Search results for "SINGLE"
showing 10 items of 4920 documents
Watching the photo-oxidation of a single aromatic hydrocarbon molecule
2001
International audience; The photooxidation of single dye molecules (see scheme) can be followed by confocal fluorescence microscopy. The self-sensitized reaction with singlet oxygen leads to a suite of products, which may be differentiated spectrally. Tentative structures for certain photoproducts have been obtained from quantum-chemical calculations.
A new experimental protocol for intrazeolite photooxidations. The first product-based estimate of an upper limit for the intrazeolite singlet oxygen …
2002
The intrazeolite photooxidations of several alkenes have been examined in hexane and in perfluorohexane slurries. The ability of perfluorohexane to increase the affinity of alkenes for the interior of the zeolite was documented. The nearly identical reaction rates in the two slurry solvents are attributed to a leveling of the singlet oxygen lifetime by the zeolite framework. A consideration of the rates of the various intrazeolite processes was used to estimate an upper limit for the intrazeolite lifetime of singlet oxygen.
New Triterpene Saponins fromAcanthophyllum pachystegium
2004
Four new triterpenoid saponins, pachystegiosides A (1), B (2), C (3), and D (4), were isolated from the roots of Acanthophyllum pachystegium K. H. Their structures were elucidated by means of a combination of homo- and heteronuclear 2D-NMR techniques (COSY, TOCSY, NOESY, HSQC, and HMBC) and by FAB-MS. The new compounds were characterized as 3-O-{O-β-D-galactopyranosyl-(12)-O-[β-D-xylopyranosyl-(13)]-β-D-glucuronopyranosyl}quillaic acid 28-{O-β-D-xylopyranosyl-(13)-O-β-D-xylopyranosyl-(14)-O-α-L-rhamnopyranosyl-(12)-O-[3,4-di-O-acetyl-β-D-quinovopyranosyl-(14)]-β-D-fucopyranosyl}ester (1), 3-O-{O-β-D-galactopyranosyl-(12)-O-[β-D-xylopyranosyl-(13)]-β-D-glucuronopyranosyl}quillaic acid 28-{O-…
Oxidative DNA damage of mixed copper(II) complexes with sulfonamides and 1,10-phenanthroline
2003
Abstract Mixed coordination compounds of Cu(II) with sulfonamides and 1,10-phenanthroline as ligands have been prepared and characterised. Single crystal structural determination of the complex [Cu( N -quinolin-8-yl- p -toluenesulfonamidate) 2 (phen)] shows Cu(II) ions are located in a highly distorted octahedral environment, probably as a consequence of the Jahn–Teller effect. The FT-IR and electronic paramagnetic resonance (EPR) spectra are also discussed. The mixed complexes prepared undergo an extensive DNA cleavage in the presence of ascorbate and hydrogen peroxide. Two of the complexes have higher nucleolytic efficiency than the bis( o -phenanthroline)copper(II) complex.
Copper Complexes with Sulfonamides Derivatives of Natural Amino Acids as Chemical Nucleases
2007
Three new coordination compounds have been prepared by reacting copper salts with sulfonamides derived from amino acids. Their molecular structures have been determined with the aid of single crystal X-ray diffraction. The copper cations are four-coordinated in all cases and the local environment is almost planar. Compound [Cu(ts-gly)(NH3)2]·H2O (1) crystallizes in monoclinic space group P21/c (no 14) with Z = 4 and with unit cell parameters a = 6.0490(12) A, b = 24.719(5) A, c = 9.159(2) A, α = γ = 90°, and β = 94.69(3)°. Compound [Cu(ts-isoleu)(NH3)2] (2) crystallizes in monoclinic space group C2/c (no 8) with Z = 15 and with unit cell parameters a = 30.800(6) A, b = 6.5510(13) A, c = 15.…
Solvothermal synthesis, crystal structure and magnetic properties of homometallic Co(II) and Cu(II) chains with double di(4-pyridyl)sulfide as bridges
2012
Abstract Two new coordination polymers {[Co(μ-4,4′-dps)2(H2O)2](NO3)2·2(4,4′-dps)·4H2O}n (1) and {[Cu(μ-4,4′-dps)2(H2O)2](NO3)2·2H2O}n (2) [4,4′-dps = di(4-pyridyl)sulfide] have been synthesized by solvothermal reactions between the nitrate salts of cobalt(II) (1) and copper(II) (2) and the 4,4′-dps molecule. Compounds 1 and 2 have been characterized by elemental analysis, thermal analysis (TG/DTA), vibrational spectroscopy, single crystal X-ray diffraction analysis and variable-temperature magnetic measurements. Compounds 1 and 2 are cationic chain compounds of formula {[M(μ-4,4′-dps)2(H2O)2]n2n+ [M = Co(II) (1) and Cu(II) (2)] with double 4,4′-dps bridges, uncoordinated nitrate anions, an…
Copper(II) complexes with sulfonamides derived from 2-picolylamine and their use as chemical nucleases
2006
Reaction between 2-picolylamine (2-aminomethylpyridine) with 2-mesitylenesulfonyl and 4- tert -butylbenzene sulfonyl chlorides leads to the formation of 2,4,6-trimethyl- N -[pyridin-2-ilmethyl]benzenesulfonamide (Hpmesa) and 4-ter-butyl- N -[pyridin-2-ilmethyl]benzenesulfonamide (Hptbsa). These compounds react with Cu(II) salts to yield coordination compounds with CuL 2 stoichiometry. The immediate environment of the metal ion is a highly distorted tetrahedron, the sulfonamide ligands acting in a bidentate fashion. Compound Hpmesa crystallizes in monoclinic space group P 2 1 /c (number 14), with Z = 4; complex [Cu(pmesa) 2 ] crystallizes in monoclinic space group P 1 ¯ (number 2), with Z …
Synthesis, structure, physicochemical characterization and theoretical evaluation of non-covalent interaction energy of a polymeric copper(II)-hydraz…
2019
Abstract One dimensional polymeric copper-hydrazone complex {[Cu(H0.5L)(µ1,3-SCN)]0.5ClO4·0.5MeOH}n (1) has been synthesized with Cu(ClO4)2·xH2O and N'-(1-(pyridin-2-yl)ethylidene)acetohydrazide (HL) in presence of NaSCN. The ligand and the complex have been characterized by several spectroscopic techniques (IR, UV–Vis and EPR), cyclic voltammetry and the structure of 1 has been determined by single crystal X-ray diffraction. The complex is an infinite one dimensional polymer bridged by thiocyanate. The magneto-structural correlation has been determined and the non-covalent interactions present in the molecule have been energetically evaluated by means of DFT calculations.
Syntheses, crystal structures and magnetic properties of mono- and polynuclear [bis(2-arylcarbonyl)amidate]copper(II) complexes
2008
Abstract Five copper(II) complexes of formulas [Cu(bpcam)(CN)(H2O)] (1), [Cu(bpcam)(N3)(H2O)]2 (2), [Cu(bpcam)(NCS)(H2O)] (3), [Cu(bpcam)(dca)(H2O)]2 (4) and [Cu(bpca)(tcm)]n (5) [bpcam = bis(2-pyrimidylcarbonyl)amidate, bpca = bis(2-pyridylcarbonyl)amidate, dca = dicyanamide and tcm = tricyanomethanide] have been prepared and their structures determined by single crystal X-ray diffraction. Compounds 1 and 3 are mononuclear species where each copper atom is five coordinated with a tridentate bpcam and a terminally bound cyanide (1)/thiocyanate (3) ligands creating a basal plane with a water molecule in the axial position of a distorted square pyramid. Compound 2 is made of neutral di-μ-1,1-…
Triterpenoid saponins from Piptadeniastrum africanum (Hook. f.) Brenan
2013
One new triterpenoid saponin, named piptadeniaoside (1), along with two known saponins (2–3) have been isolated from the stem bark of Piptadeniastrum africanum. After previous isolation of flavone derivatives from this plant, new phytochemical investigations were performed for its saponin content. Their structures were established by direct interpretation of their spectral data, mainly HRESIMS, 1D NMR (1H, 13C NMR, DEPT) and 2D NMR (COSY, NOESY, HSQC and HMBC), and by comparison with the literature data.