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71.
Åse Støg»rd 《Chemical physics letters》1975,36(3):357-360
Ab initio as well as semi-empirical SCF MO calculations are presented for ClCN and ONCl. The relative intensities for Cl Kβ emission in the two molecules were calculated. The calculated spectra from the ab initio wavefunctions are in excellent agreement with experiments. 相似文献
72.
This review addresses the special problems associated with the micro-structural characterization of thin and ultrathin organic films, primarily by optical spectroscopies. Films which are deposited by Langmuir-Blodgett techniques, self-assembly chemistry, and bulk film deposition techniques are considered. The use of enhanced optical excitation using surface phasma resonances and integrated optical structures is discussed extensively, as is the use of ellipsometry. Discussion of the spectroscopies used is broken into a section on electronic spectroscopies and an extensive discussion of vibrational spectroscopies. Vibrational information may be obtained with photons (absorption or scattering) or electrons (loss spectra), and the types of experimental systems amenable to each, along with the advantages and disadvantages of each are explored. 相似文献
73.
M. Mintas Z. Orhanović K. Jakopčić H. Koller G. Stühler A. Mannschreck 《Tetrahedron》1985,41(1):229-233
N-Aryl-4-pyridones 1–6 were synthesized by condensation of the corresponding 4-pyrone with anilines. The enrichment of the enantiomers was achieved by liquid chromatography on triacctylcellulose, enantiomeric purities of(+)-1 and (+ )-2 being measured by 1H-NMR in the presence of an optically active auxiliary. Barriers to partial rotation about the C-N bond in 1-4 were determined and compared with corresponding biphenyls. 相似文献
74.
Stéphanie Ricol Etienne Vernaz Philippe Barboux 《Journal of Sol-Gel Science and Technology》1997,8(1-3):229-233
Gels have been synthesized in the SiO2-Na2O-ZrO2 system and calcined at various temperatures up to 700°C. They have been studied by infrared absorption spectroscopy. The position of the asymmetric stretching frequency of the SiO4 unit is used as a tracer of the homogeneity. It is shown that sodium increases the solubility of zirconium in the silica matrix as already observed in fused glasses. 相似文献
75.
Fiona Sim Dennis R. Salahub Steven Chin 《International journal of quantum chemistry》1992,43(4):463-479
Dipole moments and static dipole polarizabilities have been calculated for a number of small molecules using the linear combination of Gaussian-type orbitals–local spin density method. The effect of augmenting standard orbital basis sets with polarization functions has been investigated. A set of optimum ζd, for use in calculating polarizabilities, has been derived for the first-row atoms C, N, O, and F. The results of this optimized doubly polarized double-zeta basis set compare well with results obtained using a double-zeta basis set augmented by four even-tempered ζd polarization functions. The results of the optimized basis set, and a basis set augmented with only a single ζd polarization function derived from it, compare very favorably with those obtained from Møller–Plesset perturbation theory and with experimental data. They show a marked improvement on results obtained using standard Hartree–Fock self-consistent-field molecular orbital methods where no treatment of electron-correlation is included. 相似文献
76.
Structural characterization of nanosized CeO(2)-SiO(2), CeO(2)-TiO(2), and CeO(2)-ZrO(2) catalysts by XRD, Raman, and HREM techniques 总被引:1,自引:0,他引:1
Reddy BM Khan A Lakshmanan P Aouine M Loridant S Volta JC 《The journal of physical chemistry. B》2005,109(8):3355-3363
Structural characteristics of nanosized ceria-silica, ceria-titania, and ceria-zirconia mixed oxide catalysts have been investigated using X-ray diffraction (XRD), Raman spectroscopy, BET surface area, thermogravimetry, and high-resolution transmission electron microscopy (HREM). The effect of support oxides on the crystal modification of ceria cubic lattice was mainly focused. The investigated oxides were obtained by soft chemical routes with ultrahighly dilute solutions and were subjected to thermal treatments from 773 to 1073 K. The XRD results suggest that the CeO(2)-SiO(2) sample primarily consists of nanocrystalline CeO(2) on the amorphous SiO(2) surface. Both crystalline CeO(2) and TiO(2) anatase phases were noted in the case of CeO(2)-TiO(2) sample. Formation of cubic Ce(0.75)Zr(0.25)O(2) and Ce(0.6)Zr(0.4)O(2) (at 1073 K) were observed in the case of the CeO(2)-ZrO(2) sample. Raman measurements disclose the fluorite structure of ceria and the presence of oxygen vacancies/Ce(3+). The HREM results reveal well-dispersed CeO(2) nanocrystals over the amorphous SiO(2) matrix in the cases of CeO(2)-SiO(2), isolated CeO(2), and TiO(2) (anatase) nanocrystals, some overlapping regions in the case of CeO(2)-TiO(2), and nanosized CeO(2) and Ce-Zr oxides in the case of CeO(2)-ZrO(2) sample. The exact structural features of these crystals as determined by digital diffraction analysis of HREM experimental images reveal that the CeO(2) is mainly in cubic fluorite geometry. The oxygen storage capacity (OSC) as determined by thermogravimetry reveals that the OSC of the mixed oxide systems is more than that of pure CeO(2) and is system dependent. 相似文献
77.
Werner Stöber 《Colloid and polymer science》1957,151(1):42-47
Zusammenfassung Die in einer früheren Arbeit gemachte Annahme, da\ ein echtes thermodynamisches Gleichgewicht zwischen den einzelnen Kondensationsstufen
der Kiesels?ure existiert, wird im Hinblick auf die theoretischen Konsequenzen für die insgesamt im Gleichgewicht in L?sung
zu findende Kiesels?uremenge untersucht. Es wird für pH < 12 eine Formel für die „Gesamtl?slichkeit der Kiesels?ure“ entwickelt, die unter plausiblen Annahmen gut mit bisher vorliegenden
experimentellen Erfahrungen in übereinstimmung gebracht werden kann. 相似文献
78.
This review presents the recent advances in the achievement of organized proteo-lipidic nanostructures based on Langmuir-Blodgett technology and their potential applications in the nanobioscience area. By using the self-assembled properties of amphiphilic biomolecules at the air-water interface, the Langmuir-Blodgett (LB) technique offers the possibility to prepare ultrathin layers suitable for biomolecule immobilization at the molecular level. This review will provide a general overview of the enzyme association with preformed Langmuir-Blodgett films in connection with their potential applications in biosensing device developments, and then introduce the design of a new functionalised biomimetic nanostructure with oriented recognition site. The potential applications of such an organized proteo-lipidic nanostructure for biocatalysis investigations of an immobilised enzyme in a biomimetic situation and for the development of bioelectronic devices are finally discussed. 相似文献
79.
UV/Vis-spectra of Cyclosilanes (SiX
2)
n
withX=Cl, Br, I, OMe andn=4, 5, 6 are recorded and interpreted qualitatively. The spectra exhibit increasing influence of the substituents on the Si-Si-bond system within the rings in the order Cl OMe Br I. At the low energy side of the spectra weak absorption bands, possibly due to intramolecular charge transfer transitions, appear. The strong inductive effect of the electronegative substituents is documented by a marked increase of the first IP's compared to permethylcyclosilanes. 相似文献
80.
7-Benz[c] acridinemethanols as tetracyclic analogs of the 2-phenyl-4-quinolinemethanol antimalarials
Andre Rosowsky Michael Chaykovsky Sandra A. Yeager Richard A. St. Amand May Lin Edward J. Modest 《Journal of heterocyclic chemistry》1971,8(5):809-820
A series of new 7-benz[c]acridinemethanols and 5,6-dihydro-7-benz[c]acridinemethanols was prepared as rigid, tetracyclic analogs of the antimalarial 2-phenyl-4-quinolinemethanols. Condensation of 5,7-dichloroisatin with 6-chloro-, 7-chloro-, and 6,7-dichloro-1-tetralone furnished halogenated 5,6-dihydro-7-benz[c]acridinecarboxylic acids, which were transformed into the corresponding acid chlorides, acyl malonates, α-bromomethyl ketones, and epoxides. Fully aromatic members of the series obtained via dehydrogenation of the 5,6-dihydro acids were likewise converted into epoxides via the acylmalonate route. Although all the epoxides studied proved to be exceptionally resistant to ring-opening by di-n-butylamine, probably on account of steric effects, they could be cleaved readily with piperidine or morpholine. Nmr spectra of the resulting amino alcohols suggest that these compounds exist in a single preferred conformation stabilized by internal O-H····N hydrogen bonding, and that free rotation about the side chain C-C bond does not occur at room temperature. 相似文献