Supramolecular gels formed by amphiphilic low-molecular-weight gelators of N alpha,N epsilon-diacyl-L-lysine derivatives

Simple L-lysine derivatives, N(alpha)-hexanoyl-N(epsilon)-lauroyl-L-lysine (1), its alkali metal salts (2-4), and two-component compounds that consist of 1 with 2 to 4, were synthesized and their hydrogelation and organogelation properties were studied. Addition of hydrochloric acid to an aqueous solution of the alkali metal salt at room temperature produced a translucent hydrogel. This hydrogelation occurred as a result of a change in nanostructure from micelle-like aggregates to nanofibers, which was induced by partial protonation of the carboxylate to form a carboxylic acid. On the other hand, two-component low-molecular-weight gelators exhibited amphiphilic gelation behavior and functioned as not only hydrogelators, but also as organogelators. FTIR studies revealed that lateral ionic interactions between the carboxylate, alkali metal cation, carboxylic acid, and protons, in addition to hydrogen-bonding and van der Waals interactions play a very important role in hydrogelation. Furthermore, it was found that the water-insoluble carboxylic acid compound underwent a precipitation-dissolution transition with a thermally reversible sol-gel transition in the two-component gelator systems.     

Neutralization of 1-(Aminoethyl)phosphonic Acid and Protonation of Its Salt Anion. Processing Dilatometric Data with the CPESSP Program

Volume changes resulting from neutralization of 1-(aminoethyl)phosphonic acid and protonation of the anion of its bis(tetraethylammonium) salt were determined by the dilatometric method. Protonation constants, apparent molar volumes of the acid and its ionized forms, and volume changes on neutralization of the acid and protonation of its salt were calculated. The presence of the betaine form of the acid in solutions was detected. The rule of the constancy of the sum of the volume effects of the protonation and neutralization reactions was shown to be valid for conjugate acid-base pairs of dibasic acids.     

Qualitative and quantitative end-group analysis of a small molecular weight polyester by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry was used for qualitative and quantitative end-group analysis of a small molecular weight polyester, poly(2-butyl-2-ethyl-1,3-propylene phthalate). The presence of carboxyl-terminated linear and cyclic polyester oligomers was confirmed with the help of simple sample preparation methods. The presence of carboxyl end-groups in the polyester chains was verified through their formation of carboxylate salts with alkali metal cations. Cyclic oligomers were identified through deuterium exchange of the exchangeable protons of the polyester. Various inorganic salts were tested for salt formation of the carboxyl end-groups, but only the alkali metal salts proved effective. The influence of the alkali metal salts on the results of the quantitative end-group analysis was also studied. The relative amounts of differently terminated and cyclic oligomers were calculated when the alkali metal salts were used with different matrices. The results showed that both the salts and the matrices used in sample preparation can have a marked effect on the quantitative results of the end-group analysis. The measurements were carried out using 2,5-dihydroxybenzoic acid (DHB), 1,8, 9-trihydroxyanthracene (dithranol), and 2-(4-hydroxyphenylazo)benzoic acid (HABA) as matrix compounds. Dithranol and HABA repeatably exhibited similar results, and these results differed from those obtained with DHB probably because of the different ionization mechanisms in the MALDI process. Copyright-Copyright 2000 John Wiley & Sons, Ltd.     

Studies on the melts of alkali metal acetates

The density, viscosity, and electrical conductivity of alkali metal acetates were measured over the temperature interval between melting and decomposition. The apparent activation energies of the equivalent conductivities and viscosities were calculated. It has been concluded from the results that alkali metal acetates, similarly to alkali metal benzenesulphonates studied earlier, exhibit properties quite unlike those of alkali metal halides. In the dependence of equivalent conductivity on the nature of the cation, the anomalous behaviour of lithium salts appears to be due to association prevailing in the melt phase.     

Phosphinoselenothioic acids and their salts: synthesis, characterization, and reaction with electrophiles

[reaction: see text] Phosphinoselenothioic acid ammonium salts were synthesized in good yields by reacting phosphinoselenothioic acid S-[2-(trimethylsilyl)ethyl] esters with ammonium fluorides. Phosphinoselenothioic acid alkali metal salts were obtained as 18-crown-6 ether complexes with high efficiency by treating the esters with alkali metal fluorides and 18-crown-6 ether. The salts were stable under air and soluble in water. The structures of the phosphinoselenothioic acid tetramethylammonium salt and P-methylseleno-P-methylthiophosphonium triflate were determined by X-ray molecular structure analyses. These salts exhibited monomeric structures, and the central phosphorus atoms adopted tetrahedral structures. Alkylation of the ammonium salts selectively gave phosphinoselenothioic acid Se-alkyl esters, whereas acylation of the salts preferentially gave S-acyl products. Protonation of the salts selectively gave the phosphinoselenothioic S-acid. The S-acid generated in situ was reacted with alpha,beta-unsaturated carbonyl compounds and cyclohexene oxide to give the adducts. Molecular orbital calculations were carried out for the model compound H2P(Se)S- to elucidate the electronic structure.     

Alkali metal salts doped pluronic block polymers as electron injection/transport layers for high performance polymer light-emitting diodes

A series of alkali metal salts doped pluronic block copolymer F127 were used as electron injection/transport layers (ETLs) for polymer light-emitting diodes with poly[2-(4-(3′,7′-dimethyloctyloxy)-phenyl)-p-phenylenevinylene] (P-PPV) as the emission layer. It was found that the electron transport capability of F127 can be effectively enhanced by doping with alkali metal salts. By using Li2CO3 (15%) doped F127 as ETL, the resulting device exhibited improved performance with a maximum luminous efficiency (LE) of 13.59 cd/A and a maximum brightness of 5529 cd/m2, while the device with undoped F127 as ETL only showed a maximum LE of 8.78 cd/A and a maximum brightness of 2952 cd/m2. The effects of the doping concentration, cations and anions of the alkali metal salts on the performance of the resulting devices were investigated. It was found that most of the alkali metal salt dopants can dramatically enhance the electron transport capability of F127 ETL and the performance of the resulting devices was greatly improved.     

Aluminium‐27 NMR investigation of the influence of cation type on aluminosilicate solutions

The effects of tetraalkylammonium (TAA) and alkali metal cations on the equilibrium distribution of aluminosilicate oligomers in aqueous alkaline aluminosilicate solutions were investigated using ²⁷Al NMR spectra and their evolution with time. The results indicate that there are no differences in the initial equilibria involving solutions containing both TAA and alkali metal cations on the one hand and those containing alkali metal cations only. However, re‐equilibration of the aluminosilicate species for TAA/Na aluminosilicates is slow (usually not detectable on the time‐scale of the experiments), whereas when purely alkali metal cations are used, the spectra alter over a period of ～1 h, such that resolution is degraded substantially. In the latter case, it is suggested that the anions aggregate into larger systems, although the solutions are still clear. ²⁹Si NMR evidence for slow equilibration of silicate and aluminosilicate solutions at higher concentrations is also discussed. Copyright © 2002 John Wiley & Sons, Ltd.     

Croconic acid and alkali metal croconate salts: some new insights into an old story

The solid-state structures of a series of alkali metal salts of the croconate dianion (C(5)O(5)(2-)) and of croconic acid (H(2)C(5)O(5)) have been determined. The alkali metal croconates were obtained by ring contraction of rhodizonic acid (H(2)C(6)O(6)), upon treatment with alkali metal hydroxides and recrystallisation from water. The novel species Na(2)C(5)O(5) x 2H(2)O, Rb(2)C(5)O(5) and Cs(2)C(5)O(5), as well as the mixed hydrogencroconate/croconate salt K(3)(HC(5)O(5))(C(5)O(5)) small middle dot2 H(2)O are described and compared with the Li(+), K(+) and NH(4)(+) salts. Single crystals of croconic acid were obtained by crystallisation of croconic acid in the presence of HCl. Crystal structure determinations showed that the C(5)O(5)(2-) ions tend to organize themselves in columns. The interplanar separations lie in the narrow range 3.12-3.42 A and do not necessarily reflect the presence of pi-stacking interactions. It is argued that the small interplanar separation is the result of a compromise between packing of flat croconate units and the spherical cations together with the water molecules that fill the coordination spheres of the alkali metal atoms.     

七甲茚基稀土络合物和碱金属盐的化学反应

本文用核磁共振等方法研究了稀土络合物和碱金属盐中的七甲茚基的质子化或氘化反应、亲核取代反应及络合物中稀土离子的还原反应。七甲茚基络合物比相应的茂基或茚基化合物更易与盐进行上述反应。三氘代七甲茚基在氘化反应中显示了同位素效应。     

Thermodynamic quantities of surface formation of aqueous electrolyte solutions X. Aqueous solution of 2:1 valence-type salts

The behaviors of a series of calcium halides and of alkali earth metal chlorides in the air/water surface region were studied in comparison with those of alkali metal halides by measuring the surface tension increments of solutions. The effect of salts with divalent cations on the surface tension increments is more pronounced than that of uni-univalent salts, but there are some similarities between these two types. It seems that the anions cause a marked effect on surface tension which is proportional to the magnitude of hydration in the bulk water. We also observed a decrease in the entropy change of surface formation with increasing concentration. The importance of an electrical double layer at the surface is discussed in relation to these surface tension increments.     

Molecular structure of 3-aminobenzoic acid complexes with alkali metals

The vibration (FT-IR, FT-Raman), electronic (UV-Vis) and NMR (1H and 13C) spectra for 3-aminobenzoic acid and its alkali metal salts were recorded. The influence of lithium, sodium, potassium, rubidium and cesium on the electronic system of the 3-aminobenzoic acid was studied. The assignment of the vibration spectra was done. Characteristic shifts of band wavenumbers and changes in band intensities along the metal series were observed. Good correlation between the wavenumbers of the vibrational bands in the IR and Raman spectra for 3-aminobenzoates and ionic potential, electronegativity, atomic mass and affinity of metal cations were found. The chemical shifts of protons (1H NMR) and carbons (13C NMR) in the series of studied alkali metals were also observed. Optimized geometrical structures of studied compounds were calculated by ab initio and density functional methods.     

Copolymerization of methacrylic acid alkali metal salts and polyether-containing monomers in solid polymer electrolytes

Copolymerization of methacrylic acid alkali metal salts (MAAM; M = Li, Na, K, Rb or Cs) and oligo(oxyethylene) methacrylate (MEO) was carried out in bulk or in poly(oligo(oxyethylene) methacrylate) (PMEO) at 60°C. The copolymers of MAAM and MEO which were obtained by bulk polymerization showed a cation conductivity of around 1 × 10^?7 S/cm at room temperature. On the other hand, the copolymers obtained by radical polymerization in PMEO, showed a higher cation conductivity (10^?6–10^?5 S/cm). Furthermore, higher cation conductivity was observed for the copolymer systems containing alkali metal cations with a larger ion radius. This tendency was explained by the strength of the bond between alkali metal cation and ether oxygens. The degree of dissociation had little effect on this difference in the conductivity. The effective dissociation of methacrylic salts was enhanced in the copolymer compared to the homopolymer because of the suppression of the adjacent dissociative carboxylic acid groups. Arrhenius plots for ionic conductivity show the migration of ions along with the segmental motion of the polymer matrix.     

Changes in the activity of Ru/Fe2O3 catalysts modified with alkali metal salts in the water-gas shift reaction

A study was undertaken to determine the activity of ruthenium catalysts, obtained by deposition of Ru₃(CO)₁₂ on products of iron oxide-hydroxide calcination modified with alkali metals, in the water-gas shift reaction. The activity depends on the kind of starting iron support, the ruthenium precursor and the amount of alkali metal salts. The most active were the catalysts obtained by deposition of Ru₃(CO)₁₂ on calcination products of σ-FeOOH, both modified and unmodified with alkali metal salts, and of α-FeOOH modified with alkali metal salts.     

Computational study of aza-adamantanes as multivalent bases

Structure and bonding characteristics, and gas phase stepwise basicities of proposed multivalent bases 1,3,5,7-tetraazatricyclo[3.3.1.1(3,7)]decane, 1,3,5,7,9,10-hexaazatricyclo[3.3.1.1(3,7)]decane and tricyclo[3.3.1.1(3,7)]azadecane, named and abbreviated here respectively as tetra-aza-adamantane (TAA), hexa-aza-adamantane (HAA) and deca-aza-adamantane (DAA), have been studied using B3LYP/6-311++G** method. Effects of protonation on the bond lengths and angles, and atomic charges, and on their correlations are studied in detail. Results show that the most affected characteristics by protonation are the N–H bond lengths and the charge of the hydrogen atoms. It is found, interestingly, that in the protonation of DAA, electric charges of the unprotonated nitrogen atoms are increased more than that of the protonated nitrogen atoms. Because of very small effects of protonation on the skeletal C–N and N–N bond lengths, it can be said that the aza-adamantane cage volume is not changed significantly upon protonation. The protonation energies approve multivalent nature of these bases with the order of TAA ≈ HAA > DAA. Different isomers for the unprotonated and protonated HAA and DAA are also studied.     

三硝基均苯三酚及其碱金属盐晶体的周期性密度泛函理论研究

对三硝基均苯三酚(TNPG)及其碱金属盐晶体进行DFT-B3LYP周期性计算研究, 求得其能带和电子结构, 探讨了结构-性能关系. 研究结果表明, 晶胞结构参数的计算值与实验值吻合较好. TNPG的导电性介于半导体和绝缘体之间, 而其碱金属盐均为半导体. 金属离子的引入使TNPG阴离子和金属阳离子通过配位键形成三维无限网状结构, 这种网状结构与晶体的半导体性质相关联. TNPG及其碱金属盐的前线轨道主要是由C—NO₂的原子轨道组成, 配位水和金属离子对前线轨道的组成没有贡献. TNPG碱金属盐的带隙均比TNPG的小, 根据“最易跃迁原理”可推测碱金属盐均比TNPG敏感, 这与实验事实相符. 同时, 金属离子的引入增大了酚羟基上的氧原子的活性, 这也可能是导致碱金属盐比TNPG敏感的原因之一.     

Synthesis and Some Properties of 1,2-Dinitroguanidine

1,2-Dinitroguanidine is a product of nitroguanidine nitration with nitric acid and its mixtures with sulfuric acid and oleum. It is a diacid (pK _a 1.11, 11.5) and at the same time a weak base undergoing protonation at the nitrogen of the amino group (pK _BH+ -5.81). The decomposition kinetics of 1,2-dinitroguanidine was studied by spectrophotometric method both in acid and alkaline media, and the mechanism of the process was assumed. In the media of high acidity (H_o > -8) the 1,2-dinitroguanidine suffers reversible denitration into nitroguanidine. At lower acidity its conjugate acid or molecular form undergoes hydrolysis yielding nitrourea. Monoanion of 1,2-dinitroguanidine in a weak acid or in an alkali is hydrolyzed into N,N'-dinitrourea. The reaction of 1,2-dinitroguanidine with alkali in alcohol provides its salts, with nitrogen-containing bases form both salts and derivatives of 2-nitroguanidine. The treatment of 1,2-dinitroguanidine with haloalkanes results in its N-alkylated products.     

Alkali cation binding of polymers with different sized crown ethers and photodimerizable units

The polymers which have different sized crown ethers as alkali cation binding sites and photodimerizable cinnamoyl units were prepared by the cationic copolymerization of corresponding monomers. The crown–cation complexation ratio (1:1 or 2:1) was investigated by measuring quantum yields ? of the photodimerization of the crown-connected cinnamoyl units in the presence of alkali metal chlorides and also by measuring the shift of λ_max of alkali metal picrates in THF on addition of the crown polymers. A significant 1:2 complex formation of alkali cations with two different sized crown ether units in the side chain of the polymers was confirmed. The alkali metal cation binding ability and selectivity of the polymers, which were studied by a method of picrate salts extraction, were markedly different from those expected from the combination of polymers of same ring-size crown ether units. When irradiated with ultraviolet (UV) light, the cinnamic acid ester groups of the polymers caused dimerization even in dilute solutions. The cation binding ability of the polymers was largely enhanced by the photodimerization of the cinnamoyl moieties with suitable template cations.     

Alkali‐Metal‐Ion‐Assisted Hydrogen Atom Transfer in the Homocysteine Radical

Intramolecular hydrogen atom transfer (HAT) was examined in homocysteine (Hcy) thiyl radical/alkali metal ion complexes in the gas phase by combination of experimental techniques (ion‐molecule reactions and infrared multiple photon dissociation spectroscopy) and theoretical calculations. The experimental results unequivocally show that metal ion complexation (as opposed to protonation) of the regiospecifically generated Hcy thiyl radical promotes its rapid isomerisation into an α‐carbon radical via HAT. Theoretical calculations were employed to calculate the most probable HAT pathway and found that in alkali metal ion complexes the activation barrier is significantly lower, in full agreement with the experimental data. This is, to our knowledge, the first example of a gas‐phase thiyl radical thermal rearrangement into an α‐carbon species within the same amino acid residue and is consistent with the solution phase behaviour of Hcy radical.     

Characteristics of proflavine solubilized in complexes of anionic polymers with a cationic surfactant

Absorption and emission spectra of 3,6-diaminoacridine (proflavine) are reported in mixed solutions of dodecyltrimethylammonium bromide (DTAB) with various polyelectrolytes including the sodium salts of poly(acrylic acid) (PAA). poly(methacrylic acid) (PMA), poly(styrenesulfonic acid) (PSS), poly(garacturonic acid) (pectate), and the alternating copolymers of maleic acid with ethylene (PMA-E) and styrene (PMA-S). The spectral change indicates the association of the dye (blue-shift) on these polyions except on PSS, the easy dissociation of the aggregated form into the monomeric form and the solubilization into the hydrophobic PMA-S/DTAB complex (red-shift), the little dissociation in the PAA/DTAB, PMA/DTAB and PMA-E/DTAB complexes, and the liberation of the bound dye in the case of pectate/DTAB complexes. In the PSS system, the strong interaction of the dye with the styrene groups induces the completely different spectral behavior. These results are discussed with the cooperative binding of the dye and the surfactant ion.     

固体杂多酸盐催化性能 Ⅰ．钨磷、钨硅杂多酸碱金属盐的合成、表征和催化酯化反应

合成了ＨＰＷ１２、ＨＳｉＷ１２杂多酸的一系列铯盐：ＣｓｘＨ３－ｘＰＷ１２（ｘ＝０～３），ＣｓｘＨ４－ｘＳｉＷ１２（ｘ＝０～４）．测定了它们的酸强度、ｐＨ滴定曲线、ＮＨ３－ＴＰＤ、ＩＲ光谱和比表面积．以乙酸和正丁醇的酯化为探针反应，考察了催化剂的酸催化活性．实验发现，碱金属取代后，ＰＷ１２系列的多数催化剂的酸强度提高，而ＳｉＷ１２系列的则降低，但对同一系列来说，由ＮＨ３－ＴＰＤ测得的酸强度和酸量均随取代量增加而减小，ｐＨ滴定的结果与此类似，当ｘ＝２．５时，两系列催化剂的比表面积均存在一个极值．对乙酸和正丁醇的催化酯化活性只与总酸量有关，与表面积无关，属假液相反应．