Multicyclic polyethers derived from 1,1,1‐tris(4‐hydroxyphenyl)ethane and 2,6‐dihalopyridines

Poly(pyridine ether)s were prepared in two ways: the polycondensation of silylated 1,1,1‐tris(4‐hydroxyphenyl)ethane (THPE) with 2,6‐difluoropyridine (method A) and the polycondensation of free THPE with 2,6‐dichloropyridine (method B). With method A, the THPE/difluoropyridine feed ratio was varied from 1.0:1.0 to 1.0:1.6. Cycles, bicycles, and multicycles were the main reaction products, and crosslinking was never observed. When ideal stoichiometry was used exclusively, multicycles free of functional groups were obtained. These multicycles were detectable in matrix‐assisted laser desorption/ionization time‐of‐flight (MALDI‐TOF) mass spectra up to B₃₈C₇₆ with a mass of approximately 32,000 Da. With method B, the reaction conditions were varied at a fixed feed ratio to achieve an optimum for the preparation of multicyclic polyethers, but because of the lower reactivity of 2,6‐dichloropyridine, a quantitative conversion was not achieved. The reaction products were characterized with MALDI‐TOF mass spectrometry, viscosity measurements, and size exclusion chromatography. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 5725–5735, 2004     

Miscible blends of modified poly(aryl ether ketones) with aromatic polyimides

The phase behavior of binary blends of poly(ether ether ketone) (PEEK), sulfonated PEEK, and sulfamidated PEEK with aromatic polyimides is reported. PEEK was determined to be immiscible with a poly(amide imide) (TORLON 4000T). Blends of sulfonated and sulfamidated PEEK with this poly(amide imide), however, are reported here to be miscible in all proportions. Blends of sulfonated PEEK and a poly(ether imide) (ULTEM 1000) are also reported to be miscible. Spectroscopic investigations of the intermolecular interactions suggest that formation of electron donoracceptor complexes between the sulfonated/sulfamidated phenylene rings of the PEEKs and the n-phenylene units of the polyimides are responsible for this miscibility. © 1993 John Wiley & Sons, Inc.     

Novel aromatic polyamides bearing pendent diphenylamino or carbazolyl groups

Two new diamines, 2,4‐diaminotriphenylamine ( 3 ) and N‐(2,4‐diaminophenyl)carbazole ( 4 ), were synthesized via the cesium fluoride‐mediated aromatic substitution reactions of 1‐fluoro‐2,4‐dinitrobenzene with diphenylamine and carbazole, followed by palladium‐catalyzed hydrazine reduction. Amorphous and soluble aramids having pendent diphenylamino and carbazolyl groups were prepared by the phosphorylation polycondensation of aromatic dicarboxylic acids with diamines 3 and 4 , respectively. The aramids derived from diamine 3 had sufficiently high molecular weights to permit the casting of flexible and tough films. They exhibited excellent mechanical properties and moderately high softening temperatures in the 221–298 °C range. However, the reactions of diamine 4 with aromatic diacids gave relatively lower molecular weights products that could not afford flexible films. For a comparative purpose, the parent aramids derived from m‐phenylenediamine and aromatic diacids were also prepared and characterized. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 3302–3313, 2004     

Catalysis by Ir(III), Rh(III) and Pd(II) metal ions in the oxidation of organic compounds with H2O2

Catalytic activities of three transition metals, as iridium (III) chloride, rhodium (III) chloride and palladium (II) chloride, were compared in the oxidation of six aromatic aldehydes (benzaldehyde, p‐chloro benzaldehyde, p‐nitro benzaldehyde, m‐nitro benzaldehyde, p‐methoxy benzaldehyde and cinnamaldehyde), two hydrocarbons (viz. (anthracene and phenanthrene)) and one aromatic and one cyclic alcohol (cyclohexanol and benzyl alcohol) by 50% H₂O₂. The presence of traces (substrate: catalyst ratio equal to 1:62500 to 1:1961) of the chlorides of iridium(III), rhodium(III) and palladium(II) catalyze these oxidations, resulting in good to excellent yields. It was observed that in most of the cases palladium(II) chloride is the most efficient catalyst. Conditions for the highest and most economical yields were obtained. Deviation from the optimum conditions decreases the yields. Oxidation in aromatic aldehydes is selective at the aldehydeic group only and other groups remain unaffected. This new, simple and economical method, which is environmentally safe, also requires less time. Reactive species of catalysts, existing in the reaction mixture are also discussed. Copyright © 2007 John Wiley & Sons, Ltd.     

Existence of aromatic sp~2 C-H…O = C intramolecular interaction similar to hydrogen bond

A 'H NMR signal shifted drastically to down field (δ - 10.0) at the bay area and in dose proximity to C = O group for H-1 was observed through complete assignments of 1H NMR spectra for pyridino- and benzobenzanthrones. It is concluded that this phenomenon is due not only to the anisotropy effect of C=O plus aromatic ring current effect, but also to the electrostatic attraction of C-H (δ+)…O(δ-)=C interaction. The evidence for the sp2C-H…O = C intramolecular interaction similar to hydrogen bond has also been given by EI-MS and MS/MS (CID) spectroscopy and IR spectroscopy, as well as MNDO-PM3 calculations. This new kind of interaction might be called 'quasi-hydrogen bond'.     

Reactions of (η6-Arene)tricarbonylchromium Complexes: Hydrogenation,Nitration, and Bromination

In this study, we explore the reactions of coordinated arenes, e.g., hydrogenation, nitration, and bromination, to prepare compounds which are not accessible from conventional organic synthesis. The reaction products formed from reactions with the coordinated and the uncoordinated arenes are compared. The polycyclic aromatic hydrocarbons (PAHs) employed for this study include phenanthrene, methyl- and acetyl-phenanthrene, and benz[a]anthracene (BA), The tricarbonylchromium group demonstrated various characteristics which influence the reactions in this work, such as an electronic effect to deactivate hydrogenation, a steric effect to exhibit, highly positional selective nitration, and a free radical mechanism to direct bromine to attack at the ring coordinated to tricarbonylchromium.     

Self-Assembly of Gold Nanoclusters on Molecularly Modified GaAs

The elaboration of closed-packed monolayers of Au₅₅(PPh₃)₁₂Cl₆ clusters on oxidized and non-oxidized GaAs surfaces is reported. The first part of this work describes the use of silanethiol modified GaAs oxide surfaces to trap 18 nm gold colloids and Au₅₅(PPh₃)₁₂Cl₆ clusters. The surfaces characterized by AFM measurements present high-quality coverage on a quite long range for both metallic species. The second part is devoted to the elaboration of Au₅₅(PPh₃)₁₂Cl₆ cluster monolayers on non-oxidized p-type GaAs substrates, functionalized with dithiol molecules. AFM measurements demonstrate the presence of closed-packed two-dimensional arrangements of Au₅₅ clusters.     

Computer interactive identification system for polycyclic aromatic hydrocarbons in reversed-phase microcolumn liquid chromatography

Summary A computer interactive identification system is proposed which is based on the relationship between retention and molecular properties such as the size and shape of polycyclic aromatic hydrocarbons (PAHs). This system offers an automatic analytical process for liquid chromatography, providing a reliable identification of the separated components. The identification can be further enhanced by the use of multiple detectors such as a multichannel UV detector. The system can be used for optimization procedures, resulting in a highly automatic complex analytical system.     

A new class of aromatic polyetheraroylhydrazides. I. Synthesis and chemical–physical characterization

A series of new aromatic polyetheraroylhydrazides incorporating 4-oxybenzoyl units has been synthesized, whose general formula was [CONHNHCO? O? O–(CH₂)_x? O? phenyl O-CONHNHCOO]_n with x values in the range of 2 to 12. The increasing number of methylene units in the backbone gave rise to polymers which melted before the hydrazidic linkage underwent thermal cyclation to oxadiazole. Moreover, many polymers showed multiple endotherms on melting. X-ray diffraction studies confirmed a crystalline organization of polyhydrazides for methylene units above 4. © 1993 John Wiley & Sons, Inc.