Abstract The indirect spin-spin coupling is a molecular internuclear interaction, which is observable by utilizing NMR spectroscopy. This coupling, denoted J, is a second-order tensorial property that consists of rank-0, 1, and 2 components. The present thesis deals with the experimental determination of the rank-0 and rank-2 components of J tensors for different pairs of interacting nuclei by utilizing liquid crystal NMR (LC NMR) method. The experimental information of the rank-2 component of the J tensor appears as Janiso, a combination of tensor elements. In LC NMR, Janiso is manifested as a contribution to the experimental anisotropic coupling (Dexp ) that contains also the corresponding internuclear dipolar coupling, D. The dipolar coupling is defined by the molecular geometry and average orientation, and affected by the molecular motions. Therefore, the molecular geometry and orientation have to be determined together with the studied Janiso couplings. The contributions to D couplings arising from the molecular vibrations and solvent-induced deformation of the molecular geometry are taken into account in the analysis of the experimental data; the contributions are presented briefly in this thesis. The LC NMR experiments are performed for C6H6, HCONH2, C2H2, C2H4, C2H6, 1,4-C6H4F2, CH3F, CH2F2, CHF3, and CSiH6 molecules, and some important aspects of the liquid crystal NMR method are discussed. The obtained information of J tensors is compared with the theoretical ab initio MCSCF results. Finally, the systematics of the J tensors in different structural surroundings is found and the significance of the indirect contribution to the corresponding Dexp coupling is discussed.

Neste trabalho investigamos os efeitos das interações na expansão de um condensado de átomos de Rb. Dois problemas são abordados: o efeito de temperatura finita e as alterações introduzidas pela interação dipolar. No primeiro caso, dados experimentais não puderam ser explicados por meio da aproximação de Thomas-Fermi (TF) no regime de T = 0. Num condensado de cerca de 1 - 2 x 105 átomos condensados, o desvio da aproximação de TF ocorreu pelo fato de termos desconsiderado a interação dos átomos térmicos com os do condensado. Elaboramos um modelo teórico, baseado em modelos existentes de temperatura finita, o qual explicou relativamente bem os nossos resultados experimentais. No segundo problema atacado, foi analisada a variação na expansão do gás condensado quando a interação dipolar é incluída no sistema. Ambos os problemas mostram aspectos importantes da expansão de gases quânticos. / In this study we investigated the effects of interactions on the expansion of a condensate of Rb atoms. Two problems are addressed: the effect of finite temperature and the changes introduced by the dipolar interaction. In the first case, experimental data could not be explained by the Thomas-Fermi (TF) approach in the T = 0 regime. In a condensate of about 1 - 2 x 105 condensed atoms, the deviation of TF approach was due to the fact that we disregarded the interaction of thermal atoms those of the condensate. We developed a theoretical model, based on existing models of finite temperature, which explained relatively well our experimental results. In the second problem considered, we analyzed the variation in the expansion of the condensate gas when the dipolar interaction is included in the system. Both problems show important aspects of the expansion of quantum gases.

No description available.

<p> LiHoxY1-xF4 is an insulating system where the Ho ions are magnetic. The crystal field gives an Ising character to the Ho ions, and the dominant interaction between them is through magnetic dipolar fields. For x=1, the system is a ferromagnet with a critical temperature of 1.54 K. The critical temperature decreases as x is decreased until x~0.25. At that point the long range order is destroyed, giving rise to a state with some characteristics of spin glass behavior.</p> <p> The study of this system is important because its Ising nature makes it a test ground for theoretical models. Interestingly, not only experiments and theory diverge in many points, but experimental data from different research groups are contradictory. In order to contribute to a clearer experimental picture, we performed μSR measurements in this system and we present our results in this thesis.</p> <p> In the ferromagnetic samples (x=1 and 0.45) we found that the internal field distribution at the muon site is quite broad, even in the x=1 system. Then it is possible that the magnetic field distribution at the Ho ions is broad as well. We show qualitatively how this broadening could explain a feature of the field-temperature phase diagram which is still not understood.</p> <p> For the more diluted samples (x=0.25, 0.12, 0.08, 0.045 and 0.018), we found that they all have the same qualitative behavior as a function of temperature and magnetic field. Our analysis of the data did not show any feature of canonical spin glass behavior. Instead, an analysis using dynamical Kubo-Toyabe functions show a temperature independent fluctuation rate of the Ho moments below ~0.5 K for all these samples. This behavior is characteristic of cooperative paramagnetic systems. We also found that the low temperature fluctuation rate decreases as x is decreased.</p> <p> To analyze the data from LiHoxY1-xF4 we developed microscopic models of μSR signals. These models are presented in this thesis and they correspond to stochastic models of signals using stretched magnetic field distributions; and the modeling of signals from systems with F-μ-F bond formation where the set of bonds does not have cubic symmetry.</p> / Thesis / Doctor of Philosophy (PhD)

La presente tesis doctoral describe la investigación sobre reacciones de cicloadición 1,3-dipolares, concretamente, la síntesis de moléculas que presentan pirrolidinas, pirrolizidinas δ-lactamas y dicetopiperacinas en su estructura. La preparación de estos compuestos se debe, principalmente, a las actividades biológicas que presentan dichas estructuras heterocíclicas. Además, la tesis está constituida por una introducción general y tres capítulos, los cuales describen la síntesis de compuestos N-heterocíclicos de manera diastereoselectiva. La introducción general describe las reacciones de cicloadición 1,3-dipolares, su importancia y sus características. El capítulo 1 describe la síntesis diastereoselectiva de pirrolidinas espirocíclicas catalizada por acetato de plata. El capítulo 2 se basa en el estudio de reacciones multicomponente para la preparación de pirrolizidinas. En concreto, la reacción se lleva a cabo de manera diastereoselectiva y el proceso se rige por 1,2-prototropía en una reacción 1,3-dipolar via descarboxilativa. El capítulo 3 detalla la síntesis secuencial de derivados de exo-3,5-difenil-4-nitroprolinatos de metilo sustituidos mediante una cicloadición 1,3-dipolar enantioselectiva seguido de una adición de tipo Michael diastereoselectiva. / The present work has been possible thanks to funding from the Spanish Ministerio de Economía, Industria y Competitividad, Agencia Estatal de Investigación (AEI) and Fondo Europeo de Desarrollo Regional (FEDER, EU) (projects CTQ2016-76782-P, CTQ2016-80375-P, CTQ2017-82935-P and PID2019-107268GB-I00), Generalitat Valenciana (APOTIP/2020/002) and the University of Alicante.

Dans ce mémoire nous présentons plusieurs études expérimentales des propriétés magnétiques d’un condensat de Bose-Einstein de Chrome chargé dans un réseau 3D, en nous focalisant sur les effets associés aux interactions dipolaires. Nous montrons que dans un réseau 3D, la relaxation dipolaire est un processus résonant du fait de la réduction de la densité d’états orbitaux accessibles. Les résonances sont observées à des champs magnétiques Bres tels que l’énergie Zeeman relâchée soit égale à l’énergie nécessaire à exciter les atomes dans une bande d’énergie supérieure du réseau. Nous pouvons inhiber ce processus en appliquant un champ différent de Bres. L’analyse des résonances a permis de sonder la structure de bande 3D du réseau, ainsi que la mise en évidence de l’effet des interactions entre atomes. Nous avons étudié la dynamique d’échange de spin dans un réseau 3D. Nous présentons en particulier la première observation d’échange de spin entre atomes localisés dans des sites séparés. Ces études permettent une exploration nouvelle du magnétisme en réseau. En variant la profondeur du réseau, nous étudions ces effets dans le régime superfluide, bien décrit par une théorie de champ moyen, et dans le régime fortement corrélé, dont la description théorique est difficile. Enfin, nous étudions l’évolution de deux spins géants interagissant par interaction dipolaire. Le condensat initialement divisé en deux, les atomes des deux nuages sont préparés dans des états de spin opposés formant ainsi deux spins géants ±3xN. Nous montrons que toute dynamique de spin est énergétiquement inhibée pour de grands spins ce qui est bien reproduit par une théorie classique. / This Thesis reports on several experimental studies of magnetic properties of a Chromium Bose-Einsteincondensate loaded into a 3D optical lattice, focusing on the effects induced by dipolar interactions.We show that in a 3D lattice dipolar relaxation is a resonant process due to the reduction of the density ofaccessible orbital states. These resonances are observed for magnetic fields Bres such that the Zeeman energyreleased matches an excitation towards higher-energy bands of the lattice. We can thus inhibit those processes byapplying a field different from Bres. Analyses of the resonances allowed us to probe the lattice 3D band structureas well as to demonstrate the effects of local interactions between atoms.We study spin exchange dynamics in a 3D lattice. We especially observed for the first time spin exchangebetween atoms localized in different lattice sites mediated by dipolar interactions. These studies are the firststep toward a new exploration of magnetism in lattice. Varying the depth of the lattice we study these effects inthe superfluid regime, well described by mean filed theories, as well as in the strongly correlated regime, whosetheoretical description is still challenging.Finally, we study the evolution dynamics of two giant spins interacting through dipolar interactions. Thecondensate being initially splitted in half, atoms from the two clouds are prepared in opposite spin states thusproducing two giant spins ±3×N. We show that any spin dynamics is energetically inhibited for large spinswhich is well accounted for by a classical theory

Esta tese relata um estudo pormenorizado, efetuado através da técnica de Ressonância Paramagnética Eletrônica (RPE) em bandas X (~ 9.5 GHz) e Q (~ 34.5 GHz), de amostras nas formas cristalina e pulverizada dos compostos dinucleares Cu2(TzTs)4, C40H36Cu2N8O8S8, e [Cu(flu)2DMF]2, C62H50Cu2F12N6O10. Tratamentos meticulosos dos espectros de RPE pertinentes a tais compostos propiciaram determinar tanto o parâmetro de interação antiferromagnética, J0, entre pares de íons Cu(II) existentes em uma unidade dinuclear (Hex = J0 S1·S2) como também os valores principais alusivos às matrizes g e D; onde a primeira refere-se à interação Zeeman [Hz = BB0(g1·S1 + g2·S2)] e a última reporta as interações spin-spin anisotrópicas (Hani = S1·D·S2) entre pares de íons Cu(II) presentes em uma unidade dinuclear. Ademais, medidas de RPE realizadas com um monocristal do composto Cu2(TzTs)4 permitiram detectar e estimar, no contexto interdinuclear, o fraco acoplamento de exchange, |J\'| = (0.060 ± 0.015) cm-1, existente entre unidades dinucleares vizinhas: este acoplamento existente entre uma unidade dinuclear e o meio randômico constituído pelas unidades dinucleares vizinhas conduz à decoerência (i.e. uma transição de fase quântica que colapsa a interação dipolar quando a magnitude do acoplamento de exchange isotrópico entre as unidades dinucleares vizinhas iguala-se à magnitude do acoplamento dipolar intradinuclear). No âmbito concernente ao composto [Cu(flu)2DMF]2, foi possível simular acuradamente as sete linhas de ressonância características do desdobramento hiperfino advindo de n = 2 núcleos equivalentes de centros paramagnéticos Cu2+ (I = 3/2) e, por conseguinte, os valores principais pertinentes à matriz de interação hiperfina A (Hhyper = S1·A·I1 + S2·A·I2) puderam ser precisamente determinados. / We report detailed Electron Paramagnetic Resonance (EPR) studies at X-band (~ 9.5 GHz) and Q-band (~ 34.5 GHz) of powder and single-crystal samples of the dinuclear compounds Cu2(TzTs)4, C40H36Cu2N8O8S8, and [Cu(flu)2DMF]2, C62H50Cu2F12N6O10. Meticulous investigations of their EPR data allow determining the antiferromagnetic interaction parameter, J0, between Cu(II) ions in the dinuclear unit (Hex = J0 S1·S2) as well as the principal values of both matrices g and D, where the first one is related to the Zeeman interaction [Hz = BB0(g1·S1 + g2·S2)] and the latter is associated with the anisotropic spin-spin interactions (Hani = S1·D·S2) between Cu(II) ion pairs in a dinuclear unit. In addition, EPR measurements of single-crystal samples of the compound Cu2(TzTs)4 allow detecting and estimating very weak exchange couplings between neighbour dinuclear units with an estimated magnitude |J\'| = (0.060 ± 0.015) cm-1: this coupling with the environment leads to decoherence (i.e. a quantum phase transition that collapses the dipolar interaction when the isotropic exchange coupling with neighbor dinuclear units equals the magnitude of the intradinuclear dipolar coupling). With reference to [Cu(flu)2DMF]2 compound, it was possible to simulate precisely the seven-line copper hyperfine splitting arising from n = 2 nonequivalent nuclei related to paramagnetic Cu2+ (I = 3/2) centers and, as a consequence of these accurate simulations, the principal values of the hyperfine interaction matrix A (Hhyper = S1·A·I1 + S2·A·I2) could be reliably obtained.

This PhD thesis presents a study of structure-composition correlations of bioactive glasses (BGs) by employing solid-state Nuclear Magnetic Resonance (NMR) spectroscopy. Silicate-based Na2O−CaO−SiO2−P2O5 BGs are utilized clinically and are extensively investigated for bone regeneration purposes. Once implanted in the human body, they facilitate bone regeneration by partially dissolving in the body fluids, followed by the formation of a biomimetic surface-layer of calcium hydroxy-carbonate apatite (HCA). Eventually, the implanted BG totally integrates with the bone. The bioactivity of melt-prepared BGs depends on their composition and structure, primarily on the phosphorus content and the average silicate-network connectivity (NC). We explored these composition-structure relationships for a set of BGs for which the NC and phosphorus contents were varied independently. The short-range structural features of the glasses were explored using 29Si and 31P magic-angle-spinning (MAS) NMR spectroscopy. 31P MAS NMR revealed that the orthophosphate content is directly proportional to the total P content of the glass, with a linear correlation observed between the orthophosphate content and the silicate network connectivity. The bearings of the results for future BG design are discussed. By using multiple-quantum coherence-based 31P NMR experiments, the spatial distribution of orthophosphate groups was probed in the melt prepared BGs, as well as in two mesoporous bioactive glasses prepared by an evaporation-induced self-assembly technique. The results evidence randomly distributed orthophosphate groups in the melt-prepared BGs, whereas the pore-walls of the mesoporous bioactive glasses constitute nanometer-sized clusters of calcium phosphate. The distribution of Na+ ions among the phosphate/silicate groups were studied by heteronuclear dipolar-based 23Na−31P NMR experiments, verifying that sodium is dispersed nearly randomly in the glasses. The phosphorus and proton environments in biomimetically grown HCA were investigated by using 1H and 31P MAS NMR experiments. Our studies revealed that the biomimetic HCA shared many local structural features with synthetic and well-ordered hydroxy-apatite. / <p>At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Accepted.</p>

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / The present dissertation describes a chemical methodology for the synthesis of three series containing fourteen new molecules of trifluoro(chloro)methyl substituted 1H-1,2,3-triazoles, which are structural analogues to the antiepileptic drug Rufinamide. The protocol used consisted in reactions of 1,3-dipolar cycloaddition of 2,6-difluorobenzyl azide and 4-alkoxy-4-alkyl(aryl/heteroaryl)-1,1,1-trifluoro(chloro)-3-alken-2-ones, where the 4-substituents are H, Me, Ph, 4-OMeC6H4, 4-NO2C6H4,4-FC6H4,2-Thienyle 4,4 -Biphenyl. The optimized reactios were carried-out in absense of solvente, in reaction times of 48 to 96 hours at 100-150°C and in yields of 30-75%. The reactions employing the 4-alkoxy-4-aryl(heteroaryl)-1,1,1-trifluoro-3-alken-2-ones 1and 2,6-difluorobenzyl azidedemonstrated a 4-substituent dependency of the enones precursors (above mentioned) and conducted to the formation of isomeric mixtures of 4-trifluoroacetyl substituted and/or 5-trifluoromethyl substituted triazoles in varying proportions, which were separated and purified by chromatographic columns. On the other hand, the reactions employing the 4-alkoxy-4-alkyl(aryl/heteroaryl)-1,1,1-trichloro-3-alken-2-ones and the same 2,6-difluorobenzyl azide produced exclusively a series of 4- trichloroacetyl substituted triazoles without the detection of the respective 5-trichloromethyl substituted regioisomer. The synthesized triazoles were characterized by 1H, 13C, uni- and two-dimensional NMR Spectroscopy techniques as HMQC, gas chromatography coupled to mass spectrometry (GC-MS), mono-crystal X-ray diffraction, high resolution mass spectrometry (HRMS) and their purity determined by CHN Elemental Analysis. / A presente dissertação descreve uma metodologia química para a síntese de três séries de 1H-1,2,3-triazóis trifluor(cloro)metil substituídos, totalizando quatorze moléculas inéditas, as quais são análogas estruturais do fármaco antiepiléptico Rufinamida. O protocolo consistiu na realização de reações de cicloadição 1,3-dipolares envolvendo 2,6-difluorbenzil azida e 4-alcóxi-4-alquil(aril/heteroaril)-1,1,1-trifluor(cloro)-3-alquen-2-onas, sendo os substituintes 4-alquila(arila/heteroarila) iguais a H, Me, Ph, 4-OMeC6H4, 4-NO2C6H4,4-FC6H4,2-Tienila e 4,4 -Bifenila. As reações otimizadas se processaram na ausência de solvente, em tempos reacionais de 48 a 96 horas a 100-150°C e levaram a rendimentos na faixa de 30-75%. As reações que utilizaram 4-alcóxi-4-aril(heteroaril)-1,1,1-triflúor-3-alquen-2-onase 2,6-difluorbenzil azida apresentaram uma dependência quanto a substituição da posição 4 das enonas precursoras (acima descritos) e conduziram à formação de misturas isoméricas de triazóis 4-trifluoracetil substituídos e/ou 5-trifluormetil substituídos em proporções variadas, as quais foram passíveis de separação e purificação por cromatografia em coluna. Por outro lado, as reações empregando 4-alcóxi-4-alquil(aril/heteroaril)-1,1,1-tricloro-3-alquen-2-onas e a mesma 2,6-difluorbenzil azida produziram, exclusivamente, uma série de triazóis 4-tricloroacetil substituídos sem a detecção dos respectivos regioisômeros 5-triclorometil substituídos. Os triazóis sintetizados foram caracterizados por espectroscopia de RMN de 1H, 13C por técnicas uni- e bidimensionais (HMQC), cromatografia a gás acoplada à espectrometria de massas (GC-MS), difração de raios-X em mono-cristal, espectrometria de massas de alta resolução (HRMS) e a sua pureza determinada através de análise elementar CHN.

Esta tese relata um estudo pormenorizado, efetuado através da técnica de Ressonância Paramagnética Eletrônica (RPE) em bandas X (~ 9.5 GHz) e Q (~ 34.5 GHz), de amostras nas formas cristalina e pulverizada dos compostos dinucleares Cu2(TzTs)4, C40H36Cu2N8O8S8, e [Cu(flu)2DMF]2, C62H50Cu2F12N6O10. Tratamentos meticulosos dos espectros de RPE pertinentes a tais compostos propiciaram determinar tanto o parâmetro de interação antiferromagnética, J0, entre pares de íons Cu(II) existentes em uma unidade dinuclear (Hex = J0 S1·S2) como também os valores principais alusivos às matrizes g e D; onde a primeira refere-se à interação Zeeman [Hz = BB0(g1·S1 + g2·S2)] e a última reporta as interações spin-spin anisotrópicas (Hani = S1·D·S2) entre pares de íons Cu(II) presentes em uma unidade dinuclear. Ademais, medidas de RPE realizadas com um monocristal do composto Cu2(TzTs)4 permitiram detectar e estimar, no contexto interdinuclear, o fraco acoplamento de exchange, |J\'| = (0.060 ± 0.015) cm-1, existente entre unidades dinucleares vizinhas: este acoplamento existente entre uma unidade dinuclear e o meio randômico constituído pelas unidades dinucleares vizinhas conduz à decoerência (i.e. uma transição de fase quântica que colapsa a interação dipolar quando a magnitude do acoplamento de exchange isotrópico entre as unidades dinucleares vizinhas iguala-se à magnitude do acoplamento dipolar intradinuclear). No âmbito concernente ao composto [Cu(flu)2DMF]2, foi possível simular acuradamente as sete linhas de ressonância características do desdobramento hiperfino advindo de n = 2 núcleos equivalentes de centros paramagnéticos Cu2+ (I = 3/2) e, por conseguinte, os valores principais pertinentes à matriz de interação hiperfina A (Hhyper = S1·A·I1 + S2·A·I2) puderam ser precisamente determinados. / We report detailed Electron Paramagnetic Resonance (EPR) studies at X-band (~ 9.5 GHz) and Q-band (~ 34.5 GHz) of powder and single-crystal samples of the dinuclear compounds Cu2(TzTs)4, C40H36Cu2N8O8S8, and [Cu(flu)2DMF]2, C62H50Cu2F12N6O10. Meticulous investigations of their EPR data allow determining the antiferromagnetic interaction parameter, J0, between Cu(II) ions in the dinuclear unit (Hex = J0 S1·S2) as well as the principal values of both matrices g and D, where the first one is related to the Zeeman interaction [Hz = BB0(g1·S1 + g2·S2)] and the latter is associated with the anisotropic spin-spin interactions (Hani = S1·D·S2) between Cu(II) ion pairs in a dinuclear unit. In addition, EPR measurements of single-crystal samples of the compound Cu2(TzTs)4 allow detecting and estimating very weak exchange couplings between neighbour dinuclear units with an estimated magnitude |J\'| = (0.060 ± 0.015) cm-1: this coupling with the environment leads to decoherence (i.e. a quantum phase transition that collapses the dipolar interaction when the isotropic exchange coupling with neighbor dinuclear units equals the magnitude of the intradinuclear dipolar coupling). With reference to [Cu(flu)2DMF]2 compound, it was possible to simulate precisely the seven-line copper hyperfine splitting arising from n = 2 nonequivalent nuclei related to paramagnetic Cu2+ (I = 3/2) centers and, as a consequence of these accurate simulations, the principal values of the hyperfine interaction matrix A (Hhyper = S1·A·I1 + S2·A·I2) could be reliably obtained.