Search results for "RACE"

Intercorrelation between Structural Ordering and Emission Properties in Photoconducting Polymers

2009

We investigated the structural properties of anthracene containing poly(p-phenylene−ethynylene)-alt-poly(p-phenylene−vinylene) polymers with general constitutional unit: (−Ph−C≡C−Anthr−C≡C−Ph−CH═CH−Ph−CH═CH−)n by means of wide-angle X-ray scattering and fluorescence spectroscopy. Interchain interactions were systematically modified by decorating the conjugated polymer backbone with linear or branched or combinations of linear and branched alkoxy side chains. Special emphasis is taken on an evaluation method for fiber scattering spectra that allows the deduction of important structural details of polymer materials with limited degree of order. These include positional correlations along the …

Cover Picture: Palladium-Catalyzed Arylation of Linear and Cyclic Polyamines (Eur. J. Org. Chem. 2/2005)

2005

The cover picture shows the model structures of four compounds among the hundred of arylated linear and cyclic polyamines prepared by palladium-catalyzed coupling of mono- and dihalogenoarenes with various aliphatic or aromatic polyamines. The reaction is strongly dependent on the nature and the concentration of the catalytic system, as well as the nature of the base. The competitive reaction between primary and secondary amines and the monoamination of dihalobenzenes have also been detailed in the article by R. Guilard et al. on p. 261 ff. In the following article by the same authors on p. 281 ff, the method has been applied to the synthesis of numerous nitrogen- and oxygen-containing macr…

2,4,5-Trimethylimidazolium Scaffold for Anion Recognition Receptors Acting Through Charge-Assisted Aliphatic and Aromatic C–H Interactions

2016

A series of two-armed 2,4,5-trimethylimidazolium-based oxoanion receptors, which incorporate two end-capped photoactive anthracene rings, being the central core an aromatic or heteroaromatic ring, has been designed. In the presence of HP2O7(3-), H2PO4(-), and SO4(2-) anions, (1)H- and (31)P NMR spectroscopical data clearly indicate the simultaneous occurrence of several charge-assisted aliphatic and aromatic C-H noncovalent interactions, i.e., significant downfield shifts were observed for the imidazolium C(2)-CH3 protons, the methylene N-CH2 protons, and the inner aromatic proton or the outer heteroaromatic protons. Density functional theory calculations confirm the occurrence of these non…

1989

Poly(9,10-dihydroanthrylenetrimethylene) (2) comprises a novel chain-type structure in which 9,10-dihydroanthracene units are linked by flexible spacer groups. Upon dehydrogenation with sulfur at elevated temperature, polymer 2 is converted into the corresponding polyanthrylene system 3. NMR- and UV-spectroscopic data provide firm evidence for the dehydrogenation process. The polymer 3 was subjected to reduction with active lithium, and the resulting polyanions were characterized by NMR spectroscopy and by quenching experiments. It appears that each anthracene unit of the chain can be charged with two electrons.

Selective access to either a doubly boron-doped tetrabenzopentacene or an oxadiborepin from the same precursor

2019

Depending on the solvent, a brominated arylborane gave the multiple helicene B2-TBPA (pyridine) or the oxadiborepin ODBE (THF) after intramolecular Yamamoto coupling.

Pressure-Induced Polymerization of Polycyclic Arene-Perfluoroarene Cocrystals: Single Crystal X-ray Diffraction Studies, Reaction Kinetics, and Desig…

2020

Pressure-induced polymerization of aromatic compounds leads to novel materials containing sp3 carbon-bonded networks. The choice of the molecular species and the control of their arrangement in the crystal structures via intermolecular interactions, such as the arene–perfluoroarene interaction, can enable the design of target polymers. We have investigated the crystal structure compression and pressure-induced polymerization reaction kinetics of two polycyclic 1:1 arene–perfluoroarene cocrystals, naphthalene/octafluoronaphthalene (NOFN) and anthracene/octafluoronaphthalene (AOFN), up to 25 and 30 GPa, respectively, using single-crystal synchrotron X-ray diffraction, infrared spectroscopy, a…

A study of weathered coal spectroscopic properties

2017

Abstract Current coal industry causes significant environmental pollution and the most air pollution deaths in the world, making the development of new eco-friendly applications one of the top priorities. Coal contains up to 50 % humic substances (HS), the majority of which is humic acid (HA). HA is well known for its beneficial properties and thus compounds extracted from coal can be used to develop new applications. To address this issue, we assessed structural composition of coal HS by measuring their spectroscopic properties. As the result, obtained spectra can be used to identify information about the molecules and thus allowing describing the composition of HS. The purpose of this stu…

Palladium-Catalyzed Reaction of Boronic Acids with Chiral and Racemic ?-Bromo Sulfoxides.

2005

Palladium-catalyzed cross-coupling reactions of racemic α-bromo sulfoxides with boronic acids are carried out in either aqueous or nonaqueous medium with formation of a new C sp3−C sp2 bond. The arylation of chiral α-bromo sulfoxides occurs without racemization. The cross-coupling reaction is general and gives high yields with arylboronic acids substituted with either donor or acceptor groups but gives poor results with heteroarylboronic acids. The best yields are obtained using degassed solvents and CsF instead of aqueous base. The use of aqueous base and the presence of oxygen favor the homocoupling side reaction.

Development of a Matrix-Matched Sphalerite Reference Material (MUL-ZnS-1) for Calibration of In Situ Trace Element Measurements by Laser Ablation-Ind…

2016

Sphalerite (ZnS) is an abundant ore mineral and an important carrier of elements such as Ge, Ga and In used in high-technology applications. In situ measurements of trace elements in natural sphalerite samples using LA-ICP-MS are hampered by a lack of homogenous matrix-matched sulfide reference materials available for calibration. The preparation of the MUL-ZnS1 calibration material containing the trace elements V, Cr, Mn, Co, Ni, Cu, Ga, Ge, As, Se, Mo, Ag, Cd, In, Sn, Sb, Tl and Pb besides Zn, Fe and S is reported. Commercially available ZnS, FeS, CdS products were used as the major components, whereas the trace elements were added by doping with single-element ICP-MS standard solutions a…

New tracer compounds for secondary organic aerosol formation from β-caryophyllene oxidation

2013

Abstract Five products from β-caryophyllene oxidation (β-caryophyllonic acid (I), 3,3-dimethyl-2-(3-oxobutyl)cyclobutanecarboxylic acid (βCA198) (II), β-nocaryophyllonic acid (III), β-caryophyllinic acid (IV), and 2-(2-carboxyethyl)-3,3-dimethylcyclobutanecarboxylic acid (βCA200) (V)) were synthesized and their structures confirmed by nuclear magnetic resonance spectroscopy. Reaction chamber experiments with β-caryophyllene at two different ozone mixing ratios were performed and the carboxylic acid oxidation products in the particle phase were characterized by APCI–MS and HPLC–ESI–MS. All five synthesized acids were found as β-caryophyllene oxidation products in the reaction chamber aerosol…