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On Ternary Thallium Chalcogenides with Thallium Selenide Structure. By means of single crystal investigations, it has been confirmed that the compounds TlGaTe2, TIInSe2, and TIInTe2 crystallize in the TISe type (B37). As an univalent cation thallium is surrounded by eight chalcogen atoms. Gallium and indium are trivalent with tetrahedral coordination and covalent bonds. The interatomic distances as well as coordination and bonding resulting from them are discussed. 相似文献
34.
On Thorium Silicide and Germanide Chalcogenides The compounds ThSiS, ThSiSe, ThSiTe, ThGeS, ThGeSe, and ThGeTe were synthetized from the elements at temperatures ranging from 800 to 1050°C. For structural X-ray investigation single crystals of the compound ThGeS were grown. ThGeS is tetragonal, space group I4/mmm with a = 3.9411(7), c = 17.1395(40) Å, and Z = 4. In order to refine the structure parameters intensity measurements were carried out by means of a four-circle single crystal diffractometer. By indexing the Debye-Scherrer diagrams the remaining ternary thorium chalcogenides were proved to be isostructural with ThGeS. This structure type is identical with the anti-Ti2Bi-type structure and closely related to the PbFCl structure in the sense of a transposition structure. The interatomic distances, the relations to comparable structures and possible reasons for the formation of the anti-Ti2Bi-type structure by ternary chalcogenides of the actinides are discussed. 相似文献
35.
Infrared absorption, vibrational circular dichroism, and two-dimensional infrared pump-probe and photon echo spectra of acetylproline solutions are theoretically calculated and directly compared with experiments. In order to quantitatively determine interpeptide interaction-induced amide I mode frequency shifts, high-level quantum chemistry calculations were performed. The solvatochromic amide I mode frequency shift and fluctuation were taken into account by carrying out molecular dynamics simulations of acetylproline dissolved in liquids water and chloroform and by using the extrapolation method developed recently. We first studied correlation time scales of the two amide I vibrational frequency fluctuations, cross correlation between the two fluctuating local mode frequencies, ensemble averaged conformations of the acetylproline molecule in liquids water and chloroform. The corresponding conformations of the acetylproline in liquids water and chloroform are close to the ideal 3(10) helix and the C(7) structure, respectively. A few methods proposed to determine the angle between the two transition dipoles associated with the amide I vibrations were tested and their limitations are discussed. 相似文献
36.
Lakshman MK Ngassa FN Bae S Buchanan DG Hahn HG Mah H 《The Journal of organic chemistry》2003,68(15):6020-6030
Single-electron oxidation of the carcinogenic hydrocarbon benzo[a]pyrene (BaP) is thought to result in a radical cation intermediate and this species has been proposed to cause alkylation at the nitrogens of the purine nucleobases. Although several different nucleoside adducts have been isolated as arising from this mode of metabolic activation, there are no selective, total syntheses of the stable exocyclic amino group adducts formed by the single-electron oxidation of any hydrocarbon with the purine 2'-deoxynucleosides to date. In this paper we disclose the synthesis of the model adducts N(6)-(1-pyrenyl)-2'-deoxyadenosine and N(2)-(1-pyrenyl)-2'-deoxyguanosine as well as the first synthesis of the carcinogen-linked nucleoside derivatives N(6)-(6-benzo[a]pyrenyl)-2'-deoxyadenosine and N(2)-(6-benzo[a]pyrenyl)-2'-deoxyguanosine via a palladium-mediated C-N bond formation. Two different coupling strategies were attempted: coupling of an aryl bromide with a suitably protected nucleoside and the coupling of an arylamine with a suitable halonucleoside. The former had somewhat limited applicability in that only N(6)-(1-pyrenyl)-2'-deoxyadenosine was prepared by this method; on the other hand, the latter was more general. However, there are noteworthy differences in the amination reactions at the C-6 and C-2 positions. Reactions at the C-6 resulted in the competing formation of a 1:2 amine-nucleoside adduct in addition to the desired monoaryl nucleoside. Such a dimer formation was not observed at the C-2. The C-2 adducts, however, displayed an interesting conformational behavior. 相似文献
37.
The electrochemical oxidation of methanol was investigated on a Pt–Ru–Mo catalyst with an in situ infrared reflectance spectroscopy. The electrocatalysts were prepared by an electrochemical deposition and dispersed in a conducting three-dimensional matrix of polyaniline (PAni). We observed that CO2 is produced from methanol oxidation at 350 mV vs. RHE on PAni/Pt–Ru–Mo, which is 100 mV less negative than on PAni/Pt–Ru and 200 mV less than on PAni/Pt. The results suggest that Pt–Ru–Mo is less sensitive to COADS poisoning than Pt–Ru and much more sensitive than Pt. Large differences are observed concerning the average wavenumber of ADS between Pt–Ru–Mo, Pt–Ru, and Pt. 相似文献
38.
Contributions to the Chemistry of Phosphorus. 167. Constitutional and Configurational Isomers of Pentaphosphane(7), P5H7 Phosphane mixtures containing 10—15 P-% of pentaphosphane(7), P5H7, are obtained by thermolysis of diphosphane, P2H4, or as residue from distillation of crude diphosphane [3]. According to the complete analysis of the 31P{1H}-NMR spectrum on the basis of selective population transfer experiments, P5H7 exists as a mixture of three diastereomers of n-P5H7 — 1a (erythro, erythro), 1b (erythro, threo), 1c (threo, threo) — and of the constitutional isomer 2-phosphinotetraphosphane 2 (iso-P5H7, largest relative isomeric abundance). The correlation between the diastereomers and the observed spin systems results from the preferred gauche orientation of neighboring free electron pairs, the dependence of 1J(PP) on dihedral angles, and the 3J(PP) long range couplings. From the 31P-NMR data of the phosphane molecules PnHn+2 with n = 1—5 general relationships for the δ(31P) values and the 1J(PP) coupling constants of chain-type phosphorus hydrides as a function of their structural parameters are derived. 相似文献
39.
Alkynylxenon(II) fluorides, RCC(triple bond)XeF, have been prepared from the reactions of the corresponding trimethyl(alkynyl)silanes, Me3(-)SiC(triple bond)CR, and XeF2 in the presence of [NMe4F in common organic solvents at low temperature. The existence of the linear unit C(triple bond)C-Xe-F was proved for PhC(triple bond)CXeF by the 19F-13C NMR correlation method using the HMBC pulse sequence. 相似文献
40.
A method is described for the potentiometric titration of milligram quantities of the uranium(IV) ion in the presence of iron. This is accomplished by complexing the iron with 1.10-phcnanthroline. The uranium can then be titrated with standard ceric sulfate without interference from the iron. 相似文献