRu}2(μ-HC=CH-Ar-CH=CH)], in which the 1,4-diethenylphenylene bridge bears two oligo(ethylene glycol)methyl ether side chains at different positions (2,5- and 2,3-positions), were prepared. The respective products were characterized by elemental analyses and NMR spectroscopy. The structures of complexes 1b and 1e were established by X-ray crystallography. The electronic properties of the complexes were investigated by cyclic voltammetry, and IR and UV-vis/NIR spectroscopies. Electrochemical studies showed that the 2,5-substituents better stabilized the mixed-valence states; the electrochemical behavior was greatly affected by lithium cations, especially complex 1g with 2,3-substituents, which was further supported by IR and UV-vis/NIR spectra changes. Spectroelectrochemical studies showed that the redox chemistry was dominated by the non-innocent character of the bridging fragment.

The structures of endohedral complexes of polyhedral oligomeric silsesquioxane (POSS) cage molecules (HSiO3/2)8, (HSiO3/2)10, and (HSiO3/2)12, containing either atomic or ionic lithium species are determined using density functional theory with the B3LYP functional and the 6-311G(d,p) and 6-311+G(d,p) basis sets. The structures and stabilities of these nanostructures depend on the cage size and the number and charge of the Li species encapsulated in the (HSiO3/2)8, (HSiO3/2)10, and (HSiO3/2)12 host cages. Li cation encapsulation shows attractive interactions with cage oxygen atoms leading to cage shrinkage. Li anion encapsulation breaks the (HSiO3/2)8 host cage. Stable endohedral POSS cages with varying number of neutral and ionic lithium were identified by calculating their inclusion energies and adiabatic and vertical ionization potentials.

We present the first neutron diffraction studies of the structure of lithium−methylamine solutions as they cross the metal−nonmetal transition. A shift in the principle scattering peak immediately reflects the overall decrease in density as the solvent expands to accommodate the excess electrons. 6Li/7Li isotopic labeling then allows us to answer key questions concerning cation solvation. We find that each lithium cation is coordinated to four methylamine molecules. However, the cation solvation shell expands as the system becomes metallic: a direct structural signature of electron delocalization. As a result of correlations between strongly solvated lithium ions, the solutions are highly structured over intermediate length scales. The valence electrons then reside primarily in polaronic cavities, formed by the solvated cations and remaining solvent molecules.

Unsymmetrically substituted fumaric esters underwent highly regioselective conjugate addition of thiols in the presence of a lithium cation in non-coordinative media.

The structure and stability of the still experimentally unknown Li + –(NF 3 ) ions have been theoretically investigated at the B3LYP, QCISD, QCISD(T), and CCSD(T) levels of theory in conjunction with the 6-311G(d), 6-311+G(2d), and 6-311+G(3df) basis sets. Irrespective of the employed theoretical level, it was found that the ligation of Li + to the F atoms of NF 3 may occur in two distinct ways, leading to the formation of the monocoordinated isomer 2 and the dicoordinated isomer 3 . These two isomeric ions are practically degenerate and more stable than the nitrogen-coordinated isomer 1 by ca. 6 kcal mol −1 . In addition, the optimized geometries of the Li + –(NF 3 ) isomers 1 , 2 , and 3 and the analysis of their chemical bonding indicate the formation of ion–dipole complexes between Li + and NF 3 . The Li + ion affinity of NF 3 at 298.15 K is computed as 15.6 kcal mol −1 at the B3LYP/6-311+G(3df) level of theory, 13.3 kcal mol −1 at the QCISD(T)/6-311+G(2d) level of theory, and 12.8 kcal mol −1 at the CCSD(T)/6-311+G(2d) level of theory. These values are large enough to suggest the possibility that lithiated NF 3 could be actually observed as a stable species in the gas phase. From the applied point of view, this finding supports the proposal that Li + ion attachment mass spectrometry, recently proposed by Fujii [J. Phys. Chem. A 104 (2000) 9613] as a conceivable technique to quantify the emissions of the greenhouse gases CF 4 , C 2 F 6 , C 4 F 8 , and SF 6 from the electronic industry, could be also employed to quantify the emissions of NF 3 , one of the perfluorocompounds most extensively used in semiconductor technology.

This work has demonstrated that the addition of optimum content of D-2000 modified montmorillonite enhances the ionic conductivity of the poly(ethyl oxide) (PEO) based electrolyte by nearly sixteen times more than the plain system. Specific interactions among silicate layer, ethyl oxide and lithium cation have been investigated using alternating current impedance (A.C. impedance), differential scanning calorimetry (DSC) and Fourier-transform infrared (FT-IR). The DSC characterization confirms that the initial addition of clay is able to enhance the PEO crystallinity due to the interaction between the negative charge from the clay and the lithium cation. Three types of complexes are present; complex I is present in the PEO phase, complex II resides at the interphase, and complex III is located within the clay domain. Complex II plays the key role in stabilizing these two microstructure phases. FT-IR spectra confirm that the existence of clay is able to dissolve the lithium salts, easier than the plain electrolyte system and thus increases the fraction of free ions.

Lithium chloride, more specifically the lithium cation, has been implicated in interference in biological systems. In the case of Escherichia coli, interference involves the Na+(Li+)/H+ antiporter transport system. The study reported here concerns the effects of LiCl on a mixed enrichment culture that is able to biodegrade both methanol and acetone under aerobic conditions. The results obtained using unsteady state continuous flow culture techniques demonstrate a significant disruptive effect of LiCl on culture performance. In addition, a reduction in the substrate-based biomass yield coefficient, which is a clear advantage as far as biotreatment process performance is concerned, also occurs. The ultimate fate of the LiCl was not determined.

Ab initio Hartree–Fock theory was used to determine the structures of model molecules of a dibutyl dicyano tetra-aza macrocycle (1) containing 2,2′-bipyridines and their lithium complexes. Energy profiles for the conformational inversion, which is closely related to the complexation process of a lithium cation, were also studied. Macrocycles having cyano groups on the bridge methylene carbons were found to be good macrocyclic models related to the macrocycle (1). The energy profiles of stationary points and the vibrational frequencies of macrocycles and their lithium complexes reveal that conformational inversion in the lithium complexes is plausible after lithium complexation. The difference in the vibrational frequencies corresponding to the movement of the lithium cation suggests that C2v-like skeletons in the macrocyclic moiety have a stronger interaction between the lithium cation and coordinating nitrogens than the C2h structure.

Phosphorylation of p-tert-butylcalix[4]arene 9 or calix[4]arene 10, having two diethoxyphosphoryl groups at distal positions on their narrow rim (phenolic oxygen atoms), by dibutyloxophosphinechloride or alkylation of 10 by methyl bromoacetate led to the corresponding tetrasubstituted calix[4]arenes 8b–d fixed in a cone conformation. The latter compounds and the similar derivative of calix[4]arene 8a with four diethoxyphosphoryl groups were found to exhibit lithium cation selectivity, which was supported by UV–Vis spectra of THF solutions of the alkali metal picrates and their water–chloroform extraction in the presence of ligands 8a–d. Calculated K/K selectivities range from 2.9 (8d) to 9.5 (8a), which are among the highest values for the calixarene-based Li+-selective receptors reported to date. Copyright © 2001 John Wiley & Sons, Ltd.

The stable isomers of the ferrocene--lithium cation gas-phase ion complex have been studied with the hybrid density functional theory. The method of calculation chosen has been tested checking its performance for the more studied protonated ferrocene species. Our calculations demonstrate that the procedure used is reliable. We have found two isomers of the ferrocene--lithium cation complex separated by a barrier of 25.6 kcal/mol. The most stable isomer of this complex has Li(+) on-top of one of the cyclopentadienyls, while in the least stable isomer Li(+) binds the central iron metal. The latter isomer has been characterized as a planetary system in the sense that Li(+) has one thermally accessible planar orbit around the central ferrocene moiety. Our calculations lead to a value of ferrocene's gas-phase lithium cation basicity of 37.4 kcal/mol for the on-top complex and 29.4 kcal/mol for the metal-bound complex.

The binding energy and the metalation site of lithium cation for the most stable tautomers of nucleic acid bases were determined by using “hybrid” B3LYP density functional computations. For each isomer of the same base the metal affinity values are very different and depend on the coordination mode of lithium. For thymine and uracil, the experimental indication on the metalation site and on the absolute value of metal affinity agrees with our data. For the remaining bases, the presence of the metal, in some case, gives rise to a complex stability order different from that of naked tautomers. Results in these cases show that there is always only one tautomer whose metal affinity value corresponds to the experimental measurements. This tautomer is not necessarily the most stable one.

Two- and three-body interactions are calculated by means of the B3LYP and MP4 methods to assess the nonadditivity of interactions in Li(NH 3 ) n and Li(NH 3 ) n + ( n =1–4) clusters. It is found that the three-body contributions to the total interaction energy are more important for Li(NH 3 ) n clusters than for Li(NH 3 ) n + ones. For lithium ion–ammonia complexes correlation effects do not contribute significantly to the interaction energy. On the other hand, for the lithium atom–ammonia complexes the electron correlation seems to be rather important. The density functional approach is reliable to estimate the total interaction energies and nonadditive effects, especially for larger systems ( n ⩾4).

The syntheses and X-ray crystal structure determinations of tBu3C6H2P(H)Li(py)3 (1) and [DmpP(H)Li(py)]2 (2) (Dmp=2,6-dimesitylphenyl) are reported. Complex 1 crystallizes in the monoclinic space group P21/c. Crystal data for 1 at 243 K: a=10.574(3); b=16.652(5); c=18.340(13) A; β=98.62(3)°; V=3193(3) A3; Z=4; Dcalc=1.085 g cm−3; RF=5.34%. Complex 2 crystallizes in the triclinic space group P 1 . Crystal data for 2 at 198 K: a=8.7750(4); b=11.3889(5); c=14.3840(7) A; α=70.8878(12); β=75.9487(8); γ=68.7190(9)°; V=1253.0(2) A3; Z=1; Dcalc=1.144 g cm−3; RF=9.72%. The molecular structure of monomeric 1 shows a four-coordinate lithium cation in a distorted tetrahedral coordination environment, while the molecular structure of dimeric 2 features formally three-coordinate lithium cations in virtually trigonal-planar coordination environments.

A series of polymer salt complexes based on poly(ethylene malonate) and lithium triflate were prepared with polymer repeat unit to cation ratios of 8, 4, 2, 1. These were characterized and then mixed with lithium triflate. The CO stretching peaks in the IR spectra of these polymers became broad when salt was introduced, indicating complex formation between the polymer and the lithium cation. Pure poly(ethylene malonate) has a glass transition at 258 K and the glass transition temperature increases with increasing salt concentration. The maximum room temperature ionic conductivity for this polymer/salt complex is 1.6×10−6 S/cm for a polymer repeat unit to cation ratio of 8, and the temperature dependence of the conductivity follows the Vogel–Tammann–Fulcher (VTF) equation.

The changes in the excited state energies of representative cyclic enones (cyclopentenone and cyclohexenone) induced by lithium ion coordination have been examined using ab initio and DFT methods. Quantitative estimates of the vertical triplet state energies were obtained using configuration interaction calculations at the CIS and CIS(D) levels with the 6-31+G(d) basis. Inclusion of perturbative doubles corrections has a marked effect on the relative energies of the $n-\pi^*$ and $\pi-\pi^*$ triplet states. At both CI and CIS(D) levels, lithium complexation is predicted to raise the energy of the $n-\pi^*$ triplet state much more than the $\pi-\pi^*$ triplet. The trends obtained at the CIS(D) level are reproduced using B3LYP/6-31+G(d) calculations. Adiabatic excitation energies were also computed by carrying out geometry optimization of the triplet states at the B3LYP level. While the separation between the geometry optimized $n-\pi^*$ and $\pi-\pi^*$ triplet states is very small for the parent enones, the $\pi-\pi^*$ triplet is clearly favored in the lithium complexes. These results suggest the possibility of reversing the reactive photoexcited state in enones through cation complexation. The conclusions provide a rationale for interesting variations in product distributions observed for enones in cation exchanged zeolites.

Molten salt hydrates proved to be alternative solvents to cellulose. Toinvestigate the reasons for this dissolving ability, information about thesolvent–cellulose interactions is essential. As well as 13CHR NMR, 7Li NMR was used to obtain further insight into thisproblem.After comparing several molten salt hydrates, the 7Li NMR spectrarevealed a smaller shielding of the lithium cation for not dissolving than fordissolving and swelling cellulose systems. In most solvent systems theshieldingat the 7Li nuclei increases with the cellulose concentration. 2D7Li-1H HOESY NMR was successfully applied to verify thepresence of cellobiose, used as a model compound for cellulose, in the firstco-ordination sphere of the lithium cation.

The microstructure of lithium cation hydration shell has been studied by means of molecular dynamics simulations. The aqueous LiCl solution has been analyzed in the temperature range from −30 to 120°C using the SPC and ST2 water models for a set of model Lennard-Jones parameters of intermolecular potentials. The results of simulations have been compared to NMR-relaxation data and concern the reorganization of the lithium-cation hydration shell with temperature variations. The obtained results show that it is necessary to modify the water model.

The electrochemical and photoelectrochemical behavior of a conducting polymer, poly-3-phenylthiophene (P3PhT), is studied in acetonitrile containing salts of tetrabutylammonium (TBA) and lithium. Like other thiophene polymers, P3PhT may or may not be doped cathodically in the presence of salts of TBA or lithium, respectively. In general, the photoelectrochemical behavior of P3PhT resembles that of polybithiophene and poly-3-methylthiophehe. In particular, P3PhT is photoactivated when exposed to light at negative potentials. Depending on the system in which measurements are taken (in the presence of salts of lithium or TBA), P3PhT undergoes photoelectrochemical undoping or photoelectrochemical cathodic doping, respectively, which is confirmed by measuring electrochemical impedance. However, the photoelectrochemical processes on P3PhT (at least in solutions containing lithium salts) proceed much slower than those on other thiophene polymers we studied earlier. The concentration of doping ions in P3PhT in the presence of lithium salts is higher than that in the presence of TBA salts even in the undoped state. This is due to a specific interaction between Li+ and the phenyl group in P3PhT.

The [(CF 3 SO 2 ) 2 N] − anion has low basicity and it does not form strong ion pairs with the lithium cation as shown by the absence of lithium coordination to [(CF 3 SO 2 ) 2 N] − in the crystal structures of [Li⊂2.2.2][(CF 3 SO 2 ) 2 N] and [Li⊂(12-C-4) 2 [(CF 3 SO 2 ) 2 N]. The structure of [Li⊂2.2.2][(CF 3 SO 2 ) 2 N] consists of a lithium cation encapsulated by the large 2.2.2-cryptand macrocycle. In the complex [Li⊂(12-C-4) 2 ][(CF 3 SO 2 ) 2 N], the lithium cation is sandwiched between two 12-C-4 macrocycles. Correlations between these structures and the previously reported [Li⊂12-C-4][CF 3 SO 2 N(CH 2 ) 3 OCH 3 ] structures are described.

Reactions of cyclopropenone derivatives with the [2-(di-tert-butylphosphanyl)ethyl]cyclopentadienylcobalt(I) chelate system were investigated. Ethene complex 2 reacts with diphenylcyclopropenone under cobalt insertion to give cobaltacyclobutenone chelate complex 6 in 91% yield. 6 was characterized crystallographically and shows a structure similar to that of a known platinacyclobutenone. Thermoanalysis of 6 indicated a reaction at elevated temperature, which was shown to be a cycloreversion at 60 °C leading to known diphenylethyne and carbonyl complexes 7 and 9. Attempts to reduce the metallacyclobutenone with lithium tetrahydridoaluminate resulted in the cycloreversion reaction at a temperature as low as −100 to −90 °C, the lithium cation acting as a Lewis acid. The reaction of dimethoxycyclopropene complex 4 with zinc triflate unexpectedly resulted in the formation of methyl acrylate complex 13, which was characterized crystallographically.

The crystal structures of the lithium salt, Li[CF3SO2N(CH2)3OCH3] and its 12-C-4 complex [Li⊂12-C-4][CF3SO2N(CH2)3OCH3] demonstrate a change in the lithium coordination environment upon complex formation. The longer Li−N bond distance in [Li⊂12-C-4][CF3SO2N(CH2)3OCH3] indicates that the 12-C-4 crown ether weakens the interactions between the lithium cation and the [CF3SO2N(CH2)3OCH3]- anion. Correlations between these structures and previously reported vibrational spectroscopy and ionic conductivity are presented.

The previously reported gas-phase lithium cation basicity (LCB) scale (Taft et al. Pure Appl. Chem. 1990, 62, 17) was revised on the basis of recent experimental and theoretical (G2 calculations) results. A new anchoring based on the experimental LCA value for H2O is suggested (all earlier reported values of LCB should be reduced by 2.6 kcal/mol). New LCBs for 28 compounds were measured using FT-ICR, and a revised LCB scale now extended to 205 compounds is given. Correlations between gas-phase basicities toward lithium cation and proton were examined. Though a general trend is discernible, fair correlations are obtained provided that separate lines are drawn for homogeneous families. The differences in slopes are traced back to the different sensitivities to structural effects. Large deviations are explained by either a different attachment center for Li+ and H+ or a chelation effect toward Li+. G2 and G2(MP2) calculations of LCBs for a wide selection of 37 compounds and density functional theory (B3LYP/6...

Seventeen aryllithium complexes were studied by 7Li solid-state NMR spectroscopy. The solid structures of most of the complexes studied are known from x-ray crystallography and include differently substituted aryllithium complexes in addition to some phenyllithium complexes. It is shown that the quadrupolar coupling constant, χ, is very sensitive to changes in aggregation and solvation. From the magnitude of χ, it is often possible to deduce the aggregation state and also obtain information about the solvation regarding the number and type of donor atoms coordinating the lithium cation. Copyright © 2000 John Wiley & Sons, Ltd.

Combined spectroscopic and theoretical studies have been performed on two recently developed calix[4]arenes in the cone conformation, L1 (bearing two –CH2C(O)NEt2 and two –CH2P(O)Ph2 substituents occupying respectively distal phenolic positions) and L2 (with four –CH2P(O)Ph2 substituents), in order to compare the Li+vs. Na+ cation binding mode. Molecular dynamics simulations indicate that coordination of the Li+ cation involves three of the four substituents (the two phosphoryl groups and one of the two amide functions of L1; three phosphoryl arms of L2). A variable temperature NMR study carried out with L1·Li+ confirms this fourfold coordination and reveals that in solution the lithium cation moves between the two adjacent OPOPOamide units. The weaker binding of the Na+ cation results in a more symmetrical coordination of the four phenolic oxygen atoms and two carbonyls of L1 or four phosphoryls of L2.

The intramolecular [4 + 2] cycloaddition of imine 1 has been examined under a variety of conditions including thermal; catalysis by acid, lithium cation, and Florisil; and the use of 5.0 M lithium ...

We investigated the influence of the state of lithium cations in a nonaqueous electrolyte on lithium metal secondary cell performance. We used 1,2-dimethoxyethane (DME) mixed with ethylene carbonate (EC) as a mixed solvent and LiPF6 as a solute. The longest cycle life for a Li/LiMn1.9Co0.1O4 cell was provided by 1.0 mol dm−3 LiPF6 EC-mixed electrolyte containing 20 vol.% of DME. This is the same point at which the state of the lithium cations in the electrolyte changes as detected by 7 Li -NMR measurement. With this electrolyte composition, most of the DME selectively solvates the lithium cations. As the amount of non-solvating DME increases in the electrolyte, the cell cycle life becomes shorter.

A new triple vanadate LiCuFe 2 (VO 4 ) 3 was synthesized by a solid-state method. The compound is isotypic with mineral howardevansite, NaCuFe 2 (VO 4 ) 3 , and crystallizes in a triclinic system (space group P 1 (No. 2); a = 8.1484(5), b = 9.8024(7), c = 6.6355(4) A, α = 103.832(3), β = 102.353(3), γ = 106.975(3), V = 468.68 A 3 , Z = 2). Crystal structure of LiCuFe 2 (VO 4 ) 3 was refined by Rietveld method with R WP = 2.32%, R P = 1.76%, R I = 2.82%, S = 1.55, using X-ray diffraction. The crystal structure has five independent cation sites. Lithium cations are located in the cavities M (1)O 6 and M (5)O 10 , which form infinite chains in the [001] direction and are linked through a common face. The lithium cation in the M (1)O 6 cavity has a square planar coordination. The lithium cation in the M (5)O 10 cavity is strongly displaced up to 1.2 A from the special position (0, 0, 0.5) to a half-occupied general position (0.037, 0.087, 0.40).