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991.
Petrovic AG Polavarapu PL Drabowicz J Zhang Y McConnell OJ Duddeck H 《Chemistry (Weinheim an der Bergstrasse, Germany)》2005,11(14):4257-4262
The enantiomers of 3,3,3',3'-tetramethyl-1,1'-spirobi[3 H,2,1]benzoxaselenole have been separated on a chiral preparative chromatographic column. The experimental vibrational circular dichroism (VCD) spectra have been obtained for both enantiomers in CH(2)Cl(2). The theoretical VCD spectra have been obtained by means of density functional theoretical calculations with the B3 LYP density functional. From a comparison of experimental and theoretical VCD spectra, the absolute configuration of an enantiomer with positive specific rotation in CH(2)Cl(2) at 589 nm is determined to be R. This conclusion has been verified by comparing results of experimental optical rotatory dispersion (ORD) and electronic circular dichroism (ECD) to predictions of the same properties using the B3 LYP functional for the title compound. 相似文献
992.
Ruta Bariseviciute Justinas Ceponkus Alytis Gruodis Valdas Sablinskas 《Central European Journal of Chemistry》2006,4(4):578-591
Ozonization reaction of simple alkenes was studied by means of FT infrared absorption gas spectroscopy. The reaction was performed
at 95 K in neat films of the reactants. IR absorption spectra of the gaseous products were recorded. The spectra were analyzed
combining experimental results with theoretical calculations performed at B3LYP 6-311++G (3df, 3pd) level. We found that among
all theoretically predicted conformers of propene secondary ozonide, only one which has the O-O half-chair configuration for
the five membered ring and the radical attached in the equatorial position was present in the sample. Samples of 1-butene and 1-heptene secondary ozonides consist from two conformers of very
similar energy (ΔH=0.3 kJ/mol). The most stable conformer for both ozonides is the one with O-O half-chair configuration of the five membered
ring and the radical attached in equatorial position and the aliphatic chain in gauche position. The second stable conformer has the aliphatic chain in anti position. 相似文献
993.
The vibrational frequencies of the N–H stretching modes of aniline after forming a strong doubly H-bonded complex with tetrahydrofuran (THF) are measured with infrared depletion spectroscopy that uses cluster-size-selective resonance-enhanced multiphoton ionization (REMPI) time-of-flight mass spectrometry. Two strong infrared absorption features observed at 3355 and 3488 cm−1 are assigned to the symmetric and antisymmetric N–H stretching vibrations of the 1:2 aniline–THF complex, respectively. The red-shifts of the N–H stretching vibrations of aniline agree with the ab initio calculated (MP2/6-31G**) aniline-(THF)2 structure in which both aniline N–H bonds interact with the oxygen atom of THF through two hydrogen bonds. The calculated binding energy is found to be 29.6 kJ mol−1 after corrections for basis set superposition error (BSSE) and zero-point energy. The calculated structure revealed that the angle between the N–H bonds in the NH2 group increased to 112.5° in the aniline–(THF)2 complex from that of 109.8° in the aniline. The electronic 0–0 band origin for the S1 ← S0 transition is observed at 32,900 cm−1 in the aniline–(THF)2 complex, giving a red-shift of 1129 cm−1 from that of the aniline molecule. 相似文献
994.
Milaeva E. R. Shpakovsky D. B. Shaposhnikova E. N. Grigor"ev E. V. Berberova N. T. Egorov M. P. 《Russian Chemical Bulletin》2001,50(4):716-719
-Aryl trans-bistriphenylphosphine complexes based on 2,6-di-tert-butylphenol containing Pt—SnCl3, Pt—GeCl3 groups were synthesized. Oxidation of these compounds gives the corresponding phenoxyl radicals, which were studied by ESR spectroscopy. The transformation of the diamagnetic complexes to the paramagnetic state is accompanied by cleavage of the Pt—Sn, Pt—Ge bonds and by elimination of SnCl2, GeCl2. 相似文献
995.
末端碳链长度对偶氮苯自组装膜结构的影响 总被引:4,自引:0,他引:4
The end-group dominated molecular orientation in the azobenzene self-assembled monolayers (SAMs), CnAzoC2SH (n=1-4), on gold was evaluated for the first time by grazing incidence reflection absorption FTIR spectroscopy (RA-FTIR). All these azobenzene SAMs have highly-organized and closely-parked structures, with the molecule tilting away gradually from surface normal direction with the increase of end group alkyl length. 相似文献
996.
Tseng HR Vignon SA Celestre PC Stoddart JF White AJ Williams DJ 《Chemistry (Weinheim an der Bergstrasse, Germany)》2003,9(2):543-556
The template-directed syntheses, employing bisparaphenylene-[34]crown-10 (BPP34C10), 1,5-dinaphthoparaphenylene-[36]crown-10 (1/5NPPP36C10), and 1,5-dinaphtho-[38]crown-10 (1/5DNP38C10) as templates, of three [2]catenanes, whereby one of the two bipyridinium units in cyclobis(paraquat-p-phenylene) is replaced by a bipicolinium unit, are described. The crude reaction mixtures comprising the [2]catenanes all contain slightly more of the homologous [3]catenanes, wherein a "dimeric" octacationic cyclophane has the crown ether macrocycles encircling the alternating bipyridinium units with the bipicolinium units completely unfettered. X-ray crystallography, performed on all three [2]catenanes and two of the three [3]catenanes reveals co-conformational and stereochemical preferences that are stark and pronounced. Both the [3]catenanes crystallize as mixtures of diastereoisomers on account of the axial chirality associated with the picolinium units in the solid state. Dynamic (1)H NMR spectroscopy is employed to probe in solution the relative energy barriers for rotations by the phenylene and pyridinium rings in the tetracationic cyclophane component of the [2]catenanes. Where there are co-conformational changes that are stereochemically "allowed", crown ether circumrotation and rocking processes are also investigated for the relative rates of their occurrence. The outcome is one whereby the three [2]catenanes containing BPP34C10, 1/5NPPP36C10, and 1/5DNP38C10 exist as one major enantiomeric pair of diastereoisomers amongst two, four, and eight diastereoisomeric pairs of enantiomers, respectively. The diastereoisomerism is a consequence of the presence of axial chirality together with helical and/or planar chirality in the same interlocked molecule. These [2]catenanes constitute a rich reserve of new stereochemical types that might be tapped for their switching and mechanical properties. 相似文献
997.
Erik Rakovský Ľudmila Žúrková Jaromír Marek 《Monatshefte für Chemie / Chemical Monthly》2002,133(3):277-283
Summary. Anhydrous 1,6-hexanediammonium dihydrogendecavanadate ((HdaH2)2H2V10O28, 1) was prepared by reaction of V2O5 with 1,6-hexanediamine in aqueous solution. The crystal structure of 1 was determined, and the proton positions in the H2V10O28
4− anion were calculated by the bond length/bond number method. The protons are bound to the centrosymmetrically oriented μ–OV3 groups of the decavanadate anion. Based on the analysis of IR spectra of 1 prepared from H2O and D2O, the absorption band at 871 cm−1 can be attributed to δ(V–Ob–H) vibrations.
Received August 3, 2001. Accepted (revised) October 8, 2001 相似文献
998.
N. V. Chernei V. A. Nadolinnyi N. V. Ivannikova V. A. Gusev I. N. Kupriyanov V. N. Shlegel Ya. V. Vasiliev 《Journal of Structural Chemistry》2005,46(3):431-437
Comprehensive investigations have been performed by EPR and optical spectroscopy for Bi3GeO4 crystals doped with chromium ions. It is demonstrated that the known optical absorption spectrum for chromium ions, specifically,
the triplet in the region 600–900 nm has an analog in the EPR spectra — the center with electron spin S = 1. The spectrum is described by the spin-Hamiltonian with the parameters D = 550 G, E = 10 G, g
xx
= g
yy
= 1.915, g
zz
= 1.932. The EPR spectrum is dictated by Cr4+ incorporation at the germanium sites. Luminescence observed in the region 1.2–1.7 μm is also caused by transitions of Cr4+ with tetrahedral surroundings to germanium sites.
Original Russian Text Copyright ? 2005 N. V. Chernei, V. A. Nadolinnyi, N. V. Ivannikova, V. A. Gusev, I. N. Kupriyanov, V.
N. Shlegel, and Ya. V. Vasiliev
__________
Translated from Zhurnal Strukturnoi Khimii, Vol. 46, No. 3, pp. 444–450, May–June, 2005. 相似文献
999.
Fourier-transform infrared (FTIR) spectroscopy has been a major point of development in many wine laboratories in recent years. It enables almost instant analysis of several properties of wine, usually with very good precision and accurate results. Nevertheless, validation procedures should not be forgotten and should be fully performed. Recovery experiments were performed by spiking wine samples with different amounts of organic acids (tartaric, malic, lactic, acetic and citric—the most prominent in wines). After FTIR analysis of the total acidity and of each organic acid concentration, recoveries were calculated. For total acidity recovery results were, in general, good and very close to 100% (64–111%). On the other hand, for individual organic acid concentrations, the recovery results were lower than 100% (11–73%) for all spiking additions. These results could be explained by spectroscopic interferences between the organic acids. Because they have similar infrared spectra, it is not easy to distinguish between them and, therefore, to achieve accurate calibration. When total acidity, with a different infrared spectrum from the other abundant compounds in the wine, was taken as a single property the recovery results were acceptable. 相似文献
1000.
Preparation and Crystal Structure of Cadmium Azide Cd(N3)2 Solvent free, binary cadmium azide was synthesized by the reaction of cadmium carbonate and a 24 weight% solution of HN3 in water. Cadmium azide is a colorless, crystalline powder which is highly sensitive to percussion and heat. Caution, the manipulation of Cd(N3)2 is very dangerous! The crystal structure was solved by single‐crystal methods and the phase purity was verified by a Rietveld refinement (Cd(N3)2, Pbca, no. 61; a = 7.820(2), b = 6.440(2), c = 16.073(3) Å; Z = 8, 1174 independent reflections, 64 parameters, R1 = 0.022). Cadmium azide crystallizes in a new structure type. In the crystal there are edge‐sharing Cd2(N3)10 double octahedrons which are further connected to other units by azide bridges. Vibrational spectroscopic investigations (Raman an IR) are discussed with respect to the crystal structure data. 相似文献