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51.
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The relative stability of the eta1mu1 (atop) and eta2mu2 (di-sigma) geometries of acetaldehyde are compared on Pt(111) and on two PtSn alloys ((2 x 2) and (square root(3) x square root(3))R30 degrees) by means of density functional theory (DFT) calculations. At low coverage on Pt (1/9 ML), the two forms are equivalent in energy, with eta1mu1 being slightly more stable. At high coverage (1/4 and 1/3 ML), eta2mu2 is less competitive and acetaldehyde is adsorbed through the aldehydic hydrogen. The evolution of the adsorption energy with the coverage and the apparition of the structure adsorbed through the aldehydic hydrogen are explained by the existence of attractive dipole-dipole interactions. On PtSn, only the eta1mu1 geometry is stable with an adsorption energy equal to that on Pt, in agreement with temperature-programmed desorption (TPD) experiments. The calculated vibrational spectra allow us to conclude that the experimental spectrum corresponds to a mixture of eta1mu1 (majority) and eta2mu2 (minority) structures on Pt and to only eta1mu1 on PtSn. The various interactions and the relative stability of the species on Pt and PtSn are explained by the density of states (DOS) curves. 相似文献
53.
Thanks to the use of localized orbitals and the subsequent possibility of neglecting long-range interactions, the linear-scaling methods have allowed to treat large systems at ab initio level. However, the limitation of the number of active orbitals in a complete active space self consistent-field (CASSCF) calculation remains unchanged. The method presented in this paper suggests to divide the system into fragments containing only a small number of active orbitals. Starting from a guess wave function, each orbital is optimized in its corresponding fragment, in the presence of the other fragments. Once all the fragments have been treated, a new set of orbitals is obtained. The process is iterated until convergence. At the end of the calculation, a set of active orbitals is obtained, which is close to the exact CASSCF solution, and an accurate CASSCF energy can be estimated. 相似文献
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Aurlie Mac Nora Hellou Joanna Hammoud Clothilde Martin Etienne S. Gauthier Ludovic Favereau Thierry Roisnel Elsa Caytan Ghassan Nasser Nicolas Vanthuyne J. A. Gareth Williams Fabienne Berre Bertrand Carboni Jeanne Crassous 《Helvetica chimica acta》2019,102(4)
A new enantiopure cyclometallated iridium complex bearing a [4]helicenic ‐coordinating and two ‐coordinating dfppy (2‐(2,4‐difluorophenyl)‐pyridyl) ligands was prepared. This complex displayed long‐lived phosphorescence both in solution and in the solid state. Its chiroptical properties, namely electronic circular dichroism and circularly polarized luminescence, were also examined. Comparison with former chiral complexes enabled assignment of the ΔIr‐(?) and ΛIr‐(+) absolute configurations. 相似文献
56.
Jean M. J. Tronchet Guido Zosimo-Landolfo Fabienne Villedon-Denaide Mirna Balkadjian Daniel Cabrini Françoise Barbalat-Rey 《Journal of carbohydrate chemistry》2013,32(6):823-835
ABSTRACT Cyclopentylidene ketals, moderately more acid-labile than their isopropylidene analogs, offer an alternative to the latter blocking groups. They have been shown to resist a large variety of reaction conditions commonly encountered in carbohydrate chemistry. 相似文献
57.
Nader Saad Brosse Nicolas Khadraoui Malek Fuentealba Cecilia Ziegler-Devin Isabelle Quils Fabienne El-Kirat-Chatel Sofiane Mauret Evelyne 《Cellulose (London, England)》2022,29(10):5593-5607
Cellulose - Micro- and Nano-Fibrillated Cellulose (MNFC) have gained increasing attention due to their remarkable properties, but their production usually requires an intensive multi-step process.... 相似文献
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59.
Fabienne Quilès François Humbert Anne Delille 《Spectrochimica acta. Part A, Molecular and biomolecular spectroscopy》2010,75(2):610-616
Attenuated total reflection Fourier transform infrared (ATR-FTIR) spectroscopy is a useful method for monitoring biofilm in situ, non-destructively, in real time, and under fully hydrated conditions. In this work we focused on changes in Pseudomonas fluorescens ATR-FTIR fingerprint accompanying the very early stages of biofilm formation: initial bacterial adhesion and the very beginning of biofilm development in the presence of nutrients. To help interpreting variations in the ATR-FTIR fingerprint of sessile bacteria, ATR-FTIR spectra of planktonic bacteria in different growth phases were also examined, and the average surface coverage and spatial arrangement of bacteria on the ATR crystal were determined by epifluorescence microscopy. The proteins, nucleic acids and polysaccharides ATR-FTIR spectral data recorded during growth of sessile bacteria were shown to be linked to changes in the physiological state of the bacteria, possibly accompanied by extracellular polymeric substances production. This work clearly showed by spectroscopic method how bacteria change drastically their metabolism during the first hours of biofilm formation. 相似文献
60.
Abécassis B Testard F Arleth L Hansen S Grillo I Zemb T 《Langmuir : the ACS journal of surfaces and colloids》2006,22(19):8017-8028
The ternary catanionic system octylammoniumoctanoate/octane/water is studied by combined SANS, light scattering, conductivity, and phase diagram approach in the water-poor microemulsion region. The sphere-to-cylinder growth and branching depends on the concentration, the water-to-surfactant ratio, and the temperature. The unidimensional growth leads to a network of interconnected wormlike micelles. Like most studied linear nonionic surfactants, in this true catanionic system at equimolarity of anionic and cationic surfactant, the curvature toward water increases with temperature, making connections between cylinders less frequent. 相似文献