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21.
22.
Mironov YV Yarovoi SS Naumov DY Kozlova SG Ikorsky VN Kremer RK Simon A Fedorov VE 《The journal of physical chemistry. B》2005,109(50):23804-23807
The novel vanadium thiobromide, V4S9Br4, with a square-planar metal cluster core was synthesized and characterized by single-crystal X-ray diffraction, measurements of magnetic properties and the heat capacity, and DFT calculations of the electronic structure. At the room temperature, the compound displays paramagnetic properties with an independent spin on each V atom and with a weak exchange constant (J approximately 10 cm(-1)). The paramagnetic state is transformed into a low-spin state (AF-type ordering) at low temperatures. This change is accompanied by a heat-capacity anomaly. The observed magnetic and heat-capacity anomalies can be explained by the thermal excitation of electrons on the closely spaced molecular energy levels in the presence of the Jahn-Teller effect. 相似文献
23.
CuAl2Cl8. Preparation and Crystal Structure. Crystals of CuAl2Cl8 have been prepared. Their remission spectrum agrees with that of gaseous CuAl2Cl8. The crystal structure (P21/c;a = 6.614, b = 7.376, c = 12.319 Å; β = 94.11°) shows a molecular lattice with Cu in square planar coordination, which is completed to a stretched octahedron (as in solid CuCl2) by two Cl atoms from neighbour molecules. Al has tetrahedral coordination. 相似文献
24.
25.
γ-Lactone-cis-annulation to Δ2- and Δ3- Cholestene. From Δ2- and Δ3- cholestene the γ-lactones 11a , 11b , 12a , and 12b are synthesized through the dibromocarbene adducts 3 and 4 , the bromohydrines 5 and 6 , the oxapiropentanes 7 and 8 , and the cyclobutanones 9a , 9b and 10a , 10b , respectively. The 13C-NMR.-spectra of 1–8 and 11 as well as the ORD.-spectra of the cyclobutanones 9 and 10 are reported. 相似文献
26.
A rapid field screening test for 2,4,6-trinitrotoluene (TNT) in water and soil is described. The immunofiltration assay is based on a simplified enzymelinked immunosorbent assay (ELISA) performed in a pre-packed portable device. Performance of the test was assayed in spiked water, methanolic soil extracts (dilution 1: 10) and natural water samples. A quantitative colour response to concentrations of TNT in the range of 1 to 30 g/l in water and 50 to 1000 g/kg in soil is demonstrated. The relative average standard deviations are 11.9% and 14.1%, respectively. High correlations between immunofiltration, ELISA and gas chromatography have been demonstrated. The cross reactivities of the antibody are comparable in both techniques.Dedicated to Professor Dr. Dieter Klockow on the occasion of his 60th birthday 相似文献
27.
Philippe Guerry Philippe Blanco Heinz Brodbeck Olivier Pasteris Reinhard Neier 《Helvetica chimica acta》1991,74(1):163-178
1-Methoxycarbonyl-Substituted 2,3-Dihydropyridin-4(1H)-one(= Methyl 1,2,3,4-Tetrahydro-4-oxopyridine-1-carboxylate) as Chromophore for Photochemical [2 + 2]-Cycloadditions With olefins having an electron-acceptor as well as with olefins having an electron-donor substituent, 1-methoxycarbonyl-substituted dihydropyridinone 12 undergoes [2 + 2] cycloaddition in good preparative yields. The photochemical cycloaddition is highly regioselective. For preparative purposes, the ring junction can be equilibrated to the thermodynamically more stable cis-junction. Only the ‘endo’/‘exo’ selectivity at the C-atom bearing the olefin substituent cannot be controlled. The photodimerization of 12 is the only side reaction. Using a slight excess of the olefin, the photodimerization can be suppressed. The protecting group at the N-atom of the dihydropyridinone can be varied in order to introduce an internal sensitizer, as shown with 1-acyl-substituted compound 29 , which underwent the cycloaddition process even with sunlight. 相似文献
28.
The 1-ferrocenyl-2-methyl-1-propylamine (2a)is the most effective chiral template in asymmetrically induced peptide synthesis by stereoselective four component condensation (4CC). Two routes for the synthesis of this amine via its N,N-dimethyl derivative (12a) an described. One route involves the conversion of 12a into the corresponding azide 14a by treatment with methyl iodide/sodium azide in diglyme/water and subsequent reduction of the azide. The preferred other route consists of treating 12a with thioglycolic acid/formic acid to yield the carboxymethylmercapto derivative 9a and transformation of the latter into 2a with aqueous ammonia/ammonium chloride/mercuric chloride. Some related reactions are also discussed. 相似文献
29.
The 13C NMR spectra of a series of 7-substituted 1,4-dialkylspiro[4.5]decanes and of suitable reference compounds are assigned and the derived substituent effects upon the chemical shifts are discussed. In particular, consideration of γ and δ-effects allows the differentiation between 1,4-cis- and 1,4-trans-compounds. Furthermore, the (relative) configuration of the chiral spiroatom C-5 is determined. 相似文献
30.
Reinhard Schubert Achim Ansmann Paul Bleckmann Bernhard Schrader 《Journal of Molecular Structure》1975,26(2):429-438
By using the values of the vibrational frequencies of normal and deuterated cyclopropenone (II-d0 , II-d2 ) and 16 O-and 18 O-substituted dimethylcyclopropenone (III) as -well as the infrared and Raman intensities of II a consistent set of force constants has been derived for the cyclopropenone skeleton. The derived values show that the zwitterionic form makes a substantial contribution to the electronic ground state of the molecule. The combined frequency and intensity calculation - simulation of the infrared and the Raman spectrum - is shown to be a good method for making a proper assignment of calculated and observed vibrations and deriving realistic sets of force constants. 相似文献