Le développement de l’hydrogène en tant que nouveau vecteur d’énergie demande de pouvoir le stocker à grande échelle, dans des conditions d’encombrement, de coût énergétique et de sécurité acceptables. Le stockage sous forme solide dans des hydrures métalliques réversibles, constitue une solution particulièrement sûre et intéressante pour des applications dans le secteur des transports. Parmi de nombreux matériaux possibles, le système Mg/MgH2, constitue l’un des meilleurs candidats : abondant, bon marché, capacité de stockage réversible et élevée (7,6 % H2 en masse). Son utilisation à l’échelle industrielle est néanmoins limitée par les cinétiques de sorption très lentes et la stabilité thermodynamique importante (enthalpie de formation élevée) nécessitant des températures de fonctionnement supérieure à 300 °C. Ce projet vise au développement de composites à base de MgH2 et d’additifs avec des propriétés de stockage améliorées. L’originalité des travaux menés repose sur le type d’additifs choisi, les complexes de métaux de transition (centre métallique : Ni et Ru, ligands organiques : phosphines). En effet, ces derniers ne sont pour le moment que très peu utilisés dans la littérature. L’objectif de ce travail de thèse est donc d’explorer leur potentiel et leur efficacité pour améliorer les propriétés de stockage du système Mg/MgH2. Différents composites "MgH2 + complexe" ont été préparés par broyage et imprégnation et les cinétiques de sorption des systèmes obtenus ainsi que leurs paramètres thermodynamiques ont été déterminés par analyse thermique (DTP, DSC, PCT). Enfin, de nombreuses techniques de caractérisation physico-chimiques (DRX, RMN, XPS, MEB, MET) ont été utilisées afin de comprendre les phénomènes se déroulant lors de l’hydrogénation et la déshydrogénation des composites préparés. Le meilleur système « MgH2 + complexe » préparé durant ce travail (MgH2 dopé avec 20 % du complexe NiHCl(PCy3)2) est capable d’absorber 6 % en masse d’H2 à 100 °C en 30 min et de libérer son hydrogène sous vide à 200 °C. Les énergies d’activation apparentes et enthalpies de formation de ce composite sont respectivement de 22 et –65 kJ/mol H2 pour l’hydrogénation (contre 200 et –74,7 kJ/mol H2 pour du Mg commercial) et de 127 et 63 kJ/mol H2 pour la déshydrogénation (contre 239 et 74,7 kJ/mol H2 pour du MgH2 commercial) / Although hydrogen is widely recognized as a promising energy carrier, its widespread adoption as alternative to fossil fuels depends critically on the ability to store hydrogen at adequate densities, cost and security. Application devices are far from a valuable technology, and fundamental research is still required. In this regard, solid-state systems present the advantage of denser and safer hydrogen storage. Among them, Mg/MgH2 is considered as a highly promising material in terms of reversibility, cost, gravimetric and volumetric capacity. However, high thermodynamic stability (high formation enthalpy) and slow hydrogen sorption kinetics limits its practical applications.This project aims to develop Mg/MgH2-based systems with improved hydrogen storage properties thanks to the use of additives. The originality of this work is brought by the kind of additive chosen, transition metal complexes (Ni and Ru based, with phosphine ligands). Indeed, they are, for now, only very little used in the literature. The objective of this work is therefore to study their potential and their efficiency to improve the hydrogen storage properties of the Mg/MgH2 system. Different “MgH2 + complex” composites were prepared by ball milling and impregnation method and the sorption kinetics and thermodynamic parameters of the formed systems were studied by TPD, DSC and PCT analyses. Finally, XRD, NMR, XPS, SEM and TEM techniques were used to understand the phenomena taking place during the hydrogenation and the dehydrogenation of the prepared composites.The best “MgH2 + complex” system prepared during this work (MgH2 doped with 20 wt% of NiHCl(PCy3)2 complex) is able to absorb 6 wt% of H2 at 100 °C in 30 min, and to release the stored hydrogen at 200 °C under vacuum. The apparent activation energies and the formation enthalpies of the composite are respectively of 22 and –65 kJ/mol H2 for the hydrogenation reaction (against 200 and –74,7 kJ/mol H2 for commercial Mg) and of 127 and 63 kJ/mol H2 for dehydrogenation (against 239 and 74,7 kJ/mol H2 for commercial MgH2).

This research focused on the development of new metal triimine complexes of Pt(II), Pd(II), and Ni(II) for use in three types of molecular electronic devices: dye sensitized solar cells (DSSCs), organic light-emitting diodes (OLEDs), and organic field effect transistors (OFETs). Inorganic complexes combine many advantages of their chemical and photophysical properties and are processable on inexpensive and large area substrates for various optoelectronic applications. For DSSCs, a series of platinum (II) triimine complexes were synthesized and evaluated as dyes for nanocrystalline oxide semiconductors. Pt (II) forms four coordinate square planar complexes with various co-ligands and counterions and leads to spanning absorption across a wide range in the UV-Vis-NIR regions. When those compounds were applied to the oxide semiconductors, they led to photocurrent generation thus verifying the concept of their utility in solar cells. In the OLEDs project, a novel pyridyl-triazolate Pt(II) complex, Pt(ptp)2 was synthesized and generated breakthrough OLEDs. In the solution state, the electronic absorption and emission of the square planar structure results in metal-to-ligand charge transfer (MLCT) and an aggregation band. Tunable photoluminescence and electroluminescence colors from blue to red wavelengths have been attained upon using Pt(ptp)2 under different experimental conditions and OLED architectures. In taking advantage of these binary characteristics for both monomer and excimer emissions, cool and warm white OLEDs suitable for solid-state lighting have been fabricated. The OFETs project represented an extension of the study of pyridyl-triazolate d8 metal complexes due to their electron-transporting behavior and n-type properties. A prescreening step by using thermogravimetric calorimetry has demonstrated the stability of all three M(ptp)2 and M(ptp)2(py)2 compounds and their amenability to sublimation. Preliminary current-voltage measurements from simple diodes has achieved unidirectional current from a Pt(ptp)2 neat layer and demonstrated its n-type semiconducting behavior.

<p dir="ltr">Interfaces play an important role in a broad range of physical, chemical, and biochemical processes. For example, nutrient transport from and to cells happens at the cellular membrane interface, the corrosion of metals occurs due to chemical reactions at the solid/air interface, and the development of waterproof clothing relies on the modification of the clothing surface with hydrophobic species. The importance and complexity of interfaces make a detailed understanding of the interfacial physicochemical processes central to both the fundamental science and the development of new technologies. Specifically in the fields of energy storage/production and heterogeneous catalysis, understanding the transformations of the active species on surfaces leads to the development of high-performance, stable interfaces. In the thesis presented herein, ion soft landing was used as a preparative technique to understand the chemical changes that ions undergo on surfaces. Ion soft landing is a mass spectrometry technique in which polyatomic ions are deposited onto surfaces while preserving their chemical structure and charge state. The advantage of using ion soft landing to study interfaces is that it enables the preparation of well-defined ionic interfaces by the deposition of mass-selected ions on a defined surface area with high control over the amount of deposited material. Because ion soft landing uses purified ion beams formed in the gas phase, it also allows to study the chemical properties of the analytes in the absence of counterions or solvent molecules. Collectively, these capabilities make ion soft landing a powerful approach for preparing ionic interfaces and studying their chemical properties. A new direction in ion soft landing research takes advantage of gas phase ion chemistry techniques, such as collision-induced dissociation, to generate well-defined reactive fragment ions as unique building blocks for studying chemistry at interfaces. <b>Chapter 2 </b>of this thesis discusses the development of an ion soft landing instrument that enables high transmission of fragment ions for their deposition onto surfaces. Ion soft landing of reactive fragment ions opens up possibilities for studying their stability and reactivity on surfaces providing a path to the controlled preparation of unique ionic interfaces. <b>Chapters 3 </b>and <b>4 </b>describe an unusual spontaneous ligand loss observed for soft landed [Ni(bpy)₃]²⁺⁰, an ion of interest in the field of catalysis, and its stabilization by codeposition with anions. We compared the reactivity of [Ni(bpy)₃]²⁺on surfaces against that of [Ni(bpy)₂]²⁺and [Ni(bpy)]⁺species (both formed by ligand removal in the gas phase). This comparison indicates that the dissociation of [Ni(bpy)₃]²⁺ occurs both due to its reorganization on a surface and by charge-reduction. Both processes substantially reduce ligand binding energy and facilitate ligand loss from the complex.</p><p dir="ltr"><b>Chapter 5 </b>diverges from ion soft landing and instead presents a gas-phase ion chemistry study on the stability of cucurbituril-viologen host-guest complexes to better understand the intrinsic properties that influence the strength of their interaction. We found that there is a “perfect fit” size of the host that maximizes interactions with the guest thus increasing its stability. In addition, guests of smaller sizes that are better incorporated into the host have a substantial stability compared to those that have functional groups extending outside of the protecting cavity of the host. The results of this work reveal a strategy to stabilize viologens in the gas phase for the preparation of functional interfaces using ion soft landing.</p><p dir="ltr">Finally, <b>Chapter 6 </b>shows the results of a work at the teaching/learning interface, specifically regarding an undergraduate research project developed for the Analytical Chemistry I course (CHM323) at Purdue University. The goal of this project was to further develop students’ scientific skills on planning, problem-solving, and critical thinking to assess the performance of two analytical techniques. Specifically, the project described in <b>Chapter 6 </b>was designed in such a way that students had to do research on appropriate analytical techniques to quantify ascorbic acid in an unknown sample, propose an experimental protocol, perform it in the laboratory, and concisely summarize the results of their work in a lab report.</p><p dir="ltr">In summary, the work presented in this thesis encompasses three areas. First, it shows the advantages of using fragment ions produced in the gas phase to study the complex physicochemical processes occurring at interfaces. Second, it presents a study on the gas-phase stability of viologen-based host-guest complexes with the prospect of making viologens accessible for the preparation of functional interfaces using ion soft landing. Finally, it describes an undergraduate laboratory project aimed at developing the scientific skills of students in an analytical chemistry course.</p>

Tyrosine (4-hydroxyphenylalanine) is one of the naturally occurring 22 amino acids. The importance of tyrosine is due to the presence of its phenolic side chain. In biological systems, the tyrosyl residue in proteins is found to be sulfated, phosphorylated and nitrated. Upon oxidation with dioxygenases, Tyr residue forms dopaquinone which undergoes a series of reactions ultimately leading to the formation of melanin. Tyr is also a precursor to neurotransmitters (catechol amines namely dopamine, epinephrine and norepinephrine) and thyroid harmones T4 and T3. Tyr residue is also found to be cross linked with other amino acid residues in the active site of certain proteins. Tyr-Tyr cross link has also been associated with neurodegenerative diseases. Tyr residue in proteins has been targeted widely for site selective modifications. A series of chemical modifications like acylation, allylation, ene-type reaction, iodination with radiolabeled iodine, formation of Tyr-Tyr cross link with oxidants and aminoalkylation have been carried out on surface exposed Tyr residues in proteins. Apart from these chemical modifications of Tyr on protein surface, a couple of free Tyr-based scaffolds have also been developed for different applications. Similar to tyrosine-based scaffolds, several phenolate-based scaffolds have also been developed for various applications. Several phenolate-based binuclear metal complexes have been developed as mimics of the active site of metalloenzymes. Moreover, by varying the substituent in the phenolate scaffold, the redox properties of metal bound in these systems can be tuned. The thesis consists of five chapters. The first chapter gives general idea about tyrosine-and phenolate-based scaffolds. The first chapter also gives introduction to zinc(II)-containing enzymes metallo-β-lactamases (mβls) and phosphotriesterase (PTE) and their functional mimics. The importance of copper(II)-containing enzyme, catechol oxidase and its mimics has also been discussed. The significance and formation of o-dityrosine (Tyr-Tyr cross link) has also been briefly discussed. In chapters 2 and 3, a couple of phenolate-based ligands and their corresponding zinc(II)- and copper(II)- complexes have been synthesized and have been checked as mimics of zinc(II)-containing enzymes (mβl and PTE) and copper-containing enzyme catechol oxidase, respectively. In chapter 4, a series of tyrosine-based ligands have been designed and their in situ copper(II) complexes have been tested as mimics of catechol oxidase. In chapter 5, the effect of neighboring amino acid in the formation of Tyr-Tyr cross link has been studied. In chapter 2, a couple of zinc(II) complexes have been synthesized and studied as mimic of zinc(II)-containing enzymes mβl and PTE. Metallo-β-lactamases (mβls) are zinc(II)-containing enzymes which exist in both mono- and binuclear forms. Mβls are capable of hydrolyzing β-lactam ring in antibiotics and make them inactive (Scheme 1(A)). To date, an effective inhibitor for this enzyme is not known. Hence, in order to understand the nature of the enzyme a couple of synthetic mimics are known. However, in most of the synthetic mimics both the metal ions are in symmetrical environment. Therefore, we have attempted to design a few unsymmetrical phenolate- based ligands and their zinc(II) complexes. The unsymmetrical phenolate-based ligands HL1 and HL2 have been synthesized by sequential mannich reaction with formaldehyde and two different amines. Complexes 1 and 2 are obtained from ligands HL1 and HL2, respectively (Figure 1). For comparative purpose, the symmetrical ligands HL3 and HL4, and their zinc(II)-complexes 3 and 4 have been synthesized by reported procedures (Figure 1). The efficiency of the complexes 1-4 towards the hydrolysis of oxacillin has been studied. It has been observed that the binuclear zinc(II) complexes with metal-bound water molecule 1 and 4 are able to hydrolyze oxacillin at much faster rates compared to that of mononuclear complexes 2 and 3. However, between 1 and 4, there is no appreciable change in activity, indicating that the slight change in ligand environment has no significant role. PTE is a binuclear zinc(II)-containing enzyme, capable of hydrolyzing toxic organphosphotriesters to less toxic diesters (Scheme 1(B)). As the binuclear active site of mβl is comparable with that of phosphotriesterase (PTE), PTE activity of complexes 1-4 has been studied. Although the binuclear zinc(II)-complexes 1 and 4 are able to hydrolyze PNPDPP (p-nitrophenyl diphenyl phosphate) initially, these complexes are not able to effect complete hydrolysis. This is due to the inhibition of complexes 1 and 4 by hydrolyzed product, diester. However with mononuclear complexes 2 and 3 no such inhibitions is possible, and are capable of hydrolyzing PNPDPP at comparatively faster rates than 1 and 4. Scheme 1. Function of metallo-β-lactamase and phosphotriesterase. (A) Hydrolysis of β-lactam ring in antibiotics by metallo-β-lactamase. (B) Hydrolysis of organophosphotriesters to diesters by phosphotriesterase. Figure 1. Chemical structures of ligands HL1-HL4 and their corresponding zinc(II)complexes 1-4. In chapter 3, a couple of copper(II) complexes have been synthesized and their catechol oxidase activity has been studied. Catechol oxidase belongs to the class of oxidoreductase and it catalyzes the oxidation of a wide range of o-diphenols to o-quinones through the reduction of molecular oxygen to water (Scheme 2). A four new µ4-oxo-bridged tetranuclear copper(II) complexes (5-8) have been synthesized (Figure 2). The ability of these complexes to catalyze the oxidation of 3,5-DTBC (3,5-Di-tert-butylcatechol) to 3,5-DTBQ (3,5-Di-tert-butylquinone) has been studied. A detailed kinetic study has been carried out which reveals that the complexes with exogenous acetate ligands (5 and 6) are better catechol oxidase mimics compared to complexes with exogenous chloride ligands (7 and 8). This observation is due to the labile nature of acetate compared to chloride, as the displacement of exogenous ligand is essential for the binding of substrate to the catalyst. Based on mass spectral analysis a plausible mechanism has been proposed for the oxidation of 3,5-DTBC by these complexes. Scheme 2. Oxidation of catechol by catechol oxidase. Figure 2. Chemical structures of copper(II) complexes 5-8. In chapter 4, by following the analogy between phenol and tyrosine, a series of binucleating ligands of tyrosine or tyrosyl dipeptides (Figures 3 and 4) have been synthesized by Mannich reaction under mild conditions. The in situ complexation of these fifteen new binucleating ligands (HL5-HL19) with copper(II) chloride has been observed. In situ complexation was followed by UV-visible and mass spectral analysis. These in situ complexes were able to oxidize 3,5-DTBC at slower rate compared to that of the tetranuclear complexes reported in chapter 3. The catecholase activity has also been tested with the addition of base. A slight enhancement in activity of in situ complexes has been observed in the presence of base. Based on mass spectral evidences, a plausible mechanism for the oxidation of catechol by these in situ complexes has been proposed. Figure 3. Binucleating ligands (Mannich bases) of boc-protected tyrosine and tyrosyl dipeptides. Figure 4. Binucleating ligands (Mannich bases) of boc-deprotected tyrosyl dipeptides. In chapter 5 of the thesis, the effect of neighboring amino acid residue in the formation of o,o-dityrosine (Tyr-Tyr cross link) has been studied. o,o’-Dityrosine is a specific marker for oxidative/nitrosative stress. The increase in concentration of dityrosine is associated with several disease states. A detailed study has been carried out in order to find out the effect of neighboring amino acid residues in the rate of formation of dityrosine of several tyrosyl dipeptides. The formation of dityrosine has been carried out with horseradish peroxidase(HRP) and H2O2 (Scheme 3). Except Cys-Tyr, all other tyrosyl dipeptides, form corresponding dityrosine with HRP/ H2O2. With Cys-Tyr, the formation of corresponding disulfide is observed. The appreciably higher rate of dityrosine formation of Phe-Tyr is attributed to the presence of strong hydrophobic environment around the active site of HRP. Among the polar tyrosyl peptides, the positively charged peptides (Arg-Tyr, Lys-Tyr) undergo dityrosine formation at much faster rate compared to that of negatively charged dipepptides (Asp-Tyr, Glu-Tyr). This trend is in accordance with the pKa of neighboring amino acid residues. The positively charged neighboring residues with higher pKa stabilizes ionized tyrosine, hence the rate of dityrosine formation is higher for them. As positively charged neighboring residue enhances the rate of dityrosine formation, the effect of externally added L-Arg has been studied. A coupling of a few biologically relevant tyrosine derivatives has been studied. The derivatives in which one of the ortho-positions of tyrosine is blocked, does not undergo coupling under the experimental conditions employed. Scheme 3. Formation of dityrosine of Ile-Tyr from Ile-Tyr in the presence of H2O2 catalyzed by HRP. (For structural formula and figures pl refer the abstract pdf file)

No / A novel series of 1,4-disubstituted aminoanthraquinones were prepared by ipso-displacement of 1,4-difluoro-5,8-dihydroxyanthraquinones by hydroxylated piperidinyl- or pyrrolidinylalkyl-amino side chains. One aminoanthraquinone (13) was further derivatized to a chloropropyl-amino analogue by treatment with triphenylphosphine-carbon tetrachloride. The compounds were evaluated in the A2780 ovarian cancer cell line and its cisplatin-resistant variants (A2780/ cp70 and A2780/MCP1). The novel anthraquinones were shown to possess up to 5-fold increased potency against the cisplatin-resistant cells compared to the wild-type cells. Growth curve analysis of the hydroxyethylaminoanthraquinone 8 in the osteosarcoma cell line U-2 OS showed that the cell cycle is not frozen, rather there is a late cell cycle arrest consistent with the action of a DNA-damaging topoisomerase II inhibitor. Accumulative apoptotic events, using time lapse photography, indicate that 8 is capable of fully engaging cell cycle arrest pathways in G2 in the absence of early apoptotic commitment. 8 and its chloropropyl analogue 13 retained significant activity against human A2780/cp70 xenografted tumors in mice.

Quantum chemical calculations at BP86/TZVPP//BP86/SVP have been carried out for the Nheterocylic carbene and analogues complexes (tetrylene) [(CO)4W-NHE] (W4-NHE) with E = C – Pb. The tetrylene complexes W4-NHE possess end-on-bonded NHE ligands (E = C, Si), while for E = Ge and Sn, they possess slightly side-on-bonded ligands. The strongest side-on-bonded ligand when E = Pb has a bending angle of 102.9°. The trend of the bond dissociations energies (BDEs) for the W-E bond is W4-NHC > W4-NHSi > W4-NHGe > W4-NHSn > W4-NHPb. Analysis of the bonding situation suggests that the NHE ligands in W4-NHE are strong σ-donors and weak π-donors. This is because the tetrylenes have only one lone-pair orbital available for donation. The polarization of the W-E bond and the hybridization at atom E explain the trend in the bond strength of the tetrylene complexes W4-NHE. The W-E bonds of the heavier systems W4-NHE are strongly polarized toward atom E giving rise to rather weak electrostatic attraction with the tungsten atom which is the main source for the decreasing trend of the bond energies. The theoretical calculations suggest that transition-metal complexes tetrylenes [(CO)4W-{NHE}] (E = C – Pb) should be synthetically accessible compounds with tetrylenes NHE act as two-electron-donor ligands in complexes. / Phân tích cấu trúc và bản chất liên kết hóa học của hợp chất với kim loại chuyển tiếp chứa phối tử N-heterocyclic carbene và các đồng đẳng (tetrylene) [(CO)4W–NHE] (W4-NHE) với E = C – Pb sử dụng tính toán hóa lượng tử ở mức BP86/TZVPP//BP86/SVP. Cấu trúc của phức W4-NHE cho thấy các phối tử NHE với E = C, Si tạo với phân tử W(CO)4 một góc thẳng α = 180,0°, trong khi đó các phức W4-NHE thì phối tử NHE với E = Ge – Pb tạo liên kết với nhóm W(CO)4 một góc cong α < 180,0° và góc cong càng trở nên nhọn hơn khi E = Pb (α = 102.9°). Năng lượng phân ly liên kết của liên kết W-E giảm dần: W4-NHC > W4-NHSi > W4-NHGe > W4-NHSn > W4-NHPb. Tính toán hóa lượng tử trong phức [(CO)4W-{NHE}] (E = C – Pb) cho thấy phối tử tetrylene là chất cho electron. Điều này có thể do phối tử tetrylene chỉ giữ lại một cặp electron tại nguyên tử E để đóng vai trò là chất cho điện tử. Độ bền liên kết của phức W4-NHE được giải thích nhờ vào độ phân cực của liên kết W-E và sự lai hóa của nguyên tử trung tâm E. Nguyên nhân chính làm giảm dần năng lượng liên kết là do liên kết W-E của các phức nặng hơn W4-NHE bị phân cực mạnh về phía nguyên tử E dẫn đến lực hút tĩnh điện với nguyên tử W yếu dần. Hệ phức nghiên cứu được coi là hợp chất điển hình cho các nghiên cứu thực nghiệm.

Iron-mediated oxidative cyclisation provides an efficient approach to pyrano[3,2-a]carbazole alkaloids. Thus, improved routes to girinimbine and murrayacine as well as the first total syntheses of O-methylmurrayamine A and 7-methoxymurrayacine are reported. Asymmetric epoxidation of girinimbine led to (−)-trans-dihydroxygirinimbine and the assignment of its absolute configuration. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

Ce travail de thèse s'inscrit dans le contexte général des solutions envisageables pour répondre aux problèmes du réchauffement climatique global et de la diminution des ressources fossiles. Il a été en majeure partie consacré à l'étude et au développement d'électrocatalyseurs moléculaires pour la réduction du dioxyde de carbone. Un tel procédé pourrait permettre de transformer et valoriser le CO2 en l'exploitant comme une matière première carbonée disponible en quantité non limitée, bon marché et peu toxique. Dans une première partie, un métallocavitand, dont la structure est basée sur un calix[4]arène fonctionnalisé par quatre complexes phénanthroline tris-carbonyl de rhénium(I), a été étudié en solution et sur déposé sur surface transparente conductrice. Le but de cette étude était de contrôler par un stimulus électrochimique la fermeture et l'ouverture du bord large du cavitand. La complexité des processus rédox de ces métallo-macrocycles nous a conduits à étudier en détails les propriétés électrochimiques de complexes de rhénium(I) modèles. Ces propriétés avaient précédemment été rapportées dans la littérature mais étaient sujettes à désaccords entre les différents auteurs. Finalement l'ensemble de cette étude nous a conduits à préciser et à mieux comprendre le mécanisme de la catalyse de réduction du CO2 par ce type de complexes. Dans une deuxième partie, qui représente la partie la plus conséquente de cette thèse, la synthèse, la caractérisation physico-chimique et l'étude spectro-électrochimique de complexes bipyridine tris-carbonyle de manganèse, analogues des complexes de rhénium évoqués ci-dessus, ont été entreprises. Le but était de développer un catalyseur innovant pour la réduction électrochimique du dioxyde de carbone, du type complexe métallique, en substituant les métaux rares utilisés actuellement par un métal non-noble et abondant : le manganèse. Les propriétés électrochimiques des nouveaux complexes de Mn synthétisés ont été caractérisées en détail. La simulation des voltammétries cycliques, associée à des études mécanistiques par spectro-électrochimie UV-vis, a permis d'accéder aux données cinétiques et thermodynamiques des différentes réactions chimiques associées aux réactions de transferts d'électron irréversibles. Ces complexes de manganèse se sont révélés être des électrocatalyseurs de la réduction du CO2 au moins aussi efficaces que les complexes analogues de rhénium, décrits jusque-là comme étant les meilleurs systèmes pour cette application. Les complexes de Mn ainsi préparés montrent une excellente sélectivité (rendements faradiques élevés et peu ou pas de H2) et une bonne efficacité pour l'électro-réduction du CO2 en CO en milieu hydro-organique. Les catalyses à l'échelle préparatrice fonctionnent avec des surtensions modérées. Les mécanismes mis en jeu lors de la catalyse ont été étudiés par spectro-électrochimie UV-vis et RPE (en onde continue et pulsée) associées à des caculs théoriques DFT. Un intermédiaire-clé a ainsi pu être mis en évidence et caractérisé. Enfin, l'étude des réactions de décarbonylation photo-induites dans ces complexes est rapportée. / This PhD takes place in the general context of possible solutions to global warming and peak oil issues. It mostly deals with the study and development of molecular electrocatalysts for carbon dioxide reduction. This process may open the way to the use and valorization of CO2 as a raw material. In the first part, a metallocavitand, which structure is based on a calix[4]arene modified by four phenanthroline tris-carbonyl rhenium(I) complexes, was studied in solution and deposited on a conductive transparent surface. The aim of this study was to control through an electrochemical stimulus the closing and opening of the wide rim of the cavitand. Complexity of the redox properties of the metallocavitand led us to investigate in detail the electrochemical properties of simpler examples of these rhenium(I) complexes. These properties were previously described in the literature ; however, there was disagreement in the interpretation of the results. Finally this study led us to a more precise and better understanding of the mechanism of the reduction of CO2 by a complex of this kind. In the second part, which is the main part of this PhD, synthesis, physico-chemical characterization and spectro-electrochemical study of bipyridine tris-carbonyl manganese complexes, analogues of the rhenium complexes mentioned above, were undertaken. The aim was to develop an innovative catalyst for the electrochemical reduction of carbon dioxide, based on a metallic complex, by substituting rare and noble metals currently used by a non-noble and abundant metal: manganese. Electrochemical properties of newly synthesized manganese complexes were investigated in detail. Simulations of cyclic voltammetry, associated with mechanism studies by UV-vis spectro-electrochemistry, allowed us to determine kinetic and thermodynamic properties of the different chemical reactions coupled with the irreversible electron transfers. These manganese complexes proved to electrocatalyse the reduction of carbon dioxide at least as efficiently as the analog rhenium complexes which were, until now, the best system for this application. These manganese electrocatalysts exhibit a very good selectivity (high faradic yields and no or very little H2) and a good efficiency for reduction of CO2 to CO in aqueous-organic media. Preparative scale electrolysis operates at low overpotential. Mechanisms of the different catalytic pathways were studied using UV-vis and EPR (continuous wave or pulsed) spectro-electrochemistry associated with DFT calculations. A key-intermediate was evinced and investigated. Finally the study of photo-induced decarbonylation reactions of these complexes is also described.

Le travail présenté concerne la synthèse de calixarènes fonctionnalisés par des groupes sulfonates et carboxylates et l'étude détaillée des structures cristallines de leurs complexes moléculaires ou métalliques avec des métaux 3d et 4f. L'une des préoccupations majeures de ce travail concerne la compréhension des assemblages supramoléculaires dans ces systèmes. Le premier chapitre présente des éléments bibliographiques sur les calixarènes, leur histoire, les différentes conformations et les méthodes principales de fonctionnalisation puis la chimie supramoléculaire associée comprenant les complexes moléculaires et métalliques. Le deuxième chapitre est dédié à une série de complexes moléculaires de type hôte-invité formés entre le para-sulfonatocalix[4]arène (SC4) et différentes bipyridine En continuité avec ce travail nous présentons en suite la structure et les propriétés magnétiques d'un complexe métallique constitué d'un SC4 pontant deux entités dinucléaires de phenanthroline [FeIII2(μ-O)(H2O)5(phen)2] par la coordination des groupes sulfonates. Le troisième chapitre est consacré à la chimie de coordination des calixarènes sulfonatés avec les lanthanides. Nous avons mis en évidence trois types de structures cristallines qui sont toutes des polymères de coordination où les ions lanthanides jouent le rôle d'assembleur des calixarènes par la coordination des groupes sulfonates selon trois types de structure (A, B et C). Nous avons obtenu ces trois structures (A, B et C) pour l'ensemble de lanthanide (La, Pr, Nd , Eu, Gd, Tb, Dy, Ho, Yb). Le quatrième chapitre concerne la chimie de coordination des métaux de transition 3d (Co, Mn, Zn, Cu) avec des calixarènes fonctionnalisés par des groupes carboxylates sur leur partie basse. Avec le calixarène dicarboxylate nous avons obtenu une série de complexes isomorphes dans lesquels deux calixarènes sont coordinés à deux centres métalliques pour former des chaînes infinies. Le cinquième chapitre présente les résultats d'un travail exploratoire visant à synthétiser des azacalix[4]arènes, dans le but de complexer des métaux de transition. L'étude RPE des précurseurs a mis en évidence des espèces radicalaires / This work presents the synthesis of calixarenes functionalized with sulfonate and carboxylate groups and the detailed study of the crystal structures of their molecular or metal complexes with 3d and 4f metals ions. One of the major concerns of this work is the understanding of supramolecular assemblies in these systems. The first chapter gives bibliographic elements on the history, the different conformations and the main methods of functionalization of calixarenes and on their supramolecular chemistry comprising molecular and metal complexes. The second chapter is dedicated to a series of molecular complexes of the host-guest type formed between the para-sulfonatocalix[4]arene (SC4) and various bipyridine. In continuation with this work we then present the synthesis, structure and magnetic properties of a metal complex comprising a SC4 bridging by the sulfonate groups two iron(II) dinuclear entities with coordinated phenathroline [FeIII2 (μ-O)(H2O) 5(phen) 2]. The third chapter is devoted to the coordination chemistry of sulfonated calixarenes with lanthanides. We have found three types of crystal structures which are polymers wherein the lanthanide ion function as an assembler of calixarenes by the coordination of the sulfonate groups along three type of structure (A, B and C). We obtained these three structures (A, B and C) for all lanthanide (La, Pr, Nd, Eu, Gd, Tb, Dy, Ho, Yb). The fourth chapter concerns the coordination chemistry of 3d transition metals (Co, Mn, Zn) with calixarenes functionalized with carboxylate groups on lower rim. With calixarene dicarboxylate we got a series of isomorphic complexes in which two calixarenes are coordinated to two metal centers to form infinite chains. The fifth chapter presents the results of an exploratory work to synthesize azacalix[4]arene with the aim to complex transition metals ions. The EPR study of the precursors has evidenced free radical species

Photo sensitizers showing visible light induced DNA cleavage activity are of current importance for medicinal applications related to photodynamic therapy (PTD) considering greater skin penetration of light near 700 nm. While organic molecules and complexes of 4d-5d metal ions are extensively studied for their DNA photo-damage properties in UV and visible light, the chemistry of 3D metal complexes showing visible light-induced DNA cleavage activity is relatively unexplored efforts have been made in this thesis work to design new ternary copper (II) complexes having a-amino acids Such copper (II) complexes with tunable coordination geometry could find potential applications in PDT. Ternary Copper (II) complexes containing L-methionine, S-methy1-L-cysteine and phenanthroline bases are prepared and characterized. They display DNA binding and visible light induced DNA cleavage activity. An enhancement of the DNA cleavage activity is observed for analogous ternary copper (II) complexes contained L-lysine with a pendant cationic amine moiety as a photo-induced DNA Cleavage activity using binary and ternary copper (II) complexes of L-arginine and phenanthroline bases. We have observed AT selective DNA binding and visible light –induced DNA cleavage activity. The crescent-shaped bis-arginine Copper (II) complex mimics the natural antiviral antibiotic netropsin. T o investigate the role of the pendant groups of the amino acids, we have explored the DNA binding and DNA cleavage activity of analogues L-glutamine and L-asparagine complexes. We have prepared ternary copper (II) complexes containing two photosensitizers, viz., L-tryptophan (L-trp) and dipyridoquininoxaline/dipyridophenazine to achieve double strand breaks forming linear DNA. Complex [Cu(L-trp)(dppz)(H2O)+ shows a stacking arrangement of the indole and dppz rings giving a separation that fits with the base pair separation of ds-DNA. Photosensitizes in these complexes approach two different complementary stands of the ds-DNA, leading to double strand breaks and formation of linear DNA. Mechanistic studies on the DNA photocleavage reactions reveal the formation of singlet oxygen(1O2)species by a type-II pathway in preference to the hydroxyl radical generation. A process leading to an efficient DNA cleavage activity on visible light irradiation. The observation of sequence selectivity and double strand DNA cleavage on red light exposure by national design of the complexes is significant considering importance of the results in the chemistry of photodynamic therapy of cancer. The results of this dissertation open up new avenues for designing and developing 3d metal-based photosensitizers with potential utility in nulcleic acid chemistry.