Tesis sobre el tema "Phosphine imide"

Dans l'objectif de proposer un procédé de substitution du phosgène dans la production des isocyanates et de leurs dérivés, nous avons consacré ce travail à l'étude de la réaction phosphine imide dans le CO2 supercritique. Dans ce cadre, nous avons défini une réaction standard et nous avons étudié l'influence des paramètres opératoires sur la cinétique de cette réaction dans le CO2 grâce à un réacteur haute pression de 100 ml. Les analyses des échantillons obtenus ont été réalisées par chromatographie en phase liquide. Ces observations nous ont permis de développer un modèle cinétique du premier ordre, et les résultats obtenus par ce modèle ont permis une bonne prédiction de ceux observés dans un réacteur haute pression de 1l. Nous avons comparé les cinétiques obtenues dans le CO2 avec celles observées dans la diméthylformamide. Nous avons aussi étudié l'influence du "pseudo-catalyseur" permettant l'obtention des isocyanates, et ce dans la diméthylformamide et dans le CO2. Nous avons finalement pu réaliser la synthèse d'un composé d'intérêt pharmaceutique, qui augmente la biodisponibilité du Busulfan, dans le CO2 en utilisant la réaction phosphine imide et suivre la cinétique de cette réaction
In the aim to propose a substitution process to the use of phosgene for the production of isocyanates and their derivatives, we devoted this work to the study of the phosphine imide reaction in supercritical CO2. In this context, we have chosen a standard reaction and investigated the influence of operational parameters on the kinetic of this reaction in CO2 using a high pressure 100 ml reactor. Analyses of the samples were performed using high performance liquid chromatography. These observations permits to develop a first order kinetic model, and we have compared the results obtained using this model with the observations we realized in a high pressure 1l reactor. We have compared the kinetics obtained in CO2 with those observed in dimethylformamide. We have also studied in dimethylformamide and CO2 the influence of the "catalyst" which permits to obtain isocyanates. We've finally performed the synthesis of a compound of pharmaceutical interest, which increase the bioavailability of Busulfan, in CO2 using phosphine imide reaction and we have followed the kinetic of this reaction

Dans le développement de nouvelles synthèses, le remplacement des composés volatils organiques tels que les réactifs industriels dangereux apparaît comme important. C’est aujourd'hui le défi de la chimie verte. La réaction Phosphine imide rend facile d’accès certaines fonctions quadrivalentes tel que isocyanate, carbodiimide, thio-urée ou urée notamment dans des CDs. Nous avons pu démontré la sûreté, l'efficacité et la polyvalence de cette réaction avec PPH3 libre ou supporté sur polymère avec CS2, CO2 et le CO2 supercritique. Dans la deuxième partie, les propriétés physico-chimique de coordination sélective de cations métalliques et certaines propriétés de fluorescence des complexes « de terre rare » d'ureido-CDs ont été étudiées. Ces nouveaux systèmes se sont avérés être très sélectifs et originaux , notamment dans la coordination avec la série de lanthanide. Pour la dernière partie, la synthèse d’un récepteur C2 symétrique comprenant deux CDs reliés par des liens urée à une plate-forme chirale diaza-éther-couronne est rapportée. Ce système moléculaire s'est avéré un outil efficace de complexation du Busulfan, un agent anticancéreux utilisé pour le traitement des maladie hématologiques. Enfin, un tétrapode de bis-guanidinum , premier membre d'une nouvelle famille à centres cationiques et quantité de CDs modulable est présenté. La complexation de nucléotides avec cette structure a été étudié. On observe la formation du complexe bimoléculaire combinant des inclusions dans les cavités des hydrophobes des CDs et des interactions électrostatiques entre le guanidinium et les anion phosphate
In the development of new efficient synthetic processes, the replacement of organic volatile compounds such as hazardous industrial reagents appears as a major gaol in the present day challenge for a green chemistry. It is well know that compounds containing the urea or thiourea functionality are of extended biological. As a powerful easy access to urea functionality and other main quatrivalent functions of chemistry as eg isocyanates, carbodiimide, thiourea or urea notably in CDs series, we earlier reported and demonstrated the high safety, efficiency and versatility of the phosphine imide reaction with free or polymer supported PPH3 and with CS2, CO2 or supercritical CO2. On the second part, specific physico-chemical property related to selective metal coordination and to fluorescence properties of URTF ureido-CDs “rare earth” complexes were investigated. This new systems were found to have very selective and original coordination processes notably with lanthanide series. For the last part, the synthesis of C2 symmetric receptor including two CDs connected by urea linkers to the chiral diazacrown ether o platform is reported. This molecular system was found to be an efficient complexion tool towards the Busulfan anticancer agent used for the treatment of haematological disorders. A novel bis-guanidinum tetrapode, the first member of a new host family with a checked number of cationic centres and CDs is presented. Its molecular recognition towards nucleodides guest was investigated. The formation of ditopic bimolecular complexe was observed combining host-guest hydrophobic inclusion into CDs and electrostatic interactions between guanidinium and phosphate anion

This thesis concerns synthetic and structural studies of a range of main group compounds from the p-block (Groups 13 to 15 of the Periodic Table) containing phosphorus and nitrogen ligand frameworks. Chapter 1 describes the synthesis and structural studies of a diverse range of Group 13 (A1-In), Group 14 (Sn in particular), and Group 15 (As-Bi) nitrogen and phosphorus bonded complexes reported previously in the literature; the major focus being on imido (RN^2-) and phosphinidine (RP^2-) complexes. Chapter 2 gives experimental and general experimental details concerning the starting materials used and the twenty-five novel species produced in this thesis (which have been fully characterised using a range of analytical, spectroscopic and structural techniques). The experimental results are discussed in chapters 3-6. Chapter 3 concerns the syntheses of new Group 15-nitrogen bonded species, focusing on the use of dimmers of the type [(Me₂N)E(μ-NR)]₂ (E= As, Sb, Bi) as precursors on other Group 15 molecular arrangements. In Chapter 4, attempts are made to use [(RP)_nAs]^- anions as ligands to main group and transition metals. There studies were largely unsuccessful owing to an undesired As-As coupling reaction. However, insights into the composition of the reaction mixtures formed between E(NMe₂)₃ and RPH^- ions have been obtained from structural studies. In Chapter 5, several novel Sn(II)-phosphinidine complexes are synthesised from the reactions of Sn(NME₂)₂ with RPHM (M= alkali metal). These studies help in unravelling the mechanism of the P-P bond-forming reaction; in particular suggesting that the tendency to form P-P bonds in the products stems from the increase in nucleophilicity of the RPH^- anions as the size of the alkali metal is increased. Chapter 6 presents studies of Group 13 phosphinidine complexes. Several new heterometallic alkali metal-A1(III) and –In(III) complexes of this type are prepared and fully characterised, containing a variety of mixed-metal compositions.

L'objectif de ce travail est de développer et caractériser un prépolymère hyperbranché thermodurcissable dont les propriétés rhéologiques avant polymérisation répondent au procédé de mise en œuvre par RTM. Pour cela nous avons envisagé la préparation d'un précurseur du type AB2 avec B sont des fonctions aminées et A des fonctions hemiester. Ce précurseur est préparé suivant une synthèse multi étape (8 étapes) et chaque intermédiaire ainsi que le produit final ont été identifiés par RMN 1H, 13C, 31P et par des méthodes couplées chromatographie/spectrométrie de masse. Dans une première approche la polymérisation du monomère AB2 pour former le polymère hyperbranché a été réalisée en solution. Dans une deuxième étape, des motifs réticulant thermostables comme le phénylacétylène, ont été fixés sur les fonctions terminales de la structure hyperbranchée, afin d'obtenir un polymère à propriété spécifique. Nous avons étudié le comportement thermomécanique de ce polymère dans des zones de températures bien définies afin d'établir ses propriétés thermiques

This thesis describes the synthesis, reactivity and coordination chemistry of a range of bidentate phosphino-imine ligands. The reactivity of the resultant complexes is also probed, while testing of the complexes for catalytic activity in a range of carbon-carbon bond-forming reactions is documented. Chapter 1 introduces the concepts of 'hemi-lability' and 'trans-influence', along with heteroditopic bidentate ligands, and specifically examines imine- and phosphine-based ligands, particularly aminophosphines. The nature of the phosphorus centre in terms of its steric and electronic properties is surveyed, and the bonding of phosphines and imines with metals is discussed. A review of transition metal-catalysed olefin oligomerisation and polyketone formation then follows. Finally, the aims of this work are outlined. Chapter 2 introduces the PNP ligand {(Pri2N)2PCH2C(=NPri)CH2P(NPri2)2}, previously synthesized within the Dyer group. The reactivity and coordination chemistry of this ligand are then explored, and the reactivity of the resultant complexes probed. The complex [PdCl(Me)(PNP)] has been crystallographically characterised. Chapter 3 briefly introduces guanidines, before describing the synthesis of two new types of phosphino-imine ligand derived from bicyclic and acyclic guanidines {R2P(TBD), R = Ph, Mes, Pri 2N, Ph2N and Ph2P(DMC), respectively}. The reactivity and coordination chemistry of these ligands is then explored, with particular attention paid to the effects of varying the substituents at phosphorus in R2P(TBD). The reactivity of the resulting complexes is then documented. The molecular structures of the ligands Ph2P(TBD), (Pri2N)2P(TBD) and Ph2P(DMC), and of twenty of their complexes have been determined. Chapter 4 describes the synthesis of the new P.;N ligand Ph2P(2-IP). The reactivity and coordinationchemistry of this ligand is then appraised, as is the reactivity of the resulting complexes. The structures of four complexes of this ligand have been probed crystallographically, as has a serendipitously formed nickel complex. Chapter 5 documents the catalytic testing conducted, using the complexes prepared in the chapters 2-4.

Chiral molecules as with biological activity are plentiful in nature and the chemical literature; however they represent a smaller portion of the pharmaceutical drug market. As asymmetric methodologies grow more powerful, the tools are becoming available to synthesize chiral molecules in an enantioselective and efficient manner. Recent breakthroughs in our understanding of phosphoric acid now allow for Lewis acid catalysis via pairing with alkaline earth metals. Using alkaline earth metals with chiral phosphates is an emerging approach to asymmetric methodology, but already has an influential record. The development of new conditions for the phosphoric acid-catalyzed highly enantioselective ring-opening of meso-aziridines with a series of functionalized aromatic thiol nucleophiles is described in this thesis. This methodology utilizes commercially available aromatic thiols, a series of meso-aziridines, and a catalytic amount of VAPOL calcium phosphate to explore the substrate scope of this highly enantioselective reaction. Additionally, the development of new conditions for a catalytic asymmetric aza-Darzens aziridine synthesis mediated by a vaulted biphenanthrol (VAPOL) magnesium phosphate salt is described in this thesis. Using simple substrates, this methodology explores the scope and reactivity of a new magnesium catalyst for an aziridination reaction capable of building chirality and complexity simultaneously.

Le présent travail concerne l'étude de la réactivité du di(dichlorophosphoryl)imide, HN(POCl2)2, vis-à-vis de la N,N-bis(chloro-2 éthyl)amine (bCEA), avec comme objectif la synthèse de molécules présentant une activité antitumorale. Nous avons pu mettre en évidence la formation des dérivés de mono, di et tétrasubstitution, ainsi que l'existence de diastéréoisomères pour les dérivés mono et bismonosubstitués. L'utilisation conjointe de la RMN (31P, 13C, 1H) et de la spectrométrie de masse a permis de montrer l'instabilité du dérivé tétrasubstitué qui se transforme en dérivé O-alkylé avec perte de HCl. Nous avons ensuite étudié les réactions de cosubstitution de HN(POCl2)2 par la bCEA et l'ammoniac d'une part, la bCEA et la glycine éthyl ester (NH2CH2COOEt) d'autre part. Les études spectroscopiques des produits formés montrent dans ce cas l'intervention de réactions de N-alkylation. Tirant parti de l'expérience acquise par le laboratoire dans le domaine des polyorganophosphazènes, nous avons enfin synthétisé et caractérisé un copolymère de type [NP(NHCH2COOEt)2-x(N(CH2CH2Cl)2)x]n (x=0,6). L'efficacité antitumorale de cinq composés ou mélanges de composés préparés au cours de ce travail a été évaluée. Cette évaluation a permis de montrer que seul le dérivé ayant conservé la structure d'un agent alkylant bifonctionnel présentait une activité antitumorale

Dans le but de valoriser les agroressources régionales, nous avons synthétisé des glycodendrimères à partir de deux pentoses (le D-xylose et le L-arabinose) utilisables dans des réactions micellaires enantiosélectives ou dans le domaine biomédical en tant que récepteurs artificiels. La première partie de ce mémoire porte sur la synthèse de glycodendrimères azotés à partir de PAMAMs (PolyAMidoAMines) ou de PPIs (PolyPropylène Imines) possédant des fonctions amines en surface. Par réaction de condensation entre ces fonctions et des pentonolactones, issues des deux pentoses, nous avons réussi à obtenir des glycodendrimères de première génération. Toutefois l’optimisation aux générations supérieures reste à mettre au point. Dans une deuxième partie, nous avons voulu obtenir des glycodendrimères siliciés à partir de trois types de réaction : les réactions d’hydrosilylation, de silylation et de type « click ». Aucun résultat probant n’a été obtenu à partir des réactions d’hydrosilylation, en revanche, des petites molécules et des glycodendrimères de première génération ont été obtenus par une séquence « hydrosilylation/condensation » et par réaction de silylation. Des glycodendrimères de génération 1 à 3 ont été obtenus par réaction de type « click », cependant la méthode de purification reste à mettre au point. Enfin, la troisième partie s’est révélée beaucoup plus enrichissante car nous avons réussi à obtenir de façon très simple et quantitative les premiers glycodendrimères phosphorés à partir d’un dérivé du D-xylose, de la génération 1 à 3 et à déprotéger les entités pentosidiques
With the aim of developing renewable ressources from the region of Champagne-Ardenne, we synthesized glycodendrimers, starting from two pentoses (D-xylose and L-arabinose), usable in micellar reactions or like artificial receptors in biomedical field. The first part of this memory relates to the synthesis of nitrogen-based glycodendrimers starting from PAMAMs (PolyAMidoAMines) or PPIs (PolyPropylene Imines) having both the functions amines on the surface. By reaction of condensation between these functions and the pentonolactones, resulting from the two pentoses, we succeeded in obtaining glycodendrimers of first generation. However optimization with the higher generations remains to be developed. Then, in a second part, we wanted to obtain silicon glycodendrimers starting from three kinds of reaction: hydrosilylation, silylation and click chemistry. No convincing results were obtained starting from the reactions of hydrosilylation some either catalyst used and some length of the chain. On the other hand, small molecules and dendrimers of first generation were obtained by a sequence “hydrosilylation/condensation” and by reaction of silylation. Glycodendrimers of generation 1 to 3 were obtained by click chemistry but the method of purification remains to be developed. Lastly, the third part appeared much more encouraging because we succeeded in obtaining the phosphorated first glycodendrimers, starting from a derivative of D-xylose, of generations 1 to 3 by reaction of substitution with quantitative yields. A simple method of purification by successive precipitations was also developed as well as the deprotection of the acetyls groups

This master´s thesis deals with the properties of gel polymer electrolytes, brief characteristics of other types of electrolytes and materials that are used for preparing polymer electrolytes. The thesis explains the use of the gel electrolytes in practice, the current conduction in the electrolytes and the properties of ionic liquids, and flame retardants. This thesis also focuses on methods of measurement of mechanical properties of gel polymer electrolytes. The practical part is focused on preparation of methacrylate gel electrolytes and their modifications with the use of flame retardant - triethyl phosphate (TEP) and ionic liquid - 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide (Emim TFSI). In this part there are evaluations of their potential funcionality (potential window) and specific conductance conductivity using the method LSV (linear sweep voltammetry) and impedance spectroscopy. The practical part also includes a thermal analysis of selected samples by TGA, DTA and EGA methods.

Cette étude développe les avantages de la voie carbanionique dans la préparation des phosphonates fonctionnels. La condensation des carbanions d'alkyphosphonates avec des précurseurs fonctionnels appropriés permet d'accéder aux énamines, amides et esters alpha-phosphorylés alpha-substitués. Elle permet d'introduire sur le carbone en alpha des substituants non accessibles par la synthèse traditionnelle de Michaelis-Arbusov. La stabilisation de l'intermédiaire réactionnel par complexation du cation avec le groupe phosphoryle assure sa formation facile et sa protection contre des attaques secondaires non-desirées. Toutefois, cette espèce carbanionique est suffisamment nucléophile vis-a-vis de divers aldéhydes et peut être utilisée directement dans une réaction de Wittig-Horner "in situ" pour la synthèse des imines, amides et esters alpha, bêta-insaturés, alpha-substitués. Ce schéma permet donc de préparer des phosphonates fonctionnels alpha-substitués ou de transférer directement la fonction lors de la réaction d'oléfination sans isoler le phosphonate intermédiaire

La montmorillonite K10 et la silice ont été activées par des acides de Lewis, et nous y avons incorporé ensuite des greffons chiraux (diéthyltartrate, diisopropyltartrate, phénylalaninol, éphédrine, et salen). Des silices ont également été greffées avec des esters d'allyles et ont été activées ensuite avec des acides de Lewis. Ces catalyseurs ont été caractérisés par absorption atomique, analyse élémentaire, et infrarouge. Ils ont été utilisés dans trois réactions types : la formation de phosphonates - fonctionnels, la réaction d'aldolisation et la réaction de cyanosilylation. La première réaction se fait par addition d'un aldéhyde ou d'une imine à un phosphite (silylé ou non) ; les rendements obtenus sont dans l'ensemble satisfaisants, et mettent en évidence l'influence de la présence d'un motif chiral sur le pouvoir catalytique de nos supports. La réaction d'aldolisation a été étudié par addition d'un énoxysilane à un aldéhyde, voie qui ne fournit pas de résultats satisfaisants ; le remplacement de l'énoxysilane par un acétal de cétène silylé permet d'obtenir de bons rendements, mais pas d'énantiosélectivité. La réaction de cyanosilylation a été étudiée par addition de cyanotriméthylsilane au benzaldéhyde, et permet d'obtenir le mandélonitrile avec un rendement quantitatif et jusqu'à 40% d'excès énantiomérique ; le catalyseur peut être recyclé sans perte de rendement et avec une légère baisse d'énantiosélectivité. L'ensemble de ce travail montre que les catalyseurs supportés sur montmorillonite et silice sont efficaces, sont compatibles avec des réactifs très sensibles à l'hydrolyse et qu'ils produisent dans certains cas une énantiosélectivité tout en permettant de limiter les quantités de solvants utilisés.

碩士
國立勤益科技大學
化工與材料工程系
103
The main studies of this dissertation are divided into two parts: (1) preparation and appraisal of the α-Zirconium Phosphate ( α-ZrP )；(2) synthesize and characterize of the Polyimide/Zirconium Phosphate ( PI/ZrP ) and Poly(amide-imide)/Zirconium Phosphate ( PAI/ZrP ) nanocomposite films. In this study, – the α-zirconium phosphate ( α-ZrP ) was prepared by thermal reflex method.The characterization and structure was confirmed by FTIR, XRD spectroscopy and SEM, TEM images. The composite films are synthesized from 4,4'-oxydianiline ( ODA ), Pyromellitic dianhydride ( PMDA ) and trimellitic anhydride chloride ( TMAC ) via polymerization method, which change molar ratio of anhydride monomer PMDA and TMAC, the contents of ZrP, and then a series of composite films characteristic analysis. The water vapor transmission rate ( WVTR ) of series of PI-1-TMAC/ZrP films are the lowest one compared with series of PI-0.5-TMAC/ZrP films. A significant decrease in WVTR by 88%, from 116.36 to 13.43 g/ m2-day, was observed upon the addition of 5 wt% of ZrP in PI-1-TMAC matrix. The the strong interfacial adhesion between ZrP and PI-1-TMAC matrix, distribution of ZrP with the features of high aspect ratio and high specific surface area in PI-1-TMAC matrix could effectively extend the path of the water vapor passing through the thin film, thus significantly improved water vapor barrier property. In electrochemical corrosion measurements of PI/ZrP nanocomposites. The CRS coated with PI/5 shows the best anticorrosion than those coated with pure PI and uncoated CRS.

Dendrimers are hyperbranched macromolecules, with branches-upon-branches architectures, precise constitutions and molecular weights of several kiloDaltons (Figure 1). The dendritic structure remains to be an influential feature in the developments of dendrimer chemistry at large. Organometallic catalysis forms an active area, wherein the dendrimers find a defined importance. A number of dendrimer types have been utilized to study organometallic catalysis that combine the dendritic architectural principles. Chapter 1 of the Thesis summarizes the advances in the dendrimer-mediated catalyses, apart from an overview of the methods adopted to synthesize dendrimers. Chapter 2 describes the synthesis of newer types of larger generation poly(propyl ether imine) (PETIM) dendrimers. The molecular structure of a sixth generation PETIM dendrimer is shown in Figure 2. The PETIM series of dendrimers are synthesized by iterative synthetic cycles of two reductions and two Michael addition reactions. Modifications of the synthetic methods were identified, so as to facilitate the synthesis and purification of the higher generation dendrimers. Formation of the PETIM dendrimers, possessing a tertiary amine as the branch juncture and ether as the linker component, is assessed systematically by routine analytical techniques. The peripheries of these dendrimers possess either alcohols or amines or carboxylic acids or esters or nitriles, thereby opening up possibilities for varied studies. Architecturally-driven effects are searched constantly while integrating dendrimers in wide ranging studies. With knowledge that un-functionalized PAMAM and PPI dendrimers show fluorescence properties, we tested the PETIM dendrimers for their luminescence property. The photophysical properties of PETIM dendrimers presenting esters, alcohols, acid salts, nitriles and amines at their peripheries were studied. The anomalous fluorescence arising from alcohol terminated PETIM dendrimers (Figure 3) was established through a series of experiments. Various experimental parameters including pH, viscosity of the solvents, aging, temperature and concentration were used to assess the photochemical properties of the PETIM dendrimers. It was observed that generations 1 to 5 absorbed in the region of 260-340 nm, in MeOH and in aqueous solutions. Excitation of the OH-terminated dendrimer solutions at 330 nm led to an emission at ~390 nm (Figure 4). Dendrimers presenting esters, acid salts and amines at their peripheries also exhibited a similar excitation and emission wavelengths. An increase in the fluorescence intensity was observed at low pH and with more viscous solvents. Lifetime measurements showed at least two species (~2.5 and ~7.0 ns) were responsible for the emission. The quenching of the fluorescence originating from the PETIM dendrimers by inorganic anions was also established in the present study. The periodate, persulfate, perchlorate and nitrite anions quenched the fluorescence efficiently among several anions tested. An ‘oxygen-interacted moiety’, in addition to altered hydrogen bonding properties of the dendrimers, was presumed contribute to the anomalous fluorescence behavior. Chapter 3 of the Thesis elaborates photophysical studies of several PETIM dendrimers. Incorporation of catalytically active moieties at the peripheries of dendrimers was identified as an important avenue, in order to explore the effect of the dendritic architectures on the catalytic activities of chosen catalytic moieties. In order to assess the effect of the dendritic scaffold, in relation to both numbers and locations of the catalytic units, an effort was undertaken to study the catalytic activities of catalytic units, that are present in varying numbers within one generation. Partial and full phosphine-metal complex substituted three generations of dendritic catalysts were synthesized, by using a selective alkylation as a key step. The number of the primary amine groups led to define the number of phosphine groups at the peripheries. The primary amine groups were, in turn, prepared by a Michael addition of acrylonitrile and hydroxyl groups, followed by a reduction of the nitrile moieties to the corresponding amines. The first and the second generation PETIM dendrimers utilized in this study present up to four and eight hydroxyl groups at their peripheries. A partial etherification was exercised in order to mask few hydroxyl groups, useful to prepare the partially substituted phosphine groups. Subsequent Michael addition of acrylonitrile with remaining hydroxyl groups, to afford the nitrile terminated dendrimers, and a metal-mediated reduction of the nitrile to amine led to the required number of amine functionalized dendrimers. Functionalization of the peripheries with alkyldiphenyl phosphine moieties was conducted through a Mannich reaction of the amines with formaldehyde and diphenyl phosphine. The subsequent metal complexation with Pd(COD)Cl2 afforded a series of phosphine-Pd(II) complexes, for the zero, first and second generation PETIM dendrimers. Figure 5 shows the molecular structures of a partially and a fully substituted second generation dendrimer. Catalytic activities of the dendrimer-Pd(II) complexes were assessed in both Heck and Suzuki coupling reactions. A C-C bond forming reactions were studied, with the series of dendritic-Pd(II) catalysts, using Cs2CO3 as a base and at 40 oC. In an overall observation, it was found that an individual catalytic site showed a considerable increase in the catalytic activity when it was present in multiple numbers than as a single unit within the same generation (Figure 6). Figure 6. Bar diagrams of (a) Heck reaction and (b) Suzuki reaction, employing the dendritic catalysts 1 - 11. The Heck coupling reaction involved tert-butyl acrylate and iodobenzene, and the Suzuki coupling reaction involved phenyl boronic acid and iodobenzene. The observations revealed that: (i) the higher generation dendritic catalysts exhibited higher catalytic activities per catalytic site and (ii) the dendritic scaffold has a role in enhancing the activities of the individual catalytic sites. The catalysis study identified the catalytic activities that occurred when a series of catalysts within a given dendrimer generation was used. Such a study is hitherto unknown and the observations of this study address some of the pertinent queries relating to the efficiencies of multivalent dendritic catalysts. Chapter 4 of the Thesis describes the synthesis and characterization of series of organometallic PETIM dendrimer and studies of their catalytic activities. Studies on solid-supported catalysis present a significant importance in heterogeneous organometallic catalysis. Silica is a prominently utilized heterogeneous metal catalyst support. Functionalization of the solid supports with suitable chelating ligands is emerging as a viable strategy to circumvent not only the pertinent metal catalyst deterioration and leaching limitations, but also to stabilize the metal particles and to adjust their catalytic efficiencies. In exploring heterogeneous organometallic catalysis, functionalization of silica with a first generation phosphinated dendritic amine was undertaken. The synthetic scheme adopted to synthesize dendrimer functionalized silica is shown in Scheme 1. The reaction of the chloropropylated silica 4 with amine 3 was conducted in CHCl3. Complexation of the functionalized silica 5 with Pd(COD)Cl2 led to isolation of Pd(II)- impregnated silica. Scheme 1. Preparation of Pd nanoparticles stabilized by functionalized silica. It was anticipated that the ratio of phosphine to Pd(II) would be 1:0.5, resulting from a bidendate binding of the phosphine ligand to Pd metal. The observed ICP-OES result indicated that all phosphine ligands did not chelate the metal. With the desire to obtain the metal nanoparticles, the metal complex was subjected to a reduction, which was performed by conditioning 5-Pd(II) complex in EtOH. The Pd metal nanoparticle thus formed was characterized by physical methods, and the spherical nanoparticles were found to have >85 % size distribution between 2-4 nm (Figure 7). Analyses of the Pd(0) impregnated in dendrimer functionalized silica were performed using NMR, XPS spectroscopies, elemental analysis and microscopies. Figure 7. Transmission electron micrograph and histogram of 6, obtained after treatment with EtOH. The Pd-nanoparticle stabilized silica was used in the hydrogenation of several α, β-unsaturated olefins. The catalyst recycling experiments were conducted more than 10 times, and no loss in the catalytic activities were observed. Chapter 5 describes the functionalization of the silica support with diphenylphosphinomethyl-derivatized dendritic amine, palladium nanoparticle formation and the catalysis studies. Overall, the Thesis establishes the synthesis of larger generation PETIM dendrimers, studies of their anomalous fluorescence behavior, organometallic catalysis in solution, as well as, in heterogeneous conditions, pertaining to the C-C bond forming reactions and hydrogenation reactions. (For figure, graph and structural formula pl see the pdf file)

A wide variety of computational methods are available for exploring molecular structures and reactivity in chemistry. These range from molecular mechanics calculations allowing determination of the geometry of a molecule to ab initio calculations for the electronic structure of compounds. Electronic structure calculations can be carried out with sufficient rigor so that the results are now comparable with experimental results in many cases. Density Functional Theory (DFT) with hybrid functional like B3LYP, for example, is very popular especially for studies on organometallic molecules and their reactions. Traditional ab initio approaches including Hartree-Fock (HF) and post-HF methods that include configuration interaction, such as MP2 and MP4 continue to be used, often for comparison with DFT based methods. Semi-empirical methods now appear to have only limited use except in large systems, in combination with molecular mechanics (MM) calculations. A relatively new use of MM for large systems is in hybrid calculations where the reactive center of the system is treated at a higher level leaving the remainder to be treated at the MM level. These hybrid QM/MM (quantum mechanics/molecular mechanics) calculations, such as ONIOM (our own n-layered integrated molecular orbital and molecular mechanics developed by Morokuma and co-workers) enable one to treat the steric bulk of the big system effectively and computationally efficiently. They appear to be very standard methods particularly in studies relating to reactions of organometallic systems and structures of large biomolecules. A short description of these methods is given below. • ab initio: a wide variety of programs that calculate the electronic structure of molecules using the Schrödinger equation, the values of the fundamental constants and the atomic numbers of the atoms present (Atkins, 1991). Molecular structures, optimized as a function of the electronic structure, are valuable starting points for many studies. • Density Functional Theory (DFT): a theoretical model in which the energy of an N-electron system is described as a functional of the density. • Semi-empirical techniques use approximations to evaluate the overlap, repulsion and exchange integrals in solving the Schrodinger equation. Often, these integrals are not evaluated but estimated to reproduce experimental data. • Molecular mechanics uses classical physics to explain and interpret the behavior of atoms and molecules. • Molecular dynamics (MD): Newton’s laws of motion are used to examine the time-dependent behavior of systems, including vibrations and Brownian motion, using a classical mechanical description. When combined with DFT, it leads to the Car-Parrinello method. • QM/MM method: It is a molecular simulation method that combines the strength of both QM (accuracy) and MM (speed) calculations, thus resulting in an extremely powerful tool for the study of bigger systems like chemical process in solution, interaction of drugs with biomolecules etc. Several commercial and educational packages in computational chemistry include a suite of programs that enable study of organic and organometallic molecules in an integrated fashion. While no list can be comprehensive, those that are more popular and useful are listed in several websites URL (http://www.ccl.net/chemistry/links/software/index.shtml). In the early days of computational chemistry up to 1980's, detailed studies were only carried out on small organic compounds or empirical studies were carried out on transition metal containing organometallics. However, in recent times, significant advancements in theoretical methods and computer capability (hardware and software), have led to the acceleration of theoretical and computational studies of complex systems including compounds containing transition metal elements. Computational and theoretical studies of organometallic complexes and their reactions have gained immense popularity and the numbers of papers including theoretical studies are dramatically increasing. One reason for this popularity is that organometallic complexes exhibit unusual geometries, bonding, and reactivity which often do not fall into the domain of inorganic or organic chemistry making them difficult to understand. Catalysis is one of the most extensively studied areas in organometallic chemistry where computational studies already make a real and valuable contribution to the analysis and interpretation of experimental data. However, what might be called ‘in silico’ catalyst screening and design, has rarely been achieved. One might say that successful prediction of catalyst performance is still a dream. A recent review summarizes the current state of the art in computational chemistry as applied to organometallic catalysis, covering both calculated ligand property descriptors and mechanistic studies of catalytic cycles.1 Some of the widely studied catalytic reactions of current interest, that provide huge scope for computational and theoretical analysis, are allylic alkylation (Pd),2 hydrogenation (Rh),3 hydroformylation (Rh),4 alkene metathesis (Ru),5 cross-coupling (Pd),6 C–H activation (Pd)7 and amination (Pd).8 There are many more examples where computational studies appear to be very useful for analysis of crystal structures and NMR structures or prediction of structures where no experimental data are available for complicated organometallic systems. There are a number of studies on drug-DNA/nucleobases interactions using QM/MM-MD simulations where people have investigated the interactions of metal complexes with double stranded (ds) DNA/nucleobases and the effects of their binding on the local and the global structure of DNA. QM/MM methods are also very helpful for studying catalytic reactions, interpretation of structure of large systems (proteins) and understanding reactions in biological systems. Scope of the Thesis In this thesis an attempt is made to use computational chemistry to understand organometallic reactions that are of significance from biological and synthetic view points, such as the action of organometallic complexes on DNA and the mechanism of some catalytic reactions. In many of these cases, the key step involved a nucleophillic attack. Specifically four such problems have been addressed where experimental results are not sufficient to provide a complete mechanistic picture of the reaction. Hence, the thesis contains four chapters with each having an independent brief introduction. The first chapter deals with the substitution reaction where water replaces chloride ion in the piano stool type ruthenium (II)-arene complexes and subsequently coordination of Ru to guanine/adenine occurs in these complexes. These steps have been studied using density functional theory at the B3LYP level. The complexes have promising anticancer activity. These nucleophilic substitution reactions are very important for activating these complexes so that they can interact with DNA, because DNA is thought to be primary target for their anticancer activity. In this chapter, both associative and dissociative pathways have been explored in the gas phase, as well as in the presence of other solvents for substitution reactions. Among the associative paths, a variety of possibilities can exist for the hydrolysis based on the direction of the nucleophilic attack by a water molecule. The proposed theoretical model for hydrolysis provides new insight into the hydrolysis process in half sandwich ruthenium complexes. The second chapter deals with the QM/MM calculations to investigate the structural and electronic properties of drug-DNA interactions, where DNA acts as nucleophile towards the metal complex. A series of piano-stool type ruthenium (II)-arene complexes were selected for the present study. These interactions were analyzed using the two layer ONIOM method. The importance of this study lies in the detailed understanding of factors that govern DNA binding and reactivity which is clearly of great pharmacological interest, as it may provide the basis for designing better anticancer agents. Experimental results that explore the structural feature of DNA-metal complexes at a molecular level are very limited. Thus theoretical calculations of molecular and electronic structure represent a valuable complement to experiments. They provide an alternative way to explore structure-activity relationships, and the drug binding mechanism, in detail. The third chapter reports the use of QM/MM methods in understanding the reaction mechanism and enantioselectivity in an organic transformation. In this section, a computational investigation of the enantioselectivity observed in the allylation of cinnamaldehyde, catalyzed by chiral platinum phosphinite complexes, have been carried out. The catalysts are ascorbic acid based phosphinite complexes where enantioselectivity depends on the substitution of benzyl groups on the chiral phosphinite ligands. From the experiment, it is not clear how the effect of an ancillary ligand can make such a big impact on enantioselectivity. To find out the origin of stereoselectivity, a computational study was taken up. A reaction mechanism was established where the nucleophilic attack determines the rate of the reaction and the corresponding enantioselectivity. A screening process has been utilized to select relevant reactant adducts and corresponding transition states from approximately 200 theoretically possible conformers using MM calculations. Finally with the help of QM/MM calculations, the numbers of contributions of these conformers were estimated. This approach correctly predicts the enantioselectivity in these reactions catalyzed by these complexes especially when the experimental enantioselectivity is very high. The fourth chapter of the thesis discusses the use of computational techniques to study the nucleophilic attack of an imine on a Ti-olefin complex. The reaction of Grignard reagents with imines mediated by stoichiometric amounts of titanium isopropoxide has been reported recently. On the basis of deuterium labeling experiments, nucleophilic attack of an imine on a Ti-olefin complex was believed to be a key step. Effect of deuterium labeling on the ratio of products formed is not easy to understand from experiments. Hence a computational study was performed using the DFT method to establish the mechanism of substitution and to understand the role of deuterium labeling. The thesis also includes a study of Cu-Cu interactions using Atoms in Molecules (AIM) theory in copper complexes with reasonably short Cu-Cu distances. The concept of bond critical points (BCP) from AIM analysis is employed to investigate the CuI-CuI bonding interactions in ligand unsupported copper complexes where the CuI-CuI contacts are shorter than the sum of their van der Waals radii. There is extensive debate about the nature of interactions between d10 "closed shell" systems in copper (CuI) complexes, which is known as cuprophilicity. In this study, an attempt has been made to compute the electron density between the two CuI centers and examine the nature of this “interaction”. As this falls outside the main theme of nucleophilic interactions in metal complexes, it has been relegated to an appendix.