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31.
A new ternary polar intermetallic, Ca(18)Li(5)In(25.07), was obtained from high-temperature reactions of the elements in welded Nb tubes. Its crystal structure, established by single-crystal X-ray diffraction, was found to crystallize in the orthorhombic space group Cmmm (No. 65). Unit cell parameters are a = 9.9151(6) A, b = 26.432(2) A, and c = 10.2116(6) A; Z = 2. The structure of Ca(18)Li(5)In(25.07) features two distinct types of indium anionic layers. An "electron-deficient" layer is made up of Li-centered In(12) icosahedra that are interconnected by bridging planar In(4) units and In atoms. A second In(3)(5-) layer is an electron-precise Zintl layer formed by fused four-, five-, and six-membered rings of three- and four-bonded indium atoms. The two distinct layers are alternately stacked and linked into a complex three-dimensional network. Vacancies are observed to occur only at the In(12) icosahedral and the bridging indium units within the "electron-deficient" layers. Magnetic property measurements indicate that Ca(18)Li(5)In(25.07) exhibits temperature-independent paramagnetism consistent with metallic behavior. Band structure calculations were performed to elucidate the role of defects and vacancies in the electronic structure of the electron-deficient "metallic" Zintl phase. 相似文献
32.
The mass spectral fragmentation of carbazole was reinvestigated using metastable ion studies, exact mass measurements and 1,8-dideuteriocarbazole. 1,8-Dideuteriocarbazole was prepared by successive metalations and deuterations of carbazole. The 1H- and 13C-nmr spectra of 1,8-dideuteriocarbazole confirmed earlier assignments for carbazole. 相似文献
33.
By means of the quasi-isothermal-quasi-isobaric thermogravimetry (Q-TG) technique ideal experimental conditions can be realized. This provides a possibility to compare the measured data with data from other phase equilibrium (solubility, tension) examinations.On the example of the Ca(NO3)2-H2O system it is demonstrated that the phase diagrams can be used to interpret thermoanalytical (especially Q-TG) curves, or conversely, the results of thermoanalytical (Q-TG, DTA) examinations can serve for the control of equilibrium data of phase diagrams or to supply missing data.
The authors are indebted to Prof. E. Pungor for valuable discussions, and thank Mrs. M. Kiss and Miss I. Fábián for their technical assistance. 相似文献
Zusammenfassung Mit Hilfe des quasi-isothermischen-quasi-isobaren thermogravimetrischen (Q-TG) Verfahrens können ideale Versuchsbedingungen realisiert werden. Das ermöglicht es, die gemessenen Daten mit von anderen Phasengleichgewicht-Untersuchungen (Lösbarkeit, Tension) stammenden Daten zu vergleichen.Durch das Beispiel des Ca(NO3)2-H2O-Systems wurde es gezeigt, dass die Phasendiagramme zur Erklärung von thermoanalytischen (insbesondere Q-TG) Kurven können angewandt werden, oder umgekehrt, die Ergebnisse der thermoanalytischen (Q-TG, DTA) Untersuchungen als Kontrolle der Gleichgewichtsdaten der Phasendiagramme dienen können, oder die fehlenden Daten liefern können.
- (Q-) . ( , ). Ca(NO3)2-H2O , ( Q-) , .
The authors are indebted to Prof. E. Pungor for valuable discussions, and thank Mrs. M. Kiss and Miss I. Fábián for their technical assistance. 相似文献
34.
Pradeep Mathur Bala Manimaran Md. Munkir Hossain Arnold L. Rheingold Louise M. Liable-Sands Glenn P.A. Yap 《Journal of organometallic chemistry》1997,540(1-2):165-168
The tris-methylene bridged compound (NO)4Fe2Se(μ-CH2)3 has been isolated. It has been characterised by IR and 1H, 13C, and 77Se NMR spectroscopy. Its structure has been determined by single-crystal X-ray diffraction methods. The structure consists of a heavy atom triangle consisting of one Se and two Fe atoms. The Fe-Fe and the two Fe-Se edges are bridged by methylene groups. 相似文献
35.
The influence of localized excited (LE) states on the spectroscopy of charge transfer (CT) complexes has been examined for a series of complexes formed between methyl-substituted benzene donors and 1,2,4,5-tetracyanobenzene as acceptor in 1,2-dichloroethane and octanenitrile solvents. A molecular orbital model was used to describe the appearance of multiple CT absorption bands that occur in the spectra of these complexes. The influence of LE states in these CT absorptions was explored using time-resolved linear dichroism spectroscopy where the direction of the CT transition moment vector (TMV) was used to probe the magnitude of intensity borrowing. The TMV directions for each of the observed CT transitions within the absorption spectra were determined for several complexes. In some cases, the observed CT transitions were interpreted as being pure CT transitions; in others the observed transitions are influenced significantly by a LE transition. The correlation between the TMV directions and the transition energy suggests that the magnitude of intensity borrowing is influenced not only by the energy difference between the CT and LE transitions but also by the specific character of the transitions under consideration. 相似文献
36.
Bruce M. Howard William Fenical Edward V. Arnold Jon Clardy 《Tetrahedron letters》1979,20(31):2841-2844
The structure of a unique bromine-containing ketal, obtusin (), has been determined by spectral and X-ray crystallographic techniques. Obtusin is a natural component of the Mediteranean red alga . 相似文献
37.
Abdol R. Hajipour Majid Mostafavi Arnold E. Ruoho 《Monatshefte für Chemie / Chemical Monthly》2007,138(6):569-572
Summary. A straightforward and effective procedure for the deprotection of thioacetals to the corresponding carbonyl compounds using
potassium persulfate and the ionic liquid [bmim]Br under solvent-free conditions is reported. A variety of aliphatic and aromatic 1,3-dithiolanes or 1,3-dithanes was deprotected
to the corresponding carbonyl derivatives by this procedure. 相似文献
38.
van Wijk AA Spaans A Uzunbajakava N Otto C de Groot HJ Lugtenburg J Buda F 《Journal of the American Chemical Society》2005,127(5):1438-1445
To resolve the molecular basis of the coloration mechanism of alpha-crustacyanin, we used (13)C-labeled astaxanthins as chromophores for solid-state (13)C NMR and resonance Raman spectroscopy of [6,6',7,7']-(13)C(4) alpha-crustacyanin and [8,8',9,9',10,10',11,11',20,20']-(13)C(10) alpha-crustacyanin. We complement the experimental data with time-dependent density functional theory calculations on several models based on the structural information available for beta-crustacyanin. The data rule out major changes and strong polarization effects in the ground-state electron density of astaxanthin upon binding to the protein. Conformational changes in the chromophore and hydrogen-bond interactions between the astaxanthin and the protein can account only for about one-third of the total bathochromic shift in alpha-crustacyanin. The exciton coupling due to the proximity of two astaxanthin chromophores is found to be large, suggesting that aggregation effects in the protein represent the primary source of the color change. 相似文献
39.
Negative ion photoelectron spectroscopy of solvated electron cluster anions, (H2O)
n
−
and (NH3)
n
−
G. H. Lee S. T. Arnold J. G. Eaton H. W. Sarkas K. H. Bowen C. Ludewigt H. Haberland 《Zeitschrift für Physik D Atoms, Molecules and Clusters》1991,20(1):9-12
The photodetachment spectra of (H2O) n =2?69/? and (NH3) n =41?1100/? have been recorded, and vertical detachment energies (VDEs) were obtained from the spectra. For both systems, the cluster anion VDEs increase smoothly with increasing sizes and most species plot linearly withn ?1/3, extrapolating to a VDE (n=∞) value which is very close to the photoelectric threshold energy for the corresponding condensed phase solvated electron system. The linear extrapolation of this data to the analogous condensed phase property suggests that these cluster anions are gas phase counterparts to solvated electrons, i.e. they are embryonic forms of hydrated and ammoniated electrons which mature with increasing cluster size toward condensed phase solvated electrons. 相似文献
40.
Ashok G. Bajaj Sukh Dev Edward Arnold Bruce Tagle Jon Clardy 《Tetrahedron letters》1981,22(46):4623-4626
The steroechemistry of guggulsterol-1, a component of the exudate of , is shown to be 20(R), 22(R)(). 相似文献