Magnetic anisotropy in the excited states of low symmetry lanthanide complexes

Ab initio investigation of multiplet spectrum of lanthanides in archetypal coordination geometries shows an unexpected regular structure consisting of (i) mirror symmetry of anisotropic magnetic properties of doublet states, (ii) high magnetic axiality of low-lying and high-lying doublets, comparable to complexes with ideal axial symmetry, and (iii) the strong rotation of the anisotropy axes of individual doublets. The obtained high axiality of the ground doublet states explains the SMM behaviour of low-symmetry lanthanide complexes.     

NMR study of cation, anion, and solvent mobilities in macroporous poly(vinylidene fluoride)

The mobilities of lithium, PF6- and solvents in the electrolyte LiPF6-(ethylene carbonate-dimethyl carbonate-diethyl carbonate) were measured using the pulsed gradient spin-echo NMR. They were compared to those of the same electrolyte filling a macroporous poly(vinylidene fluoride) membrane. The conductivity decrease resulting in the incorporation of this macroporous membrane and the cationic transport number were analyzed in terms of (i) solvent/polymer and solvent/salt interactions, (ii) ionic dissociation, and (iii) tortuosity.     

Synthesis and transformations of 1-(1,3-butadien-1-yl)benzotriazoles

1-[α-(Phenylthio)alkyl]benzotriazoles were converted into the corresponding 1-(1,3-butadien-1-yl)benzotriazoles in good yields by one-pot sequential reactions with (i) lithium diisopropylamide, (ii) allyl bromide or cinnamyl chloride, and (iii) potassium t-butoxide. Diels-Alder and hetero [4 + 2] cycloadditions of 1-(1,3-butadien-1-yl)benzotriazoles and some transformations of their α-lithio derivatives were studied.     

Garnet-type Solid-state Electrolyte Li7La3Zr2O12: Crystal Structure,Element Doping and Interface Strategies for Solid-state Lithium Batteries

The continuous development of solid-state electrolytes(SSEs) has stimulated immense progress in the development of all-solid-state batteries(ASSBs). Particularly, garnet-typed SSEs in formula of Li₇La₃Zr₂O₁₂(LLZO) are under intensive investigation to exploit their advantage in high lithium ions conductivity(>1 mS/cm), wide electrochemical window(>5 V), and good chemical electrochemical stability for lithium, which are critical factors to ensure a stable, and high performance ASSBs. This review will focus on the challenges related to LLZOs-based electrolyte, and update the recent developments in structural design of LLZOs, which are discussed in three major sections:(i) crystal structure and the lithium-ion transport mechanism of LLZO; (ii) single-site and multi-site doping of Li sites, La sites and Zr sites to enhance Li ions conductivity(LIC) and stability of LLZO; (iii) interface strategies between electrodes and LLZO to decrease interface area-specific resistance(ASR).     

Isotope selective element analysis by diode laser atomic absorption spectrometry

The analytical figures of merit of isotope selective diode laser atomic absorption spectrometry (DLAAS) in low-pressure graphite furnaces are given for lithium and rubidium. While⁶Li and⁷Li were measured by Doppler-limited as well as by Doppler-free absorption spectroscopy of the 670.79 nm resonance line, Doppler-free saturation spectroscopy was applied for analysis of the⁸⁵Rb and⁸⁷Rb D2 resonance line at 780.03 nm. Three different modulation techniques were applied and compared: (i) intensity modulation, (ii) wavelength modulation, and (iii) a combination of intensity and wavelength modulation.     

Synthesis and characterization of poly([3H]-thiazole-2-thione)s

The reaction of dithiocarbamate salts with α-haloketones is extended to (i) dithiocarbamate salts with bis(α-haloketones), (ii) bis(dithiocarbamate salts) with α-haloketones, and (iii) bis(dithiocarbamate salts) with bis(α-haloketones). Both (i) and (ii) give bis([3H]-thiazole-2thiazole-2-thiones) in high yields, and (iii) gives the corresponding polymers which are described and characterized.     

Polymer migration in newtonian fluids

The theory of Freed and Edwards is used to investigate polymer migration in nonhomogeneous flow fields with confined geometry. Polymer migration from the main flow originates in three effects: (i) nonhomogeneous flow-field effect, (ii) the confined-geometry effect, and (iii) the concentration effect. General correlation function formulas for these three effects are explicitly derived. Some specific examples are illustrated and solved by using the harmonic dumbbell and Rouse–Zimm models.     

Deactivation pathways of ethylene polymerization catalysts derived from titanium and zirconium 1,3-bis(furyl)-1,1,3,3-tetramethyldisilazide complexes

The stoichiometric reaction between the previously described lithium amide salts, LiN(SiMe2R)2 [Li{i}, R = furyl, Li{ii}, R = 2-methylfuryl] and titanium(iv)chloride at low temperature afforded the mono-amide compounds Ti{i}Cl3 (1a) and Ti{ii}Cl3 (1b). The analogous zirconium derivatives Zr{i}Cl3 (3a) and Zr{ii}Cl3 (3b) were accessed via the reaction of excess trimethylsilylchloride with the mixed tetra-amide species, Zr{i}(NMe2)3 (2a) and Zr{ii}(NMe2)3 (2b). The bis-amide complexes Ti{ii}2Cl2 (4b), Zr{i}2Cl2 (5a) and Zr{ii}2Cl2 (5b) were synthesized in a straightforward salt metathesis reaction employing two equivalents of Li{i} or Li{ii} with the metal salts, MCl4(THF)2. The reactivity of the halide compounds 1 and 3-5 with a variety of alkylating agents was studied, with ligand transfer from the transition-element to the main group metal-alkyl reagent being the predominant reaction pathway. The reaction of 4b with MeLi was, however, partially successful affording the titanium(III) complex, Ti{ii}2X (X = Cl/Me, 6b'); this compound was subsequently made as the pure chloride from the reaction of two equivalents of Li{iii} with TiCl3(THF)3. The targeted dialkyl species, Ti{ii}Me2 (7b), was successfully isolated from the reaction between the dichloride 4b and dimethylmagnesium. The molecular structures of 1a, 1b, [3a]2 [3b]2, 4b, 5b and 6b have been solved using single-crystal X-ray diffraction techniques, indicating varying nuclearity of the complexes and hapticities for the amide ligands in the solid-state. The catalytic activity of selected complexes in the polymerization of ethylene is reported.     

Influence of adsorbed polar molecules on the electronic transport in a composite material Li(1.1)V3O8-PMMA for lithium batteries

The broadband dielectric spectroscopy (BDS) technique (40 to 10(10) Hz) is used here to measure the electronic transport across all observed size scales of a Li(1.1)V(3)O(8)-polymer-gel composite material for lithium batteries. Different electrical relaxations are evidenced, resulting from the polarizations at the different scales of the architecture: (i) atomic lattice (small-polaron hopping), (ii) particles, (iii) clusters of particles, and finally (iv) sample-current collector interface. A very good agreement with dc-conductivity measurements on a single macro-crystal [M. Onoda and I. Amemiya, J. Phys.: Condens. Matter, 2003, 15, 3079.] shows that the BDS technique does allow probing the bulk (intrinsic) electrical properties of a material in the form of a network of particles separated by boundaries in a composite. Moreover, this study highlights a lowering of the surface electronic conductivity of Li(1.1)V(3)O(8) particles upon adsorption of polar ethylene carbonate (EC) and propylene carbonate (PC) that trap surface polarons. This result is meaningful as EC and PC are typical constituents of a liquid electrolyte of lithium batteries. It is thus suggested that interactions between active material particles and the liquid electrolyte play a role in the electronic transport within composite electrodes used in a lithium battery.     

New developments and directions in the area of elastomers and rubberlike elasticity

There are number of important developments in the area of elastomeric polymers, including (i) network chains of controlled stiffness, (ii) model elastomers (including dangling-chain networks), (iii) fluorosiloxane elastomers, (iv) new thermoplastic elastomers, (v) other new elastomers, (v) bimodal network chain-length distributions, (vi) cross linking in solution or in a state of deformation, and (vii) gel collapse. Interesting elastomeric composites include those with (i) in-situ generated ceramic-like particles, (ii) ellipsoidal fillers, (iii) clay-like layered fillers, (iv) polyhedral oligomeric silsesquioxane (POSS) particles, (v) porous fillers, (vi) elastomeric domains modifying ceramics, and (vii) controlled interfaces. New characterization techniques are being developed for elastomers, and there have been new developments in elasticity theory and in elastomer processing. Some examples of societal aspects of relevance are (i) synthesis of elastomers in environmentally-friendly solvents, (ii) biosynthesis, (iii), recyclability, (iv) improved adhesion to tire cords, and (v) better barrier properties in anti-terrorism clothing. Educational topics include curriculum development, and mobile laboratories for elastomer experiments and demonstrations.     

Synthesis, characterization of silica gel phases-chemically immobilized-4-aminoantipyrene and applications in the solid phase extraction, preconcentration and potentiometric studies.

Two new 4-aminoantipyrene chemically-immobilized silica gel phases: ii (N,N-donor) and iii (N,O-donor), were synthesized and characterized by IR and surface coverage determination. The latter was accomplished by thermal desorption and metal probe methods, giving 0.300 and 0.312 mmol g(-1) for ii and 0.220 and 0.250 mmol g(-1) for iii. Moreover, potentiometric titration provided a surface coverage of 0.323 mmol g(-1) for ii. The metal capacity values in mmol g(-1) of ii, iii and the active silica gel phase i for a series of di- and trivalent metal ions were determined at pH 1.0 - 6.7. Phase i showed the lowest values, while ii and iii reflected higher affinity toward most of the metal ions. The highest values were 0.300 for Hg(II)-ii and 0.220 mmol g(-1) for Cd(II)-iii. Distribution coefficients (log Kd) were in the range of 3.57 - 4.76 for ii and 2.32 - 3.46 for iii, thus confirming certain selectivity characters of the solid extractors. The application of the phases as solid extractors and preconcentrators for some heavy metal ions is presented. Good percentage extraction and removal of 94 - 98 +/- 4 - 6% of the spiked 1.000 microg ml(-1) of Hg(II), Cd(II), Pb(II), Cu(II) and Zn(II) and good percentage recovery of 94 - 99 +/- 3 - 6% of 50 ng ml(-1) of these ions from tap water samples were obtained. Stability constants of H(I) and Cu(II) with ii for the two-phase mixture at 25 degrees C and I = 0.1 (KCI) were determined potentiometrically. The pKa of ii are 5.6 and 8.4, while the log K values for CuHL and CuL (L = ii) are 6.3 and 5.8, respectively, leading to the determination of several analytical data for Cu(II)-ii.     

Insertion reactions of silylenoid Ph2SiLi(OBu-t) into X-H bonds (X = F, OH, and NH2)

The insertion reactions of silylenoid [(tert-butoxy)diphenylsilyl]lithium Ph(2)SiLi(OBu-t) into HF, H(2)O, and NH(3) molecules have been studied by using density functional theory at the B3LYP/6-31G(d) level. To better understand the reactivity of silylenoid Ph(2)SiLi(OBu-t), its two most stable isomers, the p-complex (1) and the three-membered ring (2), were selected for reactants. Natural bond orbital (NBO) analysis has been performed to study the effects of charge transfer and to understand the nature of different interactions between atoms or groups. The results indicate that (i) the insertion of Ph(2)SiLi(OBu-t) into X-H bond proceeds in a concerted manner via a three-membered-ring transition state to form substituted silane Ph(2)SiHX with dissociation of LiOBu-t; (ii) the activation barrier increases in the order of HF < H(2)O < NH(3), and the barrier heights of the 1 insertions are higher than those of the 2 insertions, respectively; (iii) both 1 and 2 display ambiphilic character in their insertion reactions.     

Possible Mechanisms of Intercalation

Recent knowledge of the kinetics and intercalation mechanisms are summarized and accompanied by examples of intercalation reactions of water and ethanol into anhydrous vanadyl phosphate and redox intercalation of alkali metal cations into vanadyl phosphate dihydrate. Three possible mechanisms of intercalation are presented which are based on: (i) a concept of exfoliation of layers; (ii) the formation of stages and randomly stacked layers; (iii) co-existence of intercalated and non-intercalated parts of crystals of the host separated by an advancing phase boundary. The corresponding kinetic curves are ascribed to mechanisms (ii) and (iii).     

Effects of isolated impurities on atom scattering from crystalline surfaces: Exact quantum-mechanical calculations

A recent method for time-dependent wavepacket scattering calculations is applied to He scattering from a Cu surface with isolated Ar impurities. Several effects are found: (i) broad tails superimposed on each diffraction spike; (ii) shallow impurity rainbow maxima; (iii) impurity—surface interference peaks. A sudden approximation is applied to the interpretation of the newly found features.     

Hydrothermal carbon-carbon bond formation and disproportionations of C1 aldehydes: formaldehyde and formic acid

Hydrothermal reaction pathways and kinetics of C1 (carbon-one) aldehydes, formaldehyde (HCHO) and formic acid (HCOOH = HOCHO), are studied at 225 degrees C without and with hydrochloric acid (HCl) up to 0.6 M (mol dm(-3)). Reactions unveiled are the following: (i) the self-disproportionation forming methanol and formic acid, a redox reaction between two formaldehydes, (ii) the cross-disproportionation forming methanol and carbonic acid, a redox reaction between formaldehyde and formic acid, and (iii) the acid-catalyzed C-C bond formation producing glycolic acid (HOCH2COOH) as a precursor of the simplest amino acid, glycine. Reaction iii is a hydrothermally induced chemical evolution step from C1 aldehydes, formaldehyde and formic acid. Disproportionations i and ii are found to proceed even without base catalysts unlike the classical Cannizzaro reaction. Acid catalyzes the self-disproportionation (i) and the C-C bond formation (iii), but retards the cross-disproportionation (ii). The rate constants of noncatalyzed and acid/base-catalyzed paths for reactions i, ii, and iii are given additively as 2 x 10(-4) + (2 x 10(-3))[H+], 10(-4) + 10(3)[OH-], and (2 x 10(-3))[H+] M(-1) s(-1), respectively; the concentrations of proton [H+] and hydroxide ion [OH-] are expressed in M. The rate constant of the noncatalytic (neutral) cross-disproportionation is 1 order of magnitude larger than that of the self-disproportionation. The reaction pathways are controlled on the basis of the kinetic analysis to make the glycolic acid and methanol productions dominant by tuning the concentrations of formaldehyde, formic acid, and HCl. The conversion to glycolic acid reaches approximately 90% when formaldehyde, HCl, and formic acid are mixed in the ratio of 1:2:17. The conversion of formaldehyde to methanol reaches approximately 80% when formic acid is added in excess to formaldehyde.     

Rational Lithium Salt Molecule Tuning for Fast Charging/Discharging Lithium Metal Battery

The electrolytes for lithium metal batteries (LMBs) are plagued by a low Li⁺ transference number (T₊) of conventional lithium salts and inability to form a stable solid electrolyte interphase (SEI). Here, we synthesized a self-folded lithium salt, lithium 2-[2-(2-methoxy ethoxy)ethoxy]ethanesulfonyl(trifluoromethanesulfonyl) imide (LiETFSI), and comparatively studied with its structure analogue, lithium 1,1,1-trifluoro-N-[2-[2-(2-methoxyethoxy)ethoxy)]ethyl]methanesulfonamide (LiFEA). The special anion chemistry imparts the following new characteristics: i) In both LiFEA and LiETFSI, the ethylene oxide moiety efficiently captures Li⁺, resulting in a self-folded structure and high T₊ around 0.8. ii) For LiFEA, a Li−N bond (2.069 Å) is revealed by single crystal X-ray diffraction, indicating that the FEA anion possesses a high donor number (DN) and thus an intensive interphase “self-cleaning” function for an ultra-thin and compact SEI. iii) Starting from LiFEA, an electron-withdrawing sulfone group is introduced near the N atom. The distance of Li−N is tuned from 2.069 Å in LiFEA to 4.367 Å in LiETFSI. This alteration enhances ionic separation, achieves a more balanced DN, and tunes the self-cleaning intensity for a reinforced SEI. Consequently, the fast charging/discharging capability of LMBs is progressively improved. This rationally tuned anion chemistry reshapes the interactions among Li⁺, anions, and solvents, presenting new prospects for advanced LMBs.     

Expert system for nuclide identification and interpretation of gamma-spectrum analysis

Trace element data (Sc, Cr, Co, Hf, Ta and Th) are reported for a weathering profile of gabbroic rocks located near Serpa, Portugal. The results obtained for the whole rock samples showed that: (i) Co and Sc contents decrease upwards the profile. Co appears to be mobilized in the soil probably as soluble cation; (ii) Cr tends to remain in the profile; and (iii) Hf and Th concentrate in the upper horizons. Trace element distribution in different size fractions of the upper horizons revealed: (i) Sc, Cr and Co have a more uniform distribution than Hf, Ta and Th; (ii) Hf and Ta are concentrated in the intermediate fractions; and (iii) Th is concentrated in the finer fractions, probably due to incorporation in weathering resistant minerals, specially in the initial stages of weathering.     

Synthesis of chromogenic crown ethers and liquid-liquid extraction of alkali metal ions

New crown ethers carrying a pendent phenolic chromophore were synthesized. These crown ethers, on dissociation of the phenolic proton, provide lipophilic anions which can extract alkali metal cations into 1,2-dichloroethane by forming highly-colored uncharged metal complexes. Structural effects on the extraction were studied for possible use of these crown ethers as extraction—spectrophotometric reagents selective for alkali metals. The following factors are discussed in detail: (i) nature of the crown ether ring (ring size. aza-crown or standard crown ether), (ii) nature of the pendent phenolic group, and (iii) geometry between the crown ether center and pendent phenolic group. 15-Crown-5 or smaller ring-sized reagents favored the extraction of lithium ion when the basicity of the pendent phenolate was relatively high and a six-membered “chelate” ring was possible for the phenolate and the crown ether-bound metal. 15-Crown-5 type reagents were sodium-selective when an eight-membered “chelate” ring was possible between the phenolate and the crown ether-bound metal. 18-Crown-6 type reagents were generally potassium-selective. However, these selectivities were not absolute, and other structural parameters, steric and conformational, must be considered to explain in detail the selectivities of the individual reagents.     

Stereoselective synthesis of protected (2S,3S)-N-methyl-5-hydroxyisoleucine, a component of halipeptins

The stereocontrolled synthesis of the protected (2S,3S)-N-methyl-5-hydroxyisoleucine, a component of halipeptins A and B with potent anti-inflammatory activity, has been achieved. The key steps include (i) installation of a double bond to bicyclic lactam 4 using N-tert-butyl phenylsulfinimidoyl chloride, (ii) highly exo-selective Michael reaction with lithium dimethylcuprate in the presence of chlorotrimethylsilane, and (iii) Ru-catalyzed oxidative deprotection of N,O-benzylidene acetal to the acid anhydride.     

Addition d'un polymère “flexible” la polyvinylpyrrolidone à des solutions aqueuses mésomorphes d'un polymère semirigide l'hydroxypropylcellulose

Mesomorphic solutions of a semi-rigid polymer, hydroxypropylcellulose in water, have been studied; the effects of the replacement of a part of the solvent by a flexible polymer, polyvinylpyrrolidone, have also been investigated. The principal effects are (i) lowering of the critical concentration of onset of the anisotropic phase, (ii) raising of the temperature of appearance of the “gel”, (iii) decrease of the pitch of the cholesteric structure. Investigations on different molecular weights of PVP seem to show a modification of the mesomorphic phase in the blend without demixing.