Positron annihilation studies of poly(N‐isopropyl acrylamide) gel in mixed solvents

Positron annihilation lifetime spectroscopy was used to characterize the reentrant volume‐phase‐transition behavior of poly(N‐isopropyl acrylamide) hydrogel in an ethanol/water mixed solvent. The polymer gel was synthesized with γ irradiation. The ortho‐positronium lifetime (τ₃) in the gel slowly increased with an increase in the ethanol content in the mixed solvent. τ₃ was not influenced by the volume phase transition. The ortho‐positronium intensity decreased with the collapse of the gel in an approximately 10% ethanol/water mixture. When swelled in pure ethanol, τ₃ initially increased with the solvent amount in the gel, showing the destruction of intramolecular hydrogen bonding and the relaxation of polymer chains. The lower critical solution temperature of the gel in the 10% ethanol/water mixture was lower than that in pure water, and τ₃ for various solvent contents showed behavior similar to that seen in pure solvent. © 2002 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 40: 1028–1036, 2002     

Selective functionalization at the small rim of calix[6]arene. Synthesis of novel non-symmetrical N3, N4 and N3ArO biomimetic ligands

Eight novel calix[6]arene-based biomimetic ligands for transition metal ions have been synthesized. They display a non-symmetrical N₃, N₄ or N₃ArO binding core that mimics enzyme active sites presenting histidine and tyrosine residues. The key step for their synthesis is the mono-alkylation at the small rim of the C_3v symmetrical trimethyl ether derivative of tBu-calix[6]arene with N-Boc-2-chloroethylamine to yield a novel calix[6]arene synthon. Its combined O-alkylation with a chloromethyl aromatic amine and N-deprotection or alkylation or reductive alkylation with a salicylaldehyde derivative yielded the calix[6]arene-based ligands with mixed N/O donors.     

Effects of Nonionic, Cationic, and Mixed Nonionic-Cationic Surfactants on the Acid-Base Behavior of Phenyl Salicylate

The effects of Brij 35 micelles, CTABr micelles, and mixed Brij 35–CTABr micelles on the acid–base behavior of phenyl salicylate (PST) have been studied in aqueous solution containing 2% v/v acetonitrile. The apparent pK_b (pK^app_b) of PST is decreased by 1.5 pK units with the increase in [Brij 35] from 0 to 0.02 M which is attributed to micellar medium effect. The values of pK^app_b remain almost independent of [CTABr] within its range 0.01–0.03 M. The increase in [CTABr] from 0 to 0.03 M in aqueous solution containing 0.02 M Brij 35 has not resulted in a change in pK^app_b. This shows that the characeristic structural features of nonionic Brij 35 micelles remain essentially unchanged on addition of CTABr under the present experimental conditions.     

Preparation and characterization of Mg(II)-, Ca(II) and Cd(II) complexes of 1,2-ethanediol and water

Mixed ligand complexes of different compositions were prepared with water, sulfate ion and 1,2-ethanediol as ligand. IR spectra and the thermoanalytical curves of the complexes were recorded. Oxygen atoms bound by one or two coordinate bonds to the metal ion, or by hydrogen-bonds in the crystal, were observed. As for the water molecule, 1,2-ethanediol molecules of crystal and monohydrate type were found, depending on the type of binding of the oxygen atoms.This revised version was published online in November 2005 with corrections to the Cover Date.     

Mixed strategy solutions forN-person quadratic games

Mixed strategy -equilibrium points are given forN-person games with cost functions consisting of quadratic, bilinear, and linear terms and strategy spaces consisting of closed balls in Hilbert spaces. The results are applied to linear-quadratic differential games with no information and quadratic integral constraints on the control functions.This work was supported by a Commonwealth of Australia, Postgraduate Research Award.     

Studies on the mixed-ligand complexes of copper(II) with gallic acid and pyridine carboxylic acids and their benzologues

Summary The ternary complex formation of copper(II) with gallic acid (gal) and 2-hydroxy nicotinic acid (hyna), 2-mercapto nicotinic acid (mena), salicylic acid (sa) or thiosalicylic acid (tsa) as a second ligand in a 1:1:1 molar ratio has been investigated in 40% (v/v) ethanol using spectrophotometric andpH titration methods. The solution equilibria of the ternary systems have been determined and the stability constants of the mixed complexes has been evaluated. Considering all parameters, the Cu-gal-sa ternary system was proved as a suitable, rapid, and sensitive spectrophotometric indicator for determining traces of copper.The ternary system containingsa obeysBeer's law up to 3.4 µg·ml^–1 copper. The optimum range for the determination of copper (Ringbom) atpH 6.0 ranges from 0.63 to 1.74 µg·ml^–1 of copper. The molar absorptivity of the ternary complex is 1.3×10⁴l·mol^–1·cm^–1.

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Untersuchungen anmixed-ligand — Komplexen von Kupfer(II) mit 3,4,5-Trihydroxybenzoesäure und Pyridincarbonsäuren und ihren C-Homologen

Zusammenfassung Die Bildung ternärer Komplexe von Kupfer(II) mit 3,4,5-Trihydroxybenzoesäure (gal) und 2-Hydroxynicotinsäure (hyna), 2-Mercaptonicotinsäure (mena), Salicylsäure (sa) oder Thiosalicylsäure (tsa) in einem molaren Verhältnis von 1:1:1 wurde mittels spektrophotometrischer und potentiometrischer Methoden in 40% (v/v) Ethanol untersucht. Die Lösungsgleichgewichte der termären Systeme und die Stabilitätskonstanten der gemischten Komplexe wurden bestimmt. Unter Berücksichtigung aller Parameter erwies sich das termäre System Cu-gal-sa als geeigneter schneller und empfindlicher Indikator zur Spurenanalyse von Kupfer.Dassa enthaltende ternäre System gehorcht demBeerschen Gesetz bis zu einer Kupferkonzentration von 3.4 µg·ml^–1. Der optimale Bereich zur Bestimmung von Kupfer (Ringbom) beipH 6.0 erstreckt sich von 0.63 bis 1.74 µg Cu pro ml. Die molare Extinktion des ternären Komplexes beträgt 1.3×10⁴l·mol·cm^–1.

     

Superconductivity in copper, silver, and gold compounds

High-temperature superconductivity exists in layered, square-planar cuprates, but is almost absent in most other Cu(II) compounds and in most Ag(II) and Au(II) compounds. Valence state II is quite unusual in silver and gold and often disproportionates to valence states I and III ("negative-U compounds"). The two-electron difference in oxidation state is suggestive of electron pairing, a prerequisite for superconductivity. In the present paper the connection between disproportionation and geometrical structure on one hand and superconductivity on the other is discussed by using the accepted theory for mixed valence complexes. It is concluded that absence of superconductivity in gold and silver compounds can be connected to the instability of oxidation state II and the large difference in equilibrium geometry between oxidation states I and III.     

Bola型阴离子表面活性剂与溴化十二烷基三乙铵混合体系的表面性质与聚集行为

研究了具有简单结构的bola型阴离子表面活性剂二十酸二钠（C_(20)Na_2)与 阳离子型普通表面活性剂溴化十二烷基三乙铵（C_(12)Et_3）混合体系的表面性质 ，发现混合体系的cmc和γ_(cmc)比C_(12)Et_3单一体系未有显著降低。以负染色 ，FF-TEM，动态光散射（DLS）及粘度方法研究了混合体系的聚集行为，发现混合 体系中同时形成球形囊泡和管状聚集体，提出了产生这种聚集行为的机制。     

Highly substituted azulene dyes as multifunctional NLO and electron-transfer compounds

Two highly substituted azulene derivatives were synthesised by Pd-mediated dimerisation from the corresponding tolan species. One azulene derivative (2) has donor functionalities (dianisylaminophenyl and dianisylamino) in the 1-, 2-, 3- and 6-positions, while the other (1) has donors (dianisylaminophenyl) in the 2- and 6-positions and acceptors (nitrophenyl) in the 1- and 3-positions. Each azulene derivative shows strong bond length alternation in the solid state, determined by X-ray crystal analysis, and an intense CT band around 450-500 nm in its UV/Vis spectrum. The first-order hyperpolarisability of 1 and of 2 was measured by hyper-Rayleigh scattering and is about that of disperse red DR1. Both azulene derivatives show multiple oxidation processes. The intramolecular adiabatic ET behaviour of the mixed valence radical cations of 1 and of 2 was investigated by UV/Vis/NIR spectroelectrochemistry. The intervalence-CT band of 1(+) could be analysed by the Generalised Mulliken-Hush theory, which yields an electronic coupling V=1140 cm(-1) for the optically induced adiabatic hole transfer.     

对称性和配合物的构型——Ⅱ.混合配体配合物

从库仑定律出发,采用最优化法,计算了MLaL_b′型配合物各种几何异构体的几何构型稳定化能。在计算中考虑了配体L、L′的相对电荷。 计算结果表明,对称性是决定构型的首要因素。具体构型与配体的相对电荷有关。 在若干配合物中,中心原子的dⁿ构型决定其构型的骨架。 配体对构型的作用也应予考虑。对共价性程度大的配合物,应考虑轨道重叠对构型的影响。