none

We prepared a seties of tridentate amido diphosphine ligands, including symmetrical [N(o-C6H4PR2)2]- ([R-PNP]- ; R = Ph, iPr, Cy) and unsymmetrical [N(o-C6H4PPh2) (o-C6H4PiPr2)]-. Deprotonation of neutral ligands, H[R-PNP] ( R = Ph, iPr, Cy) or H[Ph-PNP-iPr], with n-BuLi in ether solutions at -35oC produced the lithium complexes, [R-PNP]Li(solv)n ( R = Ph, iPr, Cy; solv = THF, OEt2; n = 1,2) or [Ph-PNP-iPr]Li(solv)n (solv = THF, OEt2; n = 1,2), respectively. The reactions of the lithium complexes or neutral ligands with NiCl2(DME) in THF solutions generated nickel(II) chloride complexes, [R-PNP]NiCl ( R = Ph, iPr, Cy) or [Ph-PNP-iPr]NiCl, which was then reacted with a variety of Grignard reagents to afford the corresponding hydrocarbyl complexes. Of particular interest among the compounds isolated are alkyl complexes that contain £]−hydrogen atoms. The metathetical reactions of nickel(II) chloride complexes with LiNHPh, NaOPh, NaSPh, or NaOtBu, respectively, produced the correspounding nickel anilide, nickel phenolate, nickel thiophenolate and nickel tert-butoxide derivatives. Protonolysis studies of nickel(II)-heteroatom complexes revealed the basic reactivity of these £k-donor ligands. The basicity follows the order OtBu > NHPh > OPh > SPh. Treatment of Ni(COD)2 (COD = cycloocta-1,5-diene) with neutral ligands produced the correspounding four-corrdinate nickel hydride complexes, [R-PNP]NiH (R = Ph, iPr, Cy) or [Ph-PNP-iPr]NiH. The olefin insertion reactions of [iPr-PNP]NiH or [Ph-PNP-iPr]NiH with ethylene, 1-hexene, and norbornene, respectively, generated the corresponding ethyl, n-hexyl, and 2-norbornyl complexes. The formation of [iPr-PNP]Ni(n-hexyl) or [Ph-PNP-iPr]Ni(n-hexyl) is indicative of exclusive 1,2-insertion of 1-hexene. In contrast, styrene inserts into the Ni-H bond of [Ph-PNP-iPr]NiH in an exclusively 2,1-manner to afford [Ph-PNP-iPr]NiCH(Me)Ph. The selective 2,1-insertion products [R-PNP]NiCH(Me)CO2Me (R = Ph, iPr, Cy) or [Ph-PNP-iPr]NiCH(Me)CO2Me were also isolated from the reactions of methyl acrylate with the corresponding nickel hydride complexes. The effects of the phosphorus and olefin substituent on the reactivity and regioselectivity of the olefin insertion reactions are discussed. We also prepared nickel acyl complexes and nickel complexes catalyzed C-N bond formation. In addition to solution NMR spectroscopic data for all new compounds. X-ray diffraction revealed solid structures. A series of five-coordinate aluminum complexes supported by o-phenylene - derived amido diphosphine ligands have been prepared and structurally characterized. Alkane elimination reactions of trialkylaluminum with neutral ligands, H[R-PNP] ( R = Ph, iPr) and H[Ph-PNP-iPr] in toluene solution at -35oC respectively produced the corresponding dialkyl complexes [iPr-PNP]AlR'2, [Ph-PNP]AlR'2 and [iPr-PNP-Ph]AlR'2 (R' = Me, Et, iBu) in high isolated yield. The dihydride complexes [iPr-PNP] AlH2, [Ph-PNP]AlH2 and [iPr-PNP-Ph]AlH2 prepared in one-pot reactions of in situ prepared dichloride precursors with LiAlH4 in THF at room temperature. X-ray diffraction studies revealed a distorted trigonal-bipyramidal structure for these molecules in which the two phosphorus donors are mutually trans. The solution structures of these complexes were all characterized by 1H, 13C, and 31P NMR spectroscopy. The NMR data are indicative of solution C2 symmetry for [iPr-PNP]- and [Ph-PNP]- complexes, whereas they are indicative of C1 for [iPr-PNP-Ph]- derivatives. The 1H NMR spectra of [iPr-PNP]AlR'2, [Ph-PNP]AlR'2 and [iPr-PNP-Ph]AlR'2 (R' = Et, iBu) revealed diastereotopy for the £\-hydrogen atoms in these molecules.

none

none

Made available in DSpace on 2014-12-17T15:42:03Z (GMT). No. of bitstreams: 1 HugoFLS_DISSERT.pdf: 2820205 bytes, checksum: ad87619352b0e479d50e7f9093be5ec0 (MD5) Previous issue date: 2012-10-15 / This work is a study of coordination compounds by quantum theory of atoms in molecules (QTAIM), based on the topological analysis of the electron density of molecular systems, both theoretically and experimentally obtained. The coordination chemistry topics which were studied are the chelate effect, bent titanocene and chemical bond in coordination complexes. The chelate effect was investigated according to topological and thermodynamic parameters. The exchange of monodentate ligands on polydentate ligands from same transition metal increases the stability of the complex both from entropy and enthalpy contributions. In some cases, the latter had a higher contribution to the stability of the complex in comparison with entropy. This enthalpic contribution is explained according to topological analysis of the M-ligand bonds where polidentate complex had higher values of electron density of bond critical point, Laplacian of electron density of bond critical point and delocalization index (number of shared electrons between two atoms). In the second chapter, was studied bent titanocenes with bulky cyclopentadienyl derivative π-ligand. The topological study showed the presence of secondary interactions between the atoms of π-ligands or between atoms of π-ligand and -ligand. It was found that, in the case of titanocenes with small difference in point group symmetry and with bulky ligands, there was an nearly linear relationship between stability and delocalization index involving the ring carbon atoms (Cp) and the titanium. However, the titanocene stability is not only related to the interaction between Ti and C atoms of Cp ring, but secondary interactions also play important role on the stability of voluminous titanocenes. The third chapter deals with the chemical bond in coordination compounds by means of QTAIM. The quantum theory of atoms in molecules so far classifies bonds and chemical interactions in two categories: closed shell interaction (ionic bond, hydrogen bond, van der Waals interaction, etc) and shared interaction (covalent bond). Based on topological parameters such as electron density, Laplacian of electron density, delocalization index, among others, was classified the chemical bond in coordination compounds as an intermediate between closed shell and shared interactions / Esse trabalho consiste no estudo dos compostos de coordena??o pela teoria qu?ntica de ?tomos em mol?culas, do ingl?s, QTAIM, fundamentada na an?lise topol?gica da densidade eletr?nica dos sistemas moleculares obtida tanto teoricamente quanto experimentalmente. Os temas escolhidos para serem estudados s?o o efeito quelato, os metalocenos de tit?nio de estrutura pseudotetra?drica e a liga??o coordenada. No primeiro cap?tulo, foi investigado o efeito quelato de acordo com par?metros termodin?micos e topol?gicos. A troca de ligante monodentado am?nia pelo ligante bidentado 1,2-etanodiamina de mesma natureza qu?mica aumenta a estabilidade do ?on complexo, tanto pela contribui??o da entropia, quanto da entalpia, em alguns casos, esta ?ltima teve maior participa??o para a estabilidade do ?on complexo que a entropia. Em todos os ?ons complexos, a troca de ligante monodentado para bidentado levou ao aumento dos valores eletr?nicos da topologia como densidade eletr?nica, Laplaciano da densidade eletr?nica e ?ndice de deslocaliza??o (n?mero de el?trons compartilhados entre dois ?tomos). No segundo cap?tulo, foram estudados os metalocenos de tit?nio de estrutura pseudotetra?drica com ligantes-π volumosos ciclopentadienila (Cp) e seus derivados. O estudo topol?gico mostrou a presen?a de intera??es secund?rias entre os ?tomos dos ligantes-π ou dos ligantes-σ. Verificou-se que, para os metalocenos de tit?nio com pequena diferen?a de simetria pontual e ligantes volumosos, havia uma rela??o quase-linear entre a estabilidade e o ?ndice de deslocaliza??o envolvendo ?tomos de carbono do anel (Cp) e o tit?nio. Contudo, a estabilidade n?o ? relacionada apenas ?s intera??es entre o ?tomo de tit?nio e o anel ciclopentadienila, mas ?s intera??es secund?rias influenciando na estabilidade dos titanocenos com ligantes volumosos. O terceiro cap?tulo trata da liga??o qu?mica nos compostos de coordena??o por meio da QTAIM. A teoria qu?ntica de ?tomos em mol?culas, at? ent?o, classifica as liga??es e intera??es qu?micas em duas categorias: intera??o de camada fechada (liga??o i?nica, liga??o de hidrog?nio, intera??o de van der Waals, entre outras) e intera??o compartilhada (liga??o covalente). Baseado nos par?metros topol?gicos como densidade eletr?nica, Laplaciano da densidade eletr?nica, entre outros, classificou-se a liga??o coordenada como intermedi?ria entre as intera??es de camada fechada e intera??es compartilhadas

L’autoassemblage de diverses biomolécules pour former des complexes moléculaires est à la base de la machinerie cellulaire et des processus biologiques qui s’y rattachent. Il est typiquement considéré qu’un assemblage de plusieurs protéines offre des avantages régulatifs comparativement à une structure protéique similaire construite avec une ou un nombre inférieur de composantes. Ces assemblages offrent, par exemple, la possibilité de contrôler l’activité d’un complexe grâce à la dépendance directe de l’assemblage sur la concentration de ces composantes. De plus, la coopérativité d’interaction entre ces diverses composantes ouvre la voie vers l’obtention de nouveaux mécanismes de régulation. Toutefois, les avantages et les inconvénients directement reliés au nombre de composantes impliquées dans un assemblage ne sont pas totalement bien compris puisque les protéines ont évolué et ont divergé suivant des millions d’années d’évolution. L’objectif principal de cette thèse est d’abord de créer un modèle moléculaire simplifié permettant de mieux comprendre les avantages coopératifs des autoassemblages biologiques pour ensuite s’en inspirer afin de mettre au point de nouveaux mécanismes moléculaires permettant d’optimiser la plage dynamique d’interrupteurs moléculaires autoassemblés. En même temps, il sera possible de mettre en lumière certains avantages évolutifs qui ont poussé les protéines à acquérir plus de composantes moléculaires. Tout d’abord, la création d’assemblages moléculaires fut effectuée en fragmentant une structure unimoléculaire en plusieurs fragments qui pourront, grâce à leurs interactions, reformer la structure originale. Grâce à une nanostructure simple d’ADN, c.-à-d. une jonction à trois branches, il fut possible d’étudier directement l’impact du nombre de composantes sur la fonctionnalité et la régulation d’assemblages multimériques. Il fut observé, malgré l’association plus lente d’un assemblage de trois composantes, que ce même assemblage s’associe de manière plus coopérative tout en permettant la création de nouveaux mécanismes de régulation (p. ex. plage dynamique étendue, auto-inhibition et minuterie moléculaire). Ce système simplifié d’ADN a donc permis de conclure que la fragmentation d’une nanostructure en plusieurs composantes est une méthode simple permettant d’optimiser un nanosystème artificiel ou naturel. Ensuite, une autre méthode de création d’assemblages moléculaires fut étudiée. Celle-ci consiste à fusionner des domaines interagissant par le biais d’un espaceur. Dans une telle stratégie, l’espaceur est appelé à jouer un rôle important dans les propriétés de l’assemblage. Ainsi, en utilisant le même modèle d’ADN à trois composantes, il fut en effet observé que les propriétés de l’espaceur (p. ex. sa longueur, sa composition ou sa nature chimique) affectent grandement les propriétés d’assemblage d’un système à trois composantes (p. ex. sa stabilité, son niveau de coopérativité ou sa plage dynamique d’assemblage). En effectuant une étude thermodynamique approfondie sur divers assemblages trimériques d’ADN, il fut découvert qu’un espaceur optimal stabilise l’association des diverses composantes en créant une structure plus compacte où les espaceurs se cachent au coeur de la jonction. Il fut aussi démontré qu’en optimisant l’espaceur, il est possible de programmer précisément la plage dynamique d’un assemblage moléculaire à trois composantes. Finalement, ces découvertes sur les avantages d’un assemblage à trois composantes ont permis la création d’une nouvelle stratégie afin d’optimiser la plage dynamique d’interrupteurs moléculaires. À l’inverse des activateurs allostériques classiques qui altèrent la force d’interaction d’un ligand, c.-à-d. le KD, en modifiant la conformation de l’interrupteur, un activateur multivalent permet de programmer précisément la plage dynamique de l’interrupteur en exploitant une nouvelle surface d’interaction grâce à la formation d’un assemblage à trois composantes. Cette nouvelle stratégie d’optimisation des interrupteurs moléculaires fut validée grâce à une tige-boucle d’ADN servant comme balise moléculaire. Cette preuve de concept permet de démontrer la viabilité des assemblages moléculaires pour conceptualiser de nouvelles nanotechnologies avec une plage dynamique optimisée. Il est donc possible d’imaginer que les assemblages moléculaires auront un impact immédiat dans divers domaines de la nanotechnologie comme en diagnostic médical, en délivrance contrôlée de médicaments ou en imagerie moléculaire. / The self-assembly of various biomolecules to form molecular complexes is at the basis of the cellular machinery and their related biological processes. It is typically thought that an assembly of several proteins provides regulatory advantages compared to a similar protein built with one or fewer molecular components. These molecular assemblies offer, for example, the possibility to control their activity through the direct dependency of the assembly on the concentration of its components. Moreover, the cooperativity of interaction between their multiple components opens the door to acquiring novel regulation mechanisms. However, the advantages and disadvantages directly related to the number of components involved in an assembly are not totally understood since proteins have evolved and diverged over millions of years of evolution. The main objective of this thesis is to first create a simplified molecular model that will enable to better understand the cooperative advantages of biological self-assemblies. Then, inspired by these new understandings, novel molecular mechanisms will be developed to enable the optimization of the dynamic range of self-assembled molecular switches. Meanwhile, it will be possible to highlight some advantages that have pushed proteins to acquire more molecular components. The creation of molecular assemblies was demonstrated by fragmenting a nanostructure into multiple fragments which, through their intermolecular interactions, reassemble into the original structure. Using a simple DNA-based nanostructure, i.e., a three-way junction, it was possible to directly study the impact of the number of components on the functionality and regulation of multimeric assemblies. It was found that despite the slower assembly rate of a three-component assembly, this same assembly undergoes a more cooperative assembly enabling the creation of new regulatory mechanisms (e.g., extended dynamic range, self-inhibition and molecular timers). This simplified DNA-based system has therefore made it possible to conclude that fragmenting a nanostructure into multiple components is a simple method to optimize an artificial or a natural nanosystem. Next, another method to create molecular assemblies was studied. This method consists in fusing interacting domains through a linker. In this strategy, the linker will play an important role in dictating the properties of the assembly. Therefore, by using the same three-component DNA-based model, it has been observed that the chemical properties of the linker (e.g., its length, its composition, or its chemical nature) considerably affect the assembly properties of a three-component system (e.g., its stability, its level of cooperativity, or its dynamic range). Through an exhaustive thermodynamic study on various trimeric DNA-based assemblies, it was determined that the optimal linker stabilizes the association of all components by creating a more compact assembly where the linkers are buried within the core of the junction. It was also demonstrated that the optimization of the linkers allows to precisely program the dynamic range of the assembly. Finally, these discoveries on the advantages of a three-component assembly have enabled the creation of a new design strategy to optimize the dynamic range of molecular switches. In contrast to the classic allosteric activator which alters the affinity of a ligand (i.e., the KD) by changing the conformation of the switch, a multivalent activator enables to precisely program the dynamic range of a switch by exploiting a new interacting interface through the formation of a three-component assembly. This new strategy to optimize molecular switches was validated using a DNA-based molecular beacon. This proof of concept demonstrates the viability of molecular assemblies to design novel nanotechnologies with optimized dynamic range. It is possible to imagine that these molecular assemblies could have a direct impact on multiple fields of nanotechnology including medical diagnostics, controlled drug delivery and molecular imaging.