Improvement of the crystal rotation method to measure the flexoelectric difference (e1–e3) in achiral materials using AC electric fields

We show that the crystal rotation method for measuring the difference between splay and bend flexoelectric coefficients (e₁–e₃) [Outram and Elston, Liq. Cryst. 39, 149 (2012)] can be improved by using AC instead of DC fields. The field frequency is small (~0.05 Hz), yet sufficient to get rid of the difficulties connected with the migration of charge carriers. The method is sensitive enough so as to use fields with amplitudes as small as 1 V/mm. This has the advantage of avoiding the consideration of the interaction due to the dielectric anisotropy, and greatly simplifies the analysis of data. The results are extracted from a simple fitting scheme, which involves two parameters. In particular (e₁–e₃) is obtained from a scale factor in a one-parameter fit. Measurements of the temperature dependence of (e₁–e₃) are presented for two classical nematic materials.     

Sul riconoscimento microchimica della β-fenil isopropilamina

Riassunto Viene proposto l'impiego di una speciale soluzione di jodobismutito potassico per il riconoscimento e la differenziazione microchimica della-fenil-isopropil-amina e della N-metil-fenil-isopropilamina.Mentre la prima di tali basi forma due composti aventi abito cristallino caratteristico e ben differenziati tra loro, con diversa costituzione chimica, dalla seconda si ottiene un solo composto dotato di forma cristallina caratteristica.Inoltre mentre la-fenil-isopropilamina dà con soluzione di acido bromobismutico un composto cristallino avente forma caratteristica e costituzione chimica ben definita, la N-metil-fenil-isopropilamina non reagisce con tale reattivo.

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Summary It is proposed that a special potassium-bismuth iodide solution be used for the microchemical detection and the differentiation of-phenylisopropylamine and N-methylphenyl-isopropylamine.The first of these bases forms two compounds, which display a characteristic crystal habit and which are readily distinguished because they have different chemical constitutions. On the other hand, the second base yields only one compound, which is marked by a characteristic crystal form. In addition, the-phenylisopropylamine reacts with bromobismuthic acid to give a compound possessing a characteristic crystal form and a well defined chemical constitution, while N-methylphenyl-isopropylamine does not react with this reagent.

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Zusammenfassung Die Anwendung einer speziellenKalium-Wismutjodid-Löaung wird für den mikrochemischen Nachweis und die Unterscheidung von-Phenylisopropyl-amin und N-Methyl-phenyl-isopropyl-amin vorgeschlagen. Während die erstgenannte Base zwei Verbindungen bildet, die einen charakteristischen Kristallhabitus aufweisen und bei verschiedener chemischer Konstitution sich gut voneinander unterscheiden, erhält man aus der letzteren nur eine Verbindung, die sich durch eine charakteristische Kristallform auszeichnet. Während ferner das-Phenyl-isopropyl-amin mit Bromwismutsäure eine Verbindung mit charakteristischer Kristallform und wohldefinierter chemischer Konstitution ergibt, reagiert das N-Methyl-phenyl-isopropyl-amin mit diesem Reagens nicht.

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Résumé On conseille l'emploi d'une solution spéciale d'iodure de potassium et de bismuth pour l'identification microchimique et la différenciation de la-phénylisopropylamine et de la N-méthylphénylisopropylamine.Tandis que la première de ces deux bases donne naissance à deux combinaisons qui ont un aspect cristallin caractéristique et qui se différencient aisément l'une de l'autre par leurs constitutions chimiques, la seconde ne fournit qu'une seule combinaison qui se distingue par sa forme cristalline caractéristique. En outre, tandis que la-phénylisopropylamine donne avec l'acide bromobismuthique une combinaison de forme cristalline caractéristique et de constitution chimique bien définie, la N-méthylphénylisopropylamine ne réagit pas.

     

Tuning the Photoluminescence of Zn(Ⅱ) Coordination Polymers by Changing the Coordinated Solvent

By using solvothermal method,two new Zn(Ⅱ) coordination polymers based on 2,5-furandicarboxylic acid(H_2FDA) ligand,[Zn(FDA)(CH_3OH)]_n(1) and [Zn_2(FDA)_2(CH_3CH_2OH)_2]_n(2),were synthesized and structurally characterized by single-crystal X-ray diffraction as well as elemental analysis and IR.Complexes 1 and 2 are isostructural coordination polymers with two-dimensional sheet structures bridged by the protonated carboxylates ligands.The 2D network can be rationalized as a 3-c net with Schl?fli symbol is 82·10.Although 1 and 2 are isostructural,the photoluminescent intensity of 2 is almost twice that of 1 due to the difference of coordinated solvents.     

A study of the quenching of PCl(b1∑+) by the E-V model

Using the reaction of Ar(3Po,2) + PCl3 as a source of PCl(b1 +), we have measured the quenching rate constants of PCl(b,v'=0) for more than 20 quenchers. The E-V model is used to calculate the rate constants. The comparison of the calculated values with the experimental ones shows that the quenching of PCl(b) by the reagent molecules results from the electronic to vi-brational energy near resonance transfer and has been related to the Franck-Condon factors for the PCl(b,v'=0-a,v"=m) transition and to the anharmonicities of the terminal bonds of the quenchers. In addition, the influence of the polarizability of the reagent molecule on the quenching rate constant is discussed.     

Introduction to the dynamic theory of the (H+, e−) couple insertion in γ-MnO2

This paper presents a phenomenological theory of coupled H⁺ and e⁻ diffusion in γ/ɛ-MnO₂. A set of five dynamic regimes governs the (H⁺, e⁻) insertion during the entire reduction (0.08 < r < 1) of the dioxide. It is imposed by a global balance of several physical quantities which depend on the reduction level r. The principal potential factor for the diffusion in a given direction is the difference between the components, along this direction, of the self velocities V _e− and V _H+. The longitudinal component E _ld of the internal electric field vector E _d plays, with respect to electrons and protons, the velocity regulator role. The transversal component E _td allows some homogenisation of (H⁺,e⁻) concentration during the first half of the reaction and trapping of electrons in the second half. Towards r≈ 0.50, V _e− and V _H+ are equal, the internal electric field reverses its orientation after taking a null value and the first Mn³⁺ ions appear. This introduction to the dynamic theory of γ/ɛ-MnO₂ is a new finding and can interpret most of its physical/chemical properties, especially the behaviour change around r≈ 0.50. Received: 11 November 1998 / Accepted: 25 March 1999     

简法制备光学活性化合物(100% e.e.)

近年来,有机合成化学家对制备高纯度光学活性化合物极感兴趣。1984年,美国Purdue大学Brown教授等曾报道获得高纯度光学活性化合物的简单方法。该方法是以手性试剂单异松蒎烯基硼烷(mono-isopinocampheylborane,IpcBH_2)1,与二取代、三取代烯烃2发生不对称诱导的硼氢化反应,此时可引入一个或二个手性中心。由于主、副产物结晶性质有明     

Ternary surface complexes by the E(%)-pH curve method

A new method for the study of ternary surface complexes at liquid-solid interface,the E(%)-pH curve method,was proposed.Four types of E(%)-pH curves,namely,phenomenon of left-right shifts of S-shaped curve,V-shaped curve,monodirection shift curve and X-shaped curve,were discovered.Correspondingly,apart fromtype (Ⅰ) ternary surface complex -S-O-M-L and type (Ⅱ) ternary surface complex -S-L-M,a newtype of ternary surface complex -S-O-L-M was discovered.     

Energy-transfer Process Accelerated by the Formation of Electrostatically Stabilized Aggregate (ESAg)

We have proposed that oppositely-charged long-chain molecules with roughly eight to sixteen carbons might form electrostatically stabilized aggregates (ESAgs) by both the hydrophobic-lipophilic interaction (HLI) and the electrostatically attractive force in the concentration range of 10-7 mol/L to 10-5 mol/L1,2. Thus ESAg is yet another structural niche for molecular assemblages in-between the simple aggregate and the micelles. That ESAg species existing at concentrations much lower tha…     

Modulating the light switch by (3)MLCT-(3)ππ* state interconversion

The spectroscopic, electronic, and DNA-binding characteristics of two novel ruthenium complexes based on the dialkynyl ligands 2,3-bis(phenylethynyl)-1,4,8,9-tetraaza-triphenylene (bptt, 1) and 2,3-bis(4-tert-butyl-phenylethynyl)-1,4,8,9-tetraaza-triphenylene (tbptt, 2) have been investigated. Electronic structure calculations of bptt reveal that the frontier molecular orbitals are localized on the pyrazine-dialkynyl portion of the free ligand, a property that is reflected in a red shift of the lowest energy electronic transition (1: λ(max) = 393 nm) upon substitution at the terminal phenyl groups (2: λ(max) = 398 nm). Upon coordination to ruthenium, the low-energy ligand-centered transitions of 1 and 2 are retained, and metal-to-ligand charge transfer transitions (MLCT) centered at λ(max) = 450 nm are observed for [Ru(phen)(2)bptt](2+)(3) and [Ru(phen)(2)tbptt](2+)(4). The photophysical characteristics of 3 and 4 in ethanol closely parallel those observed for [Ru(bpy)(3)](2+) and [Ru(phen)(3)](2+), indicating that the MLCT excited state is primarily localized within the [Ru(phen)(3)](2+) manifold of 3 and 4, and is only sparingly affected by the extended conjugation of the bptt framework. In an aqueous environment, 3 and 4 possess notably small luminescence quantum yields (3: ?(H(2)O) = 0.005, 4: ?(H(2)O) = 0.011) and biexponential decay kinetics (3: τ(1) = 40 ns, τ(2) = 230 ns; 4: τ(1) ～ 26 ns, τ(2) = 150 ns). Addition of CT-DNA to an aqueous solution of 3 causes a significant increase in the luminescence quantum yield (?(DNA) = 0.045), while the quantum yield of 4 is relatively unaffected (?(DNA) = 0.013). The differential behavior demonstrates that tert-butyl substitution on the terminal phenyl groups inhibits the ability of 4 to intercalate with DNA. Such changes in intrinsic luminescence demonstrate that 3 binds to DNA via intercalation (K(b) = 3.3 × 10(4) M(-1)). The origin of this light switch behavior involves two competing (3)MLCT states similar to that of the extensively studied light switch molecule [Ru(phen)(2)dppz](2+). The solvent- and temperature-dependence of the luminescence of 3 reveal that the extended ligand aromaticity lowers the energy of the (3)ππ* excited state into competition with the emitting (3)MLCT state. Interconversion between these two states plays a significant role in the observed photophysics and is responsible for the dual emission in aqueous environments.     

Preparation of the pigment mixtures (“masterbatches”) using rubbers Li-PBR synthesized by the solution polymerization

A method of liquid phase filling by hydrophobized aerosil (white carbon) of the solution styrenebutadiene rubbers SSBR of different structures for use in the tread rubbers in the production of “green” tires. Surface modification of the silicic filler was carried out in a hydrocarbon solvent environment by various silicon and nitrogen-containing agents.     

Study on the Synthesis of β-FeOOH by the Microemulsion Method

Monoclinic-FeOOH with: a = 0.9981 nm, b = 0.2948 nm, n = 1.0485 nm, β = 92.26° was synthesized by the hydrolysis of FeCl₃ · 6H₂O in micro emulsion including NP-4, octane, water. In this paper, the various morphology and size of the nano particles under different conditions are discussed, and it is found that the optimum conditions for synthesizing acicular β-FeOOH is that R = 6.0, [Fe³⁺] = 0.02 mol/L within the pH range 1.6–2.0. The text was submitted by the authors in English.     

Condensed aromatics—XXIII. Cyclo[d.e.d.e.d.e.d.e.d.e.d.e]dodecakisbenzene (kekulene)

Some topological properties of coronoids are given. These systems have chemical counterparts in cycloarenes. For one of these molecules, viz. C₄₈H₂₄ kekulene, the simple Hückel molecular orbital analysis has been performed and employed in the construction of a harmonic force field. Finally the set of calculated vibrational frequencies is reported.     

Effect of Cationic Surfactant on the Gelation of HPAM by Cr(III)

Aqueous gels formed by the crosslinkage of Cr(III) with partially hydrolyzed polyacrylamide (HPAM), have been commonly applied in the field of petroleum production1. Polymer and surfactants are used in enhancement of oil recovery2. Some studies3 indicate that a strong interaction is existent between polyeletrolytes and oppositely charged surfactants. So it is very important to study the effect of cationic surfactants on the gelation process of crosslinkage of Cr(III) with HPAM. To o…     

Synthesis of substituted benzoxazoles by the iron(Ⅲ)-catalyzed aerobic oxidation process

The FeCl3-catalyzed aerobic oxidation process for the synthesis of benzoxazoles,benzothiazole and benzimidazole has been discovered.This method has proved to be effective to a wide range of substrates,and it has been applied for the synthesis of JTP-426467.     

Determination of the Absolute Configuration of the (−)-Me(EtO)(HO)P-Mo(CO)5 Coordination Complex by Decomplexation of the Organophosphorus Ligand

Abstract

The resolution of a chiral coordination complex (1) was recently carried out in our laboratory, and some stereochemical transformations of the resolved specie have been reported (L. P. Reiff, L. J. Szafraniec, D. I. Rossman and H. S. Aaron, Inorg. Chem. 1986, 25, 0000). Decomplexation studies of its organophosphorus ligand have now been carried out. Thus, treatment of the (?)-1 complex with two molar equivalents of triphenylphosphine yields (+)-ethyl methylphosphinate (2), considerably racemized, however, due to the 120°C temperature required to achieve decomplexation. To determine its optical purity and its absolute configuration, the latter was converted into the known S-(?)-3 thioic acid and S-(?)-4 methyl ester, respectively. While the method does not appear to be of synthetic utility for the preparation of optically active (decomplexed) organophosphorus species, the absolute configuration of the S-(?)-1 coordination complex is established on the basis of these stereochemical relationships.