Au-delà de son importance dans l’industrie nucléaire, la chimie d’oxydoréduction de l’uraniumretient de plus en plus l’attention des chercheurs. En effet, la capacité toute particulière descomplexes d’uranium à bas degré d’oxydation à promouvoir des réductions originales par desvoies inhabituelles suscite actuellement un grand intérêt, tout particulièrement leur aptitude àactiver dans des conditions douces des petites molécules telles CO, CO2, N2, ou encore descomposés aromatiques et des azotures. Les composés d’uranium, de part leurs propriétés decoordination tout à fait uniques pourraient offrir une alternative aux métaux de transitionclassiques pour la conception de catalyseurs. Cependant, comparativement aux métaux du bloc d,les processus polyélectroniques sont rares dans la chimie de l’uranium à bas degré d’oxidation quiest dominée par les transferts monoélectroniques. C’est pourquoi le développement de nouveauxcomplexes d’uranium capables de réaliser des réductions poly-électroniques est particulièrementintéressant. Le premier objectif de ce travail était d’associer à l’uranium des ligands non-innocentsservant de réservoir d’électrons. Ainsi nous avons utilisé des bases de Schiff p-conjuguées pourexplorer la chimie de cet élément à bas degree d’oxydation. Cela nous a permis d’isoler descomplexes riches en électrons dans lesquels des électrons sont stockés sur le ligand via laformation de liaisons C-C. Ces mêmes liaisons sont rompues en présence d’agent oxydant, et lesélectrons sont libérés pour réaliser des transformations polyélectroniques. Ce procédé a étéobservé pour plusieurs bases de Schiff, permettant de moduler les propriétés des composés. Dansune seconde approche, nous nous sommes intéressés à la synthèse et à l’étude de la réactivité denouveaux complexes d’uranium trivalent supportés par des ligands silanolates. De nouveauxcomposés dinucléaires d’uranium à basse valence ont été obtenus. Ces composés très réactifsdécomposent spontanément en clivant des groupements tertiobutyls des ligands, conduisant à laformation de complexes d’uranium(IV). En parallèle, un complexe monoanionique mononucléaired’U(III) a été isolé, nous permettant de comparer la réactivité de l’uranium trivalent dans différentsenvironnements stériques et électroniques. Ces études de réactivité ont permis de stabiliser unexemple rare de dimère d’uranium ponté par un groupement CS22- et ont mis en évidence lacapacité de l’uranium trivalent à promouvoir la dismutation de CO2 en carbonate et CO. La réactionde ces composés d’uranium trivalent vis-à-vis d’azotures organiques et inorganiques a produit denouveaux nitrures et nitrènes d’uranium originaux. Enfin, la capacité de ces agents réducteurspuissants à transférer des électrons au toluène a permis d’isoler une famille de complexessandwiches inversés où deux cations uranium sont liés de part et d’autre d’un cycle aromatique. / Beyond its importance in nuclear industry the redox chemistry uranium is attracting increasinginterest because complexes of low-valent uranium can promote unusual reductive chemistrythrough unusual reaction pathways, including attractive examples of CO, CO2, N2, arenes andazides activation in mild condition. Due to the unique coordination and bonding properties ofuranium, its compounds could provide an attractive alternative to transition metals for thecatalytic transformation of small molecules. However, metal-based multi-electron processesremain uncommon in uranium chemistry especially in comparison with the d-block metals, thechemistry of low-valent uranium being dominated by single-electron transfers. In this context, thefirst aim of this project was to investigate the association of low-valent uranium to a non-innocentligand acting as an independent electron reservoir at a same molecule. Accordingly, weinterrogated the use of highly p-delocalized Schiff bases ligands for supporting low-valent uraniumchemistry. This led to the isolation of electron-rich complexes which are stabilized by storingelectrons on the ligands through the formation of C-C bonds. Interestingly, these C-C bonds can becleaved by oxidizing agents and the electrons released to participate in multi-electron redoxreactions. This process was observed within different Schiff-base ligand scaffolds, allowing atuning of the properties of the compounds. The second part of this work was dedicated to thesynthesis of novel trivalent uranium complexes supported by siloxy ligands and the study of theirredox reactivity and coordination properties. Novel dinuclear highly-reactive low-valent uraniumassemblies were developed. The study of their limited stability revealed that these compounds arespontaneously decomposing through the cleavage of tBu groups from the supporting ligandsresulting in the formation of U(IV) species. In parallel, a mononuclear trivalent uranium atecomplex was obtained, allowing to compare the reactivity of U(III) in different steric and electronicenvironements. Hence we became interested in studying the redox reactivity of these compoundswith different substrates including CO2, CS2, azides and arenes. These investigations led to thestabilization of a rare CS22- sandwich complex of uranium, and highlited the ability of U(III) topromote reductive disproportionation of CO2 to carbonate and CO. The reaction of these trivalenturanium siloxide species with organic and inorganic azides produced original uranium imidos andnitridos compounds with original topologies. Finally the capacity of these strongly reducing agentsto transfer electrons to the toluene fragment lead to the isolation of a family of arenes invertedsandwich complexes.

Au-delà de son importance dans l'industrie nucléaire, la chimie d'oxydoréduction de l'uraniumretient de plus en plus l'attention des chercheurs. En effet, la capacité toute particulière descomplexes d'uranium à bas degré d'oxydation à promouvoir des réductions originales par desvoies inhabituelles suscite actuellement un grand intérêt, tout particulièrement leur aptitude àactiver dans des conditions douces des petites molécules telles CO, CO2, N2, ou encore descomposés aromatiques et des azotures. Les composés d'uranium, de part leurs propriétés decoordination tout à fait uniques pourraient offrir une alternative aux métaux de transitionclassiques pour la conception de catalyseurs. Cependant, comparativement aux métaux du bloc d,les processus polyélectroniques sont rares dans la chimie de l'uranium à bas degré d'oxidation quiest dominée par les transferts monoélectroniques. C'est pourquoi le développement de nouveauxcomplexes d'uranium capables de réaliser des réductions poly-électroniques est particulièrementintéressant. Le premier objectif de ce travail était d'associer à l'uranium des ligands non-innocentsservant de réservoir d'électrons. Ainsi nous avons utilisé des bases de Schiff p-conjuguées pourexplorer la chimie de cet élément à bas degree d'oxydation. Cela nous a permis d'isoler descomplexes riches en électrons dans lesquels des électrons sont stockés sur le ligand via laformation de liaisons C-C. Ces mêmes liaisons sont rompues en présence d'agent oxydant, et lesélectrons sont libérés pour réaliser des transformations polyélectroniques. Ce procédé a étéobservé pour plusieurs bases de Schiff, permettant de moduler les propriétés des composés. Dansune seconde approche, nous nous sommes intéressés à la synthèse et à l'étude de la réactivité denouveaux complexes d'uranium trivalent supportés par des ligands silanolates. De nouveauxcomposés dinucléaires d'uranium à basse valence ont été obtenus. Ces composés très réactifsdécomposent spontanément en clivant des groupements tertiobutyls des ligands, conduisant à laformation de complexes d'uranium(IV). En parallèle, un complexe monoanionique mononucléaired'U(III) a été isolé, nous permettant de comparer la réactivité de l'uranium trivalent dans différentsenvironnements stériques et électroniques. Ces études de réactivité ont permis de stabiliser unexemple rare de dimère d'uranium ponté par un groupement CS22- et ont mis en évidence lacapacité de l'uranium trivalent à promouvoir la dismutation de CO2 en carbonate et CO. La réactionde ces composés d'uranium trivalent vis-à-vis d'azotures organiques et inorganiques a produit denouveaux nitrures et nitrènes d'uranium originaux. Enfin, la capacité de ces agents réducteurspuissants à transférer des électrons au toluène a permis d'isoler une famille de complexessandwiches inversés où deux cations uranium sont liés de part et d'autre d'un cycle aromatique.

Der Großteil der Erdkruste besteht aus Metalloxiden, wobei Siliziumdioxid, Aluminiumoxid und Eisenoxide die Hauptbestandteile sind. Waren Metalloxide in der Menschheitsgeschichte zunächst hauptsächlich als Pigmente und als Rohstoffe zur Metallgewinnung interessant, so wuchs ihre Bedeutung mit wachsendem chemischem Wissen. Die Mechanismen der Bildung und des Zerfalls von Metalloxiden sind sehr komplex und bisher kaum verstanden. Genau dieses Wissen wird aber benötigt, um Metalloxide mit bestimmten Eigenschaften herzustellen und nutzen zu können. In dieser Arbeit werden daher einfache Silanole als molekulare Modelle für Silikate als Ligandvorläufer verwendet, um Eisensilanolatkomplexe zu synthetisieren. Die daraus erhaltenen Eisensilanolatkomplexe können als strukturelle Modelle für natürliche und synthetische Eisensilikate angesehen werden. Zur Aufklärung der Bildung von Eisensilikaten sowie der Struktur des aktiven Zentrums von eisenhaltigen Zeolithen werden diese Eisensilikate sowohl strukturell als auch spektroskopisch eingehend untersucht und mit den Ergebnissen von natürlichen und synthetischen Eisensilikaten verglichen. Die außergewöhnliche Kombination aus quadratisch planarer Koordination und high-spin Konfiguration der Eisen(II)ionen der in dieser Arbeit diskutierten entstehenden Komplexe entpuppt sich als charakteristisch für das aktive Zentrum von eisenhaltigen Zeolithen, weshalb die Eisensilanolatkomplexe in dieser Arbeit als gute strukturelle Modelle solcher angesehen werden können. / The main part of the earth’s crust consists of metal oxides with silica, alumina and iron oxide as major constituents. Metal oxides were used as pigments and as raw material for metal production, but with increasing chemical knowledge their importance grew. The mechanism of formation and decomposition is complex and still rarely understood. But this knowledge is needed, to synthesize and use metal oxides with distinct properties. In this work simple silanols as molecular models for silicates are used as ligand precursors to synthesize iron silanolate complexes. Those complexes can be considered as structural models for natural and synthetic iron silicates. To understand the mechanism of formation of iron silicates and also the structure of the active centre of iron containing zeolites, those iron complexes are analysed structurally and spectroscopically. The results are compared to those of natural and synthetic iron silicates. The extraordinary combination of square planar coordination and high-spin configuration of the iron(II) ion in the discussed iron complexes turns out to be characteristic for the active centre of iron containing zeolites, thus making the resulting complexes good structural models for the active centre of iron containing zeolites.

With the increasing importance of hand-held devices with touch displays, the need for flat panel displays (FPDs) will likely increase in the future. Glass is the most important substrate for FPD manufacturing, where both its bulk and surface properties are critical for its performance. Many properties of the glass used in FPDs are controlled by its surface chemistry. Surface hydroxyls are the most important functional groups on a glass surface, which control processes that occurs on oxide surfaces, including wetting, adhesion, electrostatic charging and discharge, and the rate of contamination. In this dissertation, I present a new approach for determining surface silanol densities on planar surfaces. This methodology consists of tagging surface silanols using atomic layer deposition (ALD) followed by low energy ion scattering (LEIS) analysis of the tags. The LEIS signal is limited to the outermost atomic layer, i.e., LEIS is an extremely surface sensitive technique. Quantification in LEIS is straightforward in the presence of suitable reference materials. An essential part of any LEIS measurement is the preparation and characterization of the sample and appropriate reference materials that best represent the samples. My tag-and-count method was applied to chemically and thermally treated fused silica. In this work, I determined the silanol density of a fully hydroxylated fused silica surface to be 4.67 OH/nm2. This value agrees with the literature value for high surface area silica powder. My methodology should be important in future glass studies. Surface Science Spectra (SSS) is an important, peer-reviewed database of spectra from surfaces. Recently, SSS has been expanding to accept spectra from new surface techniques. I created the first SSS submission form for LEIS spectra (see appendix 5), and used it to create the first SSS LEIS paper (on CaF2 and Au reference materials, see chapter 3). I also show LEIS reference spectra for ZnO, and copper in the appendix 1. The rest of my dissertation focuses on my chemometrics/informatics and data analysis work. For example, I showed the performance and capabilities of a series of summary statistics as new tools for unsupervised exploratory data analysis (EDA) (see chapter 4). Unsupervised EDA is often the first step in understanding complex data sets because it can group, and even classify, samples according to their spectral similarities and differences. Pattern recognition entropy (PRE) and other summary statistics are direct methods for analyzing data - they are not factor-based approaches like principal component analysis (PCA) or multivariate curve resolution (MCR). I show that, in general, PRE outperforms the other summary statistics, especially in image analysis, although I recommend a suite of summary statistics be used in exploring complex data sets. In addition, I introduce the concept of divided spectrum-PRE (DS-PRE) as a new EDA method and use it to analyze multiple data sets. DS-PRE increases the discrimination power of PRE. I have also prepared a guide that discusses the vital aspects and considerations for chemometrics/informatics analyses of XPS data along with specific EDA tools that can be used to probe XPS data sets, including PRE, PCA, MCR, and cluster analysis (see chapter 5). I emphasize the importance of an initial evaluation/plotting of raw data, data preprocessing, returning to the original data after a chemometrics/informatics analysis, and determining the number of abstract factors to keep in an analysis, including reconstructing the data using PCA. In my thesis, I also show the analysis of commercial automotive lubricant oils (ALOs) with various chemometrics techniques (see chapter 6). Using these methods, the ALO samples were readily differentiated according to their American Petroleum Institute (API) classification and base oil types: mineral, semi-synthetic, and synthetic.

A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds. Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.

A new method, probability distribution of diffusivities (time scaled square displacements between succeeding video frames), was developed to analyze single molecule tracking (SMT) experiments. This method was then applied to SMT experiments on ultrathin liquid tetrakis(2-ethylhexoxy)silane (TEHOS) films on Si wafer with 100 nm thermally grown oxide, and on thin semectic liquid crystal films. Spatial maps of diffusivities from SMT experiments on 220 nm thick semectic liquid crystal films reveal structure related dynamics. The SMT experiments on ultrathin TEHOS films were complemented by fluorescence correlation spectroscopy (FCS). The observed strongly heterogeneous single molecule dynamics within those films can be explained by a three-layer model consisting of (i) dye molecules adsorbed to the substrate, (ii) slowly diffusing molecules in the laterally heterogeneous near-surface region of 1 - 2 molecular diameters, and (iii) freely diffusing dye molecules in the upper region of the film. FCS and SMT experiments reveal a strong influence of substrate heterogeneity on SM dynamics. Thereby chemisorption to substrate surface silanols plays an important role. Vertical mean first passage times (mfpt) in those films are below 1 µs. This appears as fast component in FCS autocorrelation curves, which further contain a contribution from lateral diffusion and from adsorption events. Therefore, the FCS curves are approximated by a tri-component function, which contains an exponential term related to the mfpt, the correlation function for translational diffusion and a stretched exponential term for the broad distribution of adsorption events. Lateral diffusion coefficients obtained by FCS on 10 nm thick TEHOS films, thereby, are effective diffusion coefficients from dye transients in the focal area. They strongly depend on the substrate heterogeneity. Variation of the frame times for the acquisition of SMT experiments in steps of 20 ms from 20 ms to 200 ms revealed a strong dependence of the corresponding probability distributions of diffusivities on time, in particular in the range between 20 ms and 100 ms. This points to average dwell times of the dye molecules in at least one type of the heterogeneous regions (e.g. on and above silanol clusters) in the range of few tens of milliseconds. Furthermore, time series of SM spectra from Nile Red in 25 nm thick poly-n-alkyl-methacrylate (PnAMA) films were studied. In analogy to translational diffusion, spectral diffusion (shifts in energetic positions of SM spectra) can be studied by probability distributions of spectral diffusivities, i.e. time scaled square energetic displacements. Simulations were run and analyzed to study contributions from noise and fitting uncertainty to spectral diffusion. Furthermore the effect of spectral jumps during acquisition of a SM spectrum was investigated. Probability distributions of spectral diffusivites of Nile Red probing vitreous PnAMA films reveal a two-level system. In contrast, such probability distributions obtained from Nile Red within a 25 nm thick poly-n-butylmethacrylate film around glass transition and in the melt state, display larger spectral jumps. Moreover, for longer alkyl side chains a solvent shift to higher energies is observed, which supports the idea of nanophase separation within those polymers.