Search

The activation energy involved in the Li+ ion conduction in NASICON materials of composition LiMM'(PO4)3; M, M' = Ge, Ti, Sn, Hf was investigated using electrical conductivity measurements. Two lithium sites inside the conduction channels can be identified and are joined through triangular bottlenecks of oxygen atoms. The size of the bottleneck was calculated from refined and simulated structures for each composition. Two regimes exist as shown by the plot of activation energy versus bottleneck size.

The interactions of protons and Li+ with Hzub2Osub3 or Hsub2O/Osub2 are reported, including equilibrium structure, interactions of Hsub2OLi+ with Osub2 and Osub2Li+ with Hsub2O. The aim was to interpret experimental topics on lithium ion links to the Hsub2Osub3 species in the gas phase, which is important in the future development of the Li+ ion attachment/mass spectrometry method for Hsub2Osub3 detection.

A detailed NMR investigation of alpha-heterosubstituted chloroethyllithiums in tetrahydrocortisol was conducted. The generation and NMR study results of (2-(alpha-chloroethyl)benzothiazolyl)lithium and (4,4-dimethyl-2-(alpha-chloroethyl)oxazolinyl)lithium are described. Semiempirical calculations were also included to complement and support the NMR results.

Research was conducted to examine chelated lithium phenolates using NMR and X-ray spectrometry. Lithium phenolates with carbonyl functionalities in both the 2 and 6 positions enabled the metal to chelate to two oxygens. It was also observed through dynamic NMR that lithium has the ability to oscillate between the two chelating sites. Results indicate that lithium is static toward oscillation and that lithium phenolates form dimeric or tetrameric aggregates having a trigonal or a tetrahedral metal geometry.

Asymmetric deprotonation-substitution pathway provides products with high enantioselectivities in replacements of prochiral methylene protons with carbon-carbon bonds. Analyses of this pathway show that either enantiomer of products with one or two new carbon-carbon bonds can be obtained by proper choice of the electrophile or by use of lithiation-substitution-lithiation sequences. The electrophile-dependent stereochemistry of the reactions of the configurationally stable organolithium intermediates were analyzed through the assignment of absolute configurations.

A study was conducted on the performance of an optical parametric generator. The type-II phase-matched device employs a lithium triborate crystal pumped at 266 nm. A narrow linewidth signal of 0.1 nm with excellent spatial quality at 326.7 nm was achieved with the device without diffractive optics. The optical parametric generator has potential applications in vacuum ultraviolet plasma laser injection seeding.

The solvation of the Li+-Br--Li+ triple ion with oxygen-donor Lewis bases was investigated in the gas phase through Fourier-transform ion cyclotron resonance spectrometry. In every step of solvation, vibrational predissociation competed with the association processes. The association-to-predissociation branching ratio varied with the salt binding energy, solvent binding energy, heat capacity, steric hindrance, and conformational change of solvent.

Comparison of the carbonyl-carbon kinetic isotope effect (KIE) and its substituent effect of the reaction of lithium penacolone enolate with benzaldehyde and that for other lithium reagents reveal that electron transfer is not involved during the reaction of lithium penacolone enolate with benzaldehyde. The primary KIE and its subsequen effect as well as chemical probe experiments indicate that a polar mechanism governs the reaction of lithium penacolone enolate with benzaldehyde. Results also indicate a mechanistic gap between lithium and the other reagents.

Chemical research has established a method of synthesizing new iminophosphide/phosphinoamide anions from the deprotonation of aminodiphenylphosphines. The chemical structures of iminophosphide/phosphinoamide ions lithium (meopentyl)(diphenylphosphino)amide, lithium(isopropyl)(diphenylphosphino)amide and lithium (2,4,6-tri-tert-butylphenyl)(diphenylphosphino)amide are described.

A method of dilute-melt proton exchange employing a mixture of glycerol and [KHS0.sub.4] with lithium benzoate added is used to fabricate planar waveguides in c-cut LiNb[O.sub.3]. With this exchange melt system the waveguide refractive-index profiles can be fabricated with a high degree of reproducibility. In contrast with the traditional dilute-melt method, which uses benzoic acid and lithium benzoate, the need for sealed containers during the exchange process can be avoided when the glycerol, [KHSO.sub.4], and lithium benzoate system is used for the exchange process. A new characterization method for determining the waveguide refractive-index profile from the measured-mode indexes is introduced. The main advantage of this characterization method compared with other methods is that it also applies to single-mode waveguides. Using the new characterization method, we investigate in detail the relation between waveguide refractive-index change and composition of this glycerol, [KHSO.sub.4] and lithium benzoate exchange melt system. Key words: Planar waveguides, lithium niobate, proton exchange.

Chemical research has established a method of creating the novel lithium amide LiN(SiMe2CH2NMe2)2 using NH3, silylamine Me2NSiMe2CH2NMe2 and butyllithium. The lithium amide dimer reacts with a series of group four starting halides, MCL4, to produce the complexes MCl3[N(SiMe2CH2NMe2)2]. Each trihalide structure is described.

Aggregation and solvation studies on dehydrobrominations of (+-)-2-exo-bromonorbornane (RBr) by lithium diisopropylamide (LDA) shows that LDA/nBuOMe eliminates RBr through the deaggregation of disolvated dimers via a monosolvated monomer transition structure such as (i-Pr2NLi.n-BuOMe.RBr). The presence of a universal ground state is highly unlikely under usual conditions. The relative merits of LDA-mediated dehydrobrominations using chelating ligands in the monomeric fragment of LDA are discussed.

Sodium bis(trimethylsilyl)amide (NaN(SiMe3)2) and lithium diisopropylamide (LiN(i-Pr)2) were utilized for the demethylation, debenzylation and demethynelation of alkyl aryl ethers. The utilization of Nan(SiMe3)2 and LiN(i-Pr)2 as nucleophiles for omicron-demethylations led to the efficient deprotection of aryl methyl ethers and benzodioxoles. The debenzylation of aryl benzyl ethers by LiN(i-Pr)2 also exhibited higher nucleophilicity compared to deprotection reactions involving NaN(SiMe3)2.

The reaction pathways of the polymetallic lithium organocuprate clusters reacting with C-C multiple bonds were established through ab initio molecular orbital and density functional methods. Results have shown that the C-C bond forming reaction was insensitive to the difference of cluster sttructures. Lithium organocuprate clusters have a built-in function to mediate carbocuprate reactions, which was lacking in noncluster copper reagents.

Observers have found a small number of lithium-depleted halo stars in the temperature range of the Spite plateau. The current status of the mass-loss hypothesis for producing the observed lithium dip in Population (Pop) I stars is briefly discussed and extended to Pop II stars as a possible explanation for these halo objects. Based on detections of F-type main-sequence variables, mass loss is assumed to occur in a narrow temperature region corresponding to this 'instability strip.' As Pop II main-sequence stars evolve to the blue, they enter this narrow temperature region, then move back through the lower temperature area of the Spite plateau. If 0.05 [M.sub.[circle dot]] (solar mass) or more have been lost, they will show lithium depletion. This hypothesis affects the lithium-to-beryllium abundance, the ratio of high- to low-lithium stars, and the luminosity function. Constraints on the mass-loss hypothesis due to these effects are discussed. Finally, mass loss in this temperature range would operate in stars near the turnoff of metal-poor globular clusters, resulting in apparent ages 2 to 3 Gyr (gigayears) older than they actually are.

Rats acquired conditioned aversion to the context in which they received injections of lithium chloride (LiCl). This context conditioning blocked acquisition of an aversion to sucrose, when sucrose was injected in the home cage, then LiCl was administered after the rats were transferred to the context. Blocking was associated with cues related to the particular place, not to cues such as transportation or time of day. This series of experiments confirms and extends the results of Best et al (1984), and additional implications are also discussed.

Lithium compounds have possible applications as cathode materials for batteries. Layered lithium molybdate has zig-zag molybdenum chains inside its MoO2 layers, as is shown from total neutron scattering. Strong metal-metal bonds are indicated by the shortness of the lengths along the zig-zag. Radial correlation functions can be calculated using diffraction data. Total neutron scattering is a useful check, since methods using Bragg scattering may not always give useful results.

Nuclear magnetic resonance spectroscopy and chromatography were done to study the effect of alkenyllithium treatment on squarate esters. The results revealed that squarate esters enter into cascade processes involving a dianionic oxy-Cope rearrangement during treatment with the organometallic reagent. Such substitution was found to proceed only when two alkenyllithium reagents are added cis to each other, a kinetic bias which can be achieved by the proper incorporation of ethereal oxygen substituents in the first organometallic reagent.

The solid-state structure of Lewis base-free, sigma-bonded lithium aryls that are not sterically encumbered by ortho-substituents was determined using nuclear magnetic resonance (NMR) spectroscopy and X-ray crystallography. The NMR results indicated an association number of at least four in solution, a finding that is in agreement with the hexameric structure of one the aryls which also bears a distorted octahedral array of lithium ions as determined by X-ray crystallography. Six of the eight lithium faces were found to be capped by an aryl group that interacts primarily through the C(ipso) atom. Weaker Li-C(ortho) interactions were likewise observed.

The x-ray crystal structures of lithiated polar acetylides and nonlithiated acetylenes of the type featuring electrostatic alkali cation pi-interactions were investigated using an x-ray diffractometer and ab initio calculations. The acetylides considered were of the type Li-C=C-SiMe2-C6H4-OMe while the acetylenes considered were of the type Li-O-CMe2-C=C-H. The results showed the dependence of the degree of pi-interactions on the alkali cation size.

The short Li-C distances in the X-ray crystal structure of (Li-O-C(Me)-(c-CHCH2CH2)2)6 (7)6 is a unique feature of Li-cyclopropane edge coordinations. The Li-cyclopropane interactions increase the C2-C3 distances compared to those of the free cyclopropyl edges by 0.02 angstroms. The bent bonds of cyclopropane produce an electrostatic potential pattern which strongly favors edge coordination while allowing a metastable Li+ face complex.

Lithium, one of the most effective drugs for the treatment of bipolar (manic-depressive) disorder, also has dramatic effects on morphogenesis in the early development of numerous organisms. How lithium exerts these diverse effects is unclear, but the favored hypothesis is that lithium acts through inhibition of inositol monophosphatase (IMPase). We show here that complete inhibition of IMPase has no effect on the morphogenesis of Xenopus embryos and present a different hypothesis to explain the broad action of lithium. Our results suggest that lithium acts through inhibition of glycogen synthase kinase-3[Beta] (GSK-3[Beta]), which regulates cell fate determination in diverse organisms including Dictyostelium, Drosophila, and Xenopus. Lithium potently inhibits GSK-3[Beta] activity ([K.sub.i] = 2 mM), but is not a general inhibitor of other protein kinases. In support of this hypothesis, lithium treatment phenocopies loss of GSK-3[Beta] function in Xenopus and Dictyostelium. These observations help explain the effect of lithium on cell-fate determination and could provide insights into the pathogenesis and treatment of bipolar disorder.

The synthesis, crystal structures and solution dynamics of dilithiated N,N'-bis(trimethylsilyl)ethylenediamine complexes are studied using crystallography and NMR spectroscopy. The dimeric diethyl ether adduct, (Li(N(SiMe3)CH2CH2NSiMe3)Li.OEt2)2, undergoes an exchange process that involves an equilibrium between unsolvated and solvated dimers. The trimer, (Li(N(SiMe3)CH2CH2NSiMe3)Li)3, exists in equilibrium between the dimeric and trimeric forms. Fluxional processes in the trimer involve intermolecular distortion of the Li6Ni6 cage structure.

The 6Li-(13C)-heteronuclear multiple quantum coherence-total correlation spectroscopy distinguishes lithioorganic cyclic dimers and trimers by lifting the degeneracy at Li sites. The two Li sites in a 13C isotopomer of a dimer are equivalent and show a pair of cross-peaks at the chemical shift of Li signal. The Li nuclei, at a distance from 13C, does not show 6Li-13C coupling in trimers. The resonance line of this Li appears between the two lines of 13C bound-6Li nucleus. In the trimers, magnetization transfer from 13C-bound 6Li to 12C-bound region produces a third cross peak.

The thermal stability of vinylic organolithium compounds obtained from secondary aliphatic allylamines was investigated. The results revealed that when such complexes are subjected to heating at reflux of tetrahydrofuran, dimerization or cyclodimerization occurs to yield diamino 1,4-dienes or cis-2,3-disubstituted 4-methylenepyrrolidines, respectively. In contrast, the corresponding 1,3-dilithio derivatives prepared from aromatic allylamines undergo solvent-induced protonation.

Ab initio computations of gas phase reactions are carried out for fluorophenyl, phenyl, and chlorophenyl derivatives of alkali metals. The calculations are contrasted with the experimental substituent effects on the pK of benzene whereas the linear relationship of the calculations for each alkali metal, is also determined. Dichloro derivatives do not exhibit the same additivity of substituent effects excellently shown by (difluorophenyl)lithiums. This is attributed to mutual polarization of chlorine that results to weaker inductive effect in polychloro compounds.

The cesium and lithium ion pair equilibrium acidities of six polychlorobenzenes and polyfluorobenzenes were measured in THF at -20 degrees C. The negative effects of fluorine on the partial equilibrium factors, pK, for both fluorinated and chlorinated benzenes are consistent with the experimental data although the former have more precise values. The additive effects for o-, m-, and p-benzene and chlorine are 5.2, 3.0, 1.4 and 4.2, 2.7, and 2.1, respectively. The data permit the extrapolation of the pK values of benzene and chlorine at 44.8 and 47.0, repectively.

The establishment of conditioned taste avoidance (CTA) associated with morphine and lithium is attenuated by administration of ibogaine, which has been reported to reduce craving for addictive substances such as morphine, cocaine, alcohol and nicotine. Ibogaine administered 22 hours before conditioning trials interfered with CTA induced by morphine and lithium. The same effect was not produced by exposure to morphine or lithium 22 hours before the conditioning trials, indicating that the effect is due to ibogaine rather than a nonspecific drug pre-exposure. Ibogaine may inhibit learning by acting as an N-methyl-D-aspartate (NMDA) receptor antagonist.

Lithium is the treatment of choice for manic depression, but therapy often results in nephrogenic diabetes insipidus and lithium intoxication. To investigate the effects of dietary potassium on potential side effects of lithium therapy, a mathematical model was built using the modeling program SAAM (Simulation, Analysis, And Modeling). Experimental data modeled were from adult male Sprague-Dawley rats fed diets with or without lithium and one of three levels of potassium for 17 d. A five-compartment model of lithium dynamics was built that was consistent with data from rats fed a lithium-containing diet adequate in potassium. This model was then compared with data from rats fed the other two lithium-containing diets. The model predicts that both the fractional transfer coefficient and rate of transport of lithium to the serum compartment from the kidney compartment are lower in rats fed the potassium-adequate diet than in those fed the potassium-deficient diet, and even lower in those fed the potassium-supplemented diet. In addition, fractional transfer coefficients into the serum compartment from the sampled and simulated tissue compartments changed differently with time depending on the amount of dietary potassium. The model also predicts that there would be less accumulation of lithium in the kidney, sampled tissue and simulated tissue compartments with supplemental dietary potassium. The model suggests that potassium supplementation, after a 7-d delay, protects against nephrogenic diabetes insipidus and the potentially toxic accumulation of lithium by decreasing the reabsorption of lithium from the kidneys and increasing lithium efflux from the tissues. J. Nutr. 126: 1445-1454, 1996. INDEXING KEY WORDS: * lithium dynamics * potassium * compartmental analysis * rats * mathematical modeling

The equilibrium geometries of alkali metal pseudohalides LiOCP, NaOCP, LiSCP and NaSCP, determined at the MP2 and QCISD levels of theory, show that the four complexes exhibit pi-type cyclic conformations. LiOCP and NaOCP have one linear and one cyclic stable isomers each with the cyclic pi-complex as the global minimum whereas LiSCP and NaSCP both have cyclic conformations. The structural behavior in solution is also investigated by semiempirical quantum chemical and molecular mechanics simulations.

Bromodimethylborane reacts with 2-lithiopyridine to yield lithium dimethylbis(2-pyridyl)borate, Li(py)2BMe2, which subsequently hydrolyzes to hydrogen dimethylbis(2-pyridyl)borate, H(py)2BMe2. Li(py)2BMe2 reacts with bromodimethylborane or bromodiphenylborane to form tricyclic bis(organo)boronium dimethylbis(2-pyridyl)borate species. H(py)2BMe reacts with zinc(II) chloride or nickel(II) chloride hexahydrate to produce the pseudotetrahedral bis(dimethylbis 2-pyridyl borato-N,N')zinc(II) or square planar bis(dimethylbis 2-pyridyl borato-N,N')nickel(II), respectively.

The octabrominated porphyrin OBT(4-N-MePy)P2+, the deprotonated form at of 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(N-methylpyridinium-4-yl)po rphyrin, is reportedly the most acidic porphyrin in aqueous solution. The electronic structure signifies agitations due to the combined effects of octabromination and four N-methylpyridiniumyl groups. At a pH of more than 10, protons do not vie for the inner nitrogen sites thus enabling formation of stable complexes by the weak binding metal ions. Li+ binds to the porphyrin in a 1:1 stoichiometry in aqueous solution and at pH > 9.

The lithium and cesium ion pair acidities and aggregation states of 4-ethynylbiphenyl, 3,3,3-triphenylpropyne and 1-ethynyladamantane in solutions of tetrahydrofuran have been investigated. The results showed the relatively minor influence of the electronic effects of the substituents on the acidity of acetylenes.

Nuclear magnetic resonance spectroscopic studies of lithium hexamethyldisilazide (LiHMDS) with monodentate ethereal ligand solvation is reviewed to examine a similar solvation process but with monodentate amines. Disolvated monomer stabilization was attributed to high steric demands of splaying alkyl groups on trialkylamines. LiHMDS monomer stabilization exhibited behavior similar to hydrocarbon dependence involving oligomer distribution.

The structures of aggregates composed of lithium halides with either lithium amides or lithium enolates are studied by X-ray crystallography. Solvated heterodimers and heterotrimers are the two kinds of structures found. Two compounds which have both lithium halide and lithium enolate have also been identified as heterodimers. A reaction sequence for enolization and subsequent aldol addition reaction involving halide-containing aggregates is suggested.

The lithiation reactions and alpha-silyl lithiation selectivity in two metalated glucals have been investigated. The results showed that 3,4,6-tris-O-(tert-butyldimethylsilyl)-D-glucal is lithiated predominantly on the C6 TBDMSO group while 3,4-bis-O-(tert-butyldimethylsilyl)6-deoxy-L-glucal exhibited facile and efficient lithiation on the C1 TBDMSO group.

Lithium can be inserted reversibly within most carbonaceous materials. The physical mechanism for this insertion depends on the carbon type. Lithium intercalates in layered carbons such as graphite, and it adsorbs on the surfaces of single carbon layers in nongraphitizable hard carbons. Lithium also appears to reversibly bind near hydrogen atoms in carbonaceous materials containing substantial hydrogen, which are made by heating organic precursors to temperatures near 700'C. Each of these three classes of materials appears suitable for use in advanced lithium batteries., There are hundreds of commercially available carbon types, including natural and synthetic graphites, carbon blacks, active carbons, carbon fibers, cokes, and a wide variety of other materials prepared by the [...]

The 1H-NMR spectroscopic analysis shows that (OEC-4-P)Li4 retains the alkyllithium and other lithiated functions even after the original (OEC-4-P)Li4(t-BuLi)2 was refluxed and dissoluted. The high Lewis acidity of the alkali cation mediates the coordination geometry of the carbon atom of (OEC-4-P)Li4(t-BuLi)2 complex. The synthesis of (OEC-4-P)Li4(t-BuLi)2 and (cyclohexyl2NLi)4 is discussed.

Characteristics of pulsed X-ray induced transient absorption at 1061 nm have been determined for LiNb[O.sub.3], Ti[O.sub.2]:LiNb[O.sub.3], and MgO:LiNb[O.sub.3]. The addition of the dopants Ti[O.sub.2] and MgO reduces the induced absorption significantly. The two materials, LiNb[O.sub.3] and Ti[O.sub.2]:LiNb[O.sub.3], decay with an approximate 1/[t.sup.1/4] time dependence for the time interval 0.01 to 8 ms. After 8 ms, the decay rate for LiNb[O.sub.3] is faster than [1/t.sup.1/4], and the decay rate for Ti[O.sub.2]:LiNb[O.sub.3] is slower than that initial rate. A low-intensity absorption which lasts for about 20 [[micro]second] is observed for the MgO:LiNb[O.sub.3]. Peak radiation-induced absorption coefficients for LiNb[O.sub.3], Ti[O.sub.2]:LiNb[O.sub.3], and MgO:LiNb[O.sub.3] have been determined.

Alpha-aryl-alpha-(2,3,4,5,6 pentachlorophenyl) acetonitriles and alpha-aryl-alpha-(2,3,5,6-tetrachlorophenyl)acetonitriles are formed by the reaction of alpha-arylacetonitriles (4) with (pentachlorophenyl)lithium (2) and hexachlorobenzene under mild conditions. Experimental results indicate that the process involves condensation of 2 and 4 by a four-centered transition state. Alkenes are provided by a base-controlled dimerization of alpha-chloro-alpha-arylacetonitriles formed by lithium-chlorine exchange between 2 and 4.

Research with 25 healthy volunteers revealed that endogenous lithium clearance, C(sub Li), when used to assess renal tubular sodium reabsorption, eliminates the need for lithium tablets. Results showed dietary sodium intake should be taken into account in studies of endogenous C(sub Li). Drinking water sources may also need to be accounted for, since renal lithium clearance is not independent of serum concentration.

Splitting total hydrogen (H) into optically active substitutional H and optically inactive interstitial H establishes a linear correlation between the H concentration and the refractive index in proton-exchanged lithium niobate. Optical prism-coupling measurements and numerical simulations of refractive index profiles suggest that effective index diffusivity is almost equal to diffusivity of substitution H.

Experimental studies indicate that lithiation of 1-isopropylbenzotriazole occurs at three positions in the benzene ring, while 2-isopropylbenzotriazole undergoes lithiation only at the alpha-CH of the isopropyl group. Lithiation of 1-methyl- and 1-ethylbenzotriazole occurs both in the benzene ring and at the alpha-CH. Gas chromatography/mass spectrometry help characterize the lithiated products and the experimental data help suggest mechanisms for lithiation.

Semiempirical MNDO calculations help analyze the metalation of ketones and N-alkylimines with and without the chelating NR2 moieties and the reaction pathways involving open dimer fragments of amides. Solvent dissociation and opening of the dimer ring during the open dimer transition, and deggregation during transition involving monomers helps meet the steric requirements of the solvent reactants. These calculations help understand the Syn effect, E/Z selectivity of ketone enolization, the effect of internal ligands and lowered N-alkylimine acidities.

Experimental studies indicate that both dimethyl dioxirane and Davis oxaziridine reagent are capable of alpha-oxygenating camphor-derived unsaturated ketones. Reaction of the MOM derivatives of these ketones with cyclohexenyllithium reagents, followed by anion oxy-Cope rearrangement produces tricyclic products. The C-2, C-9, C-10 B-ring oxygenation pattern of these derivatives is similar to that in taxol.

Analysis of the reaction of lithium diisopropylamide (LDA) with a geminal dichloride and a geminal diiodide indicates the involvement of a single electron transfer route in the reaction of the germinal diiodide. Geminal diiodide has more favorable reduction potential than geminal dichloride, and product analysis indicates the ability of LDA to function as a one-electron donor in the reaction with geminal diiodide.

Application of ab initio calculations predicts monomeric lithioboranes and their dimethyl, diamino and difluoro derivatives to have classical structures. The lithium-boron bond is significantly covalent while lithioboranes are moderately polar, being stabilized by electronegative substituents. Dihydroxylithioborane is most stable when a lithium cation bridges one boron oxygen bond. Formaldehyde is added to lithioboranes via a nucleophilic attack at a boryl anion, giving three membered B-C-O ring products.