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41.
Dr. Lin He Dr. Kishore Natte Dr. Jabor Rabeah Dr. Christoph Taeschler Dr. Helfried Neumann Prof. Dr. Angelika Brückner Prof. Dr. Matthias Beller 《Angewandte Chemie (International ed. in English)》2015,54(14):4320-4324
Fluorinated organic compounds are gaining increasing interest for life science applications. The replacement of hydrogen in arenes or heteroarenes by a perfluoroalkyl group has a profound influence on the physical and biological properties of such building blocks. Here, an operationally simple protocol for the direct C? H perfluoroalkylation of (hetero)arenes with RfI or RfBr has been developed, using a robust supported platinum catalyst. The ready availability of the starting materials, the excellent substrate tolerance, and the reusability of the catalyst make this method attractive for the synthesis of a variety of perfluoroalkyl‐substituted aromatic compounds. Preliminary mechanistic studies revealed the formation of radicals to be crucial in the reaction system. 相似文献
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Roxana Judele Michael J. Dix Sabine Laschat Prof. Dr. Angelika Baro Manfred Nimtz Dirk Menzel Joachim Schoenes Klaus Doll Gertrud Zwicknagl Mark Niemeyer 《无机化学与普通化学杂志》2008,634(2):299-310
Hexaalkoxy‐substituted azamacrocyclic metal complexes 1 · MXn [MXn = FeCl3, CuCl2, SrCl2, Ln(NO3)3; Ln = La, Pr, Eu, Ho, Er] with various chain lengths were prepared by a convergent approach using 1,2‐bisalkoxy‐4,5‐diamines 3 and 4‐alkoxy‐pyridine‐2,6‐dicarbaldehydes 4 as key building blocks for template‐assisted cyclocondensation. Metal complexes 1 · MXn were considered as potential metallomesogens. However, differential scanning calorimetry and optical polarizing microscopy of 1 · MXn did not reveal any mesomorphism. The magnetic susceptibility shows deviation from Curie‐like behavior. Due to ligand field effects the effective magnetic moments are a function of the temperature. In order to obtain structural informations on the free ligand 1 , which is synthetically not accessible, theoretical calculations were carried out. For the free azamacrocycle 2a and the free hexamethoxy‐substituted azamacrocycle 1a the IR spectra were computed at the level of density functional theory. A planar and a saddle‐shaped conformation was considered. The IR spectra and especially the dependence of the C=N vibration on the structural parameters and the charge distribution are discussed. 相似文献
44.
Angelika Jabłuszewska Dr. Anna Krawczuk Prof. Leonardo H. R. Dos Santos Prof. Piero Macchi 《Chemphyschem》2020,21(19):2155-2165
Within the scope of accurate structure-property correlations in biomolecules, this work investigates how conformations and electronic configurations of biologically relevant macromolecules affect their intermolecular potentials. With the purpose of testing the suitability of a simple and universal model, the dipeptides are made from the assembly of their building blocks, namely the amino acid residuals or, more finely tuned, the individual functional groups. The model makes use of functional-group electrostatic potentials (GEP) and distributed polarizabilities (GDP), which enable an in depth analysis of the correlation between structural features and property build-up. GEPs and GDPs are calculated for various conformers and protonation states of L-alanyl-L-alanine, glycyl-L-alanine, L-alanylglycine, and glycylglycine, which are prototypic molecules to model the pertinent functional groups. The model provides GEPs that reproduce the exact potential to an average accuracy of ca. 0.05 au. The good agreement between the properties estimated with the simple model and those calculated with state-of-the-art quantum chemical methods encourages further testing of the predictive power of this model, simulating for example interaction energies and optoelectronic properties. 相似文献
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Niemz A Bandyopadhyay K Tan E Cha K Baker SM 《Langmuir : the ACS journal of surfaces and colloids》2006,22(26):11092-11096
The fabrication of nanoporous templates from poly(styrene)-b-poly(methyl methacrylate) diblock copolymer thin films (PS-b-PMMA, volume ratio 70:30) on silicon requires precise control of interfacial energies to achieve a perpendicular orientation of the PMMA cylindrical microdomains relative to the substrate. To provide a simple, rapid, yet tunable approach for surface neutralization, we investigated the self-assembled ordering of PS-b-PMMA diblock copolymer thin films on silicon substrates modified with a partial monolayer of octadecyldimethyl chlorosilane (ODMS), i.e., a layer of ODMS with a grafting density less than the maximum possible monolayer surface coverage. We demonstrate herein the fabrication of nanoporous PS templates from annealed PS-b-PMMA diblock copolymer thin films on these partial ODMS SAMs. 相似文献
47.
Wolfgang Holzer Angelika Ebner Karin Schalle Gyselle Batezila Gernot A. Eller 《Journal of fluorine chemistry》2010,131(10):1013-1024
A straightforward, two-step synthesis of fluoro substituted chromeno[2,3-c]pyrazol- and [1]benzothieno[2′,3′:5,6]pyrano[2,3-c]pyrazol-4(1H)-ones, respectively, is presented. Hence, treatment of 1-substituted or 1,3-disubstituted 2-pyrazolin-5-ones with fluoro substituted 2-fluorobenzoyl chlorides or 3-chloro-6-fluoro-1-benzothiophene-2-carbonyl chloride using calcium hydroxide in refluxing 1,4-dioxane gave the corresponding 4-aroylpyrazol-5-ols, which were cyclized into the fused ring systems. 5-Fluorochromeno[2,3-c]pyrazol-4(1H)-one was obtained upon treatment of the 1-(4-methoxybenzyl) protected congener with trifluoroacetic acid. Treatment of 5-fluorochromeno[2,3-c]pyrazol-4(1H)-ones with methylhydrazine afforded novel tetracyclic ring systems such as 2-methyl-7-phenyl-2,7-dihydropyrazolo[4′,3′:5,6]pyrano[4,3,2-cd]indazole. Detailed NMR spectroscopic investigations (1H, 13C, 15N, 19F) with the obtained compounds were undertaken. 相似文献
48.
Vílchez A Rodríguez-Abreu C Esquena J Menner A Bismarck A 《Langmuir : the ACS journal of surfaces and colloids》2011,27(21):13342-13352
Magnetic macroporous polymers have been successfully prepared using Pickering high internal phase ratio emulsions (HIPEs) as templates. To stabilize the HIPEs, two types of oleic acid-modified iron oxide nanoparticles (NPs) were used as emulsifiers. The results revealed that partially hydrophobic NPs could stabilize W/O HIPEs with an internal phase above 90%. Depending upon the oleic acid content, the nanoparticles showed either an arrangement at the oil-water interface or a partial dispersion into the oil phase. Such different abilities to migrate to the interface had significant effects on the maximum internal phase fraction achievable and the droplet size distribution of the emulsions. Highly macroporous composite polymers were obtained by polymerization in the external phase of these emulsions. The density, porosity, pore morphology and magnetic properties were characterized as a function of the oleic acid content, concentration of NPs, and internal phase volume of the initial HIPEs. SEM imaging indicated that a close-cell structure was obtained. Furthermore, the composite materials showed superparamagnetic behavior and a relatively high magnetic moment. 相似文献
49.
Comprehensive examinations of the motional properties (rotational correlation time τ(R)) and the spin exchange ω(SS) of the spin probe TEMPOL have been carried out using ESR spectroscopy in two different solvents. For the first time, the dynamic parameters τ(R) and ω(SS) have been determined simultaneously by simulation of spectra measured at three different ESR frequencies (L-, X-, and Q-band) between 293 and 500 K using a dynamic model based on a stochastic fitting program and, for comparison, two alternative models involving the shift of the hyperfine lines and considering the line broadening due to spin exchange in a wide range of conditions. Possibilities and limits of the used models are shown upon comparing the obtained results of the spin exchange. Moreover, the analysis of the ESR spectra gave evidence for the existence of cage effects that produce re-encounters of the spin probes. This has been done for the activation energies, which have been calculated from the temperature dependence of the rate constants of the spin exchange. From the ratio of the activation energies and the influence of the viscosities on the dynamics of the examined systems in n-octanol and an ionic liquid, conclusions can be drawn for the re-encounter effects in solvent cages. However, in contrast to n-octanol, the dynamics of the spin probe in the ionic liquid depends on specific and anisotropic interactions. The temperature dependence of the Q-band measurements required the development of a novel Q-band cavity. 相似文献
50.