Enhanced Li+ binding energies of some azines: a molecular orbital study

Summary Hartree-Fock calculations with the 6–31G* basis have been performed to investigate the structure and Li⁺ binding energies of the complexes between Li⁺ and pyridine, diazines, triazines and tetrazines. Structures have been fully optimized at the 3–21G level. As for azole-Li⁺ and methyldiazole-Li⁺ complexes, a topological analysis of the Laplacian of the electronic charge density reveals that the azine-Li⁺ is a typical closed-shell interaction and that the stabilization of the complex is mainly electrostatic. BSSE is quite significant, specially for Li⁺-bridging complexes. The correlation between calculated Li⁺ binding energies and proton affinities follows two different linear relationships, one for those cases where Li⁺ is singly coordinated and a different one for those cases in which an additional three-membered ring is formed. The enhanced stability of these particular conformations explains why while polyazines are less basic than pyridine when the reference acid is a proton; pyridazine and 1,2,4 triazine are more basic than pyridine when the reference acid is Li⁺. The effect on Li⁺ binding energies of systematic nitrogen substitution roughly follows an additive model.     

The Synthesis of Dibenzo[3n]crown-n by Novel Methods and their Cation Binding Studied by Fluorescence Spectroscopy. Part IV

The dibenzo[3n]crown-n were synthesised from1,2-bis(o-hydroxyphenoxy)ethane obtained from 1,2-bis(o-formylphenoxy)ethane via Bayer-Willigeroxidations with H₂O₂/CH₃COOH in good yields. The cyclic condensation of 1,2-bis(o-hydroxyphenoxy)ethanewith dichlorides, and ditosylates of polyethylene glycols in DMF/Me₂CO₃ gave the macrocyclesdibenzo[15]crown-5, dibenzo[18]crown-6, dibenzo[21]crown-7 anddibenzo[24]crown-8. The structures were identified using IR, mass, ¹H and ¹³C NMR spectroscopy. Therecognition of the molecules for the cations, Li⁺, Na⁺, K⁺, Rb⁺ and Zn²⁺were conducted quantitatively with steady state fluorescencespectroscopy. The 1:1 association constants in acetonitrileshowed a good relation of the appropriate size of the macrocyclic ether towards the fitting cationradii. Namely, dibenzo[15]crown-5 was the best for Li⁺ binding and more than 100 times better thanNa⁺ and K⁺. Dibenzo[21]crown-7 was excellent for Rb⁺ binding while K⁺ is 100 timesless preferred. The largest crown ether studied, dibenzo[24]crown-8, exhibited the order of binding power,Rb⁺ > K⁺ > Na⁺. Zn²⁺ displayed, however, a marked binding with only dibenzo[18]crown-6.p>     

Structural and dynamical aspects of PEG/LiClO4 in solvent mixtures via NMR spectroscopy

Motivated by the potential usefulness of polyethylene glycol (PEG)/Li⁺ salt mixtures in several industrial applications, we investigated the structure and dynamics of PEG/LiClO₄ mixtures in D₂O and its mixtures with CD₃CN and DMSO-d₆, in a series of PEG-based polymers with a wide variation in their molecular weights. ¹H NMR chemical shifts, T₁/T₂ relaxation rates, pulsed-field gradient NMR diffusion experiments, and 2D HOESY NMR studies have been performed to understand the structural and dynamical aspects of these mixtures. Increasing the temperature of the medium results in a significant perturbation in the H-bonded structure of PEG in its PEG/LiClO₄/D₂O mixtures as observed from the increase in chemical shifts. On the other hand, the addition of molecular cosolvents has a negligible effect. The hydrodynamic structure of PEG shows a pronounced variation at low temperature with increasing molecular weight, which, however, disappears at higher temperatures. Increasing the temperature leads to a decrease in the hydrodynamic structure of PEG, which can be explained on the basis of solvation–desolvation phenomena. The 2D HOESY NMR spectra reveal a new finding of Li⁺-water binding in the PEG/LiClO₄/D₂O mixtures with the addition of molecular solvents, suggesting that the Li⁺ cation diffuses freely in the D₂O mixtures of polymers as compared with the polymer mixtures with DMSO or CD₃CN.     

钙钛矿结构荧光材料MZrO3:Eu3+,A (M=Ca2+, Ba2+; A=Li+, Na+, K+)的制备及其发光性质

Calcium and barium zirconate powders based upon CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) were prepared by combustion synthesis method and heating to ~1000℃ to improve crystallinity.The structure and morphology of materials were examined by X-ray diffraction (XRD) and scanningelectron microscopy (SEM). XRD results showed that CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) perovskites possessed orthorhombic and cubic structures, respectively. The morphologies of all powderswere very similar consisting of small, coagulated, cubical particles with narrow size distributions andsmooth and regular surfaces. The characteristic luminescences of Eu³⁺ ions in CaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) lattices were present with strong emissions at 614 and 625 nm for ⁵D₀→⁷F₂ transitions with other weakeremissions observed at 575, 592, 655, and 701 nm corresponding to ⁵D₀→⁷F_n transitions (where n=0, 1, 3, 4 respectively). In BaZrO₃:Eu³⁺ both the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at 595 and 613 nm were strong.Photoluminescence intensities of CaZrO₃:Eu³⁺ samples were higher than those of BaZrO₃:Eu³⁺ lattices. Thisremarkable increase of photoluminescence intensity (corresponding to ⁵D₀→⁷F_n transitions) was observedin CaZrO₃:Eu³⁺ and BaZrO₃:Eu³⁺ if co-doped with Li⁺ ions. An additional broad band composed of manypeaks between 440 to 575 nm was observed in BaZrO₃:Eu³⁺,,A samples. The intensity of this band wasgreatest in Li⁺ co-doped samples and lowest for K⁺ doped samples.     

Robust Inclusion Complexes of Crown Ether Fused Tetrathiafulvalenes with Li+@C60 to Afford Efficient Photodriven Charge Separation

Inclusion complexes of benzo‐ and dithiabenzo‐crown ether functionalized monopyrrolotetrathiafulvalene (MPTTF) molecules were formed with Li⁺@C₆₀ ( 1? Li⁺@C₆₀ and 2? Li⁺@C₆₀). The strong complexation has been quantified by high binding constants that exceed 10⁶ M ^?1 obtained by UV/Vis titrations in benzonitrile (PhCN) at room temperature. On the basis of DFT studies at the B3LYP/6‐311G(d,p) level, the orbital interactions between the crown ether moieties and the π surface of the fullerene together with the endohedral Li⁺ have a crucial role in robust complex formation. Interestingly, complexation of Li⁺@C₆₀ with crown ethers accelerates the intersystem crossing upon photoexcitation of the complex, thereby yielding ³(Li⁺@C₆₀)*, when no charge separation by means of ¹Li⁺@C₆₀* occurs. Photoinduced charge separation by means of ³Li⁺@C₆₀* with lifetimes of 135 and 120 μs for 1? Li⁺@C₆₀ and 2? Li⁺@C₆₀, respectively, and quantum yields of 0.82 in PhCN have been observed by utilizing time‐resolved transient absorption spectroscopy and then confirmed by electron paramagnetic resonance measurements at 4 K. The difference in crown ether structures affects the binding constant and the rates of photoinduced electron‐transfer events in the corresponding complex.     

FTIR and NMR studies of bis(oxaalkyl) sulphates(IV) and their complexes with proton and some metal cations

The complexation of Li⁺ and Na⁺ cations by three bis(oxaalkyl) sulphates(IV) was studied by FTIR and NMR on ¹H, ¹³C, ⁷Li and ²³Na nuclei. The NMR results have proved the formation of complexes and the fluctuation of Li⁺ and Na⁺ cations in respective circular arrangements. In the FTIR spectra of protonated sulphates intense continuous absorptions were observed indicating fast fluctuation of the protons in the respective multiminima potentials. The continuous absorptions in the far infrared region of the FTIR spectra of Li⁺ or Na⁺ complexes with three bis(oxaalkyl) sulphates(IV) indicate fast fluctuations of Li⁺ or Na⁺ cations between O-atoms of the oxaalkyl chains. The independence of the shape of the continua on the length of the oxaalkyl chains, i. e. the number of minima in the multiminima potential, demonstrates that the fluctuation of cations occurs in the respective circular arrangements.     

The Synthesis of Novel Crown Ethers, Part VII [1]. Coumarin Derivatives of Benzocrowns and Cation Binding from Fluorescence Spectra

4-[3-(1-benzopyran-2-one)] derivativesof benzo[12]crown-4, benzo[15]crown-5 andbenzo-[18]crown-6 were synthesized from4-[3-(1-benzopyran-2-one)]-1,2-dihydroxy-benzenereacting with bis-ethyleneglycol dihalides orpentaethylene glycol ditosylate in alkali carbonate/DMF/water. The original products were identified byhigh resolution EI-mass spectra as well as IR,¹H-NMR and ¹³C-NMR spectroscopy. The 1 : 1binding constants of Mg²⁺, Li⁺, Na⁺ andK⁺ with the coumarin-benzocrowns were estimated usingfluorescence emission spectroscopy in acetonitrile.The complexing enhanced quenching fluorescence spectra(CEQFS) and complexing enhanced fluorescence spectra(CEFS) exhibited the ion binding powers due tocationic recognition rules of the macrocycles.     

Enhanced Surface Interactions Enable Fast Li+ Conduction in Oxide/Polymer Composite Electrolyte

Li⁺‐conducting oxides are considered better ceramic fillers than Li⁺‐insulating oxides for improving Li⁺ conductivity in composite polymer electrolytes owing to their ability to conduct Li⁺ through the ceramic oxide as well as across the oxide/polymer interface. Here we use two Li⁺‐insulating oxides (fluorite Gd_0.1Ce_0.9O_1.95 and perovskite La_0.8Sr_0.2Ga_0.8Mg_0.2O_2.55) with a high concentration of oxygen vacancies to demonstrate two oxide/poly(ethylene oxide) (PEO)‐based polymer composite electrolytes, each with a Li⁺ conductivity above 10^?4 S cm^?1 at 30 °C. Li solid‐state NMR results show an increase in Li⁺ ions (>10 %) occupying the more mobile A2 environment in the composite electrolytes. This increase in A2‐site occupancy originates from the strong interaction between the O^2? of Li‐salt anion and the surface oxygen vacancies of each oxide and contributes to the more facile Li⁺ transport. All‐solid‐state Li‐metal cells with these composite electrolytes demonstrate a small interfacial resistance with good cycling performance at 35 °C.     

Redox-switchable binding of the Mg2+ ions by 21,31-diphenyl-12,42-dioxo-7,10,13-trioxa-1,4(3,1)-diquinoxaline-2(2,3),3(3,2)-diindolysine-cyclopentadecaphane

The binding of the Li⁺, Na⁺, K⁺, Mg²⁺, and Co²⁺ ions by 2¹,3¹-diphenyl-1²,4²-dioxo-7,10,13-trioxa-1,4(3,1)-diquinoxaline-2(2,3),3(3,2)-diindolysine-cyclopentadecaphane containing two indolysine fragments, two quinoxaline fragments, and 3,6,9-trioxyundecane spacer in the acetonitrile/0.1 M Bu₄NBF₄ environment is studied by the method of cyclic voltammetry. It is demonstrated that the Li⁺, Na⁺, K⁺, and Co²⁺ ions are not bound by this macrocycle, whereas selective redox-switchable binding is observed for the Mg²⁺ ions. The macrocycle binds the Mg²⁺ ions way more efficiently as compared with its radical cation and dication. The indolysinequinoxaline fragments play the determining role in the binding. Original Russian Text ? V.V. Yanilkin, N.V. Nastapova, V.A. Mamedov, A.A. Kalinin, V.P. Gubskaya, 2007, published in Elektrokhimiya, 2007, Vol. 43, No. 7, pp. 808–814.     

Stabilization of Th ions into mixed-valence thorium fluoride

The unusual oxidation state +3 of the thorium has been stabilized into a lithium containing non-stoichiometric mixed-valence (III/IV) thorium fluorinated phase with formula Li_2+xTh₁₂F₅₀ (0<x<1.8). This phase is closely related to the Li_5.5Ce₁₂F₅₀ one, the structure of which has been determined from the combined single-crystal X-ray diffraction and high resolution synchrotron powder diffraction. In these phases, the Li⁺ ions can be divided into two groups and are located either in locked positions or in open channels of the three dimensional framework. The amount of Li⁺ ions in open channels can be variable, so that the afore mentioned single phase may be considered as an insertion compound. The Li⁺ insertion is accompanied by the simultaneous reduction of a part of the Th⁴⁺ ions, resulting in a mixed-valence III/IV thorium fluoride. The electrochemical insertion of Li⁺ ions into the open channels of the host matrix has been carried out at 60 °C, using an alkylcarbonate PC-LiClO₄ 1 M electrolyte. The Li⁺ and Th³⁺ contents, both in the starting composition and the Li⁺ inserted ones, were investigated by high resolution solid state ⁷Li NMR and EPR, respectively.     

Specific Ion Effects on an Oligopeptide: Bidentate Binding Matters for the Guanidinium Cation

Ion–protein interactions are important for protein function, yet challenging to rationalize owing to the multitude of possible ion–protein interactions. To explore specific ion effects on protein binding sites, we investigate the interaction of different salts with the zwitterionic peptide triglycine in solution. Dielectric spectroscopy shows that salts affect the peptide's reorientational dynamics, with a more pronounced effect for denaturing cations (Li⁺, guanidinium (Gdm⁺)) and anions (I^?, SCN^?) than for weakly denaturing ones (K⁺, Cl^?). The effects of Gdm⁺ and Li⁺ were found to be comparable. Molecular dynamics simulations confirm the enhanced binding of Gdm⁺ and Li⁺ to triglycine, yet with a different binding geometry: While Li⁺ predominantly binds to the C‐terminal carboxylate group, bidentate binding to the terminus and the nearest amide is particularly important for Gdm⁺. This bidentate binding markedly affects peptide conformation, and may help to explain the high denaturation activity of Gdm⁺ salts.     

Ion-exchange chromatography using vanadyl and vandate salts as mobile phases with indirect detection

Summary Vanadyl sulfate, VOSO₄, was characterized as the mobile phase for the ion exchange separation of Li⁺, Na⁺, NH ₄ ⁺ , and K⁺ using indirect photometric detection at 254 nm. Detection limits ranged from 0.2 ppm for Li⁺ to 1 ppm for K⁺. Indirect electrochemical detection of these separated cations by reduction of VO (II) to V³⁺ was compared to spectrophotometric detection. The potential of the vanadate species, HVO ₄ ^2– , for the separation of F^–, Cl^–, and SO ₄ ^2– , with indirect photometric detection was also demonstrated.     

Porous nanostructured V2O5 film electrode with excellent Li-ion intercalation properties

Porous nanostructured V₂O₅ films were prepared by electrodeposition from V₂O₅ sol with the addition of block copolymer Pluoronic P123, and they can be readily applied as Li-ion battery cathode without adding any polymer binder or conductive additives. SEM images showed an ideal morphology for Li⁺ intercalation favored charge transfer kinetics, which is a combination of homogeneously distributed nano-pores and V₂O₅ nanoparticles. Electrochemical measurements revealed that, the porous nanostructured V₂O₅ films have a high discharge capacity of 160 mAh/g at 9 A/g, and maintain 240 mAh/g after 40 cycles at 300 mA/g. The excellent Li⁺ intercalation property could be ascribed to the high surface area, sufficient contact between electrode materials and electrolyte, short Li⁺ diffusion path, as well as the good accommodation for volume change which are benefited from homogeneously distributed nano-pores and V₂O₅ nanoparticles.     

CaWO4:xEu3+,ySm3+,zLi+红色荧光粉的制备及光学性能

采用微波固相法制备了CaWO₄：xEu³⁺,ySm³⁺,zLi⁺红色荧光粉。测量样品的XRD图、激发谱、发射谱及发光衰减曲线,研究并分析了Eu³⁺、Sm³⁺、Li⁺的掺杂浓度,对样品微结构、光致发光特性、能量传递及能级寿命的影响。结果表明,Eu³⁺、Sm³⁺、Li⁺掺杂并未引起合成粉体改变晶相,仍为CaWO₄单一四方晶系结构。Eu³⁺、Sm³⁺共掺样品中,Sm³⁺掺杂为3%时,Sm³⁺对Eu³⁺的能量传递最有效。Li⁺掺杂起到了助熔剂和敏化剂的作用,使样品发光更强。在394 nm激发下,与CaWO₄：3%Eu³⁺样品比较,3%Eu³⁺、3%Sm³⁺共掺CaWO₄及3%Eu³⁺、3%Sm³⁺、1%Li⁺共掺CaWO₄样品的发光分别增强2倍及2.4倍。同一激发波长下,单掺Eu³⁺样品寿命最短,Sm³⁺、Eu³⁺共掺样品随Sm³⁺浓度增加,寿命先减小后增加,且掺杂了Li⁺的样品比不掺Li⁺的样品⁵D₀能级寿命有所增加。     

In situ electrochemical studies for Li+ ions dissociation from the LiCoO2 electrode by the substrate-generation/tip-collection mode in SECM

This work presents the transportation of Li⁺ ions at the interface of a charging LiCoO₂ electrode through the substrate-generation/tip-collection (SG/TC) feedback mode of scanning electrochemical microscopy (SECM). The TC current, due to the reduction of the ethylene carbonate (EC) supermolecule, is collected more strongly at 1.8 V than that of the Li⁺(DEC) _n at 2.5 V near at the substrate because of the increased concentration of the supermolecule Li⁺(EC)_m, which means that the electrolyte is not uniformly distributed over the substrate. The smooth SG/TC current loop is formed at the probe position optimized by the probe scan curve technique between the LiCoO₂ substrate with 4.0 V and the probe with 1.8 V, which is applied to analyze the Li⁺ ion transport at the interface of the LiCoO₂ electrode. Moreover, the LiCoO₂ substrate, which has a flat surface, is imaged to the nonuniform surface electrochemically by the SECM. We infer that these experimental techniques will help analyze transporting Li⁺ ions at the interface and the electrochemical uniformity of the electrode.     

Li-NMR study of the stoichiometry, stability and exchange kinetics of Li ion with 12-Crown-4, 15-Crown-5 and cryptands C222, C221 and C211 in 50% ionic liquid-acetonitrile mixtures

⁷Li-NMR spectroscopy was used to study the complexation of Li⁺ ion with 12C4, 15C5, C222, C221, C211 in acetonitrile (AN) and its 50% (wt/wt) mixtures with two new room temperature ionic liquids, 1-ethyl-3-methylimidazolium hexafluorophosphate (EMim PF₆) and 1-ethyl-3-methylimidazolium tetrafluoroborate (EMim BF₄) at 298 K. Excluding the cases of Li⁺-C211 in all solvents and Li⁺-C221 in AN and 50% (wt/wt) AN-EMim PF₆, in other cases, the exchange between free and 1:1 complexed Li⁺ was fast on the NMR time scale and only a single population average ⁷Li signal was observed. Formation constants of the resulting 1:1 complexes were evaluated by computer fitting of the chemical shift-mole ratio data and integration of two ⁷Li signals. All complexes in EMim PF₆ were found to be more stable than those in EMim BF₄. ⁷Li-NMR line-shape analysis was used to determine the kinetic parameters and the mechanism for the chemical exchange of Li⁺ between the free and 1:1 complex with C221 in 50% (wt/wt) AN-EMim PF₆ mixtures solution. By comparing our study with the previous one, it is derived that, increasing the percentage of ion liquid in acetonitrile, changes the mechanism and decrease the exchange rate constant of Li⁺ ion between free and complex sites.     

Counterion mixing effects on the conformational transitions of polyelectrolytes. II. Counterion binding as measured by NMR spectroscopy of alkali metal poly(acrylate)s

Bound states of counterions during the coil‐globule transition of poly(acrylic acid) in water/organic solvent mixtures were investigated by NMR spectroscopy of alkali metal cations (Li⁺, Na⁺, Cs⁺). Accompanying the transition, the line widths of the respective NMR peaks significantly increased with increasing the organic solvent composition in the medium. Although this line width broadening suggests that some specific counterion binding with desolvation is involved with the coil‐globule transition, the most marked broadening was observed in higher organic solvent compositions than those of the coil‐globule transition region detected by the viscometry. Namely, the specific counterion binding with desolvation proceeds even after the polymer chain collapsed. This means in turn that such a strong counterion binding is not a prerequisite for the coil‐globule transition, at least at the stage of the onset. For the Li⁺/Cs⁺ mixed counterion system in 60 vol % DMSO, where our previous conductivity data suggested that the specific counterion binding occurred only for Cs⁺ during the coil‐globule transition induced on mixing with Li⁺, a significant increase in the line width was also observed only for Cs⁺. The coincidence between the conductivity and the NMR results for the Li⁺/Cs⁺ mixed counterion system strongly supports a working hypothesis, “size‐fitting effect,” that has been proposed to determine the counterion specificity observed for the conformational transitions of polyelectrolytes. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 2132–2139, 2009     

Olefin-Linked Covalent Organic Frameworks with Electronegative Channels as Cationic Highways for Sustainable Lithium Metal Battery Anodes

Despite the enormous interest in Li metal as an ideal anode material, the uncontrollable Li dendrite growth and unstable solid electrolyte interphase have plagued its practical application. These limitations can be attributed to the sluggish and uneven Li⁺ migration towards Li metal surface. Here, we report olefin-linked covalent organic frameworks (COFs) with electronegative channels for facilitating selective Li⁺ transport. The triazine rings and fluorinated groups of the COFs are introduced as electron-rich sites capable of enhancing salt dissociation and guiding uniform Li⁺ flux within the channels, resulting in a high Li⁺ transference number (0.85) and high ionic conductivity (1.78 mS cm⁻¹). The COFs are mixed with a polymeric binder to form mixed matrix membranes. These membranes enable reliable Li plating/stripping cyclability over 700 h in Li/Li symmetric cells and stable capacity retention in Li/LiFePO₄ cells, demonstrating its potential as a viable cationic highway for accelerating Li⁺ conduction.     

Defect-induced anisotropic surface reactivity and ion transfer processes of anatase nanoparticles

Surface reactivity and ion transfer processes of anatase TiO₂ nanocrystals were studied using lithium bis(trifluoromethylsulfone)imide (LiTFSI) as a probing molecule. Analysis of synthesized anatase TiO₂ by electron microscopy reveals aggregated nanoparticles (average size ~8 nm) with significant defects (holes and cracks). With the introduction of LiTFSI salt, the Li⁺-adsorption propensity towards the surface along the anatase (100) step edge plane is evident in both x-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) analysis. Ab initio molecular dynamics (AIMD) analysis corroborates the site-preferential interaction of Li⁺ cations with oxygen vacancies and the thermodynamically favorable transport through the (100) step edge plane. Using ⁷Li nuclear magnetic resonance (NMR) chemical shift and relaxometry measurements, the presence of Li⁺ cations near the interface between TiO₂ and the bulk LiTFSI phase was identified, and subsequent diffusion properties were analyzed. The lower activation energy derived from NMR analysis reveals enhanced mobility of Li⁺ cations along the surface, in good agreement with AIMD calculations. On the other hand, the TFSI^– anion interaction with defect sites leads to CF₃ bond dissociation and subsequent generation of carbonyl fluoride-type species. The multimodal spectroscopic analysis including NMR, electron paramagnetic resonance (EPR), and x-ray photoelectron spectroscopy (XPS) confirms the decomposition of TFSI^– anions near the anatase surface. The reaction mechanism and electronic structure of interfacial constituents were simulated using AIMD calculations. Overall, this work demonstrates the role of defects at the anatase nanoparticle surface on charge transfer and interfacial reaction processes.     

Studies of lithium and sodium complexation by silicon podand solvents

The complex formation of lithium and sodium ions with silicon podand solvents: phenyl-tris(1,4-dioxapentyl) silane (PhSi23) and ethyl-tris(1,4-dioxapentyl) silane (EtSi23) has been studied by FTIR, ¹H-, ¹³C-, ⁷Li- and ²³Na NMR. The far FTIR spectra show that the Li⁺ cations fluctuate very fast whereas Na⁺ cations are still localised between the oxygen atoms of the oxaalkyl chains. The ⁷Li NMR spectra prove that one Li⁺ cation can be coordinated not only by one but also two silicon podand molecules. The concentration dependence of the molar conductivity of LiClO₄ in the podand solvents indicates charge transfer between ion clusters.