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排序方式: 共有1376条查询结果,搜索用时 15 毫秒
41.
Water-soluble Co (III) and Co (II) complexes with P- or N-coordinated PTA or PTA oxide ligands, respectively, have been prepared and fully characterized, constituting the first examples of cobalt compounds bearing PTA or any ligand with a cage-like PTA core, the latter complex providing also the first PTA oxide coordination to a metal center. 相似文献
42.
Ibrahem I Rios R Vesely J Zhao GL Córdova A 《Chemical communications (Cambridge, England)》2007,(8):849-851
The highly chemo- and enantioselective organocatalytic tandem reaction between N-protected hydroxyl amines and alpha,beta-unsaturated aldehydes is presented; the reaction provides access to 5-hydroxyisoxazolidines and beta-amino acids in high yields and with 90-99% ee. 相似文献
43.
Elena Gómez Noelia Calvar Ángeles Domínguez Eugénia A. Macedo 《The Journal of chemical thermodynamics》2010,42(11):1324-1329
In this paper, the ionic liquids 1,2-diethylpyridinium ethylsulfate, EEpyESO4; 1-methylpyridinium methylsulfate, MpyMSO4; 1,3-dimethylpyridinium methylsulfate, MMpyMSO4; and 2-ethyl-1-methylpyridinium methylsulfate, EMpyMSO4; were synthesized in our laboratory, and their experimental densities, speeds of sound, dynamic viscosities, and refractive indices were studied as a function of temperature at atmospheric pressure. Thermal expansion coefficient, molar volume, and molar refraction of these ionic liquids were calculated from the experimental density and refractive index values. 相似文献
44.
Martí I Ferrer A Escorihuela J Burguete MI Luis SV 《Dalton transactions (Cambridge, England : 2003)》2012,41(22):6764-6776
A family of ligands derived from bis(amino amides) containing aliphatic spacers has been prepared, and their protonation and stability constants for the formation of Cu(2+) complexes have been determined potentiometrically. Important differences are associated to both the length of the aliphatic spacer and the nature of the side chains derived from the amino acid. In general, ligands containing aliphatic side chains display higher basicities as well as stability constants with Cu(2+). In the same way, basicities and stability constants tend to increase when decreasing the steric hindrance caused by the corresponding side-chain. FT-IR, UV-vis and ESI-MS were used for analyzing the complex species detected in the speciation diagram. UV-vis studies showed the presence of different coordination environments for the copper(II) complexes. Complexes with different stoichiometries can be formed in some instances. This was clearly highlighted with the help of ESI-MS experiments. 相似文献
45.
Journal of Solid State Electrochemistry - The voltammetry of immobilized particles is an electroanalytical technique yielding compositional, thermochemical, and even structural information on... 相似文献
46.
47.
Esther Domínguez Concepción Laborra Aranzazu Linaza Ana Madoz Issa A. Katime 《Monatshefte für Chemie / Chemical Monthly》1989,120(8-9):743-748
Summary A series of mono and diesters of itaconic acid containing alkoxy and sulfide side chains of variable lengths has been synthesized. Their structures have been established on the basis of their spectral data.
Eine Serie von Mono- und Diestern von Itaconsäure: Synthese und Strukturbestimmung
Zusammenfassung Es wurde eine Serie von Mono- und Diestern von Itaconsäure mit Alkoxy- und Sulfidseitenketten variabler Länge synthetisiert. Die Strukturaufklärung erfolgte mittels spektroskopischer Daten.相似文献
48.
R. Mateo-Castro J. V. Gimeno-Adelantado F. Bosch-Reig A. Doménech-Carbó M. J. Casas-Catalán L. Osete-Cortina J. De la Cruz-Cañizares M. T. Doménech-Carbó 《Analytical and bioanalytical chemistry》2001,369(7-8):642-646
GC-FID was used as single methodology for the identification and differentiation of proteins, lipids and ox bile from binders
used in artistic paintings. The samples were hydrolyzed by HCl. Subsequently, the simultaneous formation of volatile derivatives
of the amino, fatty and bile acids with ethyl chloroformate was performed quickly and safely in an aqueous medium. The derivatives
were separated by capillary GC and characterized by GC-MS. The ageing of drying oils was studied, identifying pelargonic acid
among other degradation products. Proteinaceous and lipoid binding media were characterized by means of the quotients between
the areas of the peaks for each amino or fatty acid with respect to the area of the peak for alanine or palmitic acid. Fatty
acids from ox bile were easily identified by their retention times characteristic for eicosanoic, docosanoic and pentadecanoic
acids. The suggested method was applied to the analysis of binders in baroque paintings by Palomino in Valencia (Spain). Animal
gelatine and linseed oil were found.
Received: 27 September 2000 / Revised: 16 January 2001 / Accepted: 17 January 2001 相似文献
49.
50.
Armando Navarro-Huerta Marcus J. Jellen Jessica Arcudia Simon J. Teat Rubn A. Toscano Gabriel Merino Braulio Rodríguez-Molina 《Chemical science》2021,12(6):2181
This work describes the use of C–H⋯F–C contacts in the solid-state from the stator towards the rotator to fine-tune their internal motion, by constructing a set of interactions that generate close-fitting cavities in three supramolecular rotors 1–3I. The crystal structures of these rotors, determined by synchrotron radiation experiments at different temperatures, show the presence of such C–H⋯F–C contacts between extended carbazole stators featuring fluorinated phenyl rings and the 1,4-diazabicyclo[2.2.2]octane (DABCO) rotator. According to the 2H NMR results, using deuterated samples, and periodic density functional theory computations, the rotators experience fast angular displacements (preferentially 120° jumps) due to their low rotational activation energies (Ea = 0.8–2.0 kcal mol−1). The higher rotational barrier for 1 (2.0 kcal mol−1) is associated with a larger number of weak C–H⋯F–C contacts generated by the stators. This strategy offers the possibility to explore the correlation among weak intermolecular forces, cavity shape, and internal dynamics, which has strong implications in the design of future fine-tuned amphidynamic crystals.This work describes the use of C–H⋯F–C contacts in the solid-state from the stator towards the rotator to fine-tune their internal motion, by constructing a set of interactions that generate close-fitting cavities in three supramolecular rotors 1–3I. 相似文献