Search results for "Ash"
showing 10 items of 1718 documents
Inside Cover: Synthesis and Characterization of Carbazole-Linked Porphyrin Tweezers (Chem. Eur. J. 34/2015)
2015
Alkyloxy modified pyrene fluorophores with tunable photophysical and crystalline properties
2019
Novel alkyloxy modified 2,7-di-tert-butyl-4,5,9,10-tetra(arylethynyl)pyrenes were prepared through a straightforward Sonogashira coupling approach. Optical properties such as quantum yields and absorption/emission spectra of the fluorophores were investigated by UV/Vis and fluorescence measurements. Aggregation induced excimer formation of the chromophores in polar solvents and in the solid state was proved by the presence of a characteristic bathochromically shifted emission band and a decrease of the emission capability. These results strongly indicate the unexpected observation that the excimer formation of adjacent pyrene rings is not prevented by the introduction of bulky tert-butyl su…
Determination of mineral and trace element concentrations in pine needles by ICP-OES: evaluation of different sample pre-treatment methods
2008
In the present study, the determination of mineral and trace elements (Al, B, Ca, Cu, Fe, K, Mg, Mn, Na, P and Zn) from pine needles using three sample pre-treatment methods followed by inductively coupled plasma optical emission spectrometry, was examined. Sample pre-treatment methods tested were microwave digestion, ultrasound-assisted digestion and dry ashing. The new ultrasound-assisted digestion method was optimised by the analysis of the standard reference material (SRM) 1575a (pine needles) sample. The speed of dry ashing method was significantly increased by ultrasound dissolution after ashing. All the ICP-OES measurements were performed in robust plasma conditions which were tested…
Photophysical Properties of Oligo(phenylene ethynylene) Iridium(III) Complexes Functionalized with Metal-Anchoring Groups
2016
[EN] The electrochemical and photophysical properties of a family of conjugated ligands and their iridium(III) cyclometallated complexes are described. They consist of a series of monocationic Ir-III bis-2-phenylpyridine complexes with p-phenylethynyl-1,10-phenanthroline ligands of different length. The structure of these ligands includes terminal acetylthiol or pyridine groups, which can provide good electrical contacts between metal electrodes. Cyclic voltammetry, absorption and emission spectroscopy, laser flash photolysis and density functional theory calculations reveal that the high conjugation of the diimine ligand affords small energy gaps between the frontier orbitals. Nevertheless…
Preliminary evaluation of durum wheat (Triticum Turgidum Subsp Durum) during malting process:
2018
Durum (T. turgidum subsp. durum) wheat production worldwide is substantially less than that of common wheat (Triticum aestivum) mainly due to the relatively limited end-users. In order to evaluate malting and brewing suitability, sixteen old durum wheat landraces were malted at micro scale. Results show malt quality parameters in the range 78.2–85.9% for the extract, 72.9–80.9% for the fermentability, 3–5 EBC units for the colour, 0.49–0.79% dm for water-extractable arabinoxylans and 0.043–0.059% dm for the β-glucans. Regarding wort viscosity (1.53–1.92 mPa s), we found negative correlation with endo-1,4-β-D-xylanase, positive correlation with endo-β-glucanases and soluble proteins, while n…
Dynamics of ground and excited state chlorophylla molecules in pyridine solution probed by femtosecond transient absorption spectroscopy
1999
Abstract Femtosecond pump–probe spectroscopy was used to investigate the ground and excited state dynamics of chlorophyll a (Chl a ) in pyridine following excitation by a 100 fs optical pulse. The transient absorption spectrum and kinetics reveal spectral evolution on two ultrafast time scales: ∼100 fs and ∼3 ps. We attribute these dynamics to ground-state transient hole-burning and solvation dynamics. Transient absorption anisotropy at early times (∼500 fs) was measured for Chl a in pyridine and shows a pronounced wavelength dependence, where anisotropy varies between 0 and 0.5. Strong contribution from excited state absorption is the origin of the variation.
Photobinding of Tiaprofenic Acid and Subprofen to Proteins and Cells: A Combined Study Using Radiolabeling, Antibodies and Laser Flash Photolysis of …
1998
Drug photoallergy is a matter of current concern. It involves the formation of drug-protein photoadducts (photoantigens) that may ultimately trigger an immunological response. Tyrosine residues appear to be key binding sites in proteins. The present work has investigated the photobinding of tiaprofenic and (TPA) and the closely related isomer suprofen (SUP) to proteins and cells by means of radioactive labeling and drug-directed antibodies. To ascertain whether preassociation with the protein may play a role in photoreactivity, two model bichromophoric compounds (TPA-Tyr and SUP-Tyr) have been prepared and studied by laser flash photolysis. The results of this work show that (a) TPA and SUP…
Ultrafast Electronic and Vibrational Energy Relaxation of Fe(acetylacetonate)3 in Solution
2007
Transient mid-infrared spectroscopy is used to probe the dynamics initiated by excitation of ligand-to-metal (400 nm) and metal-to-ligand (345 nm) charge transfer states of FeIII complexed with acetylacetonate (Fe(acac)3, where acac stands for deprotonated anion of acetylacetone) in solution. Transient spectra in the 1500-1600 cm-1 range show two broad absorptions red-shifted from the bleach of the nu(CO) (approximately 1575 cm-1) and nu(C=C) (approximately 1525 cm-1) ground state absorptions. Bleach recovery kinetics has a time constant of 12-19 ps in chloroform and tetrachloroethylene and it decreases by 30-40% in a 10% mixture of methanol in tetrachloroethylene. The transient absorptions…
ChemInform Abstract: Asymmetric Allylation/Pauson-Khand Reaction: A Simple Entry to Polycyclic Amines. Application to the Synthesis of Aminosteroid A…
2014
Asymmetric allylation of o-iodoarylsulfinylimines has been achieved in high diastereoselectivities. The thus-obtained o-iodoarylhomoallylic sulfinamides participate in a subsequent Sonogashira coupling followed by a diastereoselective intramolecular Pauson–Khand reaction. In this way, tricyclic amines showing a unique benzo-fused indenyl backbone were obtained. The methodology has been applied to the synthesis of amino steroid analogues.