Résumé : Au cours de ce projet, la faisabilité de l’insertion du CO[indice inférieur 2] dans une fonction éther aliphatique à été démontrée pour la première fois. Cette découverte à été effectuée suite à la résolution cinétique et thermodynamique de la décarboxylation du diméthyle carbonate (DMC) en diméthyle éther (DME) et CO[indice inférieur 2] à la surface d’un catalyseur faujasite échangé avec du zinc(II) (Zn-FAU). Un profile réversible typique aux carbonates a été observé, soit que le CO[indice inférieur 2] est relâché à plus haute température et inséré aux plus basses températures. La structure de l’état de transition entre le DMC et DME a ensuite été résolue en corrélant des calculs en modélisation moléculaire aux mesures thermodynamiques effectuées entre le DMC et Zn-FAU. La méthode de calcul développée lors de l’analyse mécanistique a ensuite été appliquée à l’évaluation théorique de plusieurs structures catalytiques, ce qui a permis d’identifier les paramètres structurels des catalyseurs qui sont favorables à la réaction de carboxylation du DME. // Abstract : In this study, the feasibility of the insertion of CO[subscript 2] in an aliphatic ether function was demonstrated for the first time. This finding results from a thermodynamic and kinetic study on dimethyl carbonate (DMC) decarboxylation into dimethyl ether (DME) and CO[subscript 2] at the surface of a zinc(II) exchanged faujasite catalyst. The typical reversible profile of carbonates synthesis chemistry was observed, higher temperature being favorable to CO[subscript 2] release and lower temperature being favorable to CO[subscript 2] insertion. A structural resolution of the rate determining transition structure between DMC and DME was then achieved by correlating molecular modelling calculations to the thermodynamic measurements on DMC decarboxylation. The calculation method developed during the mechanistical analysis was further applied to theoretical catalyst activity screening, which allowed determining structural catalytic sites parameters that favor DME carboxylation over DMC decarboxylation.

In this work, multinuclear solid-state nuclear magnetic resonance (NMR) spectroscopy is used to investigate a range of inorganic materials, often in combination with DFT (density functional theory) studies. Solid-state NMR is particularly suited to the study of aluminophosphates (AlPOs), as the basic components of their frameworks have NMR active isotopes (²⁷Al, ³¹P, ¹⁷O), as do many of the atoms that comprise the structure directing agent (¹³C, ¹H, ¹⁵N), and the charge-balancing anions (OH⁻, F⁻). A study of the AlPO STA-15 (St Andrews microporous solid-15) provides an introduction to using solid-state NMR spectroscopy to investigate AlPOs. More in-depth studies of AlPO STA-2 (St Andrews microporous solid-2) and MgAPO STA-2 (magnesium-substituted AlPO) examine charge-balancing mechanisms in AlPO-based materials. A range of scandium carboxylate metal-organic frameworks (MOFs), with rigid and flexible frameworks, have been characterised by multinuclear solid-state NMR spectroscopy (⁴⁵Sc, ¹³C and ¹H). The materials studied contain a variety of metal units and organic linkers. ¹³C and ¹H magic-angle spinning (MAS) NMR were used to study the organic linker molecules and ⁴⁵Sc MAS NMR was used to study the scandium environment in the MOFs Sc₂BDC₃ (BDC = 1,4-benzenedicarboxylate), MIL-53(Sc), MIL-88(Sc), MIL-100(Sc) and Sc-ABTC (ABTC = 3,3`,5,5`-azobenzenetetracarboxylate). Functionalised derivatives of Sc₂BDC₃ and MIL-53(Sc) were also studied. The ⁴⁵Sc MAS NMR spectra are found to be strongly dependant on the Sc³⁺ coordination environment. ²⁷Al and ²⁵Mg MAS NMR have been used to study Ti-bearing hibonite samples (of general formula Ca(Al, Ti, Mg)₁₂O₁₉), and results compared to a recent complementary neutron powder diffraction study, in order to investigate the substitution sites for Ti³⁺/⁴⁺ and Mg²⁺. A DFT investigation was also carried out on the aluminium end member, CaAl₁₂O₁₉, due to debate in the literature on the ²⁷Al NMR parameters for the trigonal-bipyramidal site. The substitution of Mg onto the tetrahedral site (M3) and Ti primarily onto one of the octahedral sites (M4) is supported.

La conductivité électronique de l'éméraldine sel dépend des conditions de sa synthèse (solvant et dopant utilisés) et de son traitement après synthèse. L'objectif principal de cette thèse est de démontrer et d'interpréter les corrélations entre l'environnement et les propriétés de la forme conductrice de la polyaniline. Dans la partie théorique, nous avons examiné l'influence des différents dopants et solvants sur la structure et les propriétés de la polyaniline. Pour atteindre cet objectif, un large dispositif de méthodes de chimie quantique a été testé et une méthode appropriée a été choisie. Dans la partie expérimentale nous avons utilisé une nouvelle approche pour accéder aux propriétés intrinsèques de la polyaniline i.e. sans utiliser ni solvants ni dopants autres que ceux utilisés lors de la synthèse. Les calculs montrent que la description théorique de la polyaniline dépend fortement du choix de la méthode. La modélisation de l'effet de la polarité du solvant grâce à l'utilisation de la méthode PMC semble être cruciale pour une description fiable de l'interaction polyaniline-dopant. Les résultats obtenus démontrent pour la première fois que les interactions, de la polyaniline avec les dopants dépendent de la nature chimique du solvant et pas du dopant lui-même. De plus, nous avons montré que la stabilité de la forme polaronique (conductrice) augmente avec l'augmentation de la polarité du solvant. Ces conclusions correspondent parfaitement à nos résultats expérimentaux qui montrent le rôle crucial du solvant (et pas des dopants) sur les propriétés de la polyaniline.

Ce travail a consisté à étudier des complexes de Fer (II) et plus particulièrement à décrire le phénoméne de piégeage d'états de spin excités par la lumière. La taille des molécules présentant cette propriété étant d'une centaine d'atomes, la théorie de la fonctionnelle de la densité (DFT) à été la méthode de choix. Au travers de cette étude, les limites d'application de la DFT aux complexes de Fer (II) ont été évaluées en les comparant à des calculs ab initio puis à des données expérimentales. Il a été mis en évidence que le terme d'échange des fonctionnelles l'échange-corrélation influence le plus la capacité à décrire Delta E_{HL} et Delta r_{HL}. La fonctionnelle OLYP de type GGA a permis d'obtenir la meilleure description de ces complexes. Les énergies à décrire étant de l'ordre de la précision chimique (kcal/mol), les fonctionnelles d'échange doivent être encore améliorées pour obtenir des résultats plus fiables.

NMR spectroscopy with in situ laser irradiation has been used to investigate the photo- and thermal isomerisation of eight azobenzene derivatives; diphenyldiazene (azobenzene), p-phenylazoaniline (p-aminoazobenzene), 4-(dimethylamino)azobenzene (Methyl Yellow), 4-dimethylamino-2-methylazobenzene (o-Methyl-Methyl Yellow), p-nitroazobenzene, 4-nitro-4’-dimethylaminoazobeneze (Dimethyl-nitroazobenzene), 4-(4-nitrophenylazo)aniline (Disperse Orange 3) and N-ethyl-N-(2-hydroxyethyl)-4-(4-nitrophenylazo) (Disperse Red 1). The rate constants and activation parameters of the thermal cis-to-trans isomerisation have been measured experimentally and correlated to the mechanism of isomerisation in two solvents. The experimental data show that the values of the activation energy (related to the enthalpy of activation) and the entropy of activation (related to the Arrhenius pre-exponential factor) vary significantly from molecule to molecule and thus both of these parameters influence the inter-molecule variation of the rate constant. Similarly, both of these parameters influence the solvent-dependence of the rate constant. Complementary computational studies have been carried out in the gas phase and in solution using density functional theory (DFT) to predict the structures of the cis and trans isomers and the transition state, and to explore the reaction coordinate. The theoretically predicted activation parameters are compared with those determined experimentally, and the utility of DFT calculations in predicting the effects of molecular structure and solvation on the kinetics of cis-to-trans isomerisation assessed. The DFT-predicted values of the activation energy and Gibbs free energy of activation in DMSO are in good agreement with the experimental values, while the values in benzene tend to be in less good agreement. The DFT calculations are unsuccessful at predicting the entropy of activation, where in all cases there is a large discrepancy between the theoretical and experimental values. The DFT- calculated energy differences between the activation energies of the two inversion pathways for the asymmetric azobenzenes suggests the favourable phenyl ring for inversion. The formation of a linear transition state from a dihedral rotation potential energy curve is explained in terms of the lower activation barrier of the more favourable inversion route (α-inversion) than that of the dihedral rotation pathway, and suggests the inversion through the α-phenyl ring to be the favoured pathway for substituted azobenzene. DFT calculations are able to obtain a transition state corresponding to pure rotation pathway for two azobenzene derivatives. The higher activation barrier for the formation of the transition state corresponding to this pathway compared to that of the formation of the α-transition state confirmed the previous conclusion. DFT predictions of the effect of protonation on the thermal rates of isomerisation of azobenzenes substituted with electron-donating group were in good agreement with the experimental results; both conclude faster isomerisation and lower activation barriers on protonation. However, DFT calculations could not confirm the postulation of rotational transition state for the isomerisation of the protonated molecule, as a result of weakening of the N=N bond by protonation.

Carbon-based thin films are a vast group of materials of great technological importance. Thanks to the different bonding options for carbon, a large variety of structures (from amorphous to nanostructured) can be achieved in the process of film synthesis. The structural diversity increases even more if carbon is combined with relatively small quantities of atoms of other elements. This results in a set of materials with many different interesting properties for a wide range of technological applications. This doctoral thesis is about nanostructured carbon-based thin films. In particular, the focus is set on theoretical modeling, prediction of structural features and design of sulfo carbide (CSx) and carbon fluoride (CFx) thin films. The theoretical approach follows the synthetic growth concept (SGC) which is based on the density functional theory. The SGC departure point is the fact that the nanostructured films of interest can be modeled as assemblies of low dimensional units (e.g., finite graphene-like model systems), similarly to modeling graphite as stacks of graphene sheets. Moreover, the SGC includes a description of the groups of atoms that act as building blocks (i.e., precursors) during film deposition, as well as their interaction with the growing film. This thesis consists of two main parts: Prediction: In this work, I show that nanostructured CSx thin films can be expected for sulfur contents up to 20 atomic % with structural characteristics that go from graphite-like to fullerene-like (FL). In the case of CFx thin films, a diversity of structures are predicted depending on the fluorine concentration. Short range ordered structures, such as FL structure, can be expected for low concentrations (up to 5 atomic %). For increasing fluorine concentration, diamond-like and polymeric structures should predominate. As a special case, I also studied the ternary system CSxFy. The calculations show that CSxFy thin films with nanostructured features should be possible to synthesize at low sulfur and fluorine concentrations and the structural characteristics can be described and explained in terms of the binaries CSx and CFx. Design: The carbon-based thin films predicted in this thesis were synthesized by magnetron sputtering. The results from my calculations regarding structure and composition, and analysis of precursors (availability and role during deposition process) were successfully combined with the experimental techniques in the quest of obtaining films with desired structural features and understanding their properties.

Clusters constitute an intermediate state of matter between molecules and solids whose properties are size dependent and can be tailored. In recent years, cluster science has become one of the most exciting areas of research since their study can not only bridge our understanding between atoms and their bulk but also between various disciplines. In addition, clusters can serve as a source of new materials with uncommon properties. This dissertation deals with an in-depth study of clusters as a bridge across physics, chemistry, and materials science and provides a fundamental understanding of the structure-property relationships by focusing on three different topics. The first topic deals with superatoms which are clusters that mimic the chemistry of atoms. I show that superhalogens and superalkalis can be designed to mimic the chemistry of halogen and alkali atoms, respectively. An entirely new class of salts can then be synthesized by using these superatoms as the building blocks. I have also explored the possibility of designing highly electronegative species called hyperhalogens by using superhalogens as ligands or superalkalis as core and a combination of both. Another aspect of my work on superatom is to examine if traditional catalysts (namely Pd) can be replaced by clusters composed of earthabundant elements (namely Zr and O). This is accomplished by comparing the electronic structure and reactivity of Pd clusters with isoelectronic ZrO clusters. The second topic deals with a study of the electronic structure of coinage metal (Cu and Ag) clusters and see if they remain unchanged when a metal atom is replaced by an isoelectronic hydrogen atom as is the case with Au-H clusters. The third topic deals with clusters as model of polymeric materials to understand their gas storage and sequestration properties. This is accomplished by studying the trapping of H2, CO2, CH4 and SO2 molecules in borazine-linked polymers (BLPs) and benzimidazole-linked polymers (BILPs). The first two topics provide a bridge between physics and chemistry, while the third topic provides a bridge to materials science.

Une étude théorique basée sur la théorie de la fonctionnelle de la densité (DFT) a été réalisée sur un ensemble de complexes organométalliques mono, di et trinucléaires à base de fer, de ruthénium ou de platine. Les résultats obtenus sur les complexes mononucléaires à base de fer révèlent que la longueur du chaînon π de carbone n'a qu'une influence mineure sur les propriétés électroniques mais affectent les propriétés spectroscopiques. Une étude entreprise sur des systèmes contenant un ligand aromatique polycyclique a montré que la présence de molécules de solvant coordonnant abaisse les barrières énergétiques et par conséquence, facilite le réarrangement haptotropique du greffon organoruthénium sur le ligand organique. L'étude théorique réalisée sur des nouveaux systèmes de type [2]rotaxane a révélé que la longueur du chaînon π du fil moléculaire enfilé au travers d'un macrocycle influence les énergies d'interaction non covalente dans ces systèmes. Il a été montré que ces interactions non covalentes sont principalement dues à des liaisons hydrogène formées entre le macrocycle et le fil moléculaire. / A theoretical study based on density functional theory (DFT) was performed on several series of organometallic mono, bi and trinuclear iron, ruthenium and platinum based complexes. The results on mononuclear iron based complexes indicate that the length of the π carbon bridge in these systems has only a minor influence on the electronic properties but affect somewhat the spectroscopic properties. A study was conducted on systems containing polycyclic aromatic ligand showing that the presence of a coordinating solvent molecule in the viscinity of the metal atom bound on top of the polycycle strongly lowers the energy barriers and consequently facilitates the haptotropic rearrangement of the grafted organoruthenium entity. The theoretical study of new systems of [2]rotaxane type has revealed that the length of the π bridge of the molecular wire threaded in a macrocycle influences the weak noncovalent interaction energies in these systems. It has been shown that these noncovalent interactions are mainly due to hydrogen bonds formed between the macrocycle and the threaded molecular wire.

In this study, M06-2X/6-311+G(2d,2p) level calculations were performed to examine the binding energies and vibrational frequencies of different conformers of phenylalanine dipeptide interacting with metal ions (Na+, K+, Mg2+ and Ca2+). Four conformers were selected from the list of 20 most stable structures. The main goal was to understand the influence of conformers on the binding affinity of metal ions with different conformers of phenylalanine dipeptide. In agreement with experimental results, interactions of metal ions with two aromatic rings along with lone pair electrons of oxygen produced high stability. Binding energy was lowest for the metal ion interacting with only one aromatic ring. This study revealed the binding affinity order of metal ions Mg2+ > Ca2+ > Na+ > K+ with any of the conformers considered for phenylalanine dipeptide.

This PhD thesis deals with research activity in organic electronics, an extremely exciting field offundamental science, which is complemented by relevant applications in every-day life: optoelectronics,solar energy conversion (photovoltaics), sensing and information technology, just to mentiona few. In this area, charge transfer/energy transfer processes, as well as light matter interaction,play a major role. Within this topic, this work focus on the theoretical study of the electronic structureand related charge transfer/spectroscopic properties of various molecular systems: Coronenecrystals, F4TCNQ/perylene co-crystals, polythiophenes, PCPDT/PCPDT-BT homo- and copolymerbased on thiophene, chemisorbed ferrocene on Si(111) substrate. Particular attention wasdevoted to the calculation of infrared (IR) and electronic spectra associated with the so-called “polaronsignature” in doped organic semiconductors. To assess the reliability and physical meaning of electronic quantities involved in the calculations(like the HOMO/LUMO gap, theoretical spectroscopic intensity and vibrational modes, pursuingthe comparison between neutral and charged systems) a number of different levels of the theoryhave been systematically varied from HF (Hartree-Fock) to “pure” DFT (Density Functional Theory),as well as hybrid B3LYP (Becke 3-Parameter (Exchange), Lee, Yang and Parr 1,2) and longrange corrected Coulomb-Attenuating Method (CAM-B3LYP) functionals. In the attempt to untanglethe physics underlying the polaron formation in charged molecular systems (as evidenced by theoccurrence of giant intensity bands found in IR spectra), the mapping of the vibrational mode betweenneutral and charged systems has been calculated. A major achievement in this work is thatthe vibrational (giant) mode associated with the “polaron” emerges as a new mode (peculiar of thecharged state) not related to any mode existing in the neutral system.