Determination of the Association Constants of Macrocyclic Ethers by the Aid of 13C Dipole-dipole Relaxation Time Measurements. I.,: Li+, Mg2+ and Ca2+ complexes of 1,4,7,10-tetraoxacyclododecane

Abstract

The association constants of Li⁺, Ca⁺² and Mg⁺² ions complexing with 1, 4, 7, 10-tetraoxcyclododecane in DHO were determined by the aid of ¹³C dipole-dipole relaxation time measurements. To obtain the K_a, association constant, the T^O ₁ values of the stoichiometric complex solutions and the T₁₀ of the free molecules were applied to the equation derived, 1/K_a· A_o + 2 = 1/P + P, for the 1:1 ratio of the complexing and to the equation 1/2K_a·A_o + 3/2 = P + 1/2P for the 1:2 ratio of the complexing where P, is molar ratio of the crown complexed ions.

Accordingly we found that the binding ability of the macrocyclic ether towards to the cations is in the following order of Li⁺ < Mg⁺² ? Ca⁺² in DHO solutions.     

Determination of the Complexing Constants by the Aid of 13C Dipole-Dipole Relaxation Time Measurements. Part. III. Complexing of 15-Crown-5 and 18-Crown-6 with Na+,K+ and Ca2+ in DHOX

The association constants, K_a of KI, Nal and CaCl₂ complexing with 1,4,7,10,13-pentaoxacyclopentadecane and 1,4,7,10,13,16-hexaoxacycloocta-decane in DHO were determined by the aid of ¹³C dipole-dipole relaxation time measurements.

The mole fraction of the complexed ligand, P_C were obtained by the use of the equation of 1/T^obs ₁ - 1/T₁₀ = P_C (1/T^O ₁ - 1/T₁₀) where the T₁₀ and T^o ₁ are the relaxation times of free and complexed macrocyclic ethers respectively.

K_a values obtained from the above given equation depending on the cation concentration, [A⁺ _O] typically reflected the relation between the cationic radius and cyclic ether ring size.     

掺入Mg2+对CsNiCl3晶体的基态能级、零场分裂参量及Jahn-Teller效应的影响

应用不可约张量理论构造了三角对称晶场中3d2/3d8态离子的45阶可完全对角化的微扰哈密顿矩阵,在考虑了以前工作中被忽略的自旋-自旋耦合作用的基础上计算了CsNiCl3晶体和CsNiCl3:Mg2+晶体的基态能级、晶体结构、零场分裂参量和Jahn-Teller效应,研究了掺入Mg2+对CsNiCl3晶体的光谱、零场分裂参量及Jahn-Teller效应的影响和自旋单重态对基态能级的贡献,发现掺杂使得晶体结构产生畸变,从而改变晶体光谱的精细结构和零场分裂参量,不改变Jahn-Teller效应的分裂规律但改变分裂的大小.     

Li嵌入Mg2Ge的反应次序和电子结构变化

Mg2Ge有望成为新的锂离子电池负极材料.使用基于平面波展开的第一性原理赝势法,计算并得到了Li嵌入Mg2Ge负极材料时的反应次序.Li首先占据其中的间隙位置,占满间隙位置后随着嵌Li量的进一步增加,Li将逐步替位Mg2Ge中一半的Mg位置,直到生成Li2MgGe.计算结果表明,在整个嵌Li过程中主体材料的体积先膨胀后收缩.体积胀缩量很大,这是导致Mg2Ge作为锂离子电池电极材料循环性能较差的重要原因.对材料电子结构的分析表明,随着Li嵌入量的增加,主体材料发生了从半导体性到金属性、又到半金属性的转化.     

The NaCrS2 cathode for secondary Li cells. II. Effect of the temperature of synthesis on its properties and cyclic performance

By changing the conditions of synthesis and oxidation of NaCrS₂, the coulombic efficiency and cycling life of Ni_xNa_0.1CrS₂ cathodes is significantly improved. The importance of studying the main physical and structural properties of the intercalation compound during the optimization of its electrochemical performance is demonstrated. Imitating the nonexistant CrS₂ in composition and possessing the rugged crystal structure of NaCrS₂, the optimized Li_xNa_0.1CrS₂ cathodic material exhibits high coulombic efficiency, excellent cycling resistance, and moderate power capability in nonaqueous secondary Li cells. Having in mind also the simple and reproducible preparation technique and the availability of its raw materials, Li_xNa_0.1CrS₂ appears to be a serious candidate for the future secondary Li nonaqueous cell.     

Luminescence of CuInS2: I. The broad band emission and its dependence on the defect chemistry

The emission of CuInS₂ is studied as a function of the exact composition in terms of deviations from molecularity and stoichiometry. By means of temperature-dependent (4.2–220 K) and excitation-intensity-dependent measurements, the two broad emission bands usually present are correlated with donor-acceptor transitions. In In-rich material the acceptor is located at 0.10 eV above the valence band. This acceptor is ascribed to V_Cu. In Cu-rich CuInS₂ the acceptor level is located at 0.15 eV above the valence band, which is attributed to either V_In or Cu_In. Two donor levels are identified, their ionization energies being about 35 and 72 meV. These donors are present in both In and Cu-rich samples and may originate from either intrinsic defects or impurities (Fe). Also, the influence of quenching of the crystals as well as the effect of different crystal growth methods (melt-growth and vapour-growth) on the emission is studied.     

The Effect of Shape on Intermethod Correlation of Techniques for Characterizing the Size Distribution of Powder. Part 2: Correlating the Size Distribution as Measured by Diffractometer Methods,TSI-Amherst Aerosol Spectrometer,and Coulter Counter

In an aerosol spectrometer the size of a powder grain is measured from the time-of-flight of the fineparticle between two laser beams. Due to the flow conditions, irregularly shaped fineparticles align themselves along the direction of flow of the air stream carrying them across the gap between the laser beams. The size distribution measured therefore varies with the shape of the fineparticles. This fact is demonstrated by comparing size distributions generated by image analysis, electrozone stream counter, diffractometer, and time-of-flight aerosol spectrometer.     

The d + d reactions at low energies II. Comparison of angular distributions of outgoing nucleon polarizations for the charge symmetric reactions2H(d,p)3H and2H(d,n)3He

Precision measurement of the angular distribution of polarized protons from the²H(d,p)³H reaction at about 1 MeV is compared with experimental polarization data from the mirror reaction²H(d,n)³He at the same entrance and exit channel energies. In both comparisons, differences in polarizations of outgoing nucleons from the d + d charge symmetric reactions were found to be larger than experimental uncertainties.     

Natural J coupling (NJC) analysis of the electron lone pair effect on NMR couplings: 2. The anomeric effects on 1 J (C,H) couplings and its dependence on solvent

The electronic origin of the influence of the anomeric effect (negative hyperconjugative interaction, NHI) on the Fermi contact (FC) term of ¹ J(C, H) couplings has been studied from a theoretical point of view at the DFT-B3LYP level. The HN=CH₂, molecule was chosen as the primary model compound, in which both FC ¹ J(C, H) couplings were decomposed into bond contributions with the natural J coupling dissection approach (NJC). Differences between the ¹ J (C, H)^FC couplings for C——H bonds in synperiplanar and antiperiplanar orientations with respect to the nitrogen non-bonding electron pair closely follow the experimental trend. They are made up chiefly of three NJC contributions: ‘bond’, ‘direct lone pair’ and the ‘carbon-core orbitals’. The NHI influence on these terms was studied by applying the natural bond orbital (NBO) deletion procedure to the charge transfer interaction into the antiperiplanar (C——H) antibond (n(N)→(C——H)?) prior to the NJC dissection calculation. The dielectric solvation effect on both the total FC terms and the respective NJC contributions was estimated by carrying out the calculations using the polarization continuum model. Inhibition of the anomeric effect is evident when the solvent polarity is increased. NHI saturates rapidly with increasing solvent dielectric. Specific solute-solvent interaction effects on ¹ J(C, H) couplings were estimated by evaluating molecular complex models of the form CH₂=HN…S (S = H₂O and DMSO).