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91.
Supramolecular self-assembly initiated by solid-solid wetting 总被引:1,自引:0,他引:1
Trixler F Markert T Lackinger M Jamitzky F Heckl WM 《Chemistry (Weinheim an der Bergstrasse, Germany)》2007,13(27):7785-7790
We present a preparation method for self-assembled supra-molecular monolayers of unsubstituted organic semiconductors and pigments on a solid substrate, applicable under ambient conditions. The deposition is based on a solid-solid wetting phenomenon, whereas the subsequent layer growth proceeds according to standard models. Molecular adsorption results from direct contact of the compound in a nanocrystalline state with the solid surface. Based on complementary force field calculations, we propose that molecules disintegrate from the crystalline state and adsorb on the surface because of a gain in binding energy. The preparation method is exemplified by means of a linear hydrogen-bonded system, namely quinacridone (QAC) on graphite. In addition, the chosen system allows us to actively guide the self-assembly after deliberate removal of molecules from a predefined area. 相似文献
92.
93.
94.
Four 1,1′-binaphthalene based bis-urea derivatives bearing aryl groups at end-on nitrogen atoms IIIa–d were synthesized as potential sensor molecules. These receptors show characteristic UV-VIS spectral changes on complexation
with anions and they exhibit selective recognition of F− over other halide anions. Interaction of a fluoride anion with urea NH groups was confirmed by 1H NMR data. The presence of an electron-withdrawing nitro group in N′-aryls (receptors IIIa and IIIb) appeared to be necessary for naked-eye colorimetric detection. These receptors show dramatic color change from light-yellow
to orange (IIIa) or to orange-red (IIIb) in the presence of guest fluoride anions already at concentrations of 10−5 mol dm−3 of the receptor and host. 相似文献
95.
In this paper we characterize the spectroscopy performance of a new high resolution electron energy-loss spectrometer for transmission electron microscopy, recently installed in our lab. With the event of commercially available monochromated transmission electron microscopes, equipped with improved spectrometers, experiments became feasible that allow the study of chemical bonding and electronic structures of atoms and solids at the nanometer level with an energy resolution in the range of 0.2-0.3 eV. This significant enhancement in resolution, however, can only be fully harnessed with an optimized microscope and spectrometer setup and in a suitable local environment. We attempt to quantify some of the limiting factors on our system with emphasis on spectrum mixing, spectrometer aberrations and transmissivity and we sketch proper working conditions in order to achieve the desired performance. 相似文献
96.
Gulevich AV Melkonyan FS Sarkar D Gevorgyan V 《Journal of the American Chemical Society》2012,134(12):5528-5531
The efficient Pd-catalyzed double-fold C-H oxygenation of arenes into resorcinols using the newly developed 2-pyrimidyldiisopropylsilyl (PyrDipSi) directing group is described. Its use allows for the sequential introduction of OAc and OPiv groups in a one-pot manner to produce orthogonally protected resorcinol derivatives. The PyrDipSi group is superior to the previously developed 2-pyridyldiisopropylsilyl (PyDipSi) group, as it is efficient for monooxygenation of ortho-substituted arenes. Notably, the PyrDipSi group can be easily installed into arene molecules and can be easily removed or modified after the oxygenation reaction. 相似文献
97.
S Spirk F Belaj N Hurkes R Pietschnig 《Chemical communications (Cambridge, England)》2012,48(67):8398-8400
A high yield synthesis of the first silanedithiolate silanolate is reported which spontaneously assembles forming an inorganic rugby ball shaped 32 vertex polyhedral cluster stabilized by sterically demanding 2,6-dimesitylphenyl substituents and two LiCl units. 相似文献
98.
Fraga R Zacconi F Sussman F Ordóñez-Morán P Muñoz A Huet T Molnár F Moras D Rochel N Maestro M Mouriño A 《Chemistry (Weinheim an der Bergstrasse, Germany)》2012,18(2):603-612
Based on the crystal structures of human vitamin D receptor (hVDR) bound to 1α,25-dihydroxy-vitamin D(3) (1,25 D) and superagonist ligands, we previously designed new superagonist ligands with a tetrahydrofuran ring at the side chain that optimize the aliphatic side-chain conformation through an entropy benefit. Following a similar strategy, four novel vitamin D analogues with aromatic furan side chains (3a, 3b, 4a, 4b) have now been developed. The triene system has been constructed by an efficient stereoselective intramolecular cyclization of an enol triflate (A-ring precursor) followed by a Suzuki-Miyaura coupling of the resulting intermediate with an alkenyl boronic ester (CD-side chain, upper fragment). The furan side chains have been constructed by gold chemistry. These analogues exhibit significant pro-differentiation effects and transactivation potency. The crystal structure of 3a in a complex with the ligand-binding domain of hVDR revealed that the side-chain furanic ring adopts two conformations. 相似文献
99.
Arumuganathan T Volpe M Harum B Wurm D Belaj F Mösch-Zanetti NC 《Inorganic chemistry》2012,51(1):150-156
The preparation and oxygen-atom-transfer (OAT) reactivity of oxoimido complexes [MoO(N-t-Bu)(t-Bu(2)-4-Rpz)(2)] [where R = H (1), Br (2), and Me (3); t-Bu(2)pz = 3,5-di-tert-butylpyrazolate] are reported. The reaction of the potassium salt of the respective pyrazolate ligands and the molybdenum oxoimido precursor, [MoO(N-t-Bu)Cl(2)(dme)] (dme = dimethoxyethane), in toluene afforded complexes 1-3 in good yields. The complexes were fully characterized by (1)H and (13)C NMR and IR spectroscopy, mass spectrometry, elemental analysis, and single-crystal X-ray crystallography. The solid-state structures reveal that, in each case, the molybdenum center is coordinated by one oxo, one N-t-Bu group, and two sterically demanding pyrazolate ligands via their two adjacent nitrogen atoms in an η(2) fashion. Coordination around the metal center is severely distorted from octahedral and might be seen as closely approaching a distorted trigonal-prismatic geometry, which is relevant to the active site of dimethyl sulfoxide reductase in its oxidized form. The potential utility of all of the complexes 1-3 for OAT reactivity toward PMe(3) at room temperature is examined, and plausible mechanistic pathways are explored by density functional theory calculations. Furthermore, the complexes reported here open a new and convenient entry into mixed oxoimidomolybdenum complexes. 相似文献
100.
W. Alexejew E. Gottlieb Ferdinand Fischer Stohmann und von Rechenberg 《Fresenius' Journal of Analytical Chemistry》1887,26(1):68-70
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