Crystal engineering is a rapidly developing area of research with goals aimed at designing molecular solids with desired physical and chemical properties. By utilizing reliable intermolecular interactions, the principles of supramolecular chemistry are exploited in the solid state in order to achieve favorable arrangements of molecules in a crystal lattice. We have applied crystal engineering strategies to further develop the strategy of template-directed reactivity in the solid state. An evaluation of catechol, a regioisomer of the commonly used resorcinol template, was performed. Co-crystallization of the template candidate with a bis-pyridyl olefin produced a discrete self-assembled architecture wherein hydrogen-bonded dimers of catechol pre-organize the olefins for a [2+2] photodimerization in the solid state. The dimerization was determined to proceed quantitatively and X-ray studies of a partial single-crystal-to-single-crystal reaction supported the hypothesis of the reaction proceeding exclusively within the discrete assemblies, despite the infinite stacking of the olefins. A study of substituent effects on the conformational bias of additional catechol- based template candidates was carried out. Candidates with bulky substituents a the 3- and 4-positions were observed to adopt a favorable syn-anti or syn-gauche conformer in most cases. Though conformational bias was induced and discrete assembly achieved, only one of the synthesized cocrystals met the geometric requirements for a photodimerization, however, extended UV exposure produced no evidence of product formation. We discuss the fortuitous discovery of a catechol-based cocrystal system that produces an infinite linear assembly. The fluorine atom of 3-fluorocatechol was observed to be too small to induce conformational bias in the template candidate. However, the system was observed to progress through a three-step solvent-mediated phase transformation. The second and third crystal phases were isolated and characterized by single-crystal X-ray diffraction. The X-ray data revealed that the zig-zag assembly of the first phase spontaneously transforms to a double helix topology in the second phase, before transforming to the final phase, which exhibits a quadruple helix topology. In our studies of pharmaceutical cocrystals, we sought to perform a systematic study of the solid-state behavior of the anti-cancer drug 5-fluorouracil. Inspired by previously published cocrystal structures, we performed co-crystallization experiments with a small series of structurally similar coformers. Comparison of the three structures revealed an inconsistent degree of synthon disruption between the coformers. Curiously, one of the cocrystals obtained displayed a packing arrangement consistent with the requirements of a [2+2] cycloaddition. Irradiation of the sample with UV light resulted in the quantitative formation of a cross-photocycloaddition product. The product was characterized as a pyrimidine-fused cyclobutane, the first reported synthetic derivative of 5-fluorouracil obtained from a solid-state reaction. Lastly, we utilize crystal engineering strategies to study the behavior of 2- iodohippuric acid, a common radio-imaging target. The pharmacokinetic properties of 2- iodohippuric acid make it an ideal target for renal imaging. We sought to approach a solid formulation of the target in a similar manner to that of a drug or other metabolized pharmaceutical. In doing so, we hoped to study the compound’s behavior in the solid state so that we may eventually use co-crystallization as a means of altering the properties of the target for the purpose of generalizing its use in imaging the body.

The diploma thesis deals with post-polymerization hydroxylation of polypropylene in solid state. Regarding the literature review, polypropylene was hydroxylated by radical grafting in aqueous solution of potassium persulfate at 100 °C, under nitrogen atmosphere for 60 minutes. Hydroxylation of polypropylene was performed at different concentrations of potassium persulfate (1; 5; 10 mol. %) and two different water/potassium persulfate molar ratios. The effects of reaction system composition and reaction conditions on reaction efficiency, extent of side reactions, thermal and rheological properties of hydroxylated polypropylene were evaluated. The presence and concentration of hydroxyl groups on polypropylene surface was determined by structural analysis (FTIR, XPS), while the highest efficiency was achieved in the presence of nonionic wetting agents, using 10 mol. % potassium persulfate and at lower water/potassium persulfate molar ratio. Based on changes in polypropylene structure, the modification took place mainly in the amorphous phase of the polymer. In addition to hydroxylation, concurrent side reactions have been reported, in particular the oxidation of wetting agents and polypropylene, which has resulted in chain cleavage, reducing the average molecular weight of the polypropylene.

No / Although mechanochemical synthesis is becoming more widely applied and even commercialised, greater basic understanding is needed if the field is to progress on less of a trial‐and‐error basis. We report that a mechanochemical reaction in a ball mill exhibits unusual sigmoidal feedback kinetics that differ dramatically from the simple first‐order kinetics for the same reaction in solution. An induction period is followed by a rapid increase in reaction rate before the rate decreases again as the reaction goes to completion. The origin of these unusual kinetics is found to be a feedback cycle involving both chemical and mechanical factors. During the reaction the physical form of the reaction mixture changes from a powder to a cohesive rubber‐like state, and this results in the observed reaction rate increase. The study reveals that non‐obvious and dynamic rheological changes in the reaction mixture must be appreciated to understand how mechanochemical reactions progress. / Engineering and Physical Sciences Research Council. Grant Number: EP/L019655/1

Student Number : 0009404H - PhD thesis - School of Chemistry - Faculty of Science / Six-coordinate ruthenium complexes of the type ttt-RuX2(RNC)2(PPh3)2 (X = Cl ; R = tBu, 2,6-xylyl, benzyl, 2-OMe-4-Clphenyl and iPr; X = Br; R = = tBu, 2,6-xylyl, benzyl, iPr ) were synthesized and fully characterised by IR, NMR spectroscopy and elemental analysis. These complexes were all found to undergo solid-state isomerisation from the ttt-isomer to the cct-isomer. It was found that solid state isomerisation occurred before melting i.e. in the solid state for all the ttt-RuX2(RNC)2(PPh3)2 complexes investigated . The thermal solid state isomerisation process was monitored by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), thermomicroscopy and X-ray powder diffraction techniques. The results revealed that the isomerisation process occurred exothermally with darkening of the crystal. A mechanism which involved rotation of small ligands was proposed to explain the solid-state isomerisation process. Kinetic studies of the solid-state isomerisation of some of the ttt-RuCl2(RNC)2(PPh3)2 complexes were carried out and monitored by NMR spectroscopy and compared with kinetic studies performed by XRD methods. The results are similar and also suggest that the isomerisation reaction follows first order kinetics. The crystal and molecular structure of ttt-RuCl2(2,6-xylylNC)2(PPh3)2 was determined by X-ray single crystal diffraction techniques and its structure was compared with related ttt- RuX2(RNC)2(PPh3)2 complexes. Inter-molecular and intra-molecular interactions in these molecules in the solid state were analysed and used to rationalise the solid-state isomerisation results. The results obtained for the ruthenium complexes suggested that other six-coordinate complexes could undergo solid state isomerisation reactions and this study was extended to molybdenum complexes of the type cis-Mo(CO)4L2. These complexes undergo cis to trans isomerisation in solution. The solid state reactivity of these complexes was investigated for the first time. The complexes with L = PPh2Me and PPh2Et isomerised in the melt whist complexes with L = PPh3 amd P(m-tolyl)3 were indeed found to undergo solid state isomerisation reactions. Structural studies and thermomicroscopic investigations were done on cis- Mo(CO)4(PPh3)2 and Mo(CO)4{P(m-tolyl)3)2 and the results were used to rationalize the solid state reactivity of these complexes.

Im Rahmen der vorliegenden Arbeit ist es gelungen, ein Siliciumsubnitrid der Summenformel Si2N chemisch und strukturell zu charakterisieren. Die braune, metastabile Verbindung ist über eine topotaktische Reaktion aus der Zintl-Phase Calciumdisilicid und Ammoniumbromid im molaren Verhältnis 1:2 zugänglich. Charakteristisch für das Siliciumsubnitrid sind eine schichtartige Morphologie und perfekte Spaltbarkeit parallel zu den Schichten. Thermoanalytische und röntgenografische Untersuchungen belegen, dass die Reaktion im Temperaturbereich 165°- 350°C abläuft. Beim Einsatz pulverförmiger Eduktmischungen wird das Siliciumsubnitrid als röntgenamorphes Pulver im mikroskopischen Gemisch mit kristallinem CaBr2 erhalten. Die Abtrennung des Calciumbromids gelingt bisher nur unvollständig. Mit spektroskopischen Methoden (NMR, IR und Raman) konnten die Baueinheiten im Siliciumsubnitrid identifiziert werden. Stickstoff liegt im Siliciumsubnitrid in Form einer trigonalen [N(Si)3]-Koordination vor. Über REDOR-NMR-Experimente wurde belegt, dass das Subnitrid zwei unterschiedliche Siliciumspezies, eine [Si(Si4)]- und eine [Si(Si,N3)]-Umgebung, enthält. Ergebnisse elektronenmikroskopischer Untersuchungen (REM, TEM) sind mit der Bildung des Siliciumsubnitrids über eine topotaktische Reaktion im Sinne des Erhalts schichtartiger Strukturverbände aus dem Calciumdisilicid vereinbar. Im Transmissionselektronenmikroskop werden extrem dünne Schichten beobachtet. Beugungsexperimente (SAD) an partiell geordneten Bereichen zeigen den Erhalt eines hexagonalen Reflexmusters. Die topotaktische Reaktion wurde auch mit CaSi2-Einkristallen durchgeführt, deren Oberflächen durch Aufsublimation mit Ammoniumbromid belegt waren. Die Untersuchung von Edukt und Produkt mit Röntgen-Einkristallbeugungsmethoden deutet auf weitgehende Erhaltung einer periodischen Struktur während der topotaktischen Reaktion hin. Die neue Verbindung kann durch elektrisch neutrale Schichtpakete von etwa 650 pm beschrieben werden.

Im Rahmen der vorliegenden Arbeit ist es gelungen, ein Siliciumsubnitrid der Summenformel Si2N chemisch und strukturell zu charakterisieren. Die braune, metastabile Verbindung ist über eine topotaktische Reaktion aus der Zintl-Phase Calciumdisilicid und Ammoniumbromid im molaren Verhältnis 1:2 zugänglich. Charakteristisch für das Siliciumsubnitrid sind eine schichtartige Morphologie und perfekte Spaltbarkeit parallel zu den Schichten. Thermoanalytische und röntgenografische Untersuchungen belegen, dass die Reaktion im Temperaturbereich 165°- 350°C abläuft. Beim Einsatz pulverförmiger Eduktmischungen wird das Siliciumsubnitrid als röntgenamorphes Pulver im mikroskopischen Gemisch mit kristallinem CaBr2 erhalten. Die Abtrennung des Calciumbromids gelingt bisher nur unvollständig. Mit spektroskopischen Methoden (NMR, IR und Raman) konnten die Baueinheiten im Siliciumsubnitrid identifiziert werden. Stickstoff liegt im Siliciumsubnitrid in Form einer trigonalen [N(Si)3]-Koordination vor. Über REDOR-NMR-Experimente wurde belegt, dass das Subnitrid zwei unterschiedliche Siliciumspezies, eine [Si(Si4)]- und eine [Si(Si,N3)]-Umgebung, enthält. Ergebnisse elektronenmikroskopischer Untersuchungen (REM, TEM) sind mit der Bildung des Siliciumsubnitrids über eine topotaktische Reaktion im Sinne des Erhalts schichtartiger Strukturverbände aus dem Calciumdisilicid vereinbar. Im Transmissionselektronenmikroskop werden extrem dünne Schichten beobachtet. Beugungsexperimente (SAD) an partiell geordneten Bereichen zeigen den Erhalt eines hexagonalen Reflexmusters. Die topotaktische Reaktion wurde auch mit CaSi2-Einkristallen durchgeführt, deren Oberflächen durch Aufsublimation mit Ammoniumbromid belegt waren. Die Untersuchung von Edukt und Produkt mit Röntgen-Einkristallbeugungsmethoden deutet auf weitgehende Erhaltung einer periodischen Struktur während der topotaktischen Reaktion hin. Die neue Verbindung kann durch elektrisch neutrale Schichtpakete von etwa 650 pm beschrieben werden.

Le stockage d'hydrogène en phase solide sous forme d'hydrures, est l'une des solutions non-polluantes futures pour le stockage et le transport de l'énergie. Parmi les matériaux candidats, LiBH4 a été sélectionné vu sa capacité gravimétrique élevée en hydrogène (jusqu'à 13,6 % H2 en masse). Ce matériaux possède des propriétés thermodynamiques et cinétiques insuffisamment établies pour comprendre son comportement dans les applications futures. Sa décomposition peut être facilitée en présence de l'hydrure MgH2. Ainsi, le composite MgH2-xLiBH4 / Hydrides for solid-state hydrogen storage are one of the future solutions - pollutant free - for the storage and the transport of energy. Among the candidates, LiBH4 was selected considering its high gravimetric hydrogen capacity (up to 13.6 wt.% H2). This material has thermodynamic and kinetic properties insufficiently established to be included in future applications. Its decomposition can be facilitated within the presence of the hydride MgH2. Thus, the composite MgH2-xLiBH4 (0< x< 3.5) reactivated by high energy ball-milling, was studied regarding its microstructural properties and stability of the phases. The desorption reaction of hydrogen, with or without additives, shows the appearance of additional phases accompanying the principal reaction. Heat capacity measurements of LiBH4 revealed the presence of an abnormal behaviour before the polymorphous transition (Ttrs = 386 K), attributed to the increase of crystal defects in agreement with the existence of a hypo-stoichiometric domaine LiBH4-ε observed at higher temperatures. The stability of the three-phase system LiBH4-LiH-B was studied resulting to the principal reaction of decomposition: LiBH4(s,l) → LiH(s) + B(s) + 1,5H2(g). Vapour pressure measurements of LiBH4 showed that H2 is the major component of decomposition with minor species such as B2H6 and BH3. The thermodynamic properties of LiBH4 were critically assessed, gathering the new data with those existing in the literature, in the aim of modelling of reactions occurring in hydride mixtures.

Les gains sur la vitesse de commutation des composants actifs actuels offrent la possibilité de faire fonctionner les convertisseurs de puissance à des fréquences de découpage supérieures à 1 MHz. Le principal verrou à la montée en fréquence des convertisseurs provient des matériaux magnétiques des composants passifs qui sont le siège de dissipations thermiques. Les matériaux magnétiques utilisés, présentant un niveau de pertes acceptable entre 1 et 5 MHz, sont des ferrites de structure spinelle de type (Ni,Zn,Cu)Fe2O4. L’objectif de cette thèse est d’apporter une contribution expérimentale à la compréhension des liens entre la microstructure et les propriétés magnétiques statiques et dynamiques.Nous avons étudié deux procédés de synthèse des ferrites spinelles Ni-Zn-Cu (Ni,Zn,Cu)Fe2O4, d’une part par voie solide classique et, d’autre part, par la méthode sol-gel Pechini. Les propriétés structurales et magnétiques des échantillons produits ont été caractérisées de manière systématique et corrélées. Nous avons réussi à maîtriser l’élaboration et la mise en ordre et à obtenir une microstructure contrôlée de grains de l’ordre du µm et de forte densité (d>92%dth). Les résultats suggèrent que les ferrites synthétisés par la méthode Pechini peuvent être une alternative à la voie classique céramique pour la réalisation de composants magnétiques à faibles pertes.L’analyse des pertes magnétiques en fréquence a permis de montrer que l’ensemble des résultats obtenus était compatible avec un mécanisme de dissipation lié à l’amortissement des spins dans les parois. Ces résultats justifient la réalisation de pièces massives denses composées de petits grains avec du cobalt pour obtenir de faibles pertes sur une large plage d’induction (jusqu’à environ 25mT). / The high commutation rate of the wide gap semiconductor (GaN) allows operating with switching frequency above 1MHz in power converters. However, current magnetic materials comprising passive components in power converters cannot sustain the rise in the operating frequency, especially above 1 MHz. The main limitation comes from the sharp increase in power losses creating thermal dissipation inside the magnetic core. The core-losses are due to dynamic magnetization process (including domain wall movement and spin rotation) and they increase with the frequency. (Ni,Zn,Cu)Fe2O4 spinel ferrite is currently the best magnetic material with limited core-losses. The objective of the Ph.D. is to experimentally contribute to the understanding of the link between the microstructure and the static and dynamic magnetic properties.Synthesis process of (Ni,Zn,Cu)Fe2O4 spinel ferrite such as sold-state reaction and Pechini method were studied. The structural and magnetic properties were systematically measured and correlated together. We managed to master the elaboration and produce high density ferrite with controlled grain size (about few µm) and high density (d>92% dth). Results suggest that ferrites synthesized by Pechini method can be considered as an interesting basis for the design of low-loss magnetic components alternatively to the conventional route.The analysis on core-loss showed that the results are compatible with a dissipation mechanism linked to spin damping inside domain walls. It justifies the production of well-densified massive pieces composed of small grains and cobalt to obtain low core-loss for large amplitude excitation (up to 25mT).

La plupart des matériaux ferroélectriques actuellement utilisés pour les applications industrielles sont des céramiques à base de plomb. De tels composés sont nocifs à l’environnement en raison de la toxicité et de la volatilité de l’oxyde de plomb durant le processus de préparation de ces matériaux. Dans le cadre du respect de l'environnement, la recherche de céramiques sans plomb ou de faible teneur en plomb ayant des propriétés équivalentes est devenue l'une des principales alternatives aux céramiques à base de plomb. C’est dans cette perspective que se situe le présent travail, focalisé sur l’investigation de matériaux de formules : Ba1-xPbx(Ti1-yZry)O3 (2.5% ≤ à x ≤ 10%) et Ba1-xEr2x/3Ti1-yZryO3. La synthèse par voie solide a été utilisée pour l’élaboration des matériaux. Les techniques expérimentales utilisées sont l’analyse thermogravimétrique, la dilatomètrie, la diffraction des rayons X, la microscopie électronique à balayage couplée à un système de microanalyse EDX et la spectrométrie d’impédance. L’utilisation de ces diverses techniques nous a permis d’optimiser les conditions d’élaboration et d’obtenir des céramiques denses de densité supérieures à 90%. Par ailleurs, les paramètres structuraux ont été affinés par la méthode de Rietveld puis discutés. En outre, ces céramiques possèdent des propriétés ferroélectriques classiques et/ou relaxeurs dont certaines ont des caractéristiques diélectriques très intéressantes au voisinage de la température ambiante. De telles compositions dépourvues de plomb ou contenant très peu de plomb permettent de limiter considérablement la pollution de l’environnement. Grâce à leurs bonnes performances diélectriques, ils pourraient être des candidats potentiels pour remplacer les matériaux à base de plomb actuellement usagés dans divers appareillages électroniques. / Most of ferroelectric materials currently used in the industrial applications are lead-based ceramics. Such compounds are harmful to the environment due to the toxicity and volatility of lead oxide during the preparation process of these materials. Therefore, environmental friendly lead-free ceramics or low-lead content materials with equivalent properties has become one of the main topics as an alternative to lead-based ceramics. In this view, the present work focuses on investigating materials with formulas :Ba1-xPbx(Ti1-yZry)O3 (2.5% ≤ x ≤ 10%) and Ba1-xEr2x/3(Ti1-yZry)O3.Solid state route was used for materials elaboration. The experimental techniques used are thermogravimetric analysis, dilatometry, X-ray diffraction, scanning electron microscopy coupled to an EDX microanalysis system and impedance spectrometry. The use of these various processes allowed us to optimize the synthesis conditions and to obtain dense ceramics with density superior to 90%. In addition, the structural parameters were refined by the Rietveld method and then discussed. Furthermore, these ceramics exhibited normal and/or relaxor ferroelectric properties then some of them have very interesting dielectric characteristics in the vicinity of room temperature. Such lead-free ceramics or low-lead content materials reduce significantly the environmental pollution. Due to their good dielectric performances, they could be potential candidates for replacing lead-based materials currently used in various electronic equipments.