Metastable layered perovskites containing interlayer transition metals can readily be obtained by simple ion exchange reactions on receptive hosts, such as those of the Dion-Jacobson and Ruddlesden-Popper structure types. In this work, we focused on adding to the library of layered perovskites by not only creating new compounds, but by also showing their ability to be further manipulated, and by studying the stability of the series through thermal behavior studies. The reactions with transition metal halides are particularly interesting since they often lead to novel architectures and magnetic behavior. On subsequent heat treatment, these exchange products typically decompose to thermodynamically more stable phases. The newly synthesized spin glass-like material, FeLa2Ti3O10, obtained by ion exchange of Li2La2Ti3O10 with FeCl2 at 350 °C, behaves differently. When heated to 700 °C, the compound undergoes a significant cell contraction (Δc ≈ -2.7 Å) with an increase in the oxidation state of iron present in the interlayer that not been observed before in such compounds. Efforts were also made to synthesize new series of compounds, here MSrTa2O7 (M= Co and Zn), with vacancies in the interlayer that could lead to future topochemical manipulations. The ability to vary the composition of different phases to form solid-solutions through atomic substitution at the A or B sites with ions of similar or different charge can lead to new structures as well an enhancement of the properties of the original compound or new ones. The synthesis and characterization of the new mixed A-cation containing layered perovskite RbLaNaNb3O10, where La3+ and Na+ share the same site in the perovskite slab and RbLaCaNb2MnO10 that exhibits an ordering of the B site with Mn in the center of the perovskite slab will be presented. Further topochemical manipulation of these phases via ion exchange reactions at low temperatures (< 500 °C), lead to the new series A’LaNaNb3O10 and A’LaCaNb2MnO10 where A’= H, Li, Na, K and CuCl.

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Topochemical strategies, techniques that allow one to effectively manipulate the structures of nonmolecular solids once a crystal lattice is established, are effective in the low temperature (< 500 °C) modification of solid state structures, allowing the preparation of nonmolecular compounds not accessible by standard synthetic routes. Some of the techniques, ion exchange, intercalation/deintercalation, have proven to be excellent synthetic methods for preserving specific frameworks. The combination of these techniques can allow one to create a multistep approach that can be used to design new compounds with interesting properties. As an expansion to the field of topotactic reactions, a multistep approach was developed towards the synthesis of the new compounds (A xM0.5Cly)LaNb2O7 (where A = Rb, Cs; M = Fe, Ni; x ≈ 1.5;y ≈ 1) at temperatures below 400oC. The first reaction step involved the ion exchange of the host materials (ALaNb2O7, A = Rb, Cs) to form the products M0.5LaNb2O7 (where M = Fe, Ni), a structure open to further chemistry. The next step involved reductive intercalation with Rb or Cs metal to form the air sensitive mixed-valence products with the nominal compositions, A1.5M0.5LaNb2O7. The last step involved the oxidative intercalation of chlorine using chlorine gas to obtain the final compounds. This multistep approach is a design to form mix-metal halide layers, specifically those with divalent cations, within layered perovskites, opening the doors to compounds that can have interesting properties. This reaction series was also applied to the tantalate layered oxides, leading to the formation of the new compound Ni 0.5LaTa2O7 through ion exchange. The further multistep topochemical manipulation of this new compound was not successful and was indicative of the difference in chemical behavior of the tantalates versus the niobates. We have also investigated the oxidative intercalation of halogens into a series of Ruddlesden-Popper (R-P) ruthenate oxides with the formula Ae n+1RunO3n+1 (Ae = Ca, Sr; n = 1, 2, 3) using several sources of fluorine, chlorine, and bromine. A new method was developed to intercalate chlorine into layered systems; this new approach avoids the use of chlorine gas which is highly toxic. The new phase Sr3Ru2O7Cl0.7 was synthesized by the new method and further topotactic manipulations were explored. The chemistry was not limited to the n = 2 phase but was also applied to the n = 3 phase, Sr4Ru3O10.

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.

Dans cette thèse, nous avons développé l'utilisation de l'activation microondes pour fonctionnaliser des pérovskites lamellaires et notamment la phase d'Aurivillius Bi2SrTa2O9 (BST), connue pour ses propriétés ferroélectriques. Nous sommes parvenus à protoner cette phase (HST) et à la fonctionnaliser par diverses amines et polyamines, avec des temps de réaction considérablement réduits par rapport aux fonctionnalisations en conditions classiques. Cette approche nous a permis de fonctionnaliser HST par des amines plus encombrées et plus complexes. Cette stratégie a ensuite été étendue au greffage d'alcools et de polyols. Nous avons également établi une stratégie de modification post-synthèse, pour synthétiser in situ la molécule désirée, en utilisant la chimie "click" et l'activation microondes. Enfin, nous sommes parvenus à insérer des ions métalliques et des complexes de métaux de transition, ce qui constitue une première étape vers la synthèse de nouveaux hybrides multiferroïques. / During this PhD thesis, we have developed the use of microwave activation to functionalize layered perovskites, among which the Aurivillius phase Bi2SrTa2O9 (BST), known for its ferroelectric properties. We managed to protonate this phase (leading to HST) and to functionalize it by various amines and polyamines, with reaction times much shorter than using classical conditions. This approach allowed us to functionalize HST by bulkier and more complex amines. This strategy has further been extended to the grafting of alcohols and polyols. We have also established a postsynthesis modification strategy, in order to synthesize the desired molecule in situ, within the interlamellar space, using "click" chemistry and microwave activation. Finally, we managed to insert transition metal ions and complexes, which constitutes a promising step towards the synthesis of new multiferroic hybrid materials.