In this thesis, I report the gas phase infrared spectra of some polycyclic aromatic hydrocarbons (PAHs) namely 1, 5-, 1, 6-, and 2, 6-dimethyl naphthalenes (DMNs); 2, 4-, 2, 6-, 2, 7-, and 2,8-dimethyl quinolines (DMQs); and 1, 9-, 2, 4-, and 3, 9-dimethyl phenanthrenes (DMPs) and diols such as 1, 2-ethylene glycol (1,2-EG) and 1, 4-butanediol (1,4-BD). Assignment of the IR spectra has been done with the help of DFT calculations followed by scaled quantum mechanical force field calculations. Chapter 1 gives a brief introduction to PAHs and diols. A brief survey of literature pertinent to their sources, their importance, experimental techniques for identification of PAHs and different conformers of diols and intramolecular interactions between the two hydroxyl groups in the diols are presented. The scope and motivation of the present investigation have been described at the end of the chapter. In Chapter 2, I have discussed all the methods used in carrying out this work. The details of the experimental FT IR set-up and quantum-chemical calculations employed in this work have been elaborated in this chapter. The subsequent chapters 3 - 5 deal with the experimental and theoretical results obtained for DMNs, DMQs, and DMPs. In chapter 3, infrared spectra of 1,5-, 1,6-, and 2,6-DMN have been described. The spectra have been recorded using a multi-pass gas cell coupled with Nexus-870 spectrometer (Thermonicolet, US). Qualitatively, spectral assignments have been made with the help of calculated doubly scaled (one scaling factor for the C-H stretching and another factor for the non C-H stretching frequencies) harmonic frequencies at the B3LYP/6-31G* level of theory. The spectral features to distinguish three different isomers of DMN have been identified. In chapter 4, IR spectra of 2,4-, 2,6-, 2,7-, and 2,8-DMQ in the gas phase have been recorded using a high resolution Vertex-70 (Bruker Optics, Germany) FT-IR spectrometer. DFT calculations have been carried out in order to get harmonic and anharmonic frequencies and their intensities at the B3LYP/6-31G* level of theory. Unambiguous assignments of IR bands could not be made with the help of anharmonic or selectively scaled harmonic frequencies. Therefore, scaled quantum mechanical (SQM) force field calculations were performed where force fields in local coordinates were scaled for getting frequencies in close agreement with experiment. Potential energy distributions (PEDs) of the normal modes in terms of the local coordinates of the molecule using a modified UMAT program in the QCPE package were also obtained in order to identify the nature of the fundamental vibration modes. In chapter 5, I have presented the gas phase IR spectra of 1,9-, 2,4-, and 3,9-DMP. The harmonic and anharmonic frequencies and their intensities were obtained at the B3LYP/6-31G* and B3LYP/6-311G** levels of theory. I have carried out SQM calculations for the assignment of the experimental frequencies in a similar fashion as was done for the DMQs. In chapter 6, IR spectra of two diols namely 1,2-ethylene glycol and 1,4-butane diol are reported and discussed. DFT calculations have been carried out for the harmonic fundamental frequencies and intensities at the experimental temperatures with 10 unique chosen conformers of the diols at the B3LYP/6-311++G** level of theory. Gas phase equilibrium population analysis has been done in order to generate the theoretical spectrum with the weighted average contributions from the 10 conformers to match the experimental spectrum. The hydrogen bond enthalpy, strength and nature have been investigated in details. From this experimental and theoretical studies, it has been concluded that the intramolecular hydrogen bond is absent in 1,2-EG at ordinary temperatures whereas it is present in 1,4-BD. vi Chapter 7 is the concluding chapter where the main work done in this thesis is summarized and future direction is presented.

This research explores the links between the structure and dissociation energetics of ionized non-covalent complexes. In chapter 3, a large series of similar non-covalent complexes were probed using electrospray tandem mass spectrometry (ESI-MS/MS) and RRKM modelling in order to identify any trends in the dissociation energetics based on charge state, overall size of the complex, or size of the substrate. Ion mobility spectrometry (IMS) in conjunction with molecular mechanics/molecular dynamics (MM/MD) was used to study the conformations of these non-covalent complexes in order to determine if the same trends identified in the energetics could be corroborated independently based on structure. The system of study consisted of varying lengths of the synthetic polymer, polymethylmethacrylate (PMMA) complexed with singly or doubly protonated diaminoalkanes (DAA) of varying length. The critical energies of dissociation (E0) increased as the length of the polymer increased and was not significantly affected by the length of the singly protonated DAA substrates. The E0 of dissociation of doubly protonated complexes was strongly influenced by the length of the DAA; longer DAA substrates had greater separation of charge which decreased coulombic repulsion within the complex resulting in higher E0 values. MM/MD low energy structures of all complexes were validated with experimental IMS measurements and showed that the arrangement between the polymer and DAA were similar for different singly protonated DAAs. When doubly protonated, the length of DAA was the most important factor in determining the overall structure of the complex. In chapter 4, a direct link is shown between the observed E0 dissociation energies and the molecular conformations for eight different peptide–saccharide complexes containing either a tri-saccharide (d-(+)-raffinose and d-panose) or tetra-saccharide (stachyose and maltotetraose) with a small peptide (FLEEL and FLEEV). The E0 values were highly related to the overall conformation adopted by the non-covalent complex in the gas phase. Complexes containing peptide FLEE(L/V) with the tri-saccharide raffinose or panose had similar E0 of dissociation (∼0.64 eV) and similar conformations based on MM/MD simulations and IMS drift times. Conversely, for complexes containing a FLEE(L/V) peptide with one of the isomeric tetra-saccharides; stachyose had a E0 ∼0.08 eV greater than maltotetraose. This difference of intermolecular interaction was also reflected by the IMS drift times; maltotetraose in complex with FLEEV or FLEEL had a 5.9% and 2.3% faster IMS drift time than stachyose respectively. This indicated that the molecular arrangement between maltotetraose and the peptides was more compact than the stachyose-peptide complexes. In chapter 5, RRKM modelling of breakdown diagrams is not possible when the reactant ion signal is overlapped by other isobaric species. Trimeric, non-covalent complexes that contained two PMMA molecules and a doubly protonated DAA, [(PMMAa)(DAA+2H)(PMMAb)]+2, have m/z signals that contain multiple different complexes having the same total number of polymer repeat units but differ in the length of the each polymer. In this situation, the applicability of using the simple kinetic method to gain insight into relative binding energies was explored. The major factors which determined the suitability of the kinetic method for this system were identified as the structural arrangement of the reactant ion complex, possible reverse activation barriers, and the evaluations of Δ(ΔS‡). MM/MD simulations coupled with IMS suggests that within the reactant ion, the DAA is almost equally shared between two PMMA oligomers and that the two PMMA oligomers interact predominately with the DAA, and not with each other. MS/MS of the trimeric reactant complexes proceeds by neutral loss of one polymer and is suggested to proceed with little or no reverse activation barrier based on the low coulombic repulsion factors. The IMS drift times of [(PMMAa)(DAA+2H)]+2 complexes that were generated directly by ESI-MS or by dissociation of a trimeric, [(PMMAa)(DAA+2H)(PMMAb)]+2 complex were found to be identical. This provides some evidence that Δ(ΔS‡) ≈ Δ(ΔS) and using a statistical mechanics approach, Δ(ΔS) ≈ 0. The effective temperature (Teff) variable in the kinetic method expression was found to decrease as a function of the size of the trimeric complex, suggesting that the population distribution of the dissociating ensemble of complexes narrows as size increases. Overall, when RRKM fitting is not possible, the simple kinetic method could provide relative energetic ranking of competing dissociations reactions however the Teff term contributed to the greatest uncertainty in obtaining absolute quantities. Fitting MS/MS breakdown diagrams of non-covalent complexes with multiple dissociation channels is difficult due to the number of total fitting variables. Building from the simple kinetic method, chapter 6 shows that the relationship between the natural logarithm of competing fragment ions and reciprocal collision energy yields a branching relationship that allows for the sign of Δ(ΔS‡) and Δ(E0) between the channels to be obtained. Furthermore, the relationships between the fitting variables of RRKM modelling are empirically related to the theoretical branching relationship characteristics. This allowed for the fitting variables of all dissociation channels to be expressed as a function of a single channel so that the theoretical branching relationship matches the experimental branching relationship. Using this method, RRKM fitting of a MS/MS breakdown diagram for APCI ionized anthracene determined the E0 and ∆S‡ was 4.69 ± 0.29 eV and -3 ± 17 J K-1; 4.21 ±0.29 eV and -19 ±15 J K-1; and 4.81 ± 0.29 eV and 36 ±22 J K-1 for hydrogen loss, acetylene loss and diacetylene loss respectively. With one exception, these values are within experimental error of the iPEPICO derived energetic values. In chapter 7, MS/MS of ammoniated triacylglycerides at multiple collision energies and computational analysis are used to explain the cause of uneven dissociation rates of the FAs from different positions on the glycerol backbone. The loss of sn-1 and sn-3 FAs are found to have lower activation energies than the loss of the sn-2 position FA, however the loss of the FA from the sn-2 position is more entropically favourable. Theoretical MS/MS breakdown curves were fit to experimental values using RRKM theory to estimate the E0 of dissociation of FAs from the three glycerol positions. The E0 values for cleavage from the sn-1 and sn-3 positions were found to be approximately 1.52 eV, while that for the sn-2 position was highly dependent on the identity of the FA at that position. Computational structures and energy analysis suggest that an important step in the dissociation of [TAG+NH4]+ is the loss of ammonia. In a model system, glyceryl tributyrate, the loss of NH3 produced two distinct [TAG+H]+ product structures sitting 148 kJ and 160 kJ in energy above the ammoniated structure. The [TAG+H]+ structure that leads to the loss of the sn-1(3) is 12 kJ lower than the [TAG+H]+ structure that leads to the loss of the sn-2 FA. From this, the loss of a neutral FA that follows sits only an additional 35–48 kJ above the [TAG+H]+ structures. In Chapter 8, singly deprotonated β-cyclodextrin monomers, [(β-CD-H+]-1, and doubly deprotonated dimers, [(β-CD)2-2H+]-2, are both present following ESI-MS and have the same monoisotopic m/z. Similar to chapter 5, this makes it difficult to generate an MS/MS breakdown diagrams that can be modelled with RRKM theory. IMS was used to mobility separate [(β-CD-H+]-1 and [(β-CD)2-2H+]-2 and was followed by MS/MS of the [(β-CycD)2-2H+]-2 ion. A second problem when generating a MS/MS breakdown diagram of non-covalent complexes that contain identical components is that the fragment ions could have an identical monoisotopic m/z as the reactant ion. MS/MS of [(β-CycD)2-2H+]-2 results in two [(β-CD-H+]-1 fragments. To overcome this, breakdown diagrams were then generated by monitoring the changes in the isotopic profile. The RRKM derived E0 for dissociation of [(β-CycD)2-H+]-1 and [(β-CycD)2-2H+]-2 were 1.85 ± 0.11eV and 1.79 ± 0.09eV, respectively, corresponding to a slight decrease in complex stability due to increased charge-charge repulsion in the dianion.

Depuis leur découverte dans divers environnements astrophysiques, les anions polyyne CxH¯ (x = 2, 4, 6) et les anions cyanopolyyne CxN¯ (x = 1, 3, 5) ont reçu une attention considérable. Ces anions semblent jouer des rôles importants dans leur environnement. Cependant, les données à basse température sur les voies chimiques menant à leur formation et à leur destruction sont encore rares, en particulier ce qui concerne l'identité du produit et les ratios de ramification. Pour résoudre ce problème, nous nous sommes engagés dans la recherche de la réactivité de ces anions moléculaires en utilisant des instruments dédiés couplant des jets subsonique et supersonique avec des méthodes de spectrométrie de masse. De cette façon, nous avons étudié la réactivité des anions C3N avec le cyanoacétylène (HC3N) ainsi que la réactivité de CN¯, C3N¯, et C5N¯ avec l'acide formique (HCOOH) de 298 K à des températures aussi basses que 36 K. Nous rapportons dans ce travail le taux de vitesse, les produits, et les ratios de ramification de ces réactions. Ce travail aborde également la source prototype d'ions sélectionnée, qui a récemment été mis en place dans notre laboratoire afin d'étendre notre recherche à d'autres anions d'intérêt astrophysique (e.g. les anions CxH¯ et Cx¯). Une description de cet instrument ainsi que des résultats préliminaires sont présentés dans ce travail. Cette thèse, «Reactivity of Molecular Anions at Low Temperature: Implications for the Chemistry of the Interstellar medium and Titan’s atmosphere», a été réalisée au sein de l'Institut de physique de Rennes et de l'Ecole Nationale Supérieure de Chimie de Rennes. Mots-clés: astrochimie, atmosphère de Titan, anions moléculaires, cinétique en phase gazeuse, jet supersonique, spectrométrie de masse, source d’ions sélectionnée / Ever since their discovery in various astrophysical environments, polyyne anions CxH¯ (x = 2, 4, 6) and cyanopolyyne anions CxN¯ (x = 1, 3, 5) have received a considerable attention. These anions appear to be playing important roles in their environments. However, low temperature data on the chemical pathways leading to their formation and destruction is still scarce, especially regarding product identity and branching ratios. To address this issue, we have engaged in the investigation of the reactivity of these molecular anions by employing dedicated instruments coupling subsonic and supersonic flows with mass spectrometry methods. In this fashion, we have investigated the reactivity of C3N¯ anions with cyanoacetylene (HC3N) as well as the reactivity of CN¯, C3N¯, and C5N¯ with formic acid (HCOOH) from 298 K down to temperatures as low as 36 K. We report in this work the rate coefficient, the nature of the products, and the branching ratios of these reactions.This work also addresses the prototype selected ion source in our laboratory, which was recently implemented in order to extend our investigation to other anions of astrophysical interest (e.g. CxH¯ and Cx¯ anions). A description of this instrument as well as some preliminary results are presented in this work. This thesis, «Reactivity of Molecular Anions at Low Temperature: Implications for the Chemistry of the Interstellar medium and Titan’s atmosphere», was carried out at the Institut de Physique de Rennes and the Ecole Nationale Supérieure de Chimie de Rennes.Keywords: astrochemistry, Titan’s atmosphere, molecular anions, gas phase kinetics, supersonic flow, mass spectrometry, selected ion source

Au point de convergence entre les sciences fondamentales et les sciences appliquées, les nanosystèmes connaissent depuis une dizaine d'années un développement industriel à l'échelle planétaire. Parmi ces nanosystèmes, les agrégats, petites particules constituées de quelques atomes (ou molécules) à plusieurs milliers d'unités, constituent véritablement "le chaînon manquant" entre l'atome isolé et le solide massif. L'étude des interactions dans les agrégats permettrait de comprendre comment l'atome est influencé par son environnement lorsqu'il est inclus dans un système dense au sein d'autres atomes. La nanoparticule (NP) est constituée de plusieurs milliers à millions d'atomes, ses dimensions étant exprimées en nanomètres (nm, 1 nm = 10^{-9} m).L'engouement que suscitent les agrégats et les NPs est lié à leurs propriétés physiques particulières mais également à leur grande surface spécifique (rapport surface/volume). Il en résulte une grande réactivité liée à des sites réactionnels plus nombreux. Cette caractéristique est exploitée dans de très nombreux domaines d'applications (catalyse hétérogène, dépollution, photovoltaïque, nanomédecine).Cette expansion des activités "nanotechnologiques" implique le développement de méthodes de caractérisation de ces nouveaux types de matériaux, qui sont bel et bien présents dans notre vie.Parmi les méthodes de caractérisation de la matière, la spectroscopie de photoélectrons (XPS) générés par rayonnement synchrotron a, depuis longtemps, prouvé son efficacité pour l'étude des atomes, molécules et des matériaux, et s'est imposée en tant que technique de choix en science des surfaces. L'idée de ces travaux de thèse est de combiner la sélectivité atomique de la spectroscopie appliquée à la matière diluée, avec la sensibilité de surface de la spectroscopie X-mous sur les matériaux pour étudier des nanosystèmes (agrégats et NPs) en phase gazeuse par XPS dans le domaine d'énergie allant de 100 eV à 1000 eV.Nous présentons dans cette thèse les premiers résultats obtenus par cette approche sur la ligne de lumière PLEIADES du synchrotron SOLEIL, ligne à ultra-haute résolution dédiée à l'étude de la matière diluée. Les expériences ont porté sur des matériaux très utilisés dans les secteurs industriel et biomédical, en l'occurrence les NPs de TiO2, de Silicium et les NPs de polystyrène fonctionnalisées par des dérivés glucidiques}. Nous montrons comment l'XPS de NPs isolées nous permet de répondre à des questionnements concrets, comme la réactivité de surface des NPs, les processus et les dynamiques d'oxydation, l'inclusion d'hétéroatomes ainsi que l'interface ligand/NP. Les résultats présentés ici montrent non seulement la faisabilité de la méthode, mais plus encore, prouvent qu'il est possible d'adresser des problématiques appliquées ayant trait à des phénomènes réactionnels surfaciques, sur des NPs isolées, aléatoirement orientées. / During the past decade, a world-wide industrial expansion of nanosystems has been taking place at the junction between fundamental and applied sciences. Among these nanosystems, clusters, defined as small particles whose constitution ranges from few atoms (or molecules) to several thousand units, constitute "the missing link" between the isolated atom and the bulk solid. Studying the interactions in the aggregates would allow to understand how the atom is influenced by its neighborhood when it is included in a dense system within other atoms. "Nanoparticle" (NP) is usually defined as a system extanding from several thousands to millions of atoms, and its size is expressed in nanometer (nm, 1 nm = 10^{-9} m).This interest for nanosystems mainly results from their particular physical properties at the nanometer scale, but also from their large "surface to bulk" ratio. Hence, more active sites are available at the surface, enhancing their reactivity. This characteristic is used in numerous fields of applications (heterogeneous catalysis, cleanup, photovoltaics, nanomedicine).% and is also relevant in natural processes (atmospheric sprays, volcanic eruptions).This expansion of the "nanotechnological" activities involves the development of new methods for the characterization of these new kinds of materials, which take a considerable part in our daily life. Among the methods of matter characterization, synchrotron radiation based soft X-ray spectroscopy has shown to be a powerful technique for the study of atoms and molecules as well as materials, and appears today as an efficient technique of characterization in surface science.The idea of this thesis is to combine the atomic selectivity of the spectroscopy applied to dilute matter, with the surface sensitivity of soft X-ray spectroscopy, to study isolated nanosystems (clusters and NPs) in the gas phase, by XPS in the energy range of soft X-ray (typically 100 eV to 1000 eV). We present in this thesis the first results obtained by this approach at the PLEIADES beamline of SOLEIL synchrotron radiation facility. PLEIADES is a ultra-high resolution beamline dedicated to the study of dilute matter. The experiments carried out in this work relate to materials often used in the industrial and biomedical fields: TiO2 NPs, Silicon and glycosylated polystyrene NPs. We show how XPS on isolated NPs allows us to answer concrete questions, as the surface reactivity of the NPs, processes and oxidation dynamics, the doping efficiency or the interface ligand/NP. The results presented here not only show the feasibility of the method, but much more than that, prove that it is possible to give insight about surface chemical processes occuring on isolated, randomly oriented NPs.

Le déclin de la production de pétrole, lié avec la diminution des matières premières carbonées pour la synthèse chimique ont mené les scientifiques à chercher de nouvelles sources de carbone pour l'industrie chimique. L'utilisation du dioxyde de carbone aiderait à réduire les émissions de gaz à effet de serre tout en fournissant une matière première renouvelable à base de bloc moléculaire en C1. En renversant les équilibres biologiques de trois déshydrogénases, nous avons effectué la biosynthèse multienzymatique en cascade du méthanol à partir de CO2 en utilisant la formiate déshydrogénase de Candida boidinii, la formaldéhyde déshydrogénase de Pseudomonas putida et l'alcool déshydrogénase de Saccacharomyces cerevisiae. Nous avons optimisé le système en ajustant les conditions catalytiques et la quantité relative de chaque déshydrogénase. La phosphite déshydrogénase de Pseudomonas stutzeri a été également choisi comme système de régénération du cofacteur nicotinamide adénine dinucléotide réduit (NADH) parmi 4 systèmes de régénération étudiés. L'ensemble du système a été encapsulé dans des nanocapsules poreuses de silice qui a permis d'augmenter 15 fois les productivités en méthanol. Nous avons montré que les dernières limitations rencontrées, comme la disponibilité du CO2 et l'accumulation du méthanol, peuvent être dépassées en mettant en place un système catalytique en flux continu en phase gaz. / The decline of oil production, linked with the decrease of carbon feedstock for chemical synthesis leads scientist to find new sources of carbon for the chemical industry. Use of carbon dioxide would help to reduce the greenhouse gas emissions while providing a renewable feedstock of C1 molecular building blocks. By reversing the biological metabolic reaction pathway of three dehydrogenase, we carried out multistep multienzyme biosynthesis of methanol from CO2 using formate dehydrogenase from Candida Boidinii, formaldehyde dehydrogenase from Pseudomonas Putida and alcohol dehydrogenase from Saccacharomyces cerevisiae. We improved the system active by adjusting the catalytic conditions and the relative quantity of each dehydrogenase. Phosphite dehydrogenase from Pseudomonas stutzeri was also chosen among 4 different studied systems to be introduced into the catalysis as a cofactor regenerating system for reduced nicotinamide adenine dinucleotide. The enzymatic system was then immobilized by encapsulation into novel phospholipid templated silica nanocapsules, allowing an increase of the methanol productivity by a factor 15. We show that the last limitation of the process as substrate availability and product accumulation can be overcome by running continuous enzymatic flow conversion in a gas phase.

Cette thèse vise à démontrer la pertinence de la chromatographie en phase supercritique (SFC) et de son couplage à la spectrométrie de masse tandem haute résolution (HRMS/MS) quant à l’étude de produits naturels en mélange complexe. Pour y parvenir trois projets ont été menés en parallèle.Une méthode d’analyse structurale ciblée sur les acétogénines d’Annonaceae a été développée. Le recours à une cationisation post-colonne par des sels de lithium a permis d’obtenir les informations structurales recherchées. Des études ont également été menées quant à l’influence de la nature du cation sur la conformation de l’adduit formé et les voies de fragmentation observées.Une séparation de composés polaires et ionisables a également été mise au point à travers l’étude des nucléosides modifiés de l’ARN. La SFC-HRMS permet la séparation et l’étude d’un grand nombre de modifications et constitue donc un nouvel outil d’analyse pour le biologiste.Pour finir, une étude en lipidomique globale a également été entreprise. Bien que préliminaires, les premiers résultats semblent très prometteurs avec pour but de développer des méthodes d’analyses non ciblées associés à des outils d’annotation automatique.Pour chaque projet, la pertinence de nos approches a été vérifiée par l’étude d’échantillons réels et complexes permettant de tirer des conclusions réalistes quant aux possibilités de la SFC-HRMS/MS pour l’étude de composés naturels. / This PhD work aims to demonstrate the relevance of supercritical fluid chromatography (SFC) and its hyphenation to high resolution tandem mass spectrometry (HRMS/MS) in the field of natural product analysis. Three different research projects were carried out.A new strategy for structural analysis of Annonaceous acetogenins was developed by SFC and targeted HRMS/MS including post-column lithium cationisation to give access to the relevant structural information. Investigations were conducted to observe the influence of cations onto the gas-phase conformation and fragmentation pathways.A separation of polar and ionisable compounds was also developed using modified nucleosides from RNA as models. The SFC-HRMS method led to the separation and analysis of several tens of modifications and demonstrated to be a new performant analytical tool for biologists.Finally, a global lipidomic approach was optimized. Preliminary results look compatible with the development of untargeted approaches using automatic annotation tools.For each project, the relevance of our work was evaluated analyzing complex samples to obtain a realistic point of view of the capabilities for SFC-HRMS/MS systems for natural product studies.

Chaque année, une quantité de 107tonnes de suie est produite à l'échelle mondiale. Le carbone-suie dans l'atmosphère a des effets graves sur le changement climatique et la santé humaine. Les impacts dépendent de nombreux facteurs comme les composés organiques adsorbés, le vieillissement et les processus de mélange. Par conséquent, afin de réduire la quantité de suie émise, outre l'examen des facteurs mentionnés, les études de la cinétique de formation, de la structure et des propriétés optiques des suies sont également essentielles. Il existe plusieurs méthodes optiques dans les études sur la suie. La spectroscopie Raman occupe un rôle particulier puisqu'elle est un outil puissant pour l'étude structurale des matériaux carbonés grâce à sa sensibilité aux structures à l’échelle moléculaire. Dans ce travail, des sections Raman différentielles de suies et quelques autres particules carbonées ont été mesurées pour progresser vers la spectroscopie Raman quantitative de ces particules. Les suies produites par des flammes d'éthylène pré-mélangées à basse pression ont été étudiées par mesure Raman ex-situ sur des films déposés et des mesures Raman in-situ (enligne) dans la phase gazeuse. La combinaison de la spectroscopie Raman de suies échantillonnées sur substrat avec les spectroscopies infrarouge et optique et la microscopie électronique en transmission a permis de progresser sur l'interprétation des spectres Raman de suie. Les mesures en phase gazeuse, obtenues pour la première fois, fournissent de nouvelles informations sur la naissance des suies et leurs structures dans les flammes à basse pression avec, par exemple, la détection d'une grande quantité d'atomes de carbones hybridés sp lors de la formation et de la croissance des premières suies. Ces étude s’ouvrent la voie à la détection et à l'analyse des suies directement en phase gazeuse et à leur détection quantitative dans l’atmosphère au travers de leurs spectres Raman. / Every year, an amount of 107 tons of soot is produced on the world scale. Soot, as part of atmospheric black carbon, has serious impacts on climate change and human health. The impacts depend on many factors including adsorbed compounds, aging and mixing processes. Therefore in order to reduce the soot amount, besides considering these mentioned factors, the study of formation kinetics, structure and optical properties is also essential. There are several methods applied in soot investigations. Raman spectroscopy plays a particular role as it is a powerful tool for structural investigation of the carbon-based materials because it is sensitive to molecular structures. In this work, differential Raman cross sections of soot and some other carbonaceous particles were measured to progress toward quantitative Raman spectroscopy. Soot particles produced by premixed ethylene flames at a low pressure were investigated by ex-situ Raman measurement on deposited films and in-situ(online) Raman measurement in the gas phase. Combination of the Raman spectroscopy of soot sampled on substrates with infrared and optical spectroscopy and transmission electron microscopy allowed progressing on the interpretation of soot Raman spectra. The online gas phase measurements provided a novel view on soot birth and structures in low pressure flames with, for instance, the detection of a large amount of sp hybrized carbon atoms during nascent soot growth. These studies pave the way to soot detection and analysis directly and quantitatively in the atmosphere.

The syntheses and characterization of the palladium complexes [Pd(accp)2] (7), [Pd(acch)2] (8), [Pd(η3-CH2CMeCH2)(accp)] (11), [Pd(η3-CH2CMeCH2)(acch)] (12), [Pd(η3-CH2CtBuCH2)(accp)] (13) and [Pd(η3-CH2CtBuCH2)(acch)] (14) (accp = 2-acetylcyclopentanoate; acch = 2-acetylcyclohexanoate) are reported. These complexes are available by the reaction of Haccp (2-acetylcyclopentanone) and Hacch (2-acetylcyclohexanone) with Na2[Pd2Cl6] forming 7 and 8 or with [(Pd(η3-CH2CRCH2)(μ-Cl))2] (9, R = Me; 10, R = tBu) forming 11–14. The molecular structures of 7, 8 and 14 are discussed. Complexes 7 and 8 consist of a square-planar coordinated Pd atom with two trans-positioned bidentate β-diketonate ligands. The asymmetric unit of 14 exhibits one molecule of the palladium complex and a half molecule of water. The thermal behavior of 7, 8 and 11–14 and their vapor pressure data were investigated to show, if the appropriate complexes are suited as CVD precursors for palladium layer formation. Thermogravimetric studies showed the evaporation of the complexes at atmospheric pressure upon heating. The vapor pressure of 7, 8 and 11–14 was measured by using thermogravimetric analysis, giving vapor pressure values ranging from 0.62 to 2.22 mbar at 80 °C. Chemical vapor deposition studies were carried out applying a vertical cold wall CVD reactor. Either oxygen or forming gas (N2/H2, ratio 90/10, v/v) was used as reactive gas. Substrate temperatures of 350 and 380 °C were utilized. With 11–14 dense and conformal as well as particulate palladium films were obtained, as directed by SEM studies, whereas 7 and 8 failed to give thin films, which is probably attributed to their high thermal stability in the gas phase. For all deposited layers, XPS measurements confirmed the partial oxidation of palladium to palladium(II) oxide at 380 °C, when oxygen was used as reactive gas. In contrast, thin layers of solely metallic palladium were obtained utilizing forming gas during the deposition experiments. / Dieser Beitrag ist aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

<p>Lipids are important cellular biomolecules that perform essential functional and biological roles. For instance, lipids in the cell are the compartmentalizer for the cytoplasm and an energy storage unit. The knowledge surrounding lipids is abundant, yet there is still so much to uncover. There are many categories of lipids and within each category the structural composition is extremely diverse. In turn, the dramatic structural complexity of lipids demands analytical methods capable of providing in-depth structural characterization of individual molecular structures. However, lipid structural elucidation has remained challenging, namely due to the presence of isomeric and isobaric species with a complex mixture. In particular, isomeric/isobaric lipid structures arise from variations in class, headgroup, fatty acyl chain, <i>sn</i>-position, and/or carbon-carbon double bond (C=C) position(s). Recently, recent research suggests C=C composition impacts lipid physical properties, metabolic fate, and intermolecular interactions. Thus, analytical strategies capable of localizing sites of unsaturation are of interest in the lipidomics community.</p> <p>Mass spectrometry (MS) is a leading tool for lipid analysis. Electrospray ionization (ESI), a soft ionization method, is the most commonly used method for lipid ionization as a means of taking the ions from liquid-phase to gas-phase without extensive decomposition of the species. Utilizing ESI-MS, lipids can be identified at a sum compositional level via accurate mass measurements. . With tandem mass spectrometers, lipid ions can be further probed, utilizing tandem-MS (MS/MS) to generate structurally informative product ion spectra that facilitate the assignment of lipid molecular structure. More so, gas-phase ion/ion reactions represent a unique MS-based technique that has improved the analysis of lipids structures. Gas-phase ion/ion reactions allow for lipid species to be charge inverted from one polarity to the opposite polarity. This reaction enables lipids to be ionized in a polarity that is optimal for class identification and further investigated in the opposite polarity where more structural information is obtained. All the information provided is captured without the requirement of multiple solution conditions which is necessary when analyzing in both polarities. In the case of charge inverted lipids from positive ion mode to negative ion mode, fatty acyl composition can be obtained; however, C=C information is lacking.</p> <p>MS can also be paired with other analytically technologies to assist with lipid analysis. One of those technologies is liquid chromatography (LC), which allows for the separation of lipids based on different characteristic depending on the column type being used. Reverse-phase LC (RPLC) allows for the separation of lipid molecular species based on structural composition. RPLC-MS/MS benefits from the ability to separate lipids and determine their fatty acyl chain composition but it is difficult to specify C=C location with the use of a synthetic standard that is identical to each molecular species being analyzed.</p> <p>Commonality between the gas-phase ion/ion reactions for charge inversion of lipids and RPLC-MS/MS approaches is the inability to provide C=C coverage. In-solution and unique ion activation techniques have been developed for seeking such information. The Paternò–Büchi reaction is a UV-initiated [2 + 2]-cycloaddition of an excited carbonyl containing compound onto an olefin group. This reaction can be initiated onto the alkene group within an unsaturated lipid aliphatic chain to form an oxetane ring modification. There are two product ions that can be formed upon each unsaturation site due to a lack of regioselectivity the reagent can attach at either side of the C=C. The modified lipids can be taken into gas-phase and collisionally activated via low-energy collision induced dissociation, generating product ions indictive of C=C position(s). The work herein shows the incorporation of the PB reaction into the gas-phases ion/ion reaction and RPLC-MS/MS apparatuses for C=C localization. The methods have been applied to the lipid extracts of bovine liver and human plasma for confident molecule species determination.</p>

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