نتایج جستجو برای: dft nmr
تعداد نتایج: 76720 فیلتر نتایج به سال:
Calcium is the 5th most abundant element on earth, and is found in numerous biological tissues, proteins, materials, and increasingly in catalysts. However, due to a number of unfavourable nuclear properties, such as a low magnetogyric ratio, very low natural abundance, and its nuclear electric quadrupole moment, development of solid-state (43)Ca NMR has been constrained relative to similar nuc...
Solid-state NMR spectroscopy and GIPAW DFT calculations reveal the pronounced sensitivity of (79/81)Br and (25)Mg quadrupolar coupling constants to subtle aspects of solid state structure which were not previously detected by pXRD methods.
Structural characterization of the catalytically significant sites on solid catalyst surfaces is frequently tenuous because their fraction, among all sites, typically is quite low. Here we report the combined application of solid-state (13)C-cross-polarization magic angle spinning nuclear magnetic resonance ((13)C-CPMAS-NMR) spectroscopy, density functional theory (DFT), and Zr X-ray absorption...
An NMR crystallographic approach, involving the combination of 119Sn NMR spectroscopy, XRD, and DFT calculations, is demonstrated for the characterization of La2Sn2-x Ti x O7 ceramics. A phase change from pyrochlore (La2Sn2O7) to a layered perovskite phase (La2Ti2O7) is predicted (by radius ratio rules) to occur when x ≈ 0.95. However, the sensitivity of NMR spectroscopy to the local environmen...
Ruthenium trihydrides containing N-heterocyclic carbene ligands display large quantum mechanical exchange couplings in their 1H NMR spectra: DFT calculations are used to explore this phenomenon and to compare them to their phosphine congeners.
A donor-functionalized, silyl-substituted pentadienyllithium has been synthesized and characterized by crystallography and NMR spectroscopy. The pentadienyl negative charge was found to be partially localized, which DFT revealed to be due to the polarizing power of the lithium cation.
Solid-state NMR and DFT calculation studies certified the presence of an intermolecular solvent effect for molecules confined in microporous zeolite, leading to a notable increase in Brønsted acidity of the solid acid catalyst.
We report a combined solid-state (1H, 2H, 13C, 17O) NMR and plane-wave density functional theory (DFT) computational study of the O···H···O low-barrier hydrogen bonds (LBHBs) in two 1,3-diketone compounds: dibenzoylmethane (1) and curcumin (2). In the solid state, both 1 and 2 exist in the cis-keto-enol tautomeric form, each exhibiting an intramolecular LBHB with a short O···O distance (2.435 Å...
calixarenes are a readily available and important class of macrocycles in supramolecularchemistry. calixarenes have generated considerable interest due to their basket shaped structureand as useful building blocks to synthesize selective receptors for the guest species, notably alkali,alkaline earth, lanthanide and transition metal cations. in this work studied on the complexingproperties of a ...
A series of anionic ruthenium pentahydride complexes with the general formula [M(THF)x][RuH5(PCy3)2] (M = Li, Na, K) were synthesized. Their characterization by multinuclear NMR, IR, X-ray diffraction, and DFT techniques show that these can adopt different structural features (monomer/dimer, cis/trans phosphines, hydride/dihydrogen ligands) depending on countercation, solvent, and/or temperatur...
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