Η ορυκτολογική σύσταση του αργιλικού υλικού που χρησιμοποιείται σε ένα χώρο υγειονομικής ταφής απορριμμάτων είναι καθοριστικής σημασίας όσον αφορά την πιθανή διαφυγή και μετανάστευση ρύπων στο περιβάλλον. Ο προσδιορισμός των αργιλικών ορυκτών που συμμετέχουν στο αργιλικό υλικό, θεωρείται βασική παράμετρος όσον αφορά την εκτίμηση της ικανότητας τους για συγκράτηση οργανικών και ανόργανων ρύπων. Για το σκοπό αυτό η αναγνώριση των ορυκτολογικών συστατικών του αργιλικού υλικού που χρησιμοποιήθηκε στο χώρο υγειονομικής ταφής της Ν. Ζακύνθου κρίθηκε απαραίτητη. Από τα αποτελέσματα της περιθλασιμετρίας ακτίνων Χ προέκυψε ότι στο αργιλικό υλικό που χρησιμοποιήθηκε μέσα στο χώρο υγειονομικής ταφής, διακρίθηκε μία ομάδα δειγμάτων πλούσια σε σμεκτίτη (μοντμοριλλονίτη) και μία δεύτερη πλούσια σε χλωρίτη και βερμικουλίτη. Παράλληλα, η χρήση της περιθλασιμετρίας ακτίνων Χ σε συνδυασμό με την ηλεκτρονική μικροσκοπία και τις γεωχημικές αναλύσεις έδωσαν πληροφορίες για την προέλευση των ιζημάτων, καθώς και για τη παρουσία ρύπων και τον τρόπο συγκράτησης τους στις ορυκτές φάσεις που τα απαρτίζουν. Η μελέτη των φασμάτων NMR στα εκχυλίσματα των δειγμάτων έδειξε την ύπαρξη κορυφών απορροφήσεως από πρωτόνια που σχετίζονται με ομάδες πολυσακχαριτών, πεπτιδίων/πρωτεϊνών, αλκοολών, αμινοξέων, ομάδων που περιέχουν –Cl, σουλφιδίων και μεθυλενίων –CH2– παρακείμενων σε ομάδες αιθέρων ή και εστέρων τα οποία παράγονται ως αποτέλεσμα υδρόλυσης και αναερόβιας ζύμωσης στα διαλύματα στραγγισμάτων. Επιπλέον, οι μικροαναλύσεις έδειξαν την παρουσία χλωρίου και θείου σε κρυστάλλους απατίτη, καθώς και χλωρίου, θείου και φωσφόρου σε αργιλικά ορυκτά στα δείγματα που βρίσκονταν σε επαφή με στραγγίσματα, ενισχύοντας την άποψη ότι οι παραπάνω ομάδες προέρχονται από την αλληλεπίδραση με τα στραγγίσματα. Η διαφορετική ορυκτολογική σύσταση του αργιλικού υλικού που χρησιμοποιήθηκε στο χώρο απόθεσης απορριμμάτων (χλωρίτης-μοντμοριλλονίτης) φαίνεται να ευνοεί την εκλεκτική προσρόφηση των διαφορετικών οργανικών ρύπων που συμμετέχουν στα στραγγίσματα και κατά συνέπεια θεωρείται επιθυμητή. Προς την κατεύθυνση αυτή εστιάστηκε το ενδιαφέρον της διατριβής οπότε και προέκυψε ότι ο χλωρίτης παρουσιάζει εκλεκτική προσρόφηση για τις αρωματικές ενώσεις σε αντίθεση με τον μοντμοριλλονίτη, ο οποίος επιδεικνύει εκλεκτική προσρόφηση εκείνων των αλειφατικών ομάδων που εκχυλίζονται από υδατικά διαλύματα. Επιπλέον, οι αρωματικές ενώσεις δεν εκχυλίζονται από υδατικά διαλύματα και κατά συνέπεια από ύδατα επιφανειακών απορροών με αποτέλεσμα να επιδεικνύουν περιορισμένη κινητικότητα. Αντίθετα, οι αλειφατικές ομάδες εκχυλίζονται από υδατικά διαλύματα ενώ η παρουσία τους ευνοεί το σχηματισμό ευδιάλυτων συμπλόκων με μέταλλα, γεγονός που οδηγεί τελικά σε κινητοποίηση τους μέσω των επιφανειακών απορροών. Τέλος, η προσρόφηση αμινομάδων από τα αργιλικά ορυκτά φαίνεται ότι οδηγεί μέσω μιας διαδικασίας φυσικής οργανοφιλίωσης στην μετατροπή των υδρόφιλων επιφανειών των αργιλικών ορυκτών σε υδρόφοβες και κατά συνέπεια την προσρόφηση των υδρόφοβων οργανικών συστατικών που περιέχονται στα διαλύματα στραγγισμάτων. Το γεγονός αυτό είναι ιδιαίτερα σημαντικό εφόσον δείχνει την δυνατότητα για in situ μετατροπή των αργίλων σε οργανόφιλες αργίλους δημιουργώντας νέες προοπτικές στην διαχείριση των μη πολικών οργανικών ρύπων. / The mineralogy of a clay liner used in a landfill may influence the mobility of contaminants. Therefore, the determination of the types of clay minerals that are present in the landfill is of great importance for the assessment of their efficiency in the retention of organic and inorganic pollutants. In the present work, clay materials from an operating waste disposal facility in Zakynthos Island, Western Greece were collected in order to determine the different clay minerals present and their pollutant retention potential. Mineralogical analyses by XRD of the clay material collected from the landfill revealed a smectite (montmorillonite) rich and a chlorite/vermiculite rich material. The information obtained from X-ray Diffraction and SEM-EDS combined with chemical analyses provided valuable information concerning the provenance of the sediments and their retention potential. 1H NMR revealed that some of the organic components which are present in the samples are aliphatics, polysaccharides, alcohols, esters, Cl halogens, sulphides, amines, peptide/protein groups, amide and aromatics which are produced in the landfill as a result of several complex phenomena involving solubilization, hydrolyzation and anaerobic biological processes. SEM-EDS analyses showed the presence of chlorine and sulphur in apatite crystals, and of chlorine, sulphur and phosphorus in clay minerals suggesting the interaction of these minerals with leachate. The different clay mineralogy of the material used in the landfill, smectite (montmorillonite) rich and chlorite/vermiculite rich material facilitated the adsorption of different organic compounds, which is significant for the retention of pollutants. NMR analyses showed that aromatic moieties are preferentially adsorbed on chlorite than on montmorillonite, while those aliphatic moieties that are water soluble are preferentially adsorbed on montmorillonite. Aromatics are not accessible to rainwater and therefore hardly migrate. The aliphatic chains that are water accessible can be released to the environment through natural leaching by rainwater and since they are known to form soluble metal-organic complexes, supervision of the landfill is considered essential. Moreover, the interaction of amine groups with clay minerals in an aqueous system is favoured by the formation of an "insoluble" hydrophobic product leading to the formation of naturally organically modified clays. Thus clays become organophilic and capable of removing non ionic organic contaminants. This is of great importance for environmental applications since it demonstrates the in situ formation of organophilc clays in landfills, hence enabling effective containment and immobilisation of toxic organic compounds.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Changes in land use can take into soil chemical and physical quality degradation. In the hillside areas of the Rio Grande do Sul State (RS) land degradation vulnerability is elevated, due to the combination of a strong undulated to mountainous relief and shallow soils. The general purpose of this study was to evaluate the chemical and physical attributes of soils located in the Sul-riograndense Plateau Border under different land uses. Two representative sites of the Plateau Border, characterized by steep slope areas with prevalence of family farms, were selected (Silveira Martins county (SM) and São João do Polêsine county (SJ)), and also a transition area situated between the Plateau Border and the Medium Plateau (Júlio de Castilhos county (JC)). In SM soil samples were collected in areas of no-tillage (PD), tillage (PC), reforestation (RF) and native forest (MN). In SJ soil samples were collected under native forest (MN), secondary forest (MS), old cropping (LV), new cropping (LN) and abandoned cropping (LA) areas. In JC the samples were collected under native forest (MN), native prairie (CN) and no-tillage (PD) areas. Samples were collected from 0 to 10cm and from 10 to 20cm. Modifications were observed in soil chemical and physical attributes due to the different land uses when compared to the native forest. In systems that do not receive constant external additions, a decrease in soil chemical fertility was observed. Soil organic matter content decreased as the land use intensity increased. C-O-alquyl was the carbon group that presented the largest contribution in the spectra of 13C NMR, independent of the land use system. The main physical alterations observed were the decreases of soil macroporosity, total porosity and saturated hydraulic conductivity and the increase in soil density when compared to soil natural conditions. Soil aggregation parameters did not show to be good indexes to identify changes due to the land use in this study. / As mudanças na utilização das terras podem levar à degradação da qualidade química e física do solo. Nas áreas de encosta do estado do Rio Grande do Sul (RS) a vulnerabilidade à degradação das terras é elevada, devido a combinação de relevo forte ondulado a montanhoso e solos com pequena profundidade efetiva. O objetivo geral deste trabalho foi avaliar as características químicas e físicas do solo de áreas situadas no Rebordo do Planalto na região central do RS, sob diferentes usos da terra. Para isso foram selecionadas duas áreas representativas da região denominada Rebordo do Planalto, caracterizada por áreas de encosta com predomínio da agricultura familiar em pequena escala (Silveira Martins (SM) e São João do Polêsine (SJ)) e uma área de transição entre o Rebordo do Planalto e o Planalto Médio (Júlio de Castilhos (JC)). Em SM foram coletadas amostras de solo no sistema de plantio direto (PD), plantio convencional (PC), reflorestamento (RF) e mata nativa (MN). Em SJ foram coletadas amostras de solo sob os usos na mata nativa (MN), mata secundária (MS), lavoura velha (LV), lavoura nova (LN) e lavoura abandonada (LA). Em JC as amostras foram coletadas em áreas de mata nativa (MN), campo nativo (CN) e plantio direto (PD). As amostras foram coletadas na profundidade de 0-10 e 10-20 cm. Através dos resultados obtidos, observaram-se modificações nas características químicas e físicas do solo em função dos diferentes usos da terra, ao comparar com a mata nativa. Em sistemas que não recebem adições constantes de fontes externas, ocorreu uma depressão da fertilidade química. A matéria orgânica do solo teve diminuição nos teores, conforme aumentou a intensidade de uso da terra. O grupo C-O-alquil foi o grupo de carbono que apresentou a maior contribuição nos espectros de RMN 13C, independente do sistema de uso da terra. As principais alterações físicas ocorridas em comparação com as condições naturais do solo, foram diminuições da macroporosidade, porosidade total e condutividade hidráulica saturada e aumento na densidade do solo. Os parâmetros de agregação do solo, neste trabalho, não se mostraram como bons índices de avaliação para identificar mudanças em função dos diferentes usos da terra.

Die vorliegende Arbeit befasst sich mit der Synthese, Stabilität und Reaktivität von Hydridochlorosilan-Pyridin-Addukten (RHSiCl2, RSiCl3, SiCl4; mit R=H, Me und Ph). Hydridochlorosilane, die zu den wichtigsten industriell verwendeten Siliciumverbindungen gehören, bilden in unpolaren Lösungsmitteln durch Umsetzung mit Pyridinbasen stabile Hydridochlorosilan-Pyridin-Addukte in sehr hohen Reinheiten und Ausbeuten. Neben diesen Komplexierungsreaktionen werden auch Dismutations-, Dissoziations- und Hydrosilylierungsreaktionen genauer untersucht. Die Charakterisierung der Produkte erfolgte durch Lösungs- bzw. Festkörper-NMR- und Raman-Spektroskopie, Röntgendiffraktometrie sowie Elementaranalyse, sie wurde in ausgewählten Fällen durch DFT-Rechnungen unterstützt. Durch Variation sowohl des Silicium- als auch des Liganden-Substituentenmusters wurden Rückschlüsse auf die Stabilität und Reaktivität der Addukte erhalten. Die erzielten Ergebnisse vertiefen das Verständnis von Prozessabläufen zur Dismutation von Hydridochlorosilanen und ermöglichen eine bessere Kontrolle und Steuerung dieser Reaktionen. Weiterhin erlauben die Addukte selektive Syntheserouten zu zahlreichen Derivaten, wie z.B. Dialkoxysilane, Diaminosilane, Cyclosiloxane, oder Hydrosilylierungsprodukte mit aktivierten Alkenen ohne Einsatz von Metallkatalysatoren.

No description available.

The research work reported in this thesis is focused on the chiral analysis, quantification of enantiomeric composition, assignment of absolute configuration of molecules with chosen functional groups. The weak intra-molecular hydrogen bonding interactions are detected by exploiting several multinuclear and multi-dimensional techniques. Pulse sequences have been designed to manipulate the spin dynamics to derive specific information from the complex NMR spectra encountered in diverse situations. Broadly, the thesis can be classified in to three sections. The section I containing two chapters reports the introduction of new chiral auxiliaries and protocols developed for enantiomeric discrimination, measurement of enantiomeric contents, assignment of absolute configuration for molecules possessing specific functional groups using chiral solvating and derivatizing agents. The section II, reports NMR experimental evidence for the observation of the rare type of intramolecular hydrogen bonds involving organic fluorine in biologically important organic molecules, that are corroborated by extensive DFT based theoretical calculations. The section II also discusses the H/D exchange mechanism as a tool for quantification of HB strengths in organic building blocks. The section III reports the two different novel NMR methodologies designed for deriving information on the scalar interaction strengths in an orchestrated manner. The designed sequences are able to completely eradicate the axial peaks, prevents the evolution of unwanted couplings and also yields ultrahigh resolution in the direct dimension, permitting the accurate measurement of scalar couplings for a particular spin. The brief summary about each chapter is given below. Chapter 1 provides a general introduction to one and two dimensional NMR spectroscopy. The pedagogical approach has been followed to discuss the conceptual understanding of spin physics and the NMR spectral parameters. The basic introduction to chirality, existing approaches in the literature for discrimination of enantiomers and the assignment of absolute configuration of molecules with chosen functional groups and their limitations are briefly discussed. The brief introduction to hydrogen bond, experimental methods to obtain the qualitative information about the strengths of hydrogen bonds, and the theoretical approaches employed in the thesis to corroborate the NMR experimental findings have been provided. The mechanism of H/D exchange, the utilization of exchange rates to derive strengths of intra-molecular hydrogen bond in small molecules have also been discussed. This chapter builds the bridge for the rest of the chapters. Each of these topics are discussed at length in the corresponding chapters. Part I: NMR Chiral Analysis: Novel Protocols Chapter 2 discusses a simple mix and shake method for testing the enantiopurity of primary, secondary and tertiary chiral amines and their derivatives, amino alcohols. The protocol involves the in-situ formation of chiral ammonium borate salt from a mixture of C2 symmetric chiral BINOL, trialkoxyborane and chiral amines. The proposed concept has been convincingly demonstrated for the visualization of enantiomers of a large number of chiral and pro-chiral amines and amino alcohols. The protocol also permits the precise measurement of enantiomeric composition. The significant advantage of the protocol is that it can be performed directly in the NMR tube, without any physical purification. The structure of the borate complex responsible for the enantiodifferentiation of amines has also been established by employing multinuclear NMR techniques and DFT calculations. From DOSY and 11B NMR experiments it has been ascertained that there are only two possible complexes or entities which are responsible for differentiating enantiomers. From the combined utility of DFT calculations and the 11B NMR chemical shifts, the structure of the borate complex has been determined to be an amine-coordinated complex with the N atom of the amine. Chapter 3 discusses a simple chiral derivatizing protocol involving the coupling of 2-formylphenylboronic acid and an optically pure [1,1-binaphthalene]-2,2-diamine for the rapid and accurate determination of the enantiopurity of hydroxy acids and their derivatives, possessing one or two optically active centres. It is established that this protocol is not only rapid method for discrimination of enantiomers but also highly effective for assigning the absolute configuration of various chiral hydroxy acids and their derivatives. The developed protocol involves the coupling of 2-formylphenylboronic acid with (R)-[1,1-binaphthalene]-2,2-diamine, and 2-formylphenylboronic acid with (S)-[1,1-binaphthalene]-2,2-diamine as chiral derivatizing agents. The absence of aliphatic peaks from the derivatizing agent, large chemical shift separation between the discriminated peaks of diastereomers, and the systematic change in the direction of displacement of peaks for an enantiomer in a particular diastereomeric complex, permitted the unambiguous assignment of absolute configuration. Part II : Rare Type of Intramolecular Hydrogen Bonding In chapter 4 The rare occurrence of intramolecular hydrogen bonds of the type N–H˖˖˖F–C, in the derivatives of imides and hydrazides in a low polarity solvent, is convincingly established by employing multi-dimensional and multinuclear solution state NMR experiments. The observation of 1hJFH, 2hJFN, and 2hJFF of significant strengths, where the spin polarization is transmitted through space among the interacting NMR active nuclei, provided strong and conclusive evidence for the existence of intra-molecular hydrogen bonds. Solvent induced perturbations and the variable temperature NMR experiments unambiguously supported the presence of intramolecular hydrogen bond. The two dimensional HOESY and 15N–1H HSQC experiments reveals the existence of multiple conformers in some of the investigated molecules. The 1H DOSY experimental results discarded any possibility of self or cross-dimerization of the molecules. The results of DFT based calculations, viz., Quantum Theory of Atoms In Molecules (QTAIM) and Non Covalent Interaction (NCI), are in close agreement with the NMR experimental findings. In chapter 5 the rates of hydrogen/deuterium (H/D) exchange determined by 1H NMR spectra have been utilized to derive the strength of hydrogen bonds and to monitor the electronic effects in the site-specific halogen substituted Benz amides and anilines. The theoretical fitting of the time dependent variation in the integral areas of 1H NMR resonances to the first order decay function permitted the determination of H/D exchange rate constants (k) and their precise half-lives (t1/2) with high degree of reproducibility. The comparative study also permitted the determination of relative strengths of hydrogen bonds and the contribution from electronic effects on the H/D exchange rates. Part III: Novel NMR Methodologies for the Precise Measurement of 1H-1H Couplings Chapter 6 describes two novel NMR methodologies developed for the precise measurement of 1H-1H couplings. Poor chemical shift dispersion and the pairwise interaction among the entire coupled network of protons results in the severely complex and overcrowded one dimensional 1H NMR spectra, hampering both the resonance assignments and the accurate determination of nJHH. The available two-dimensional selective refocusing (SERF) based experiments suffer from the evolution of magnetization from uncoupled protons as intense uninformative axial peaks. This creates ambiguity in the identification of peaks belonging to the coupled partners of a selectively excited proton, hindering the extraction of their interaction strengths. This challenge has been circumvented by designing two novel experimental technique, cited as “Clean-G-SERF” and “PS-Clean-G-SERF”. The Clean-G-SERF technique completely eradicates the axial peaks and suppresses the evolution of unwanted couplings while retaining only the couplings to the selectively excited proton. The method permits the accurate determination of spin-spin couplings even from a complex proton NMR spectrum in an orchestrated manner. The PS-Clean-G-SERF technique has been designed for the complete elimination of axial peaks and undesired couplings, with a blend of ultra-high resolution achieved by real time broad band mononuclear decoupling has been discussed in this chapter. The spin dynamics involved in both these pulse sequences have been discussed. The diverse applications of both these novel experiments have been demonstrated.

La SRM proton constitue un outil non invasif unique pour l'exploration biochimique quantitative des tissus vivants. Les deux études présentées dans cette thèse visent à maîtriser chacune des phases impliquées depuis l’acquisition des données jusqu’à l’estimation fiable et précise des profils métaboliques des tissus explorés. Des protocoles expérimentaux d’acquisition des signaux de spectrométrie de résonance magnétique proton in vivo à temps d’écho courts ont été définis puis optimisés pour une application pré-clinique (souris) sur un imageur 4.7T et pour une étude en environnement clinique menée à 1.5T. La première étude a permis de mesurer longitudinalement les altérations des métabolites cérébraux (N-acétyl-aspartate, choline, créatine, taurine) chez un modèle murin de neuro-inflammation sur un imageur 4.7T, et la seconde étude avait pour objectif la mesure de la quantité totale et la composition lipidique hépatique en environnement clinique à 1.5T chez des sujets stéatosiques. Des méthodes d’estimation des contributions métaboliques et lipidiques adaptées aux propriétés physiques de signaux ont été validées pour chacune de ces applications. Ces méthodes sont fondées sur des algorithmes de moindres carrés non linéaires. Des stratégies multi-tirages des valeurs initiales et des contraintes ont été favorablement validées. Les atouts et les originalités de ce projet reposent sur les développements synergiques des protocoles d’acquisitions et des méthodes de traitement du signal associées. Ces développements ont pour vocation d’enrichir la palette des informations biochimiques collectées pour l’aide au pronostic et diagnostic médical / The proton MRS is a unique non-invasive method to quantitative biochemical exploration of living tissues. The studies presented in this thesis aim to handle each one of the involved steps, from data acquisition to reliable and precise metabolic profile estimation of explored tissues. Protocols for experimental acquisition of in vivo, short echo-time magnetic resonance signals were defined, and optimized for a pre-clinical application (mice) on a 4.7T scanner and for a clinical study at 1.5T. The first study allowed yo measuring cerebral metabolite (N-acetyl-aspartate, choline, creatine, taurine) alterations along time in a murine model of neuro-inflammation on a 4.7T scanner and the second study aimed to measure the total quantity and the composition of liver fat in patients with hepatic steatosis in a clinical environment at 1.5T. Signal processing methods for metabolite and fat contribution estimates, coping with physical signal properties were validated for both studies. These methods are based on non-linear least squares algorithms. Multiple starting values and constraints strategies were successfully validated. The assets and the originality of this project are based on the synergic developments of acquisition protocols and the associated signal processing methods. These developments were designed to enrich the list of the biochemical information non-invasively measured, in order to help medical prognostic and diagnostic

La capacité à déterminer les structures moléculaires en trois dimensions à partir de monocristaux par des méthodes de diffraction a transformé la chimie des matériaux. Le problème de la détermination de structure est en grande partie non résolu, en particulier si le système étudié est situé à une surface et n'a pas de périodicité, comme dans la plupart des matériaux fonctionnels actuels. La Résonance Magnétique Nucléaire (RMN) à l’état solide serait une méthode de choix pour caractériser les surfaces mais la limite de détection de la RMN est beaucoup trop faible pour permettre à la RMN de caractériser les surfaces. L’introduction récente d’une nouvelle approche utilisant la Polarisation Dynamique Nucléaire (DNP) pour améliorer la sensibilité de la RMN des surfaces (DNP SENS) permet à présent de réaliser des expériences qui étaient totalement impossible il y a quelques années encore. Plus particulièrement, grâce à la méthode DNP SENS, les présents travaux de thèse aboutissent à la première structure tridimensionnelle d’un complexe organométallique supporté sur silice, avec une précision de 0,7 Å. De nombreux aspects de l’expérience DNP SENS ont été exploré. Le transport de de l’hyperpolarisation par diffusion de spin est primordial et un modèle numérique dans les matériaux mésoporeux a été développé. De plus, une nouvelle matrice aqueuse se basant sur des gels polyacrylamides a été mise au point et utilisée pour la caractérisation par RMN de nanoparticules permettant ainsi d’étendre les domaines d’application de DNP SENS. Enfin les premières expériences RMN DNP combinant hauts champs magnétiques et haute fréquence de rotation d’échantillon sont présentées. / The ability to understand the properties of chemical systems relies on their detailed description at the molecular level. Over the last century, several methods based on X-ray diffraction have allowed a structure-based understanding of many materials. However, several key questions often remain unanswered. In particular when the system under investigation is located on a surface. Although an extensive range of surface-sensitive methods are available for surface science and give valuable information, they only lead to a partial understanding of surfaces at the molecular level. Moreover, these methods are not compatible with all kinds of materials and usually require the use of a model and pristine surface. Solid-State NMR would be a method of choice to characterize surfaces. However, the approach suffers from its intrinsically low sensitivity and this is strongly emphasize in the case of surfaces where the atoms of interest are diluted in the matrix. Dynamic Nuclear Polarization (DNP) applied to surfaces (SENS) recently emerged as a very promising method to characterize surface sites. It offers a dramatic enhancement of NMR sensitivity and DNP applied to materials has led to many examples in the last ten years. In the present thesis, I have shown that DNP SENS, in combination with EXAFS, allowed the detailed 3D structure determination of the silica-supported organometallic complex determined with a precision of 0.7 angstroms. In parallel, some experimental aspect of DNP SENS have been explored. A spin diffusion has been developed to understand diffusion of hyperpolarization in porous media. A new aqueous DNP matrix, coined DNP Jelly, has been developed to characterize nanoparticles and thus expanding experimental range of DNP SENS. Finally, the first experiment of DNP NMR at fast magic angle spinning (up to 40 kHz) and high field are reported.

NMR spectroscopy is a very powerful technique for the characterization of structure and dynamics of a variety of systems starting from small organic molecules to large biological macromolecules. In solids, the study of protons becomes more interesting because they are very sensitive to inter-molecular packing and are directly involved in hydrogen-bonding and aromatic π-π interactions, etc. The present thesis is devoted essentially to utilizing information from proton resonances obtained using multinuclear and multiple-quantum approaches. The thesis has two parts. The first part deals with methodological developments in the area of solid-state NMR, relevant to the study of rigid powder samples as well as partially ordered liquid crystalline materials. Methods have been proposed to investigate the structure of small molecules at moderate spinning frequencies and thermotropic liquid crystals at static conditions. Proton detected heteronuclear experimental methods based on both first and second-order cross polarization at moderate and ultra-fast magic angle spinning rates are also proposed. The second part of the thesis deals with the application of both newly proposed and existing solid state NMR methods to the study of several biologically relevant systems. These include the study of several designed as well as naturally occurring peptides. The use of first-principles calculations based on GIPAW method for supporting the experimentally obtained results has also been made. The thesis is divided into five chapters. In the second chapter, a new pulse sequence to correlate Double Quantum (DQ) proton frequencies to carbon Single Quantum (SQ) chemical shifts in the solid state has been proposed. In this sequence, named as MAS-J-1H (DQ)-13C-HMQC, the correlation between 1H and 13C is achieved through scalar coupling, while the double-quantum coherence among protons is generated through dipolar couplings. This experiment is particularly suited for the study of 13C in natural abundance. The advantages of the technique with applications to alanine, histidine and a model liquid crystalline material have been demonstrated. The assignment of 13C spectra of partially ordered systems has also been considered. In this case the assignment of the spectrum is a major challenge due to the interplay of anisotropic order and chemical shift parameters. The DQ-SQ correlation experiment described in the thesis has been applied to a well known liquid crystal and also to a novel thiophene based liquid crystal and the local order parameters of the liquid-crystal have been obtained. The thesis also presents results on the azelaic acid -isonicotinamide co-crystal as well as the drug ibuprofen obtained by using novel methodologies. In the case of the former, the problem of overlap of resonances was overcome with the use of the REVERSE-CP approach to separate out the carbon attached protons from the rest of the protons. Subsequently, by the use of several combined approaches, the structural features were identified. A new heteronuclear correlation pulse sequence for solids under fast MAS conditions has also been tested. With low r.f powers, a second-order dipolar term mediated transfer of magnetization between I and S spin known as second order cross-polarization (SOCP) was exploited to obtain the entire spin system connectivity. Both carbon detected and proton detected experiments have been carried out and their utility evaluated. Similar approaches to shed light on the structure and conformation of a set of proline and pseudoproline based designed β-turn peptides that are used as templates for understanding protein folding have been made. Results of studies on two biologically important forms of the short-chain peptides namely glutathione reduced (GSH) and oxidized (GSSG) tripeptides are also presented.

Current fossil fuels (Coal and Petroleum) based economy is not sustainable in the long run because of its dwindling resources, and increasing concerns of climate change due to excessive carbon dioxide (CO2) emission. To mitigate CO2 emission and climate change, scientists across the world have been looking for clean and sustainable energy sources. Among them hydrogen gas (H2) could be more promising because it is the most clean fuel and can be produced from cheap source (water) which is renewable and abundant. Nevertheless, the bottleneck for hydrogen economy is lying in the cost of hydrogen production from water. Still there are no any efficient systems developed which can deliver hydrogen from water in economically viable way. Meanwhile, recent research on old molecule ammonia-borane (H3N•BH3, AB) as hydrogen source has increased the hope towards the hydrogen economy, however, catalytic recycling (or efficient regeneration) of AB from the dehydrogenated product polyborazylene (PB or BNHx) is the biggest hurdle which prevents use of AB as practical hydrogen storage material. Therefore, it is imperative to understand the dehydrogenation pathways of ammonia-borane (or related amine-boranes) which lead to polymeric or oligomeric product(s). On the other hand, methane (CH4) is abundant (mostly untamed) but cleaner fuel than its higher hydrocarbon analogs. To develop highly efficient catalytic systems to transform CH4 into methanol (gas to liquid) is of paramount importance in the field of catalysis and it could revolutionize the petrochemical industry. Therefore, to activate CH4, it is crucial to understand its binding interaction with metal center of a molecular catalyst under homogenous condition. However, these interactions are too weak and hence σ–methane complexes are very elusive. In this context, σ-H2 and σ-borane complexes bear some similarities in σ-bond coordination (and four coordinated boranes are isoelectronic with methane) could be considered as good models to study σ-methane complexes. Studying the H−H and B−H bond activation in H2 and amine-boranes, respectively, would provide fundamental insights into methane activation and its subsequent functionalization. Moreover, the proposed methanol economy by Nobel laureate George Olah seems more promising because methanol can be produced from CH4 (CO2 as well). This in turn will gradually reduce the amount of two powerful greenhouse gases from the earth’s atmosphere. Thus, efficient and economic production of methanol from CH4 and CO2 is one of most challenging problems of today in the field of catalysis and regarded as the holy grails. Furthermore, very recently formic acid (HCOOH) is envisaged as a promising reversible hydrogen storage material because it releases H2 and CO2 in the presence of a suitable and efficient catalyst or vice versa under ambient conditions. Objective of the research work: Taking the account of the above facts, the research work in this thesis is mostly confined to utilize electrophilic Ru(II)-complexes for activation of small molecules such as ammonia-borane (H3N•BH3) [and related amine-borane (Me2HN•BH3)], hydrogen (H2), methane (CH4), formic acid (HCOOH) and carbon dioxide (CO2) and investigation of their mechanistic pathways using NMR spectroscopy under homogeneous conditions. Though these molecules are small, they have huge impacts on chemical industries (energy sector and chemical synthesis: drugs/natural products) and environment [CO2 and CH4 are potent green house gases] as well. However, they are relatively inert molecules, especially CH4 and CO2, and impose very tough challenges to activate and functionalize them into useful products under ambient conditions. The partial oxidation of the strong C−H bond in CH4 for its transformation into methanol under relatively mild condition using an organometallic catalyst is considered as a holy grail in the field of catalysis which is mentioned earlier. More importantly, to develop better and highly efficient homogeneous catalytic systems for the activation of these molecules, it is imperative to understand the mechanistic pathways using well defined homogeneous metal complexes. Thus, an understanding of the interaction of these inert molecules with metal center is obligatory. In this context, discovery of a σ-complex of H2 gave remarkable insights into H−H bond activation pathways and its implications in catalytic hydrogenation reactions. Subsequently, σ-borane complexes of amine-boranes were discovered and found to be relatively more stable because of stronger M−H−B interaction and hence act as good models to study the M−H−C interaction of elusive σ-methane complex. On the other hand, HCOOH, a promising hydrogen storage material and its efficient catalytic dehydrogenation/decarboxylation and CO2 hydrogenation back to HCOOH using well defined homogeneous catalysts could lead to a sustainable energy cycle. Therefore, it is quite significant to understand the mechanistic pathways of formic acid dehydrogenation/decarboxylation and carbon dioxide reduction to formic acid for the development of next generation efficient catalysts. Chapter highlights: Keeping all these in view, we carried out thorough studies on the activation of these small molecules by electrophilic Ru(II)-complexes. This thesis provides useful insights and perspective on the detailed investigation of mechanistic pathways for the activation of small molecules such as H3N•BH3 [and Me2HN•BH3], H2, CH4, HCOOH and CO2 using electrophilic Ru(II)-complexes under homogeneous conditions using NMR spectroscopy. In Chapter 1 we provide brief overview of small molecule activation using organometallic complexes. This chapter presents pertinent and latest results from literature on the significance of small molecule activation. Although there are several small molecules which need our attention, however, we have focused mainly on H3N•BH3 [and Me2HN•BH3], H2, CH4, HCOOH and CO2. In Chapter 2, we present detailed investigation of mechanistic pathways of B−H bond activation of H3N•BH3 and Me2HN•BH3 using electrophilic [RuCl(dppe)2][OTf] complex using NMR spectroscopy as a model for methane activation. In these reactions, using variable temperature (VT) 1H, 31P{1H} and 11B NMR spectroscopy we detected several intermediates en route to the final products at room temperature including a σ-borane complex. On the basis of elaborative studies using NMR spectroscopy, we have established the complete mechanistic pathways for dehydrogenation of H3N•BH3/Me2HN•BH3 and formation of B−H bond activated/cleaved products along with several Ru-hydride and Ru-(dihydrogen) complexes. Keeping the B−H bond activation of amine-boranes in view as a model for methane activation, we attempted to activate methane using [RuCl(dppe)2][OTf] complex. In addition, [Ru(OTf)(dppe)2][OTf] complex having better electrophilicity than [RuCl(dppe)2][OTf], was synthesized and characterized. The [Ru(OTf)(dppe)2][OTf] complex has highly labile triflate bound to Ru-metal and therefore its reactivity studies toward H2 and CH4 were carried out where H2 activation was successfully achieved, however, no any spectroscopic evidence was found for C−H bond activation of CH4. The Chapter 3 describes the synthesis and characterization of several Ru-Me complexes such as trans-[Ru(Me)Cl(dppe)2], [Ru(Me)(dppe)2][OTf], trans-[Ru(Me)(L)(dppe)2][OTf] (L = CH3CN, tBuNC, tBuCN, H2) with an aim to trap corresponding σ-methane intermediate at low temperature. However, interestingly, we observed spontaneous but gradual methane elimination and orthometalation of [Ru(Me)(dppe)2][OTf] complex at room temperature. We thoroughly investigated mechanistic details of methane elimination and orthometalation of [Ru(Me)(dppe)2][OTf] using VT NMR spectroscopy, NOESY and DFT calculations. Furthermore, H2 activation was confirmed unambiguously by [Ru(Me)(dppe)2][OTf] and Ru-orthometalated complexes using NMR spectroscopy under ambient conditions. An effort was also made to activate methane using Ruorthometalated complex in pressurized condition of methane in a pressure stable NMR tube. Moreover, preliminary studies on protonation reaction of [Ru(Me)(dppe)2][OTf] using VT NMR spectroscopy to trap σ-methane at low temperature was carried out which provided us some useful information on dynamics between proton and Ru-Me species. The Chapter 4 provides useful insights into the mechanistic pathways of dehydrogenation/decarboxylation of formic acid using [RuCl(dppe)2][OTf]. Catalytic dehydrogenation of HCOOH using [RuCl(dppe)2][OTf] was observed in presence of Hunig base (proton sponge). In addition, a complex [Ru(CF3COO)(dppe)2][OTf] was synthesized and characterized using NMR spectroscopy, and found to readily dehydrogenate HCOOH. Moreover, preliminary results on transfer hydrogenation of CO2 into formamide using [RuCl(dppe)2][OTf] as a precatalyst and tert-butyl amine-borane (tBuH2N•BH3) as secondary hydrogen source was confirmed using 13C NMR spectroscopy. The mechanisms were proposed for HCOOH dehydrogenation and transfer hydrogenation of CO2 based on our NMR spectroscopic studies. Furthermore, a few test reactions of transfer hydrogenation of selected alkenes such as cyclooctene, acrylonitrile, 1-hexene using [RuCl(dppe)2][OTf] as pre-catalyst and tert-butyl amine-borane (tBuH2N•BH3) as secondary hydrogen source showed quantitative conversion to hydrogenated products.

My thesis is divided into five chapters, starting with a general introduction in first chapter and sample preparation and protein-NMR assignment techniques in second chapter. The remaining three chapters focus on three different areas/projects that I have worked on. Chapter 1: Introduction to nanomaterials and all the experimental techniques This chapter reviews different kinds of nanomaterials and their application utilized for protein-nanomaterial interaction in our study, along with the introduction to different spectroscopy and microscopy techniques used for the interaction studies. Starting with introduction of nanomaterials and all the experimental techniques, which constitute the arsenal for structural studies of the protein-nanomaterial interaction, different steps enroute to structural and dynamic interaction are outlined in detail. Chapter 2: Preparation and Characterization of Proteins used for nanomaterial interaction studies Proteins are generally of three kinds- globular (structured), intrinsically disordered and membrane bound. These proteins have different functions in living organisms and play a major role to maintain metabolism and other important factors. To probe protein-nanomaterial interactions, we have chosen different protein/peptides. This chapter describes the protocol/procedure used for purifying the proteins. For studying a globular protein, ubiquitin was chosen. Nanomaterial-IDP interaction was investigated using the intrinsically disordered central linker domain of human insulin like growth factor binding protein-2 (L-hIGFBP2). The hydrophobic membrane interacting part of the prion protein was chosen as a representative membrane protein. The characterization of the proteins by NMR spectroscopy is also described. Chapter 3: A nanomaterial based novel macromolecular crowding agent Carbon quantum dots (CQD) are nanomaterials with size less than 10 nm, first obtained in 2004 during purification of single-walled carbon-nanotubes. Since then CQDs have been used in a wide range of applications due to their low cost of preparation and favorable properties such as chemical inertness, biocompatibility, non-toxicity and solubility in aqueous medium. One of the applications of CQDs has been their use for imaging and tracking proteins inside cells, based on their intrinsic fluorescence. Further, quantum dots exhibit concentration dependent aggregation while retaining their solubility. Fluorescent carbon quantum dots (CQD) induce macromolecular crowding making them suitable for probing the structure, function and dynamics of both hydrophilic and hydrophobic peptides/ proteins under near in-cell conditions. We have prepared hydrophilic and hydrophobic quantum dots to see the crowding effect. After characterization of CQD, we tested the property of proteins with CQD and found that CQD behaves as a macromolecular crowding agent by mimicking near in-cell conditions. In our study, we have chosen a globular protein, an intrinsically disordered protein (IDP) and one hydrophobic membrane peptide. We have also compared the crowding property of CQD with ficoll which is widely used commercial crowding agent. The overall study tells that the CQD acts like crowding agent and can be used for the study of macromolecular crowding effect. This makes them suitable for structural and functional studies of proteins in near in-cell conditions. Chapter 4: Ubiquitin-Graphene oxide interactions Described here is the interaction of human ubiquitin with GO using NMR spectroscopy and other techniques such as Fluorescence spectroscopy, isothermal titration calorimetry (ITC), UV-Visible spectroscopy, dynamic light scattering (DLS), zeta potential measurements and transmission electron microscopy (TEM). The globular protein ubiquitin interacts with GO and undergoes a dynamic and reversible association-dissociation in a fast exchange regimen as revealed by NMR spectroscopy. The conformation of the protein is not affected and the primary interaction is seen to be electrostatic in nature due to the polar functional groups present on the protein and GO sheet surface. For the first time we have shown that the interaction between ubiquitin and GO is dynamic in nature with fast and reversible adsorption/desorption of protein from the surface of GO. This insight will help in understanding the mechanistic aspects of interaction of GO with cellular proteins and will help in designing appropriate functionalized graphene oxide for its biological application. Chapter 5: Section A: Interaction of an intrinsically disordered protein (L-HIGFBP2) with graphene oxide The interaction between intrinsically disordered linker domain of human insulin-like growth factor binding protein-2 (L-hIGFBP2) with GO was studied using NMR spectroscopy and other techniques such as isothermal titration calorimetry (ITC), dynamic light scattering (DLS), zeta-potential measurements. The study revealed that the disordered protein L-hIGFBP2 interacts with GO through electrostatic interaction and undergoes a dynamic and reversible association-dissociation in a fast exchange regime. The conformation of the protein is not affected. Section B: Stability of an Intrinsically disordered protein through weak interaction with Silver nanoparticles Using NMR spectroscopy and other techniques we probed the mechanism of L-hIGFBP2–AgNP interactions which render the IDP stable. The study reveals a mechanism which involves a relatively fast and reversible association–dissociation of L-hIGFBP2 (dynamic exchange) from the surface of AgNP. The AgNP–L-hIGFBP2 complex remains stable for more than a month. The techniques employed in addition to NMR include UV-Visible spectroscopy, dynamic light scattering (DLS), zeta potential measurements and transmission electron microscopy (TEM) to probe the protein-AgNP interaction here in this section.