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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
61

A Solid-State 11B NMR and Computational Study of Boron Electric Field Gradient and Chemical Shift Tensors in Boronic Acids and Boronic Esters

Weiss, Joseph January 2011 (has links)
The results of a solid-state 11B NMR study of a series of boronic acids, boronic esters, and boronic acid catechol cyclic esters with aromatic substituents are reported in this thesis. Boron-11 electric field gradient (EFG) and chemical shift (CS) tensors obtained from analyses of spectra acquired in magnetic fields of 9.4 T and 21.1 T are demonstrated to be useful for gaining insight into the molecular and electronic structure about the boron nucleus. It can be concluded that when adequate electronic variation is present in the compounds being studied, Ω is generally the most characteristic boron NMR parameter of the molecular and electronic environment for boronic acids and esters. Importantly, these data are only reliably accessible in ultrahigh magnetic fields. The experimental span values result from a delicate interplay of several competing factors, including hydrogen bonding, the value of the dihedral angle, and the type of aromatic ring system present.
62

Solid-State Nuclear Magnetic Resonance of Exotic Quadrupolar Nuclei as a Direct Probe of Molecular Structure in Organic Ionic Solids

Burgess, Kevin January 2015 (has links)
In the past decade, the field of NMR spectroscopy has seen the emergence of ever more powerful superconducting magnets, which has opened the door for the observation of many traditionally challenging or non-receptive nuclei. In this dissertation, a variety of ionic solids with organic coordination environments are investigated using quadrupolar solid-state NMR experiments with an ultrahigh-field magnet (21.1 T). Two general research directions are presented including a 79/81Br solid-state NMR study of a series of 6 triphenylphosphonium bromides for which single-crystal X-ray structures are reported herein. A second research direction is also presented wherein alkaline-earth metal (25Mg, 43Ca, and 87Sr) solid-state NMR is used to characterize a systematic series of 16 aryl and alkyl carboxylates. In both studies, the quadrupolar nuclei studied are deemed “exotic” due to their unreceptive nature to NMR spectroscopic analysis including low natural abundances, large quadrupole moments, or low resonance frequencies. A variety of coordination modes to alkaline-earth metals, including N-atom coordination, are characterized herein for the first time using alkaline-earth metal solid-state NMR. In all cases, the electric field gradient (EFG) and chemical shift (CS) tensors are characterized and correlated to structural features such as interatomic distances measured from the crystal structure of the compound under study. In all of the projects undertaken herein, the gauge-including projector-augmented-wave density functional theory (GIPAW DFT) method is used, which allows for the prediction and rationalization of the experimental EFG and CS tensor parameters based on the input crystal structure. In the case of 43Ca solid-state NMR experiments reported in this dissertation, a linear correlation between the calculated and experimental 43Ca quadrupolar coupling constants, CQ, is used as a calibration curve for GIPAW DFT calculations performed on the 18 structural models currently available for the vaterite polymorph of CaCO3. Vaterite cannot be fully characterized by X-ray diffraction alone; therefore an NMR crystallography protocol is used in order to identify the model that best accounts for 43Ca solid-state NMR experiments performed on vaterite. It is expected that the conclusions from this dissertation can be used for future studies involving structural refinement and elucidation of solid materials containing challenging quadrupolar nuclei.
63

Solid-State NMR Structural Studies of Proteins Using Cyclen Based Paramagnetic Metal Chelating Probes

jayasinha arachchige, Rajith Madushanka January 2016 (has links)
No description available.
64

Solid-state NMR study of nitric oxide adsorption in carboxylate based MOFs

Khan, Arafat Hossain 16 January 2020 (has links)
Solid-state NMR study of nitric oxide adsorption in MOFs. Amine functionalized Cu3btc2 MOFs shows chemisorption of NO as NONOates. NO also adsorbed in Cu open metal site(OMS). All of these information is characterized by 1H, 13C and 15N NMR studies. NO adsoprtion in Al based MOFs MIL-100(Al) is investigated to get details about direct detection of OMS site by 27Al NMR. First time detection of 15NO as dimer is acheived by 15N NMR studies.:Contents.............................................................................. v List of Figures...................................................................... vii Abbreviations............................................................................. ix 1 Motivation .............................................................................1 2 Introduction .............................................................................3 2.1 Nitric oxide (NO): A Potent Gasotransmitter . . . . . . . . . . . . . . . . . . 3 2.1.1 Biological action in human biology: . . . . . . . . . . . . . . . . . . . . 3 2.1.2 Structure and chemistry of NO . . . . . . . . . . . . . . . . . . . . . . 4 2.2 NO storage in porous materials . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2.1 Physisorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2.2 Chemisorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Current NO storage materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 Metal-organic frameworks (MOFs) . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4.1 Cu3btc2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4.2 MIL-100(Al) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3 Experimental techniques .............................................................................15 3.1 Nuclear spin interactions in solid-state NMR . . . . . . . . . . . . . . . . . . . 15 3.2 NMR Techniques and Pulse Sequences . . . . . . . . . . . . . . . . . . . . . . 19 3.3 NMR sample tube preparation . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.4 Gas adsorption procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4 Overview and enclosed papers 29 References .............................................................................121 5 Contribution .............................................................................137 / Gas storage in solids is becoming more important as a technology, with applications ranging in fields such as energy, the environment, and more importantly in biology and medicine. Porous solid storage materials are also increasingly important to advancements in science, as seen through their use in emergent gas-delivery technologies that include storage of the signaling molecule, nitric oxide (NO). The deficiencies of NO biosynthesis have been interconnected to a number of diseases, such as cardiovascular dysfunction, thrombosis and cancer. To date, one of the promising NO delivery materials are the metal-organic frameworks (MOFs), a new class of porous materials, which can store significant quantities of NO and then deliver it to specific sites in the body. MOFs contain open metal sites (OMS) that can physisorbed NO. Furthermore, amine functionalized MOFs can store NO covalently as N,N -diazeniumdiolates (NONOate). The thesis at hand is a collection of the publications written and co-authored by the author. The following thesis will investigate NO adsorption of one of the most highly studied carboxylate-based MOFs, Cu3btc2, and its amine derivatives, and MIL-100(Al) [Materials Institute Lavoisier] by magic angle spinning (MAS) NMR. However, NMR observation of Cu3btc2 is quite difficult, because it behaves as a paramagnet at room temperature. This paramagnetic behavior originates from the presence of antiferromagnetically coupled Cu-Cu ions, which result in an S=1 electronic state at higher temperatures (above 90 K). In that case, a significant insight into the understanding of NO interaction and the changing of electronic properties of NO loaded Cu3btc2 and the formation of NONOate in Cu3(NH2btc)2, which is known as University of Hamburg materials (UHM-30), has been obtained by MAS NMR. In paper (A) the effect of NO adsorption on the Cu3btc2 and UHM-30 has been followed by adsorbing different amounts of NO/Cu via the gas phase. The relevant NMR parameters, e.g., chemical shift, hyperfine coupling and 1H T1 of NO loaded MOFs displayed the change of electron density at the Cu site because of NO adsorption as well as indirect suggestion of NONOate formation. Further studies are carried out on the secondary amine functionalized MOFs, Cu3(NHRbtc)2, as they opened up the greater potential for NONOate formation in the MOFs. The structural characterization of four different Cu3(NHRbtc)2 is carried out by MAS NMR in (B) which revealed better incorporation of the btc ligand compared to NHRbtc in MOFs. In (C) NO loaded UHM-37 is extensively investigated by MAS NMR in order to understand the sorption priority, e.g., chemisorption or physiosorption. The multinuclear approach together with the fact that the MOFs contain antiferromagnetically coupled Cu-Cu pairs and NO being paramagnetic shows significant effects on spectra that allow for the deduction of adsorption effects in these MOFs. In the amine-functionalized UHM-37, first chemisorption of NO takes place to form NONOates. When this reaction is completed, additional adsorption at the OMS takes place. This observation is also in accordance with observed 13C shift changes upon NO adsorption. With 15N-labeled NO, we were able to directly determine signals of NONOate formation in UHM-37. To the best of our knowledge, this is the first report on 15N NMR data of NONOates in porous systems. In (D), NO interaction of another type of carboxylate MOF, MIL-100(Al) is investigated by 1H, 13C and 27Al MAS NMR. 27Al NMR data show that half of all Al sites are free for gas adsorption and that additional Al(OH)3 is present inside the pores, which is well-documented by 27Al 1H HETCOR spectra. 1H T1 of NO loaded MIL-100(Al) decreases with NO loading representing uniform distribution of NO in the MOF. In addition, the MIL-100(Al) five-coordinated Al site intensity is decreasing with increasing NO loading, while six-coordinated site intensity is increasing and a maximum of 1 NO per Al trimer can be adsorbed. This indicates rather weak NO adsorption. The magnetic properties of NO make it quite interesting for NMR measurements. Therefore, isotopically leveled bulk 15NO is studied for the first time by NMR in (E). The manuscript is accepted for publication and is included in this thesis. 15N NMR spectra have been obtained in the liquid and the solid state. The dynamic equilibrium ranges between (NO)2 and NO is characterized in gas - liquid transition temperature of NO. The variation of 15N chemical shift, line width and 15N T1 of NO with temperature represents the fast dynamic equilibrium. SQUID measurements are carried out on the same sample for further confirmation of the NMR results.:Contents.............................................................................. v List of Figures...................................................................... vii Abbreviations............................................................................. ix 1 Motivation .............................................................................1 2 Introduction .............................................................................3 2.1 Nitric oxide (NO): A Potent Gasotransmitter . . . . . . . . . . . . . . . . . . 3 2.1.1 Biological action in human biology: . . . . . . . . . . . . . . . . . . . . 3 2.1.2 Structure and chemistry of NO . . . . . . . . . . . . . . . . . . . . . . 4 2.2 NO storage in porous materials . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2.1 Physisorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.2.2 Chemisorption . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.3 Current NO storage materials . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.4 Metal-organic frameworks (MOFs) . . . . . . . . . . . . . . . . . . . . . . . . 8 2.4.1 Cu3btc2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11 2.4.2 MIL-100(Al) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13 3 Experimental techniques .............................................................................15 3.1 Nuclear spin interactions in solid-state NMR . . . . . . . . . . . . . . . . . . . 15 3.2 NMR Techniques and Pulse Sequences . . . . . . . . . . . . . . . . . . . . . . 19 3.3 NMR sample tube preparation . . . . . . . . . . . . . . . . . . . . . . . . . . 24 3.4 Gas adsorption procedure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26 4 Overview and enclosed papers 29 References .............................................................................121 5 Contribution .............................................................................137
65

Fast and Slow, Restricted or Free, Correlated or Random: The Complex World of Li Diffusion as Seen by Solid State NMR

Wilkening, Martin 10 September 2018 (has links)
The present talk will briefly summarize our activities in the FOR 1277 “Mobility of Li Ions in Solids” (molife) thankfully funded by the DFG.
66

Impact de l'eau dans la flexibilité des MOFs / Impact of water on MOFs flexibilty

Foucher, Damien 27 September 2016 (has links)
Les MOFs sont des matériaux hybrides (organiques/inorganiques), nanoporeux et cristallin. La périodicité et la porosité apportent à ces matériaux des propriétés modulables par la topologie des réseaux et par les interactions entre le réseau et les molécules qui peuvent pénétrer dans les nanopores. L'adsorption de molécules dans les pores permet les séparations de mélanges, la séquestration sélective de molécules, la catalyse, le stockage de l'énergie etc... La flexibilité de certains MOFs est caractérisée par des variations de volume, parfois extrêmes, pouvant modifier de manières significatives les propriétés de ces matériaux. L'eau est tout à la fois une impureté inévitable dans les usages pratiques de ces composés mais également un composant important dans la modulation de la flexibilité. Bien que les nombreuses études publiées offrent une vision globale de la flexibilité et des interactions mises en jeu lors de l'adsorption de molécules de différentes natures, l'eau reste cependant une de celles qui résistent le plus aux mesures et aux interprétations. Cette thèse a eu pour objet d'utiliser de façon conjointe la diffraction des rayons-X synchrotron, des neutrons et a résonance magnétique nucléaire (RMN), pour ré-investiguer le rôle de l'eau dans la flexibilité de deux MOFs archétypiques, le UiO-66 (ZrCDC) et le MIL-53(Al). Nos résultats ont permis d'éclairer plusieurs points critiques. Avec ZrCDC il a pu être montré qu'en présence d'eau, les deux briques de constructions, inorganique et organique, sont couplées tout en ayant chacune une flexibilité distincte. Pour MIL-53(Al), la réinvestigation a été notablement plus conséquente, reprenant le suivi de la flexibilité en température de la phase anhydre et sous l'influence des gaz composants de l'air, oxygène et azote, puis l’étude du rôle de l'eau par RMN qui permet de caractériser les modifications structurales et dynamiques des phases anhydre et hydratée. Le suivi progressif de l'adsorption et de la désorption a notamment permis de mettre en évidence des phénomènes d'échange protoniques lents responsables des hystérèses observés. Ces résultats permettent de remettre en perspective les études antécédentes et de proposer une description renouvelée de la flexibilité de ces composés, comme une "horlogerie cristalline" des mouvements moléculaires. / MOFs (metal-organic-frameworks) are hybrid (organic/inorganic) crystalline nanoporous materials. Periodicity and porosity provide to these materials modularity of properties by the topology of networks, and interactions between the framework and penetrating molecules in nanopores. Adsorption of molecules in pores allows for mixtures separation, selective sequestration of molecules, catalysis, storage of energy etc... Flexibility of some MOFs is characterized by extremes volume variations modifying properties of these materials. Water is at the same time an inevitable impurity in practical uses of such compounds and an equally significant component for modulation of flexibility. Although many published studies provide comprehensive views of the flexibility and interactions involved in the adsorption of molecules of different types, however water is one of those most resistant to measurements and interpretations. This thesis has been using jointly X-rays synchrotron and neutrons diffractions as well as nuclear magnetic resonance, to re-investigate water role on two archetypical MOFs, UiO-66 (ZrCDC) and MIL-53(Al). Our results obtained along this thesis shed some light on several critical points. With ZrCDC it has been demonstrated that both building blocks, inorganic and organic, exhibit each of them, in the presence of water a distinct flexibility, coupled together. For MIL-53(Al), this reinvestigation was noticeably more studied, covering flexibility in temperature of the anhydrous phase and under the influence of the components of air, oxygen and nitrogen. Then the study of water role in the anhydrous and hydrated phase by NMR characterized structural and dynamic changes. A progressive monitoring of adsorption and desorption, brought out slow proton exchange phenomena responsible of the hysteresis. These results allow for redefined a perspective of previous investigations and to propose a renewed description of flexibility of these materials, as a "crystalline clockwork" of molecular motions.
67

Studies on gas adsorption in porous polymers via solid-state NMR / 固体NMRによる多孔質高分子中のガス吸着に関する研究

Jiang, Weiming 23 March 2023 (has links)
京都大学 / 新制・課程博士 / 博士(理学) / 甲第24439号 / 理博第4938号 / 新制||理||1705(附属図書館) / 京都大学大学院理学研究科化学専攻 / (主査)准教授 武田 和行, 教授 吉村 一良, 教授 北川 宏 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM
68

Chemical Modification Effects on Molecular Dynamics of Complex Poly(rotaxane) Investigated by Solid-state NMR

Tang, Chuan 03 June 2013 (has links)
No description available.
69

A Characterization of CdS/Polymer Interactions by Solid State Nuclear Magnetic Resonance

Garcia, Saida Y. 09 June 2009 (has links)
No description available.
70

Spectroscopic Characterization of Organic and Inorganic Macromolecular Materials

Reinsel, Anna Michele 10 August 2011 (has links)
No description available.

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