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Showing 1 to 20 of 23 for “"NMR chemical shifts"”.
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Studies of Sterically Controlled Solvent Induced NMR Chemical Shifts
… similarly successful when applied to the proton chemical shifts of more complex molecules, and it is suggested and demonstrated that the buffeting shifts may prove useful in elucidating features of molecular structure. More importantly, the present work provides strong experimental evidence for …
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Solvent induced NMR chemical shifts that arise from molecular encounters
… approach is used to characterise the buffeting shifts induced by large solvent molecules and the approach is found to be inadequate. Consequently, improved methods of calculating and are reported. Using the improved approach it is shown that buffeting is dependent on the nature of the solvent as …
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Ab initio calculations of NMR chemical shifts for structure determination in biology
… for calculating nuclear Magnetic Resonance chemical shifts to structure determination in Biology. We investigate and summarise the most important structural contributions to the chemical shift. Even though the NMR chemical shift has direct relation to the global structure it is shown that …
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Computation of Phosphorus-31 NMR chemical shifts of nickel complexes using density functional theory
… benchmark study, to date, of calculated $^{31}P$ chemical shifts of phosphorus-containing ligands in nickel(0), nickel(II), and nickel(I) complexes is presented. Calculated shifts are directly compared to experiment. Many of these complexes are synthetically useful and on the cutting edge of …
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Prediction of proton and carbon-13 NMR chemical shifts using chemical shift prediction programs
… with one another to calculate predicted chemical shifts for a wide range of chemical compounds. 1H-spectra for several flexible and rigid organic compounds were acquired on Oxford-Broker spectrometer and interpreted using two-dimensional NMR techniques. ACD-V 4 and CHARGE-V7 programs were …
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Extending the Boundaries of the Usage of NMR Chemical Shifts in Deciphering Biomolecular Structure and Dynamics
NMR chemical shifts have an extremely high information content on the behaviour of macromolecules, owing to their non-trivial dependence on myriads of structural and environmental factors. Although such complex dependence creates an initial barrier for their use for the characterisation of the …
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Development and testing of a protocol for computational prediction of 1H and 13C NMR chemical shifts and thermochemistry and reaction analysis of benzyne formation and trapping
… of novel compounds, nuclear magnetic resonance (NMR) is by far the most widely applied. Investigation into new reactions may require any number of techniques to understand the reaction scope, kinetics, optimal conditions, mechanisms, etc. In both cases, the use of computational methods is …
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Nuclear Magnetic Resonance Studies of Catalysts and Model Catalytic Systems: Biochemical and Inorganic Applications (Minerals, Silicon-29, Oxygen-17, Shielding Tensors, Nmr)
… of silicon-29 nuclear magnetic resonance (NMR) chemical shifts in minerals, zeolite catalysts, ceramics and glasses is proposed based on a group electronegativity approach. Based on a total of 99 sites in 51 different compounds, the mean absolute deviation between theory and experiment is …
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Synthesis, structure and chirality of some neutral cobalt (III) complexes
… deshielding arguments are applied to proton nmr chemical shifts in making chiral assignments of the helical diastereomers. A comparison is made between C-O bond deshielding and N-D steric compression. The proton nmr assignments are shown to be independent of the solvent used in measuring …
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Elucidation of the aqueous equilibrium system of IrH₂(PMe₃)₃Cl and periodic trends of the iridium (III) dihydrido tris(trimethylphosphino) series, IrH₂(PMe₃)₃X
… in water. The results of extensive ³¹P NMR studies on the aqueous system of (1) indicate that (1) is in equilibrium with the iridium(III) dihydrido “aquo” complex, [IrH₂(PMe₃)₃(H₂O)]⁺, and not the μ-chloro bridged complex, { [IrH₂(PMe₃)₃]₂Cl}⁺ (2), as previously reported. The calculated …
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Síntese e caracterização de um novo agente sililante - imobilização na sílica gel em meio aquoso.
… analysis of CHNS, infrared spectroscopy, NMR 13C and 29Si, thermogravimetric analysis and surface area. The surface area were 0.43 m2g-1 and 193 for solids AMPTGA and Sil-AMPTGA, respectively, which were lower than that of silica gel precursor 484 m2g-1. The thermogravimetric analysis …
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NMR, Crystallographic and Quantum Chemical Studies of Metalloproteins and Bisphosphonate Inhibitors
… models to predict nuclear magnetic resonance (NMR) and Mossbauer spectroscopic properties in heme proteins and model systems by using quantum chemical techniques. This work includes density functional theory investigations of the 1H, 13C, 15N and 19F NMR hyperfine shifts, Mossbauer electric …
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Probing regioselectivity in the Diels -Alder cycloadditions between *[60]fullerene and aryl substituted acenes
… comes from a careful examination of 1H NMR chemical shifts for the ortho phenyl protons in fullerene-acene adducts. A careful review of the Cambridge Crystallographic Database reveals numerous instances of aryl CH/fullerene contacts within 3 A. The combined results suggest that aryl …
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Endocyclic Nucleophilic Methyl Transfer
… made use of an ('18)O isotope effect on ('13)C NMR chemical shifts showed that the intermolecular pathway for the rearrangements is a two step process. An intermolecular methyl transfer between two molecules of the amino ester gives an ion pair which then annihilates via N-methylation to give …
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Structural Modes in Proteins: A Case Study in the PDZ Domain
… physical effects by monitoring a large number of NMR chemical shifts at nuclei distributed throughout the protein. The end result is a matrix of interactions between each mutation and all residues in the protein. Analysis of this chemical shift perturbation matrix reveals subsets of residues that …
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NMR, Crystallographic and Quantum Chemical Studies of Amino Acids in Peptides and Proteins
"In this work we combined the ab initio methods, NMR and X-ray crystallography techniques to investigate the qualitative and quantitative relationships between chemical shift and geometry of amino acids in protein. First, we used ab initio quantum chemical techniques to compute the Back-bone Calpha …
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Part I. Synthesis and thermolysis of cyclopentadienyl and pentamethylcyclopentadienyl molybdenum dioxo alkoxides. Part II. Structural characterization of polysilicate intermediates formed during sol-gel polymerization
… the expected piano stool geometry. Oxygen-17 NMR chemical shifts of the terminal oxygens showed that Cp$\sp{*}$ is a better electron donor to the metal center than Cp. Oxygen-17 NMR also showed that for a series of compounds, CpMoO$\sb2$(OR) (R=Me, Et, i-Pr and t-Bu), electron donation …
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Synthetic studies of sodium aminodiboranate salts with electronwithdrawing substituents
… solve this problem is to prepare low-temperature chemical vapor deposition (CVD) precursors which would enable deposition of MgB2 at temperatures low enough to prevent loss of Mg from the thin film. In chapter 1, we describe the synthesis of three new sodium aminodiboranate salts, Na(BH3)2NRR′, …
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A unified strategy for penostatin (Bio)synthesis and forays in computational chemistry
… products chemistry. Nuclear magnetic resonance (NMR) spectroscopy is unarguably the single most powerful spectroscopic tool for this task; however, the unambiguous assignment of these structural properties via spectroscopic data alone is rarely a trivial matter. In Part 2 of this Thesis, the …
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