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11.
The photoelectron spectra of chromium-doped silicon cluster anions, CrSi-(n), were measured over the size range, n=8-12. Their vertical detachment energies were measured to be 2.71, 2.88, 2.87, 2.95, and 3.18 eV, respectively. Our results support theoretical calculations by Khanna, Rao, and Jena [Phys. Rev. Lett. 89, 016803 (2002)] which found CrSi12 to be an enhanced stability (magic) cluster with its chromium atom encapsulated inside a silicon cage and with its magnetic moment completely quenched by the effects of the surrounding cage. 相似文献
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Betaine is a permanent zwitterion. The molecular betaine anion has been generated in a hybrid, infrared desorption-electron photoemission source and its photoelectron spectrum recorded. The photoelectron spectrum of the betaine anion is characteristic of a dipole bound anion, and its vertical detachment energy was measured to be 0.29+/-0.03 eV. Calculations by Rak, Skurski, and Gutowski [J. Chem. Phys. 114, 10673 (2001)] had found the betaine anion to be a dipole bound anion with a vertical detachment energy of 0.28 eV. We also measured the vertical detachment energy of deprotonated betaine to be approximately 1.9 eV. 相似文献
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Ana Dunja Mance Marija indler-Kulyk KreImir Jakop
i Antonija Hergold-Brundi Ante Nagl 《Journal of heterocyclic chemistry》1997,34(4):1315-1322
N-Alkenyl-N-(5-substituted-2-furfuryl)-N-p-toluidines 1–10 have been selected to study the intramolecular Diels-Alder reaction of furans. New epoxyisoindolines 11–20 were prepared and fully characterised. 相似文献
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Antonija Hergold‐Brundi Gordana Pavlovi Ana Dunja Mance Kreimir Jakop
i 《Acta Crystallographica. Section C, Structural Chemistry》2000,56(11):e520-e521
The title compound, C15H14N2O3, is the first example of a structurally determined tertiary amine with both N‐5‐nitrofurfuryl and N‐prop‐2‐ynyl moieties. The molecule is not planar, i.e. the furan ring is inclined at an angle of 84.35 (4)° to the phenyl ring. The crystal structure is dominated by van der Waals forces. The terminal alkynyl group as the strongest C—H hydrogen‐bond donor is not involved in hydrogen‐bond formation. 相似文献
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Srzić D Rozman M Krizmanić I Zinić B 《Rapid communications in mass spectrometry : RCM》2003,17(5):377-382
The gas/phase behaviour of N-sulfonylated purine nucleic bases and nucleosides towards electron impact (EI) and matrix-assisted laser desorption/ionization (MALDI) occurring in a ion trap of a Fourier transform ion cyclotron resonance mass spectrometer is investigated. The influence of the storage time on the protonated molecule ([M+H](+)) abundance under EI conditions confirms that the formation of these ions proceeds through ion/molecule reactions. Using stored-waveform inverse Fourier transform (SWIFT) selective isolation of M(+.) or H(3)O(+), self-chemical ionization, M(+.)/M, and chemical ionization, H(3)O(+)/M, are detected. Investigation of specific EI expulsion of SO(2), SO(2)H and/or SO(2)H(2) from M(+.) and/or [M+H](+) shows that oxygen protonation in bond;SO(2)bond; proceeds faster than nitrogen protonation. Expulsion of SO(2) from molecular ions is not observed in MALDI mass spectra of nucleosides. 相似文献
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Mazurkiewicz K Harańczyk M Gutowski M Rak J Radisic D Eustis SN Wang D Bowen KH 《Journal of the American Chemical Society》2007,129(5):1216-1224
Photoelectron spectra of adenine-formic acid (AFA(-)) and 9-methyladenine-formic acid (MAFA(-)) anionic complexes have been recorded with 2.540 eV photons. These spectra reveal broad features with maxima at 1.5-1.4 eV that indicate formation of stable valence anions in the gas phase. The neutral and anionic complexes of adenine/9-methyladenine and formic acid were also studied computationally at the B3LYP, second-order M?ller-Plesset, and coupled-cluster levels of theory with the 6-31++G** and aug-cc-pVDZ basis sets. The neutral complexes form cyclic hydrogen bonds, and the most stable dimers are bound by 17.7 and 16.0 kcal/mol for AFA and MAFA, respectively. The theoretical results indicate that the excess electron in both AFA(-) and MAFA(-) occupies a pi* orbital localized on adenine/9-methyladenine, and the adiabatic stability of the most stable anions amounts to 0.67 and 0.54 eV for AFA(-) and MAFA(-), respectively. The attachment of the excess electron to the complexes induces a barrier-free proton transfer (BFPT) from the carboxylic group of formic acid to a N atom of adenine or 9-methyladenine. As a result, the most stable structures of the anionic complexes can be characterized as neutral radicals of hydrogenated adenine (9-methyladenine) solvated by a deprotonated formic acid. The BFPT to the N atoms of adenine may be biologically relevant because some of these sites are not involved in the Watson-Crick pairing scheme and are easily accessible in the cellular environment. We suggest that valence anions of purines might be as important as those of pyrimidines in the process of DNA damage by low-energy electrons. 相似文献
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Wagner GK Kotschenreuther D Zimmermann W Laufer SA 《The Journal of organic chemistry》2003,68(11):4527-4530
The regiospecific synthesis of 2a (Scheme 3), a novel and potent pyridinyl imidazole inhibitor of p38 MAP (mitogen-activated protein) kinase, and the regioselective preparation of its regioisomer 2b (Scheme 4) are described. Chromatographic and spectroscopic data are presented, which in this class of compounds allow the unambiguous identification of regioisomers prepared by a nonregiospecific synthetic strategy. Biological data demonstrating the importance of the correct regiochemistry for inhibition of p38 are given. 相似文献
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H Budzikiewicz T Cvitas S Kazazic L Klasinc D Srzic 《Rapid communications in mass spectrometry : RCM》1999,13(12):1109-1111
Determination of the concentration of neutral polycyclic aromatic hydrocarbon molecules in the mass spectrometer for reaction rate measurement is investigated. Copyright 1999 John Wiley & Sons, Ltd. 相似文献
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