Joint Venture of Metal Cluster and Amphiphilic Cationic Minidendron Resulting in Near Infrared Emissive Lamellar Ionic Liquid Crystals

Inorganic red-NIR emissive materials are particularly relevant in many fields like optoelectronic, bioimaging or solar cells. Benefiting from their emission in devices implies their integration in easy-to-handle materials like liquid crystals, whose long-range ordering and self-healing abilities could be exploited and influence emission. Herein, we present red-NIR emissive hybrid materials obtained with phosphorescent octahedral molybdenum cluster anions electrostatically associated with amphiphilic guanidinium minidendrons. Polarized optical microscopy and X-ray analysis show that while the minidendron chloride salts self-organize into columnar phases, their association with the dianionic metal cluster leads to layered phases. Steady-state and time-resolved emission investigations demonstrate the influence of the minidendron alkyl chain length on the phosphorescence of the metal cluster core.     

An ICMI Regional Conference: EM 2000

This text is a report of an international conference about mathematics education in French-speaking countries in the XXth century and prospects for the beginning of the XXIth century which was organised by the CFEM in Grenoble from 15 to 17 July 2000.     

用差谱法研究环氧树脂中基团的相对稳定性

环氧树脂是一类广泛应用的万能胶,其分子中各种官能团的相对热稳定性是实际应用的重要参数。本文用付里叶变换红外光谱为测试手段研究了室温与降解条件(300℃、1小时)下的己固化环氧618树脂,用差谱法得到了固化的环氧618中各官能团的热稳定性次序为:甲基>次甲基>对位取代苯环>醚健>同碳二甲基。     

土壤中常量及微量元素的ICP光谱分析

本文叙述了土壤中Ca、Mg、Na、Sr、Ba、Mn、Fe、V、Cr及Ti等元素简单快速的ICP-AES测定方法。用HClO_4、HNO_3及HF在聚四氟乙烯高压罐中溶解祥品,用H_3BO_3络合过量的HF。采用基体匹配法校正干扰。方法的准确度、精密度及检出限均较好。     

1,3-Alternate and C-1,2-Alternate Tetrahomodioxacalix[4]crowns. Crystal Structures and Metal Ion Complexation

Two novel tetrahomodioxacalix[4]crowns with crown-5 and crown-6 rings weresynthesized. From X-ray crystal structures, homooxacalix[4]crown-5 (3) andhomooxacalix[4]crown-6 (2) were found to be in the 1,3-alternate and theC-1,2-alternate conformations, respectively. Homooxacalix[4]crown-5 (1)shows a marked selectivity for cesium ion over other metal ions tested.     

Compartmental modeling of the fluorescence anisotropy decay of a cylindrically symmetric brownian rotor: Identifiability analysis.

We present the results of the deterministic identifiability analysis based on similarity transformation for models of one-state excited-state events of cylindrically symmetric rotors in isotropic environments undergoing rotational diffusion described by Brownian reorientation. Such an analysis on error-free time-resolved fluorescence (anisotropy) data can reveal whether the parameters of the considered model can be determined. The fluorescence delta-response functions I(parallel)(t) and I(perpendicular)(t), for fluorescence polarized respectively parallel and perpendicular to the electric vector of linearly polarized excitation, are used to construct, in convenient matrix form, expressions of the sum S(t) = I(parallel)(t) + 2I(perpendicular)(t), the difference D(t) = I(parallel)(t) - I(perpendicular)(t), and the time-resolved fluorescence anisotropy r(t) = D(t)/S(t). The identifiability analysis of r(t) demonstrates that the rotational diffusion coefficients D(parallel) and D(perpendicular) for rotation respectively about and perpendicular to the symmetry axis can be uniquely resolved. However, the polar and azimuthal angles defining the absorption and emission transition moments in the molecular reference frame are not individually identifiable. Nevertheless, the difference between the polar angles of these transition moments is uniquely determined.     

Determination of net atomic charges using a modified partial equalization of orbital electronegativity method. IV. Application to hypervalent sulfur- and phosphorus-containing molecules

The parameters for an empirical point charge calculation method, Mulliken Population Constrained Potential Derived–Modified Partial Equalization of Orbital Electronegativity (MPCPD–MPEOE) method, for hypervalent sulfur, phosphorus, and the atoms bonded to these atoms, were determined. A new empirical method, MPCPD, which has inherent advantages over both the Mulliken population and potential derived methods, is proposed here. The MPCPD net atomic charges are transferable and reproduce the electrostatic potential. The electrical properties were calculated with the MPCPD and MPCPD–MPEOE charges. These properties agreed well with experimental results and with 6-31G** ab initio results. The MPEOE parameters for the sulfur atom in aromatic molecules and trivalent phosphorus in phosphite molecules were also determined. The dipole moments calculated with the MPCPD–MPEOE point charges agreed well with experimental results. All the parameters obtained in this work are consistent with those obtained in our previous work. © 1995 by John Wiley & Sons, Inc.     

Syntheses and conformations of tetrahomodioxacalix[4]arene tetraamides and tetrathioamides

A series of tetrahomodioxacalix[4]arene tetraamides and tetrathioamides with four p-phenyl groups on their upper rim were synthesized. From the (1)H and (13)C NMR and crystal structure, N-butylamido homooxacalix[4]arene (4) was found to be in the 1,3-alternate conformation and has intramolecular hydrogen bonding between N-H and facing oxygen atoms of the carbonyl O=C group. This hydrogen bonding decreased the metal ion complex ability. Transformation of the 1,3-alternate N-butylamido (4) into N-butylthioamido homooxacalix[4]arene (5) using Lawesson's reagent gave a conformational change to the C-1,2-alternate.     

Nondestructive determination of crystallinity by diffuse reflectance FT-IR in composites made from polyphenylene sulphide and carbon fibres

Diffuse reflection Fourier transform infrared spectroscopy can be used for nondestructive determination of the degree of crystallinity at the surface of composite materials made from polyphenylene sulphide reinforced with carbon fibres. In particular, the ratio of the heights of the peaks at 1075 and 1093 cm^–1 can be used as a quantitative indicator of the crystallinity. This has been confirmed by annealing highly amorphous prepreg to give samples of varying degrees of crystallinity, in which case a good linear relationship is observed between the peak ratio and the enthalpy of crystallization as determined by differential scanning calorimetry.