The systematic investigation of the x-ray diffraction symmetry of scapolites covering the whole range of solid solution show that all scapolites possess space group P4(2)/n, except the pure end-members, marialite and meionite, which will possess space group I4/m, if they exist. The intensity of the weak superlattice reflections violating the body-centred symmetry, continuously increases from zero at the marialite end-member as Me% increases, reaches a maximum around 37%+/-2% Me then approximately symmetrically decreases to 75% Me followed by a slower decrease to zero at the meionite end-member. Hence, all the intermediate scapolites of the marialite-meionite series actually have a pseudosymmetric structure, i. e., a pseudobody-centred structure, and as the chemical composition approaches both end-members, the scapolite structure approaches the structure with a body-centred lattice. The weak super-lattice reflections are directly related to the following two correlated factors: (1) the relative order-disorder of A1 and Si distribution in the tetrahedral framework, and (2) the structural distortion from the body-centred symmetry. Accompanied with the above facts is the systematic deviation of cell dimensions from the linear regression in such a way that the further the structure deviates from the body-centred symmetry, the smaller the cell volume and the a(o) become relative to the evaluated one from the linear regression. Scapolites are regarded as a continuous, perfect solid solution with a long-range disordering, and unlikely to be composed of submicroscopic twins or different domains. The structural analyses and refinements of three scapolites (ON8, 20% Me; XL, 52% Me; ON45, 93% Me) have been carried out by using 3-dimensional intensity data collected by integrated precession film techniques (ON8, ON45) and an automated single-crystal diffractometer (XL), and using the full-matrix least0squares method. The result has clarified the ambiguities arising from the previous studies and showed that the crystal structure is essentially continuous along the marialite-meionite series, with a slight structural variation as a function of chemical composition and ordering of Al, Si. Several important quantitative relationships regarding the crystal structure and crystal chemistry of the scapolite solid solution series have been established, namely, (1) the relationship between the superlattice intensity r(ΣI(h+k+l=2n+1)/ΣI(h+k+l=2n)) and the chemical index % Me. (2) the exponential relationship between the superlattice intensity ration r and the atomic displacement from the mirror plane consistent with the space group I4/m. (3) The linear relationship between the superlattice intensity ratio r and the difference of Al occupancy between T2 and T3 sites. (4) The Al occupancy (%) of tetrahedral sites as a function of the chemical composition of scapolites. The ordering of Al-Si, the c-axis displacement of (Ca, Na), the tilting of CO3 and the relative amount of CO3 and Cl in the same scapolite are all inter-related. The mechanism to cause all such related structural phenomena and even the abnormal stoichiometry of scapolite can all be interpreted in terms of the internal strain created by the two greatly different anions, Cl- and CO3-,sharing the same set of equivalent sites. / Thesis / Doctor of Philosophy (PhD)

<p> This thesis reports a systematic study of geometrically frustrated f.c.c. double perovskites with both monoclinic (P2₁/n) La₂LiMO₆ and cubic (Fm3m) Ba₂YMO₆ symmetries, where M=Mo (S=1/2), Re (S=1) and Ru (S=3/2). The roles of both the spin quantum number, i.e. quantum spin fluctuations, and the local site symmetry, i.e. orbital ordering, on the determination of the ground magnetic state were studied. All the compounds were prepared by solid state reaction and the structural information and magnetic properties of the compounds were collected using diffraction techniques (X-ray and neutron), de susceptibility, heat capacity, muon spin relaxation (μSR) and solid state NMR. </p> <p> The S=3/2 materials, La₂LiRuO₆ and Ba₂YRuO₆, while highly frustrated with frustration indices f ~ 16 and 8, respectively, both show antiferromagnetic (AF) long range ordering at 24K and 37K, respectively. The Neel temperature of the latter compound was determined for the first time by the heat capacity and neutron diffraction. This compound shows an unusual AF transition as two broader peaks were observed in the susceptibility while La₂LiRuO₆ shows a typical AF behavior. There is about 1 % of Y/Ru site mixing observed by 89Y MAS NMR in Ba₂YRuO₆. </p> <p> For the S=1 materials, monoclinic La₂LiReO₆ shows collective singlet like behavior as zero magnetization was observed in the ZFC susceptibility and a static and diluted spin system was indicated by μSR. On the other hand, the cubic phase, Ba₂YReO₆ surprisingly shows a spin glass behavior confirmed by μSR while no Y/Re site mixing was observed by MAS NMR. It is also a surprising observation that this compound retains cubic symmetry down to 3K where it would have a structure transition subject to the Jahn-Teller theorem. </p> <p> Finally, the S=1/2 compounds, La₂LiMoO₆ and Ba₂YMoO₆, show quite different magnetic behavior. Monoclinic La₂LiMoO₆ shows the presence of at least short range order achieved at 18K according to the heat capacity and μSR measurements. Ba₂YMoO₆ retains cubic symmetry down to 3K and no Jahn-Teller distortion was observed at the limit of the resolution of neutron diffraction. This compound surprisingly appears to remain paramagnetic down to 2K, yet evidence for a collective singlet state was observed by a paramagnetic Knight shift measurement in NMR. This is consistent with an existing theoretical prediction. </p> <p> An extended study on other S=1/2 Mo analogues, Ba₂LuMoO₆ and Ba₂ScMoO₆ is also presented. Both compounds show cubic structure confirmed by X-ray diffraction and paramagnetic behavior down to 2K in the susceptibility. </p> / Thesis / Doctor of Philosophy (PhD)

L’étude des polymorphes, soit des composés qui peuvent cristalliser avec plus d’une forme cristalline, est un centre d’intérêt pour nombreux domaines scientifiques. Dans certains cas, les variations structurales ont pour effet de causer de majeurs changements aux propriétés physicochimiques des composés, donnant la possibilité de préparer des matériaux possédant des caractéristiques précises pour une application donnée. Le domaine des explosifs est en continuelle évolution afin de combler les besoins militaires et civils. Des matériaux détenant un bon équilibre entre une haute performance énergétique et la sécurité sont recherchés. La 6-azidotétrazolo[5,1- a]phtalazine (ATPH) est une molécule riche en azote étroitement lié aux substances conçues comme explosifs. Dans le cadre de ce mémoire, le criblage polymorphique de l’ATPH entraine la découverte et l’isolation de six nouvelles formes solides de l’ATPH. Les motifs d’empilement à feuillets et à chevrons sont retrouvés dans l’ensemble des structures par des interactions polarisées N…N/C-H…N. Les polymorphes ont été caractérisés par IR, Raman, DSC, PXRD, SC-XRD et des études de stabilité relative en solution. Le caractère hautement polymorphique de l’ATPH est supporté par les résultats d’une étude computationnelle de prédiction des structures cristallines. / The study of polymorphs, or compounds that can crystallize in more than one crystal form, is a focus of interest for many scientific fields. In some cases, structural variations cause major changes in the physicochemical properties of the compounds, making it possible to prepare materials with specific characteristics for a given application. The development of explosive materials is a continuously evolving field for military and civilian purposes. Materials with a fine balance between high energy performance and safety are sought. 6-Azidotetrazolo[5,1-a]phthalazine (ATPH) is a nitrogen-rich molecule closely related to substances designed as explosives. In this dissertation, polymorphic screening of ATPH resulted in the discovery and isolation of six new solid forms of ATPH. Sheets and chevron stacking motifs directed by polarized C-N···N/C-H···N interactions were observed in all structures. The polymorphs were characterized by IR, Raman, DSC, PXRD, SC-XRD, and relative stability studies in solution. The highly polymorphic character of ATPH is consistent with the results of computational crystal structure prediction.

No description available.

<p>A series of layered perovskite-based compounds were synthesized and studied as follows.</p> <p>La₅Mo_2.76(4)V_1.25(4)O₁₆ is a new pillared-perovskite synthesized by solid state chemistry method. It has layers of corner-sharing octahedra separated by dimers of edge-sharing octahedra, and is the first Mo-based pillared-perovskite whose magnetic structure was determined by neutron diffraction.</p> <p>Ca₂FeMnO₅ is an oxygen-deficient-perovskite with a brownmillerite-type ordering of oxygen vacancies, resulting in layers of corner-sharing octahedra separated by chains of corner-sharing tetrahedra. The octahedral layer contains mostly (~87%) Mn, while the tetrahedral layer is mainly (~91%) occupied by Fe. Long-range G-type magnetic ordering is present, where the moment on each site is coupled antiferromagnetically relative to all nearest neighbors.</p> <p>Ca₂FeCoO₅ has a brownmillerite superstructure with space group <em>Pcmb</em>, a rare space group for brownmillerites that requires doubling of one unit cell axis. Ca₂FeCoO₅is the first brownmillerite to contain intra-layer cation ordering. It has a long-range G-type ordering, and is the first brownmillerite to show spin re-orientation as function of temperature.</p> <p>Sr₂FeMnO_5+y was synthesized in both air (y~0.5) and argon (y~0), both of which resulted in vacancy-disordered cubic structures. The argon compound has a local brownmillerite structure, i.e. local ordering of vacancies. It has a superparamagnetic state below ~55K, with domains of short range (50Å) G-type ordering at 4K. For the air synthesized compound, y~0.5, long range G-type ordering is observed in ~4% of the sample.</p> <p>Sr₂Fe_1.9M_0.1O_5+y (M=Mn, Cr, Co; y= 0, 0.5) were synthesized in both air(y~0.5), and argon(y~0). All argon materials are brownmillerites with G-type magnetic ordering, but T_N’s are significantly different. The air-synthesized Co-material has long range vacancy ordering and magnetic ordering, while the Mn and Cr-materials (air) lack such orderings and both show spin-glass-like transitions.</p> <p>Sr₂Fe_1.5Cr_0.5O₅ has a vacancy-disordered cubic structure, but contains long range G-type magnetic ordering, unlike the other vacancy-disordered materials studied.</p> / Doctor of Philosophy (PhD)

Pure samples of colorless, air-stable Ba(BO2OH) crystals were obtained from Ba(NO3)2 and H3BO3 under the ultra-alkaline conditions of a KOH hydroflux at about 250 °C. The product formation depends on the water-base molar ratio and the molar ratio of the starting materials. B(OH)3 acts as a proton donor (Brønsted acid) rather than a hydroxide acceptor (Lewis acid). Ba(BO2OH) crystallizes in the non-centrosymmetric orthorhombic space group P212121. Hydrogen bonds connect the almost planar (BO2OH)2− anions, which are isostructural to HCO3−, into a syndiotactic chain. IR and Raman spectroscopy confirm the presence of hydroxide groups, which are involved in weak hydrogen bonds. Upon heating in air to about 450 °C, Ba(BO2OH) dehydrates to Ba2B2O5. Moreover, the non-centrosymmetric structure of Ba(BO2OH) crystals was verified with power-dependent confocal Second Harmonic Generation (SHG) microscopy indicating large conversion efficiencies in ambient atmosphere.

The research presented in this thesis focused on pseudorotaxanes and supramolecular polymers based on a new recognition motif, the dibenzo-24-crown-8/paraquat recognition motif. Main kinds of pseudorotaxanes and rotaxanes and various protocols used for the study of them were discussed first. By preparation and characterization of a series of pesudorotaxanes based on DB24C8 and paraquat derivatives, it was found that these complexes were stabilized by N+...O interactions, C-H...O hydrogen bonding, and face-to-face p-stacking interactions. Because methyl protons of paraquat are involved in hydrogen bonding to the host, the substitution of any methyl hydrogen on paraquat causes apparent association constant of the pseudorotaxane to decrease. The concentration dependence of apparent association constants, Ka,exp, of fast exchange host-guest systems was studied for the first time by using complexes based on viologens and crown ethers as examples. While the bis(hexafluorophosphate) salts of paraquat derivatives are predominantly ion paired in acetone (and other low dielectric constant solvents presumably) the complex based on dibenzo-24-crown-8 and paraquat is not ion paired in solution, resulting in concentration dependence of Ka,exp. However, four complexes of two different bis(m-phenylene)-32-crown-10 (BMP32C10) derivatives and bis(p-phenylene)-34-crown-10 (BPP3C10) with viologens are ion paired in solution, as shown by the fact that Ka,exp is not concentration dependent for these systems involving hosts with freer access to bound guests. X-ray crystal structures support these soluton-based assessments in that there is clearly ion pairing of the cationic guest and its PF6- counterions in the solid states of the latter four examples, but not in the former. The complexes based on the new dibenzo-24-crown-8/paraquat recognition motif are thus different from the complexes based on two old recognition motifs: the BPP34C10/BMP32C10-paraquat and DB24C8-ammonium motives. In order to compare these recognition motives further, the selectivity between two hosts, DB24C8 and BPP34C10, and two guests, dimethyl paraquat and dibenzyl ammnonium salt, was discussed. By individual and competitive complexation studies, it was demonstrated that DB24C8 is a better host than BPP34C10 for paraquat, and that paraquat is a better guest than dibenzyl ammonium salt for DB24C8. Finally the DB24C8-paraquat recognition motif was successfully applied in the preparation the first star-shaped supramolecular polymer based on a tetraparaquat guest and a DB24C8 functionalized polystyrene oligomer. A model system based on this guest and DB24C8 was also studied for comparison. It was found that the complexation in these two systems is cooperative, as are most biological complexations of multitopic species. Due to the ready availability of DB24C8 and paraquat derivatives, the new recognition motif should prove to be very valuable for self-assembly of other more sophisticated supramolecular systems. / Master of Science

No / The synthesis and crystal structure of the lithium hydrate salt of the charge transfer complex between 3,5-dinitrobenzoic acid and 4-(dimethylamino) benzoic acid is reported. It is the first crystal structure reported for such a class of hybrid inorganic/organic material. The design principles may have utility in the future creation of new ternary and higher complexes.

京都大学 / 新制・課程博士 / 博士(理学) / 甲第25128号 / 理博第5035号 / 京都大学大学院理学研究科化学専攻 / (主査)准教授 板東 俊和, 教授 深井 周也, 教授 秋山 芳展 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第25398号 / エネ博第477号 / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 片平 正人, 准教授 中田 栄司, 教授 菅瀬 謙治 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM