Thesis (Ph.D.). / Written for the Dept. of Physics. Title from title page of PDF (viewed 2009/06/08). Includes bibliographical references.

Nuclear magnetic resonance (NMR) spectroscopy has been extensively used to investigate numerous systems of interest, ranging from collections of molecules to living organisms. However, NMR suffers from one key drawback: an inherent lack of detection sensitivity, as compared to other common forms of spectroscopy. This is due to the minute nuclear magnetic moments and low nuclear spin polarization levels at thermal equilibrium (~10-5 to 10-6), and thus necessitates the use of relatively large sample volumes. One way to overcome this low detection sensitivity is to introduce a species with highly non-equilibrium nuclear spin polarization, such as `hyperpolarized' xenon-129. Hyperpolarized xenon can either be used as its own chemical sensor (due to its exquisitely sensitive chemical shift range), or the non-equilibrium polarization may be transferred from xenon to another molecule of interest (such as a protein or inclusion complex). Hyperpolarized xenon is produced through a process known as spin-exchange optical pumping (SEOP), where the angular momentum from resonant, circularly-polarized light is transferred to the electronic spins of an alkali-metal, and is subsequently transferred to the xenon nuclei through gas-phase collisions. While SEOP has been extensively characterized throughout the years, new experimental techniques and emerging technologies have considerably advanced the field in recent years, and may enable a new understanding of the underlying physics of the system. The first five chapters in this dissertation review background information and the principal motivations for this work. Chapter one reviews the basics of NMR, from the various components of the nuclear spin Hamiltonian and different spin-relaxation pathways to the reasons behind the low polarization of nuclear spins at thermal equilibrium and a few alternative methods to `boost' the NMR signal. Chapter two discusses the fundamental aspects of SEOP, including the electronic spin polarization of the alkali-metal, polarization transfer to the xenon nuclei, and different avenues for the spin polarization to be depleted. The third chapter covers the practical considerations of SEOP from the viewpoint of an experimentalist; namely, the experimental differences when using a variety of alkali metals and noble gases, as well as different SEOP apparatuses and experimental parameters. Chapter four details a variety of different light sources that may be used for SEOP; specifically, the use of laser diode arrays (LDAs) are reviewed, including LDAs that have been frequency-narrowed for more efficient light absorption by the alkali metal. The fifth background chapter covers a variety of magnetic resonance applications of hyperpolarized xenon, including molecular biosensors, specific and non-specific binding with proteins, materials studies, and in vivo applications. The sixth chapter is used as an overview of the dissertation research, which is presented in chapters seven through eleven. Chapter seven details the arrangement of the particular SEOP apparatus used in this research, as well as the experimental protocol for producing hyperpolarized xenon. The eighth chapter accounts the implementation and characterization of the first frequency-narrowed LDA used in this research, as well as an equal comparison to a traditional broadband LDA. Chapter nine introduces the use of in situ low-field NMR polarimetry, which was used to distinguish an anomalous dependence of the optimal OP cell temperature on the in-cell xenon density; the low-field set-up is also used to examine the build-up of nuclear spin polarization in the OP cell as it occurs. The tenth chapter covers the use of high power, frequency-narrowed light sources that are spectrally tunable independent of laser power; this allows for the study of changes to the optimal spectral offset as a function of in-cell xenon density, OP cell temperature, and laser power. Xenon polarization build-up curves are also studied to determine if the spectral offset of the laser affects the nuclear spin polarization dynamics within the OP cell. Finally, chapter eleven accounts the use of high power, broadband LDAs to perform SEOP in which cesium is used as the alkali metal; these results demonstrate (for the first time) that the xenon polarization generated by cesium optical pumping can surpass that of rubidium OP under conditions of high laser flux and elevated in-cell xenon densities.

No description available.

京都大学 / 0048 / 新制・課程博士 / 博士(理学) / 甲第22240号 / 理博第4554号 / 新制||理||1654(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)准教授 松田 和博, 教授 田中 耕一郎, 教授 佐々 真一 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

A novel crown ether precursor was developed in which a rigid 4-oxahexacyclo (5.4.1.26.3,10.05,9.08,11) dodecyl cage moiety ("cage functionality") was incorporated.

The effect of ultrasonic vibration on the anodic oxidation of silver foil in KOH was studied. An increase in charging capacity of approximately 20% was found to be the result of cavitation erosion. Silver wire was exposed to tension and torsion during oxidation but no change in charge acceptance was caused by these stresses. The oxide growth rate on silver foil electrodes was compared to rate equations that have been proposed for other metals. Uhlig's equations for the growth of semiconductor oxides was found to describe most of the data. The data did not fit other rate equations. Determination of the location of radioactive Ag110 in the oxide layer indicated that silver oxide grows by direct transport of the silver ion through the oxide, if a uniform oxide thickness is assumed. However, the dissolution-precipitation-model of oxide growth describes the data better and allows for the non-uniform oxide thickness which is characteristic of silver.

The development and commercialization of alkali ion secondary batteries has played a critical role in the development of personal electronics and electric vehicles. The recent increase in demand for electric vehicles has pushed for lighter batteries with a higher energy density to reduce the weight of the vehicle while with an emphasis on improving the mile range. A resurgence has occurred in lithium, and sodium, metal anode research due to their high theoretical capacities, low densities, and low redox potentials. However, Li and Na metal anodes suffer from major safety issues and long-term cycling stability. This dissertation focuses on the investigation of the interfacial chemistries between alkali metal-carbon host interactions and the electrode-electrolyte interactions of the cathode and anode with boron-based electrolytes to establish design rules for "lean" alkali metal composite anodes and improve long-term stability to enable alkali metal batteries for practical electrochemical applications. Chapter 2 of this thesis focuses on the design and preliminary investigation of "lean" lithium-carbon nanofiber (<5 mAh cm-2) composite anodes in full cell testing using a LiNi0.6Mn0.2Co0.2O2 (NMC 622) cathode. We used the electrodeposition method to synthesize the Li-CNF composite anodes with a range of electrodeposition capacities and current densities and electrolyte formulations. Increasing the electrodeposition capacity improved the cycle life with 3 mAh cm-2 areal capacity and 2% vinylene carbonate (VC) electrolyte additive gave the best cycle life before reaching a state of "rapid cell failure". Increasing the electrodeposition rate reduced cycling stability and had a faster fade in capacity. The electrodeposition of lithium metal into a 2D graphite anode significantly improved cycle life, implying the increased crystallinity of the carbon substrate promotes improved anode stability and cycling capabilities. As the increased crystallinity of the carbon anode was shown to improve the "lean" composite anode's performance, Chapter 3 focuses on utilizing a CNF electrode designed with a higher degree of graphitization and probing the interacting mechanism of Li and Na with the CNF host. Characterization of the CNF properties found the material to be more reminiscent of hard carbon materials. Electrochemical analysis showed better long-term performance for Na-CNF symmetric cells. Kinetic analysis, using cyclic voltammetry (CV), revealed that Na ions successfully (de)intercalated within the CNF crystalline interlayers, while Li ions were limited to surface adsorption. A change in mechanism was quickly observed in the Na-CNF symmetric cycling from metal stripping/plating to ion intercalation/deintercalation, enabling the superior cycling stability of the composite anode. Improving the Na metal stability is necessary for enabling Na-CNF improved long-term performance. Sodium batteries have begun to garner more attention for grid storage applications due to their overall lower cost and less volumetric constraint required. However, sodium cathodes have poor electrode-electrolyte stability, leading to nanocracks in the cathode particles and transition metal dissolution. Chapter 4 focuses on electrolyte engineering with the boron salts sodium difluoro(oxolato)borate (NaDFOB) and sodium tetrafluoroborate (NaBF4) mixed together with sodium hexafluorophosphate (NaPF6) to improve the electrode-electrolyte compatibility and cathode particle stability. The electrolytes containing NaDFOB showed improved electrochemical stability at various temperatures, the formation of a more robust electrode-electrolyte interphase, and suppression in transition metal (TM) reduction and dissolution of the cathode particles measured after cycling. In Chapter 5, we focus on the electrochemical properties and the anode-electrolyte interfacial chemistry properties of the sodium borate salt electrolytes. Similar to Chapter 4, the NaDFOB containing electrolytes have improved electrochemical performance and stability. Following the same electrodeposition parameters as Chapter 2, we find the NaDFOB electrolytes improves the stability of electrodeposited Na metal and the "lean" composite anode's cyclability. This study suggests the great potential for the NaDFOB electrolytes for Na ion battery applications. / Doctor of Philosophy / The ever-increasing demand for high energy storage in personal electronics, electric vehicles, and grid energy storage has driven for research to safely enable alkali metal (Li and Na) anodes for practical energy storage applications. Key research efforts have focused on developing alkali metal composite anodes, as well as improving the electrode-electrolyte interfacial chemistries. A fundamental understanding of the electrode interactions with the electrolyte or host materials is necessary to progress towards safer batteries and better battery material design for long-term applications. Improving the interfacial interactions between the host-guest or electrode-electrolyte interfaces allows for more efficient charge transfer processes to occur, reduces interfacial resistance, and improves overall stability within the battery. As a result, there is great potential in understanding the host-guest and electrode-electrolyte interactions for the design of longer-lasting and safer batteries. This dissertation focuses on probing the interfacial chemistries of the battery materials to enable "lean" alkali metal composite anodes and improve electrode stability through electrolyte interactions. The anode-host interactions are first explored through preliminary design development for "lean" alkali composite anodes using carbon nanofiber (CNF) electrodes. The effect on increasing the crystallinity of the CNF host on the Li- and Na-CNF interactions for enhanced electrochemical performance and stability is then investigated. In an effort to improve the capabilities of Na batteries, the electrode-electrolyte interactions of the cathode- and anode-electrolyte interfacial chemistries using sodium borate salts are probed using electrochemical and X-ray analysis. Overall, this dissertation explores how the interfacial interactions affect, and improve, battery performance and stability. This work provides insights for understanding alkali metal-host and electrode-electrolyte properties and guidance for potential future research of the stabilization for Li- and Na-metal batteries.

The rigid acridan-backbone phenyl-substituted thioether- and selenoether-containing pro-ligands H[AS2Ph2] (1) and H[ASe2Ph2] (2), and the bulky 2,4,6-triisopropylphenyl-substituted selenium and tellurium analogues, H[ASe2Tripp2] (3) and H[ATe2Tripp2] (4) were synthesized via a palladium catalyzed cross-coupling approach {for H[AS2Ph2] (1)} or a nBuLi-mediated synthesis strategy {for H[ASe2Ph2] (2), H[ASe2Tripp2] (3) and H[ATe2Tripp2] (4)}. Pro-ligands 1 and 2 were deprotonated with one equiv. of nBuLi to afford dimeric lithium complexes [Li(AE2Ph2)]2 (E = S (5), Se (6)) or with one equiv. of KCH2Ph to afford the potassium complexes [K(AS2Ph2)(dme)]x (7) and [K(ASe2Ph2)(dme)2] (8). Pro-ligands 3 and 4 were also deprotonated using KCH2Ph to afford [K(AE2Tripp2)(dme)2] {E = Se (9), Te (10)}. Compounds 1−10 were characterized by multinuclear NMR spectroscopy, where applicable, and single-crystal X-ray structures were obtained for all lithium and potassium complexes (5, 6 and 7−10), revealing the first examples of Li–SeR2 interactions in 6 and rare examples of K–SeR2 bonding in 8 and 9. DFT calculations were performed to assess the nature of bonding between the hard group 1 cations and the soft chalcogenoether donors. Dissolution of the potassium complex [K(ATe2Tripp2)(dme)2] (10) in THF, layering with hexanes, and cooling to –30 °C afforded X-ray quality crystals of [K(ATe2Tripp2)(THF)3] (11). The K–TeR2 distances in 11 are substantially shorter than those in 10, and DFT and QTAIM calculations support the presence of K–TeR2 interactions, providing the first unambiguous examples of s-block–telluroether bonding. Attempts to prepare bulk quantities of 11 afforded [K(ATe2Tripp2)(THF)2] (12), and further drying yielded [K(ATe2Tripp2)(THF)] (13) and [K(ATe2Tripp2)]x (14). The selenium analogues of 11, 12 and 13 (15, 16 and 17, respectively) were also prepared, and 11, 14, 15 and 16 were crystallographically characterized. Deprotonation of H[ATe2Tripp2] (4) with nBuLi in dme followed by recrystallization from dme/hexanes furnished crystals of [Li(dme)3][ATe2Tripp2] (18), whereas deprotonation of 4 with tBuLi in hexanes in the presence of only one equiv. of dme afforded [Li(ATe2Tripp2)(dme)] (19). The X-ray structure of 18 features lithium coordinated to three κ2-dme ligands along with a ‘naked’ ATe2Tripp ligand anion featuring no coordination to the metal centre. By contrast, the solid-state structure of 19 features coordination of lithium to one κ2-dme and one κ2-ATe2Tripp2 ligand via the nitrogen and one telluroether. Reaction of one equiv. of nBuLi with 4 in hexanes, followed by recrystallization from toluene/hexanes furnished crystals of the lithium cluster complex [Li8(ATeTripp)4(TenBu2)] (20), where ATeTripp (4-(2,4,6-triisopropylphenyltellurido)-2,7,9,9-tetramethylacridan-N,5-diide) is a dianionic CNTe-donor ligand generated in-situ by loss of a ‘TeTripp’ fragment from the ATe2Tripp2 monoanion. The complex features bridging and terminal Li–TeR2 linkages, in addition to an unsupported lithium–TenBu2 interaction. The structures of 19 and 20 contain the first examples of lithium–telluroether coordination, and complex 20 features the first unsupported s-block–telluroether interaction. DFT and QTAIM calculations on models of 19 and 20 were employed to gain insight into the nature of the Li–TeR2 interactions and probe the extent of covalency present in the bonds. Reaction of two equiv. of 7 or 8 with [UI4(dioxane)2] afforded the uranium(IV)–thioether complex [(AS2Ph2)2UI2] (21) and the first example of a uranium–selenoether complex, [(ASe2Ph2)2UI2] (22). X-ray structures revealed distorted square antiprismatic geometries in which the AE2Ph2 ligands are κ3-coordinated. The nature of the U–ER2 bonding in 21 and 22, as well as methyl-free analogues of 21 and 22 and a hypothetical ether analogue (complex 0*), was investigated computationally (including NBO, AIM, and ELF calculations), illustrating appreciable covalency increasing from O to S to Se. Reactions of the lithium complexes [Li(AE2Ph2)]2 {E = S (5) or Se (6)} with [ThCl4(dme)2] or UCl4 (for E = Se) afforded the actinide(IV) chalcogenoether chloro complexes [(AE2Ph2)2ThCl2] (E = S (23), Se (24)), and [(ASe2Ph2)2UCl2] (25). X-ray crystal structures of 23–25 revealed tetravalent actinide cations complexed to two κ3-coordinated AE2Ph2 ligands, with short Th−ER2 and U−ER2 distances (i.e. below the respective sums of the covalent radii). Complexes 23–25 provide extremely rare examples of thorium−thioether, thorium−selenoether, and uranium−selenoether bonds, and 23 and 24 contain the shortest known Th−SR2 and Th−SeR2 distances. DFT and QTAIM calculations confirm the presence of significant An(IV)−ER2 interactions in 23–25 and provide insight into the extent of covalency in the An−ER2 bonds. The THF-coordinated uranium(IV) trichloro complex [(ASe2Tripp2)UCl3(THF)] (26), featuring a single ASe2Tripp2 ligand was prepared by the reaction of [K(ASe2Tripp2)(dme)2] with one equiv. of UCl4 in THF. Two different crystal structures of 26 (26·o-DFB and 26·0.4 THF) gave structures with U–Se distances that differ by ~0.1 Å relative to each other, pointing to a shallow potential energy surface for the perturbation of U–Se bonds in 26. Treatment of 26 with LiCH2SiMe3 or LiCH2SiMe2Ph afforded the trialkyl species [(ASe2Tripp2)U(CH2SiMe3)3] (27) and [(ASe2Tripp2)U(CH2SiMe2Ph)3] (28), respectively, marking the first organouranium selenoether complexes. The X-ray crystal structure of 27 reveals substantially elongated U–Se distances relative to those in 26 likely due to steric repulsion between the relatively bulky CH2SiMe3– ligands on uranium and the flanking 2,4,6-triisopropylphenyl substituents at selenium, and quantum chemical calculations point to lower (but appreciable) covalency in the longer U–SeR2 interactions of 27 compared to the shorter ones in 26. Additional research contributions are presented, including the synthesis of a semi-bulky H[ASe2Ph2] pro-ligand analogue H[ASe2Mes2] (29; Mes = mesityl) and its deprotonation to afford the potassium–selenoether complexes [K(ASe2Mes2)(dme)] (30) and [K(ASe2Mes2)(dme)2] (31), (ii) variable temperature NMR characterization of a trivalent uranium AS2Ph2 complex [(AS2Ph2)2UI] (32) and trivalent neodymium AE2Ph2 (E = S, Se) complexes, and CV studies of complex 32, (iii) the development of new or modified syntheses for actinide starting materials, including the identification of the previously unknown etherate of UCl4 [UCl4(Et2O)2] (33), and (iv) the determination of the structure of a cationic yttrium dialkyl complex by NMR spectroscopy. / Dissertation / Doctor of Philosophy (PhD) / A series of new rigid monoanionic pincer ligands containing neutral chalcogenoether (i.e. SR2, SeR2, TeR2) donors have been developed, and their coordination chemistry with group 1 and actinide metals has been investigated. These ligands employ a highly rigid acridanide backbone featuring an amido anion flanked by neutral chalcogen donors that are directly affixed to the 4- and 5-positions of the ligand backbone. This provides a unique environment wherein a metal cation coordinating to the negatively charged nitrogen will, necessarily, be in proximity to the soft chalcogen atoms, encouraging the formation of metal–chalcogenoether bonds. This ligand strategy was successful in furnishing several complexes of lithium, potassium, and the actinide metals thorium and uranium, featuring metal coordination to the neutral chalcogen donors. These complexes demonstrate extremely rare examples of K–SeR2, Th–SR2 and Th–SeR2 interactions, and the first examples of Li–SeR2, K–TeR2, Li–TeR2 and U–SeR2 interactions. Techniques including but not limited to NMR spectroscopy, X-ray crystallography, UV-vis/NIR spectroscopy and combustion elemental analysis were used to characterize the new compounds and quantum chemical calculations were employed to provide insight into the nature of the metal–chalcogenoether bonds and probe the extent of covalency present within them. These developments contribute significantly to the very limited field of s- and f-block–chalcogenoether coordination chemistry.

No description available.

A large amount of information concerning interatomic distances in the solid state is available, but little has been done in recent times to comprehensively filter, summarize and analyze this information. Here, I examine the distribution of bond lengths for 135 ions bonded to oxygen, using 180,331 bond lengths extracted from 9367 refined crystal structures collected from the Inorganic Crystal Structure Database (ICSD). The data are used to evaluate the parameterization of the bond-length—bond-valence relation of the bond-valence model. Published bond-valence parameters for 135 cations bonded to oxygen, and the various methods used in their derivation, are evaluated. New equations to model the relation are tested and the common form of the equation is found to be satisfactory. A new method (the Generalized Reduced Gradient Method, GRG method) is used to derive new bond-valence parameters for 135 cations bonded to oxygen, leading to significant improvements in fit for many of the ions. The improved parameterization is used to gain crystal-chemical insight into the milarite structure. A literature review of 350+ published compositions is done to review the end-members of the milarite group and to identify compositions that should have been described as distinct minerals species. The a priori bond-valences are calculated for minerals of this structure, and are used to examine the controls of bond topology on site occupancy, notably by localizing the major source of strain of the structure (the B site). Examination of the compositions of all known milarite-group minerals shows that compositions with a fully occupied B site are less common than those with a vacant B site, in accord with the idea that the B site is a local region of high strain in the structure. The bond-length distributions for the ions of the alkali and alkaline-earth metal families are examined. Variations in mean bond-lengths are only partly explained by the distortion theorem of the bond-valence model. I have found that bond length also correlates with the amount of vibrational displacement of the constituent ions. The validity of some uncommon coordination numbers, e.g., [3]-coordinated Li+, [3]-coordinated Be2+, is confirmed. / October 2016