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This investigation is based on the topochemical modification of three set of phases: Sr₃Co₂O₅Cl₂, SrO(Sr(Ru_0.5M_0.5)O₃)n (M = Ti, Mn, Fe; n = 1, 2, &infin;), and SrO(SrVO₃)n (n = 1, 2, &infin;). The topochemical reduction of Sr₃Co₂O₅Cl₂ using sodium hydride as a solid state reducing agent results in the formation of a reduced phase containing cobalt centres with an average oxidation state of +2 and an overall composition of Sr₃Co₂O₄Cl₂. The resulting material adopts a structure containing double sheets of square-planar corner-sharing CoO2 units separated by rock salt SrCl layers. Variable-temperature diffraction measurements reveal that these sheets undergo a cooperative Jahn-Teller distortion at T ~ 200 K due to unevenly filled degenerate (d_xy, d_yz) orbitals. This material adopts a magnetic structure in which the moments within each sheet are ordered antiferromagnetically, but the sheets are aligned ferromagnetically. An investigation was carried on the reduction behaviour of Ru-doped Sr(Ru_xFe_1-x)O₃. It was found that the reduction was non-topochemical for values of x > 0.5. For values of 0 < x < 0.5, no single phase precursor material could be formed. For the material with x = 0.5, reduction with CaH₂ produced a new phase with composition Sr(Ru_0.5Fe_0.5)O₂. This material is the first reported instance of Ru²⁺ in an extended transition metal oxide. DFT calculations reveal that, while the iron centres adopt a high-spin configuration, the ruthenium centres are in an intermediate-spin S = 1 configuration. Resulting competing magnetic interactions lead to frustration and lack of ordering. In order to further study the reduction behaviour of extended transition metal oxides containing ruthenium, the reduction of Sr₂(Ru_0.5Fe_0.5)O₄ and Sr₃(Ru_0.5Fe_0.5)₂O₇ was performed using CaH₂ as a solid state reducing agent. In these cases, reduction leads to segregation of the materials into multiple phases adopting closely related structures that differ mainly in their oxygen content. In these materials, the ruthenium centres are preferentially reduced, such that starting from materials containing Ru⁵⁺ and Fe³⁺, materials containing Ru^(3-δ)+ and Fe³⁺ are produced. Similarly, the low-temperature oxidation using CuF₂ as a solid state fluoride source was performed on materials with composition Sr3(Ru0.5M0.5)2O7 (M = Ti, Mn, Fe). In the case of M = Mn and Ti, materials with composition Sr₃(Ru_0.5Fe_0.5)₂O₇F₂ are produced in which the ruthenium centres are oxidised to Ru⁶⁺. For the M = Fe material, oxidation results in partial exchange of O for F and a material with composition Sr₃(Ru_0.5Fe_0.5)₂O_5.5F_3.5 in which the ruthenium centres are oxidised from +5 to +5.5 while the iron centres remain in a +3 oxidation state. While fluorination of the M = Ti leads to increasing itinerant electronic behaviour, fluorination of the M = Mn and Fe materials induces a twisting of the MX₆ octahedra that enables magnetic order to emerge at low temperatures. Finally, reaction of the SrO(SrVO₃)n (n = 1, 2, &infin;) series of phases with CaH₂ results in the formation of phases with composition SrO(SrVO₂H)_n (n = 1, 2, &infin;), the first examples of stoichiometric oxyhydride materials. SrVO₂H is magnetically ordered at room temperature, while the n = 1 and n = 2 materials order at 170 K and 240 K respectively. The high magnetic ordering temperature arises from strong interactions between (d_xy, d_yz) orbitals in a manner analogous to the reduced iron-containing phases SrO(SrFeO₂)_n.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19735号 / 工博第4190号 / 新制||工||1646(附属図書館) / 32771 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 陰山 洋, 教授 安部 武志, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

This thesis is comprised of three parts. The first part concerns the investigation of the topochemical reduction of LaSrNiRuO₆ in order to prepare LaSrNiRuO₄ via anion deintercalation. The second part discusses the oxide-for-hydride anion exchanges performed in SrV_1-xTi_xO₃, and the resulting SrV_1-xTi_xO_2-yH_1+y reduction products. Finally, the results from redox-neutral topochemical cation exchange reactions conducted in the three-dimensional perovskite structure of NaTaO₃ are presented along with the characterisation of a novel product of composition Ni_0.5TaO₃. The topochemical reduction of LaSrNiRuO₆ using CaH2 was carried out to produce a novel extended oxide phase with composition LaSrNiRuO₄. This phase is composed of sheets of apex-linked Ni¹⁺O₄ and Ru²⁺O₄ squares in a checkerboard ordered arrangement. To the best of our knowledge, this material is the first example of a B-cation ordered infinite-layer oxide phase. The low oxidation states of the transition-metal cations are confirmed by DFT calculations from which a spin moment S = &frac12; is determined for the nickel while the ruthenium centres adopt an intermediate-spin S = 1 configuration. LaSrNiRuO4 behaves paramagnetically at room temperature. However, upon cooling (T &LT; 250 K) a phase transition is observed in which the nickel spins interact ferromagnetically, while the ruthenium cations appear to undergo a change in spin configuration to a diamagnetic spin state. A possible explanation is given for this observation based on an ordered arrangement of local Jahn-Teller distortions. While investigating the preparation of LaSrNiRuO₄, it was observed that different samples of the LaSrNiRuO₆ starting materials exhibited markedly different reactivity. The observed differing reactivity is inconsistent with the crystal structure and composition of the LaSrNiRuO₆ samples, from which all the materials are identical. Careful investigation of the X-ray diffraction data collected from the LaSrNiRuO6 materials revealed that the reactivity of the samples is a consequence of the microstructure. By quenching or slow-cooling the materials during their synthesis, the size of the crystalline domains formed is affected and this in turn is observed to define the extent to which the topochemical deintercalation of oxide anions takes place. A mechanism to explain this effect is presented in which the greater 'plasticity' of small crystalline domains helps to limit the influence of lattice strain during the reaction. Similar with the observations for the LaSrNiRuO₆ phases, it was found that the reactivity of SrV_0.95Ti_0.05O₃ samples towards topochemical oxide-for-hydride exchange is also determined by the characteristics of the starting materials. The cooling rate can lead to phase segregation in SrV_0.95Ti_0.05O₃ samples which in turn affects the reduction behaviour. A modification of the energy profile for the oxide-for-hydride exchange in SrV_1-xTi_xO₃ phases is proposed on the basis of the electronic configuration that the transition-metal cations adopt upon reduction (d²,V³⁺ and d¹,Ti³⁺). Finally, topochemical exchange reactions can also be carried out between cations in complex transition metal oxides when the mobility of the species to be exchanged is sufficiently greater with respect to the host lattice. The preparation of Ni_0.5TaO₃ from exchange of Na⁺ by Ni²⁺ in NaTaO3 represents a synthetic approach not yet widely explored in the long-standing challenge that the preparation of magnetoelectric multiferroic materials represents. The topochemical reactions studied in this work highlight the possibility of directing and modifying the product phases, by tuning features of the reagents. This is in contrast with the limited control available in thermodynamic processes.

Layered perovskites can be classified in three major groups: Dion-Jacobson AA′n-1BnO3n+1, Ruddlesden-Popper A2A′n-1BnO3n+1,and Aurivillius phase (Bi2O2)A′n-1BnO3n+1. (A: Alkali metal, Alkali-earth metal; A′: Lanthanides and Bi; B: Ti, Nb, Ta; n: thickness of slabs). For more than two decades researchers have shown much interest in this series because of their magnetic and electrical properties. Tuning synthesis parameters such as temperature, time, and host structure can be used to direct such properties. Low temperature synthetic methods (topochemical methods) allow the preparation of compounds not accessible by traditional high temperature reactions. This dissertation mainly considers the topochemical methods of ion exchange and reductive and oxidative intercalation to build new low temperature or metastable layered perovskites. The two-dimensional Dion-Jacobson ALaNb2O7 layered perovskites were intercalated reductively to produce A2LaNb2O7 andthen oxidized with water or hydro-chalcogenides (H2Ch, Ch: S, Se) to produce the novel alkali metal hydroxide, (A2OH)LaNb2O7, and alkali metal hydro-chalcogenides, (A2ChH)LaNb2O7, respectively. The synthesis and characterization of these compounds are presented in Chapters 2 and 3. In another set of studies, high temperature ceramic methods lead to the new host APrNb2O7. When this reaction is followed by ion exchange, (CuCl)PrNb2O7 can be prepared. The structural refinement, magnetic properties, and thermal stability of new phases have been studied in Chapter 4. The utility of praseodymium niobates for the formation of other metal oxyhalides was also developed; the series (MX)PrNb2O7 (M: Mn, Fe, Co, Cu and X: F, Cl) were prepared by the ion exchange of LiPrNb2O7 and the obtained phases characterized (Chapter 5). Further, to expand the library of materials and because of interesting properties of lanthanides (Ln: La, Pr, Nd, Sm), lanthanide tantalates have been explored for the preparation of oxyhalides and resulted in the compounds (CuCl)LnTa2O7 (Ln: Pr, Nd) (Chapter 6). Manipulation of Dion-Jacobson layered perovskites are not limited to lanthanides, other hosts with interesting properties have been examined (e.g. ABiNb2O7) (A: alkali metal, CuCl) and their crystal structures characterized along with thermal stability and magnetic response.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19187号 / 工博第4064号 / 新制||工||1627(附属図書館) / 32179 / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 陰山 洋, 教授 阿部 竜, 教授 田中 勝久 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20763号 / 工博第4415号 / 新制||工||1686(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 陰山 洋, 教授 阿部 竜, 教授 江口 浩一 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

<p>  </p> <p>Plastics play crucial rules in almost every aspect of life. Unique properties of plastics like chemical and light resistant, strong, moldable, and low cost make plastic materials useful in many aspects of our global society. However, largely relying on feedstock resources like fossil fuels, plastics production is not sustainable. Thus, plastic recycling could be an efficient alternative to save feedstock resources as well as to reduce production cost.</p> <p>Recently, a series of polymer materials synthesized via topochemical polymerization are considered as strong candidates for next generation recyclable plastics. It is well-known that topochemical polymerization has high efficiency and environment-friendly features, such as solvent-free and catalyst-free reaction conditions, high reaction yield without side reactions, and atom economy. Yet, there exist few studies on depolymerizing and recycling those polymers. A unique topochemically polymerizable polyindenedione derivative [2,2'-Bi-1H-indene]-1,1'-dione-3,3'-diyl dialkylcarboxylate (polyBIT) with rapid and quantitative depolymerization was discovered via breakage of elongated carbon-carbon (C-C) bonds with bond length of 1.57∼1.63 Å. The elongated C-C bonds have been proven theoretically and experimentally to have significantly lower bond dissociation energies than normal C-C bonds, and it is the major driving force to depolymerize polyBIT polymer single crystals. </p> <p>Different from most traditional polymers that can be dissolved or melt processed, topochemical polymer single crystals are not soluble in most common solvents due to their highly crystalline and ordered nature. This unique feature inhibited topochemical polymer crystals from practical applications. To convert needle-like polyBIT crystals into useful forms, I developed an ultrasonication method to break large polymer crystals into small fibers that can be uniformly suspended in organic solvents. Followed by vacuum filtration and heat press, polyBIT crystals can be processed into robust and freestanding polymer thin films. The processed thin films presented reasonable mechanical properties with Young’s modulus of over 600MPa and are stable under harsh conditions.</p> <p>Topochemical polymerization reactions require specific monomer packings before applying external stimuli, and a small change in monomer structure may completely alter the reactivity. Therefore, functionalizing monomer structures for topochemical reactions is quite challenging. In the polyBIT system, we attempted to functionalize BIT monomer with several linear and branched side chains. After preparing monomer crystals, only needle-like 1D monomers can be photopolymerized, while plate-like 2D monomer crystals became photostable. Introducing heteroatoms (such as oxygen, sulfur, bromine, chlorine) can induce different non-bonding interactions and interactions, which combined can push monomers away from one another to make them unreactive. Introducing branched side chains will also change the distances between two BIT monomers and leads to unreactive crystals when the branched side chain is too bulky (such as when tertbutyl group is on the end of side chain). Functionalizing side chains for polyBIT crystals can further tune the mechanical properties of the crystals: swapping end methyl group with a simple bromine atom can induce multiple intermolecular and interchain interaction including weak hydrogen bonding and C−H···Br interactions. These interactions bind all the polymer chains together to provide a strong 1D polymer fiber with elastic modulus over 10.6 GPa. These results suggest that the crystalline polymers synthesized from simple photochemistry and without expensive catalysts are promising for practical applications with complete materials circularity and wide range of structural and mechanical turnabilities.</p>

Developing new materials with desired properties is a vital component of emerging technologies. Functional hybrid compounds make an important class of advanced materials that let us synergistically utilize the key features of the organic and inorganic counterparts in a single composite, providing a very strong tool to develop new materials with ”engineered” properties. The research presented here, summarizes efforts in the development of facile and efficient methods for the fabrication of three- and two-dimensional inorganic-organic hybrids based on layered oxide perovskites. Microwave radiation was exploited to rapidly fabricate and modify new and known materials. Despite the extensive utilization of microwaves in organic syntheses as well as the fabrication of the inorganic solids, the work herein was among the first reported that used microwaves in topochemical modification of the layered oxide perovskites. Our group specifically was the first to perform rapid microwave-assisted reactions in all of the modification steps including proton exchange, grafting, intercalation, and exfoliation, which decreased the duration of multi-step modification procedures from weeks to only a few hours. Microwave-assisted grafting and intercalation reactions with n-alkyl alcohols and n-alkylamines, respectively, were successfully applied on double-layered Dion-Jacobson and Ruddlesden-Popper phases (HLaNb2O7, HPrNb2O7, and H2CaTa2O7), and with somewhat more limited reactivity, applied to triple-layered perovskites (HCa2Nb3O10 and H2La2Ti3O10). Performing neutron diffraction on n-propoxy-LaNb2O7, structure refinement of a layered hybrid oxide perovskite was then tried for the first time. Furthermore, two-dimensional hybrid oxides were efficiently prepared from HLnNb2O7 (Ln = La, Pr), HCa2Nb3O10, HCa2Nb2FeO9, and HLaCaNb2MnO10, employing facile microwave-assisted exfoliation and post-exfoliation surface-modification reactions for the first time. A variety of surface groups, saturated or unsaturated linear and cyclic organics, were successfully anchored onto these oxide nanosheets. Properties of various functionalized metal-oxide nanosheets, as well as the polymerization of some monomer-grafted nanosheets, were then investigated for the two-dimensional hybrid systems.

Les polydiacétylènes sont des polymères π-conjugués, obtenus par polymérisation topochimique à l'état solide de motifs diacétyléniques, sous l'effet d'un stimulus thermique ou photochimique. Depuis leur découverte en 1969 par Wegner, les polydiacétylènes ont fait l'objet de nombreux travaux de recherche. Ces travaux ont consisté tout d'abord à élucider le mécanisme de polymérisation, puis à étudier les diverses propriétés photophysiques, optiques, et électroniques des polymères. Néanmoins, la plupart des diacétylènes étudiés ne possédaient pas de substituants susceptibles d'être modifiés chimiquement. Le premier chapitre de cette thèse décrit la synthèse de nouvelles molécules diacétyléniques symétriques comportant des groupements azoles, et l'étude de leur polymérisation à l'état solide. La modification de l'organisation des motifs diacétyléniques.par interaction avec des molécules capables de former des liaisons hydrogène, et l'incorporation de ces motifs dans des matériaux hybrides organiques-inorganiques de type,. MOF ont également été examinées.Dans le deuxième chapitre, nous nous sommes intéressés aux composés diacétyléniques dicationiques fonctionnalisés par des groupements triéthylammoniums, imidazoliums et benzimidazoliums. La synthèse de ces composés, leur caractérisation spectroscopique, et cristallographique, ainsi que l'étude de leur réactivité thermique et photochimique ont été réalisées.Dans le troisième chapitre, nous proposons une méthode directe de préparation de carbone dopé à l'azote par pyrolyse des molécules diacétyléniques neutres, ainsi que la synthèse de carbone mésoporeux en présence d'un sel métallique. Un autre aspect de ce chapitre est l'optimisation des teneurs en azote en utilisant comme précurseurs les composés diacétyléniques dicationiques, associés à des anions riches en azote, notamment l'anion dicyanamide [dca] et tricyanométhide [tcm]. / Diacetylenes (DA) are unusual molecules owing to their ability to polymerize in the solid state. Such a polymerization is triggered off thermally or photochemicaly, and leads to the formation of enyne structures. Since their discovery in 1969 by Wegner, polydiacetylenes (PDA) have been the focus of much attention. Initially, many studies were devoted to elucidating the mechanism of polymerization, then assessment of the diverse photophysical, optical, and electronic properties of the polymers became the main goal. Yet, the vast majority of the DA that were studied did not possess substituents that could be modified chemicallyThe first chapter describes the synthesis of new symmetrical diacetylenic molecules functionalized with azole substituents and the study of the polymerization of these compounds in the solid state. Then, we present the modification of the organization of these diacetylenes by the interaction with molecules capable of forming hydrogen bonds, and the use of these molecules as ligands for the synthesis of Metal Organic Frameworks (MOF).The second chapter is devoted to the synthesis, characterization and crystallographic study of ionic diacetylenic compounds bearing triethylammonium, imidazolium and benzimidazolium groups. The photochemical and thermal behaviors of these DA have been tested.In the third chapter, we propose a straightforward route to N-doped graphitic carbon by direct pyrolysis of neutral diacetylenic precursors, and investigate the possibility of forming porous materials by adding a metal salt as a catalyst. Furthermore, another aspect of this chapter was to optimize the nitrogen content of these materials by using dicationic DA with N-rich anions, e.g. dicyanamide [dca] and tricyanomethide [tcm].