Nuclear Magnetic Resonance (NMR) and computational methods increasingly play a predominant and indispensable role in modern chemical research. The insights into the local nuclear environment that NMR can provide is unique information which allows the structural characterization of novel materials, as well as the understanding and explanation of their relevant properties on an atomic scale. Computational methods, on the other hand, can be used to support experimental findings, providing a rigorous theoretical basis. Furthermore, when more complex chemical systems are considered, calculations can prove to be invaluable for the interpretation of experimental data and often allow an otherwise impossible spectral assignment. This thesis presents a series of studies in which NMR spectroscopy, in combination with computational methods, is utilized to investigate a variety of chemical systems both in solution and the solid state. An overview of the thesis and experimental and computational details are given in Chapter 1. In Chapter 2, the quantum mechanical basis necessary for the description of the NMR phenomenon is presented. Chapter 3 explores the main experimental techniques employed routinely for the acquisition of NMR spectra in both solution and the solid state. Chapter 4 describes the main features of density functional theory (DFT) and its implementation in computational methods for the calculation of relevant NMR parameters. Chapter 5 reports an experimental solution-phase NMR study and a parallel computational investigation of the poly(CTFE-co-EVE) fluoropolymer. In Chapter 6, the combination of [superscript(14/15)]N solution-phase NMR techniques and DFT methods for the study of alkylammonium cationic templates used in the synthesis of microporous materials is presented. The characterization of a boroxoaromatic compound in the solid state and the study of its reactivity are described in Chapter 7. In Chapter 8, two experimental NMR methods for the study of the anisotropic chemical shift interaction in the solid state are compared and used to characterize a range of materials. Cross-polarization and nutation of quadrupolar nuclei are computationally investigated under both static and spinning conditions in Chapter 9. A general conclusion and a summary are given in Chapter 10.

The work is focused on the obtaining thermochemical properties of the linear polynitramines to predict their detonation properties. The basic thermochemical parameters are enthalpies ?f H° (298,g) in the gas and solid phase as well. The values of the enthalpy in the gas phase were obtained at a theoretical level by quantum chemical DFT calculations using both an isodesmic reactions and direct thermochemical G-Gaussian recipes. Conversion to the enthalpy in the solid phase ?f H° (298,s) was carried out using sublimation enthalpies ?s H° (298,g) obtained on the empirical level. The results were mutually compared and correlated with the structure of the linear polynitramines.

Pomocí molekulového modelování je možné předpovídat chování nových látek a napomáhá při jinak obtížné interpretaci experimentálních dat. Cílem práce byla predikce vybraných vlastností polymeračních katalyzátorů na bázi karbenů, predikce jejich struktur a spektrálních charakteristik a studie mechanismu polymerace za otevření kruhu laktidu. K ověření chování karbenů a jejich prekurzorů ve formě chloridů byly studovány vybrané charakteristiky molekuly. Byl proveden výpočet vybraných molekulových orbitalů a elektrostatických map. Následně pomocí počítačových programů byly získány teoretické vazebné délky a úhly vybraných imidazolových a imidazolinových sloučenin, karbenů a jejich možných produktů hydrolýzy. Data strukturně podobných, již charakterizovaných sloučenin, byla získána z CCDC (Cambridge Crystallographic Data Centre) a následně byla konfrontována s vypočítanými daty. Byla změřena infračervená a Ramanova spektra imidazolové soli a infračervené spektrum příslušného karbenu. Tato spektra byla konfrontována s napredikovanými. Pro lepší interpretaci spekter byla spočítána spektra možných produktů hydrolýzy. Následně byl studován mechanismus polymerace za otevření kruhu laktidu. Na základě spočítaných energií stacionárních bodů byl navržen nový mechanismus polymerace.

La caractérisation complète d’intermédiaires réactionnels intervenants dans des procédés de catalyse homogène est une tâche ardue en raison de leur réactivité et de leur faible concentration. Ceci est particulièrement vrai pour les espèces radicalaires telles que les complexes organométalliques réduits, qui sont des intermédiaires en photocatalyse ou lorsque ces complexes possèdent des ligands non-innocents. Par conséquent, leur structure électronique est encore mal comprise, sachant que l'électron ajouté peut être situé sur différents sites de la molécule.Dans ce contexte, nous avons développé une méthode d'analyse pour étudier en phase gazeuse des complexes organométalliques radicalaires. Des complexes organométalliques multichargés du zinc et du ruthénium avec des ligands bidentes de type bipyridine ou tridente de type bis(imino)pyridine ont d’abord été obtenus et isolés en phase gazeuse. Ils sont ensuite réduits avec les méthodes d’activation par un électron spécifiques à la spectrométrie de masse, la dissociation par capture ou transfert d’électron (ECD/ETD), permettant de former des espèces métalliques radicalaires monochargées. Celles-ci sont enfin isolés et leur spectre infrarouge est obtenu à l’aide de la spectroscopie d’action basée sur la dissociation induite par l’absorption de plusieurs photons dans l’infrarouge (IRMPD). Les méthodes DFT fournissent un complément pour modéliser la structure électronique et le spectre IR de ces espèces.Les challenges à relever pour développer ce nouvel outil d'analyse étaient de deux ordres. Tout d'abord, nous devions être en mesure d'obtenir les complexes souhaités en phase gazeuse. Ceci nous a conduit à examiner de multiples paramètres, tels que la nature des ligands ou l’énergie interne déposée lors de l’étape de réduction. Le deuxième défi portait sur l'utilisation des méthodes de modélisation. Nous avons montré l’absence de fiabilité des méthodes standards de modélisation pour décrire à la fois la structure électronique et le spectre infrarouge des complexes réduits. Les données expérimentales obtenues durant ce travail ont donc été utilisées comme références pour identifier les fonctionnelles DFT les plus appropriées pour l’étude de ces complexes radicalaires. / The complete characterization of reaction intermediates in homogeneous catalytic processes is often a difficult task owing to their reactivity and low concentration. This is particularly true for radical species such as reduced organometallic complexes, which are intermediates in photocatalysis, or when these complexes included non-innocent ligands. Consequently, their electronic structure in the ground state is still poorly understood, knowing that the added electron can be located on different sites of the molecule.In this contect, we developed an analytical method to study radical organometallic complexes in the gas phase. We started with formation of suitable multi-charged zinc organometallic complexes in the gas phase from mixture of zinc metal cation and bipyridine-type bidentate or bis(imino)pyridine tridentate ligands. Multicharged ruthenium complexes with similar ligands have also been studied. Under ideal circumstances these complexes were isolated and reduced in the gas phase to form monocationic metal species. Electron activated methods such as electron capture dissociation (ECD) and electron transferred dissociation (ETD) techniques, available in FT-ICR mass spectrometers, have been used to that end. The resulting Zn and Ru radical cation complexes are then isolated in the gas phase and probed via infrared multi photon dissociation (IRMPD) action spectroscopy. In support, DFT theoretical calculations were performed to model their electronic structure and IR spectra.Two main issues were faced during the development of this new analytical tool. First, we had to be able to obtain the desired complexes in the gas phase. This has lead to monitor various parameters, such as the nature of the ligands or the internal energy provided by the reduction step. The second challenge dealt with the use of modeling methods. We have shown that standard modelling tools lack the accuracy to predict both electronic structure and spectral signatures of reduced complexes. The experimental data gathered in this work have therefore been used as benchmarks for the identification of DFT functionals that are most appropriate for the study of these radical complexes.

The prediction of detonation properties of the new generation of high-nitrogen energetic materials (HNEM) is based on knowledge of their heats of formation, which are sum of values of particular nitrogen heterocyclic fragments. The diploma thesis describes theoretical calculations of heats of formation in gas phase ?f H°(298,g) for series of azines (number of N atoms 2-6) and azoles (number of N atoms 2-5) by means of quantum chemical methods. The semiempirical methods as PM3, DFT methods utilizing isodesmic approach and finally thermochemical G-recipes were used. All calculated values of heats of formation were scrutinized and for future application to HNEM materials the DFT B3LYP/cc-pVTZ method and thermochemical recipe T1 were recommended.