To see the other types of publications on this topic, follow the link: Quadrupole coupling.
Dissertations / Theses on the topic 'Quadrupole coupling'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 21 dissertations / theses for your research on the topic 'Quadrupole coupling.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Ylihautala, M. (Mika). "NMR of small solutes in liquid crystals and molecular sieves." Doctoral thesis, University of Oulu, 1999. http://urn.fi/urn:isbn:9514252748.
Full textAbstract:
Abstract
The present thesis deals with the nuclear magnetic resonance (NMR) spectroscopy of small solutes applied to the studies of liquid crystals and molecular sieves. In this method, changes induced by the investigated environment to the static spectral parameters (i.e. nuclear shielding, indirect and direct spin-spin coupling and quadrupole coupling) of the solute are measured.
The nuclear shielding of dissolved noble gases is utilized for the studies of thermotropic liquid crystals. The relation between the symmetry properties of mesophases and the nuclear shielding is described. The different interaction mechanisms perturbing the observed noble gas nuclear shielding are discussed, particularly, the role of long-range attractive van der Waals interactions is brought out. The suitability of the noble gas NMR spectroscopy to the studies of lyotropic liquid crystals is investigated in terms of nuclear shielding and quadrupole coupling interactions.
In molecular sieve systems, the effect of inter- and intracrystalline motions of solutes on their NMR spectra is discussed. A novel method for the measurement of the intracrystalline motions is developed. The distinctions in the 13C shielding of methane adsorbed in AlPO4-11 and SAPO-11, two structurally similar molecular sieves differing in composition, are indicated.
2
Powoski, Robert A. "Molecular Structure Analyses of Asymmetric Hydrocarbon Liquid Compounds in the Gas Phase Using Chirped-pulse Fourier Transform Microwave Spectroscopy: Acyl Chlorides and Perfluorinated Acyl Chlorides." Thesis, University of North Texas, 2011. https://digital.library.unt.edu/ark:/67531/metadc103374/.
Full textAbstract:
Examinations of the effects of (a.) alkyl carbon chain length and (b.) perfluorination of acyl chlorides; propionyl chloride, butyryl chloride, valeroyl chloride, and perfluorinated acyl chlorides; perfluoropropionyl chloride and perfluorobutyryl chloride, are reported and compared using CP-FTMW spectroscopy. All of these molecules are already published in various journals except for valeroyl chloride. The chapters are organized by molecule alkyl chain length and include some background theory. Conformational stability, internal rotation, helicity, and ionic character of the C-Cl bond via the nuclear electric quadrupole coupling constant (χzz) are analyzed. Results show syn, syn-anti/syn-gauche, and syn-anti-anti/syn-gauche-anti stable conformations. Internal rotation was only seen in propionyl chloride. Helicity was not observed. (χzz) was observed to be inert to alkyl chain length, ~ 60 MHz and ~ 65 MHz for the nonfluorinated and fluorinated acyl chlorides. Partial fluorination and varying functional groups are recommended.
3
Pennanen, T. (Teemu). "Computational studies of NMR and magneto-optical rotation parameters in water." Doctoral thesis, University of Oulu, 2012. http://urn.fi/urn:isbn:9789514297311.
Full textAbstract:
Abstract
In this thesis nuclear magnetic resonance (NMR) and magneto-optical rotation (MOR) parameters are investigated for water, paying special attention to the effect of solvation from gaseous to liquid phase. Nuclear magnetic shielding and quadrupole coupling tensors of NMR spectroscopy are studied for gaseous and liquid water. Liquid state is modelled by a 32-molecule Car-Parrinello molecular dynamics simulation, followed by property calculations for the central molecules in clusters cut out from the simulation trajectory. Gaseous state is similarly represented by a one-molecule simulation. Gas-to-liquid shifts for shielding constants obtained this way are in good agreement with experiments. To get insight into the local environment and its effect on the properties the clusters are divided into groups of distinct local features, namely the number of hydrogen bonds. The analysis shows in detail how the NMR tensors evolve as the environment changes gradually from the gas to liquid upon increasing the number of hydrogen bonds to the molecule of interest. The study sheds light on the usefulness of NMR experiments in investigating the local coordination of liquid water. To go a bit further, the above mentioned NMR parameters along with the spin-spin coupling constant are examined for water dimer in various geometries to have insight into solvation and hydrogen bonding phenomena from bottom to top. Characteristic changes in the properties are monitored as the geometry of the dimer is systematically varied from very close encounter of the monomers to distances and orientations where hydrogen bonding between monomers ceases to exist. No rapid changes during the hydrogen bond breaking are observed indicating that the hydrogen bonding is a continuous phenomenon rather than an on-off situation. However, for analysis purposes we provide an NMR-based hydrogen bond definition, expressed geometrically, based on the behaviour of the NMR properties as a function of dimer geometry. Our definition closely resembles widely used definitions and thus reinforces their validity.
Magneto-optical rotation parameters, the nuclear spin optical rotation (NSOR) and the Verdet constant, are computed for gaseous and liquid water, in the same manner as the NMR properties above. Recent pioneering experiments including NSOR for hydrogen nuclei in liquid water and liquid xenon have demonstrated that this technique has a potential to be a useful new probe of molecular structure. We reproduce computationally, applying a first-principles theory developed recently in the group, the experimental NSOR for hydrogen nuclei in liquid water, and predict hydrogen NSOR in gaseous water along with the oxygen NSOR in liquid and gaseous water. NSOR is an emerging experimental technique that needs interplay between theory and computation for validation, steering and insight.
4
Randell, J. "Microwave study of rotational isomerism in propanal, CH3̲CH2̲CHO : Nitrogen quadrupole coupling and molecular structures of [ON...NO2̲], CH2̲(CN)2̲ and C5̲H5̲NiNO." Thesis, University of Bristol, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.235288.
Full text
5
Manninen, P. (Pekka). "Breit-Pauli Hamiltonian and Molecular Magnetic Resonance Properties." Doctoral thesis, University of Oulu, 2004. http://urn.fi/urn:isbn:9514274318.
Full textAbstract:
Abstract
In this thesis, the theory of static magnetic resonance spectral parameters of nuclear magnetic resonance (NMR) and electron spin resonance (ESR) spectroscopy is investigated in terms of the molecular Breit-Pauli Hamiltonian, which is obtained from the relativistic Dirac equation via the Foldy-Wouthuysen transformation. A leading-order perturbational relativistic theory of NMR nuclear shielding and spin-spin coupling tensors, and ESR electronic g-tensor, is presented. In addition, the possibility of external magnetic-field dependency of NMR parameters is discussed.
Various first-principles methods of electronic structure theory and the role of one-electron basis sets and their performance in magnetic resonance properties in terms of their completeness profiles are discussed. The presented leading-order perturbational relativistic theories of NMR nuclear shielding tensors and ESR electronic g-tensors, as well as the theory of the magnetic-field dependent NMR shielding and quadrupole coupling are evaluated using first-principles wave function and density-functional theories.
6
Stourton, E. C. "Anisotropic interactions in solid-state nuclear magnetic resonance spectroscopy." Thesis, University of Cambridge, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.243269.
Full text
7
Ziehm, Christopher Joseph. "ENHANCEMENT OF ELECTRONIC COUPLING IN METAL-METAL QUADRUPLY BONDED COMPLEXES." The Ohio State University, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=osu1416315259.
Full text
8
Gurusinghe, Ranil Malaka. "Methyl Internal Rotation Probed by Rotational Spectroscopy." Kent State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1476282624055414.
Full text
9
Acho, Jacqueline A. "Reductive coupling, and, transition metal calixarene complexes : metal-metal quadruple bonds and pockets." Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/32149.
Full text
10
Perras, Frédéric Alain. "Structural Insights from the NMR Spectroscopy of Quadrupolar Nuclei: Exploiting Electric Field Gradient and Spin-Spin Coupling Tensors." Thesis, Université d'Ottawa / University of Ottawa, 2014. http://hdl.handle.net/10393/31883.
Full textAbstract:
NMR spectroscopy has evolved into one of the most important characterization techniques in chemistry with which it is possible to obtain valuable structural, dynamical, and mechanistic information. Most applications of NMR have however been limited to the use of nuclei having spin quantum numbers of 1/2. This thesis discusses the developments that have been advanced in order to extract quantitative structural information from the NMR spectroscopy of quadrupolar nuclei (spin, I>1/2) which account for the vast majority of the NMR-active nuclei. In a first part of the thesis, a NMR crystallographic method is developed which uses the electric field gradient tensor measured at the nuclear sites as an experimental constraint in DFT-based crystal structure refinements. This inclusion of experimental data into crystal structure refinements enables the determination of higher quality, and experimentally-relevant, structures. We apply this new methodology in order to determine higher quality crystal structures for the non-linear optical material Na2B2Al2O7, sodium pyrophosphates, and the near-zero thermal expansion material ZrMgMo3O12. In a second part of this thesis, experimental techniques are developed for the measurement of spin-spin coupling between pairs of quadrupolar nuclei; the measurement of spin-spin coupling carries with it extremely valuable distance and connectivity information. Using DOR NMR, heteronuclear residual dipolar coupling as well as homonuclear J coupling multiplets can be observed. Notably, the J coupling between quadrupolar nuclei can still be measured in A2 spin systems, unlike in the case of pairs of spin-1/2 nuclei. The theory that was developed for the characterization of these multiplets was extended for the general simulation of exact NMR spectra of quadrupolar. This program, known as QUEST, is now free to use by anyone in the scientific community. Pulsed J-resolved NMR experiments are then described which enable the facile measurement of J and dipolar coupling in homonuclear pairs of quadrupolar nuclei. Notably, the J splitting is greatly amplified in A2 spin systems which provides strong structural information and enables the precise detection of smaller J coupling constants. These techniques are applied towards directly studying gallium metal-metal bonding interactions as well as boron-boron bonds in diboron compounds of importance in β-boration chemistry.
11
Gastaldo, Vinícius Pascotto. "Multiferroicity and structural anomalies in quadruple perovskite manganites : case study (A)Mn7O12, A=Na and La." Electronic Thesis or Diss., Sorbonne université, 2019. http://www.theses.fr/2019SORUS324.
Full textAbstract:
Dans cette thèse on étude les oxydes de manganèse NaMn7O12 et LaMn7O12, qu'appartiennent à la structure de pérovskite quadruple sous les points de vue de la multiferroïcité, du couplage magnétoélectrique, et aussi des anomalies structurelles dynamiques en NaMn7O12. Ces études concernent l'existence, les mécanismes d'établissement de la multiferroïcité et le couplage entre les ordres ferroïques en ces matériaux. Les forces motrices des anomalies structurels dynamiques en NaMn7O12 sont aussi étudiés au sens de clarifier les mécanismes de déformation structurel et quel est son importance ao établissement des ordres ferroïques. Manipulations de IXS et DXS révèlent anomalies dynamiques dans la transition structurel du NaMn7O12. Un phonon amollit avec le même vecteur d’onde de la modulation structurel sont révélé lié à pics diffuses de rayons-x qui ont un vecteur d’onde diffèrent, indiquant une compétition entre différents distorsions et que la distorsion engendré par distorsions du type Jahn-Teller est finalement dominant. Une transition ferroélectrique a été trouvé simultanément à anomalies dans la chaleur spécifique et dans la magnétisation du NaMn7O12. Les courbes d’hystérésis magnétique sont bien plus larges dans la phase ferroélectrique. Ces propriétés sont expliquées dans le cadre d’un modelé de ordonnément de frontières de domaine antiferromagnétique. Au LaMn7O12, une transition ferroélectrique a été trouvé à la température de transition antiferromagnétique du site B. Malgré les péculiarité de chaque système, ses propriétés structurels et magnétiques permettent d’affirmer qui sa ferroélectricité est d’origine magnétique travers le mécanisme de striction d’échangeIn this work we study the quadruple perovskite structure manganese oxides NaMn7O12 and LaMn7O12 under the point of view of multiferroicity, magnetoelectric coupling, and also structure anomalies on NaMn7O12. These studies range from the existence to the mechanism of the establishment of multiferroicity and coupling between ferroic orders in these materials. The driving force of the dynamic structural anomalies in NaMn7O12 are also studied with the goal of clarifying the mechanisms of structural distortion and how they relate to the onset of ferroic orders. The results of IXS and DXS experiments show interesting dynamical anomalies in NaMn7O12's structural transition, a softened phonon at the structural modulation wavevector that was shown to be related to diffuse x-ray peaks with a different wavevector point in the direction of competing distortions and that the Jahn-Teller mechanism driven distortion overcome its competitor. A ferroelectric transition was found simultaneous to anomalies in specific heat and magnetization in NaMn7O12. Magnetic hysteresis loops are quite wider in the ferroelectric phase. These properties are explained in function of a magnetoelectricity mediated antiferromagnetic domain wall ordering model. As for LaMn7O12, a ferroelectric transition at the B site antiferromagnetic transition temperature. Besides the particularities of each system, structural and magnetic properties imply that their ferroelectricity is of magnetic origin through the exchange striction mechanism
12
Kantola, A. M. (Anu M. ). "Liquid crystal NMR: director dynamics and small solute molecules." Doctoral thesis, University of Oulu, 2009. http://urn.fi/urn:isbn:9789514260704.
Full textAbstract:
Abstract
The subjects of this thesis are the dynamics of liquid crystals in external electric and magnetic fields as well as the magnetic properties of small molecules, both studied by liquid crystal nuclear magnetic resonance (LC NMR) spectroscopy. Director dynamics of a liquid crystal 5CB in external magnetic and electric fields was studied by deuterium NMR and spectral simulations. A new theory was developed to explain the peculiar oscillations observed in the experimental spectra collected during fast director rotation. A spectral simulation program based on this new theory was developed and the outcome of the simulations was compared with the experimental results to verify the tenability of the theory.
In the studies on the properties of small solute molecules, LC NMR was utilised to obtain information about anisotropic nuclear magnetic interaction tensors. The nuclear magnetic shielding tensor was studied in methyl halides, the spin-spin coupling tensor in methyl mercury halides and the quadrupolar coupling tensor in deuterated benzenes. The effects of small-amplitude molecular motions and solvent interactions on the obtained parameters were considered in each case. Finally, the experimental results were compared to the corresponding computational NMR parameters calculated in parallel with the experimental work.
13
Trease, Nicole Marie. "New Theoretical Approaches for Solid-State NMR of Quadrupolar Nuclei with Applications to Glass Structure." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1243952229.
Full text
14
Walder, Brennan J. "Separating, correlating, and exploiting anisotropic lineshapes for NMR structure determination in solids." The Ohio State University, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=osu1429846088.
Full text
15
Ho, Tse-Ming, and 何志明. "AB Initio Calculation of Nuclear Quadrupole Coupling Constants." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/41830419650156549683.
Full text
16
He, Zhi-Ming, and 何志明. "Ab initio caculation of nuclear quadrupole coupling constant." Thesis, 1994. http://ndltd.ncl.edu.tw/handle/72838806841588811930.
Full text
17
劉麗文. "Probe of Pi-Bonding in Benzonitrile and Its Derivatives by Nitrogen-14 Quadrupole Coupling Constants." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/53921598976312040291.
Full textAbstract:
碩士國立成功大學
化學學系
83
It has been recently demonstrated that nuclear quadrupolar relaxation time (Tlq) measurements provide a powerful tool for determination of quadrupole coupling constants (QCC) in liquids. This technique, however, requires an accurate value of the correlation time , τc, of the electric field gradient vector. In the research, we investigate the migration of π-electron between benzonitrile and its various substitution from the measured values of QCC(14N). Substitution and solvent effects have also been examined. Measurements of the relaxation time and the nuclear Overhauser effect were first performed on the paracarbon in benzonitrile to extract the dipolar relaxation rate. This permits the determination of the correlation time, τc, of the two-fold molecular symmetry axis. Combining the calculated value of τc, 7.78ps, with the measured nitrogen-14 quadrupolar relaxation time, 0.482ms, the experimental values of QCC(14N), 4.25 MHz was obtained. In order to confirm the validity of extracting □c from TICSA, relaxation times of the cyano carbon were measured at two field strengths. Using the magnitude of τc (8.86 ps) derived from TICSA(21.1 sec), calculated values of QCC, 3.98 MHz, is in good agreement with that obtained from T1DD. The lover QCC, compared to that in HCN, manifests that pi-electron density migrates from benzene ring to the cyano pi-system. This conclusion may be applied to account for the downfield shift of the para-carbon in benzonitrile. In studies of substitution effects on magnitudes of QCC, values of τc determined by both T1DD and T1CSA were in use .Experimental results from both methods reveal that substitution with halogens or methoxyl groups yields increased magnitudes of QCC's These can be rationalized by the electron withdrawing nature of substituents which results in a reversed migration of pi-electron density between the two pi-system. More importantly, the capability for calculating reliable values of correlation times from T1CSA is verified. The research performed here, therefore, has laid the foundation for future studies of pi-bonding variations in organic nitriles, cyano halogens, and cyano metal complexes.
18
Gühne, Robin. "Electronic properties of the topological insulators Bi2Se3 and Bi2Te3." 2019. https://ul.qucosa.de/id/qucosa%3A37768.
Full textAbstract:
Die drei-dimensionalen Topologische Isolatoren Bi2Se3 and Bi2Te3 sind Modell-Systeme einer neuen Klasse von Isolatoren mit metallischen Oberflächenzuständen. Ihre kleinen Bandlücken und die schweren Elemente sind essentiell für die topologisch nicht-triviale Bandstruktur, sind aber ebenso verantwortlich für andere bemerkenswerte Eigenschaften, wie etwa für ihre Leistungsfähigkeit als Thermoelektrika.
Diese Arbeit untersucht die elektronischen Eigenschaften der Topologischen Isolatoren Bi2Se3 und Bi2Te3 mittels zahlreicher experimenteller Methoden. Es wird
gezeigt, dass Ferromagnetismus in Mn gedoptem Bi2Te3 durch sintern unterdrückt
werden kann. Zudem werden ein überraschend großer Magnetoresistiver Effekt
und ein ladungsträgerunabhängiger Vorzeichenwechsel des Seebeck-Koeffizienten mit zunehmenden Mn Gehalt diskutiert. Kernmagnetische Resonanz (NMR) von 125Te Kernen in Bi2Te3 Einkristallen lässt auf eine ungewöhnliche elektronische SpinSuszeptibilität and komplexe NMR Verschiebungen schließen. Es wird gezeigt dass die Quadrupolwechselwirkung von 209Bi Kernen in Bi2Se3 Einkristallen eine Signatur der Bandinversion ist, in quantitativer Ubereinstimmung mit DFT Rechnungen. Weiterhin wird argumentiert dass die starke Spin-Bahn Kopplung der Leitungselektronen zu einer nicht-trivialen Orientierungsabh¨angigkeit der 209Bi Quadrupolaufspaltung führt.:Contents
List of Figures
List of Tables
List of abbreviations
Introduction
1 Topological insulators in three dimensions
2 Theoretical background
3 Methods I: structural, electronic and magnetic properties
4 Methods II: nuclear magnetic resonance
5 Sample preparation and basic characterisation6 Magnetic and electronic properties of Mn doped Bi2Te3
7 NMR of spin 1/2 nuclei: 125Te in Bi2Te3
8 NMR of quadrupole nuclei: 209Bi in Bi2Se3
Conclusions and outlook
Appendix
BibliographyThe three-dimensional topological insulators Bi2Se3 and Bi2Te3 are model systems of a new class of materials with an insulating bulk and gapless surface states. Their small band gaps and the heavy elements are essential for the topologically non-trivial band structure, but these features are similarly responsible for other remarkable properties, such as their high thermoelectric performance. This thesis investigates the electronic properties of the topological insulators Bi2Se3 and Bi2Te3 with a broad range of experimental methods. Ferromagnetism in Mn doped Bi2Te3 is shown to disappear under sample sintering. A surprisingly large magnetoresistance and a charge carrier independent change in the sign of the thermopower with increasing Mn content are discussed.125Te nuclear magnetic resonance (NMR) of Bi2Te3 single crystals suggest an unusual electronic spin susceptibility and complex NMR shifts. The quadrupole interaction of 209Bi nuclei in Bi2Se3 single crystals is shown to be a signature of the band inversion in quantitative agreement with first-principle calculations. Furthermore, it is proposed that the strong spin-orbit coupling of conduction electrons causes a non-trivial orientation dependent quadrupole splitting of the 209Bi resonance.:Contents List of Figures List of Tables List of abbreviations Introduction 1 Topological insulators in three dimensions 2 Theoretical background 3 Methods I: structural, electronic and magnetic properties 4 Methods II: nuclear magnetic resonance 5 Sample preparation and basic characterisation6 Magnetic and electronic properties of Mn doped Bi2Te3 7 NMR of spin 1/2 nuclei: 125Te in Bi2Te3 8 NMR of quadrupole nuclei: 209Bi in Bi2Se3 Conclusions and outlook Appendix Bibliography
19
Cheng, Wen-Zhang, and 鄭文章. "Measurements of Quadrupople Coupling Constants in Liquids by NMR Relaxation Methods." Thesis, 1998. http://ndltd.ncl.edu.tw/handle/12427732949010059743.
Full text
20
Jadidi, Tayebeh. "In-silico Modeling of Lipid-Water Complexes and Lipid Bilayers." Doctoral thesis, 2013. https://repositorium.ub.uni-osnabrueck.de/handle/urn:nbn:de:gbv:700-2013102111709.
Full textAbstract:
In the first part of the thesis, the molecular structure and electronic properties of phospholipids at the single molecule level and also for a monolayer structure are investigated via ab initio calculations under different degrees of hydration. The focus of the study is on phosphatidylcholines, in particular dipalmitoylphosphatidylcholine (DPPC), which are the most abundant phospholipids in biological membranes. Upon hydration, the phospholipid shape into a sickle-like structure. The hydration dramatically alters the surface potential, dipole and quadrupole moments of the lipids, and probably guides the interactions of the lipids with other molecules and the communication between cells. The vibrational spectrum of DPPC and DPPC-water complexes are completely assigned and it is shown that water hydrating the lipid head groups enables efficient energy transfer across membrane leaflets on sub-picosecond time scales. Moreover, the vibrational modes and lifetimes of pure and hydrated DPPC lipids, at human body temperature, are estimated by performing ab initio molecular dynamics simulations. The vibrational modes of the water molecules close to the head group of DPPC are active in the frequency range between 0.5 - 55 THz, with a peak at 2.80 THz in the energy spectrum. The computed lifetimes for the high-frequency modes agree well with recent data measured at room temperature, where high-order phonon scattering is not negligible. The structure and auto-ionization of water at the water-phospholipid interface are investigated by ab initio molecular dynamics and ab initio Monte Carlo simulations using local density approximation and generalized gradient approximation for the exchange-correlation energy functional. Depending on the lipid head group, strongly enhanced ionization is observed, leading to dissociation of several water molecules into H+ and OH- per lipid. The results can shed light on the phenomena of the high proton conductivity along membranes that has been reported experimentally. In the second part of the thesis, Monte Carlo simulations of the lipid bilayer, on the basis of a coarse grained model, are performed to gain insight into the mechanical properties of planar lipid bilayers. By using a rescaling method, the Poisson's ratio is calculated for different phases. Additional information on the bending rigidity, determined from height fluctuations on the basis of the Helfrich Hamiltonian, allows for calculation of the Young's modulus for each phase. In addition, the free energy barrier for lipid flip-flop process in the fluid and gel phases are estimated. The main rate-limiting step to complete a flip-flop process is related to a free energy barrier that has to be crossed in order to reach the center of the bilayer. The free energy cost for performing a lipid flip-flop in the gel phase is found to be five times greater than in the fluid phase, demonstrating the rarity of such events in the gel phase. Moreover, an energy barrier is estimated for formation of transient water pores that often precedes lipid translocation events and accounts for the rate-limiting step of these pore-associated lipid translocation processes.
21
Webber, Renee. "An NMR Spectroscopic and Quantum Chemical Investigation of Hydrogen Bonding in Solids." Thesis, 2011. http://hdl.handle.net/10214/2875.
Full textAbstract:
Solid-state NMR spectroscopy is used to investigate strong hydrogen bonds in a variety of solids. NMR measurements of the 2H nuclear quadrupole coupling (CQ) and nuclear magnetic shielding tensors are performed on samples of trimethylammonium chloride (TMAC), protonated 1,8-bis(dimethylamino)napthalene (DMANH+), and potassium and sodium bifluoride. 2H CPMAS is used to obtain high quality spectra while reducing experimental time. From spectral simulations, values of 127, 36, 59 and 58 kHz are determined for the 2H CQ of TMAC, DMANH+ CF3SO3-, NaHF2 and KHF2, respectively. The 2H CPMAS spectrum of TMAC shows a minor secondary component resulting from a solid phase in which the trimethylammonium cation is experiencing precessional motion. At high temperature the 2H CPMAS spectrum of DMANH+ shows unexpected spinning sideband lineshapes because of residual dipolar coupling to 14N. The experimental 2H CQ values are corroborated by ab-initio and DFT calculations; for DMAN and the bifluorides the 2H CQ values are averaged over the potential energy surface to improve the computational quality. Large values of the isotropic chemical shift (>10 ppm) are observed for all of the hydrogen-bonded deuterons. To complement the 2H NMR work, other nuclei in the compounds of interest are investigated, for TMAC these include: 35Cl, 37Cl, 1H, 14N, 15N. The 35Cl CQ shows a small, but observable deuterium/proton isotope effect. Quadrupolar and chemical shift parameters for assorted nuclei in TMAC are calculated at various N-H distances, demonstrating the strong dependence of the chlorine and hydrogen parameters on the proton position. For DMANH+ the 15N CPMAS spectrum of a static sample of DMANH+-d1 provides a value for the average dipolar 15N-D coupling constant of 870±30 Hz, corresponding to a distance of 1.29 A. Spectra of the counterions in the bifluoride salts are obtained, providing CQ values of 123 kHz and 1.141 MHz for 39K and 23Na, respectively.