Dissertations / Theses on the topic 'Cyanide ligand'

Cette thèse porte sur la synthèse et la caractérisation de complexes octaédrique de fer(II) et fer(III) coordinés par un ligand tridente de type scorpionate (symétrie fac) et par trois ligands cyanures. Leur utilisation en tant que metalloligand face à des ions métalliques partiellement bloqués est étudiée. Les ligands cyanures, de par leur caractère ambidente, permettent un accès facile aux espèces hétérobimétalliques. De plus, ces ligands sont connus pour transmettre efficacement l'interaction d'échange magnétique et donc pour favoriser la communication électronique intramoléculaire entre les ions métalliques qu'ils relient. La fonctionalisation des ligands scorpionates permet de contrôler les propriétés électroniques intrinsèques des complexes précurseurs de fer, et donc de moduler les propriétés des espèces polynucléaires obtenues à partir de ces dernières par auto-assemblage. Dans cette thèse, un intérêt particulier est porté aux systèmes {FeCo} en raison de leur capacité à présenter une bistabilité électronique (propriétés photomagnétiques ou de molécules/chaines aimants). Les systèmes cyanuré {FeCo} sont particulièrement adaptés pour l'observation de réarrangements électroniques thermo- et/ou photo-induit, comme en témoignent le nombre important de composés cyanurés photomagnétiques dans la littérature
The work presented in this PhD dissertation focuses on the synthesis and the characterisation of octahedral iron(II) and iron(III) complexes coordinated by a tridentate ligand of the scorpionate family (fac- geometry) and three cyanide ligands. Their use as metalloligands in respect to partially blocked metal ions is studied. Because of their ambidentate character, cyanide ligands open the door to facile synthesis of heterobimetallic species. Moreover, these ligands are known to be efficient magnetic exchange interaction transmitter, thus favouring intramolecular electronic communication between the metal ions they are bridging. The functionalisation of scorpionate ligands allows control over the intrinsic electronic properties of the iron precursor complexes, thus allows to tune the properties of the obtained polynuclear species from the latter by self-assembly. In this PhD dissertation, a particular interest was taken in {FeCo} systems because of their potential ability to exhibit electronic bistability (photomagnetic properties or SMM/SCM behaviour). Cyanide-bridged {FeCo} systems are particularly suitable for the observation of thermally or light-induced electron rearrangements, as testified by the wide range of photomagnetic cyanide-bridged compounds in the literature

Cyanide-catalyzed aldimine coupling was employed to synthesize compounds with 1,2-ene-diamine and α-imine-amine structural motifs: 1,2,N,N'- tetraphenyletheylene-1,2-diamine (13) and (+/-)-2,3-di-(2-hydroxyphenyl)-1,2- dihydroquinoxaline (17), respectively. Single crystal X-ray diffraction provided solidstate structures and density functional theory calculations were used to probe isomeric preferences within this and the related hydroxy-ketone/ene-diol system. The enediamine and imine-amine core structures were calculated to be essentially identical in energy. However, additional effects-such as π conjugation-in 13 render an enediamine structure that is slightly more stable than the imine-amine tautomer (14). In contrast, the intramolecular hydrogen bonding present in 17 significantly favors the imine-amine isomer over the ene-diamine tautomer (18). Aldimine coupling (AIC) is the nitrogen analogue of the benzoin condensation and has been applied to dialdimines, providing the first examples of cyclizations effected by cyanide-catalyzed AIC. Sodium cyanide promoted the facile, intramolecular cyclization of several dialdimines in N,N-dimethylformamide, methanol, or dichloromethane/water (phase-transfer conditions) yielding a variety of six-membered heterocycles. Under aerobic conditions, an oxidative cyclization occurs to provide the diimine heterocycle. Cyanide-catalyzed aldimine coupling was employed as a new synthetic method for oligomerization. Nine rigidly spaced dialdimines were oxidatively coupled under aerobic conditions to yield conjugated oligoketimines and polyketimines with unprecedented structure and molecular weight (DP = 2 - 23, ~700 -8200 g/mol). The α- diimine linkage was established based on IR spectroscopy, NMR spectroscopy, size exclusion chromatography, and X-ray crystallographic characterization of the model oxidized dimer of N-benzylidene-(p-phenoxy)-aniline. Cyclic voltammetry indicates ptype electrical conductivity, suggesting they are promising candidates for plastic electronic devices. The cyanide-catalyzed benzoin condensation reaction of 4-substituted benzaldehydes followed by oxidation to the diketone, and the Schiff Base condensation of two equivalents of o-aminophenol provides 2,3-(4-X-phenyl)2-1,4-(2- hydroxyphenyl)2-1,4-diazabutadiene. The ligand is given the moniker X-dabphol. These ligands are readily metallated to form M-X-dabphol complexes. The copper complexes catalytically fix CO2 with propylene oxide to yield propylene carbonate. DFT studies along with a comparison with Hammet parameters help validate and elaborate on the catalytic cycle and the catalytic results obtained. The nickel complex is competent for olefin epoxidation. Synthesis, characterization, X-ray structure, DFT analysis, and catalytic activity of the parent nickel dabphol complex are reported.

The content of this thesis is concerned with two distinctly independent areas of research: (i) the synthesis and study of new poly(pyrazol-1-yl)borate ligands and their metal complexes; (ii) crystallographic and photophysical studies of new d-f hybrid complexes. Chapter One is divided into three parts: Part one gives a general introduction to poly(pyrazol-1-yl)borate chemistry along with a concise and up-to-date review of those ligands containing substituents in the C3 position of the pyrazolyl ring; part two provides a brief introduction into the physical properties of lanthanide(III) metal ions, as well as describing the practical applications of their individual spectroscopic properties; and part three contains a brief review on the structural chemistry of cyanide-bridged coordination polymers. Chapter Two describes the syntheses of four new scorpionates: dihydrobis[3-(4-pyridyl)pyrazol-1-yl]borate (Bp4py); dihydro-bis[3-(3-pyridyl)pyrazol-1- yl]borate (Bp3py); hydro-tris[3-(4-pyridyl)pyrazol-1-yl]borate (Tp4py) and hydrotris[3-(3-pyridyl)pyrazol-1-yl]borate (Tp3py). A series of X-ray crystallographic studies reveals a range of mononuclear, dinuclear and polymeric coordination complexes with various metal ions. Chapter Three describes a range of structural and photophysical studies on lanthanide(III) complexes of poly(pyrazol-1-yl)borate ligands. New mixed-ligand lanthanide(III) complexes with various combinations of the anionic ligands Tp2py , Bp2py and dibenzoylmethane (dbm) were prepared and structurally characterised. Photophysical studies on the isostructual series [Ln(Bp2py)(dbm)2] (Ln = Pr, Nd, Er, Yb) show characteristic near-IR luminescence from the lanthanide ion. Near-IR luminescence was also demonstrated from the complexes [Ln(Bp2py) 2(NO3)] and [Ln(Tp2py)(NO3) 2] (Ln = Pr, Er), upon suitable excitation of the ligand chromophores. Chapter Four describes the structural and photophysical properties of new cyanide-bridged d-f coordination polymers. Structural and photophysical studies are presented for a series of Ru-Ln complexes based on the [Ru(bipy)(CN)4] 2- donor unit connected to a Ln(III) energy-acceptor via cyanide bridges (where bipy is 2,2’- bipyridine and Ln = Pr, Nd, Er, Yb). Structural and photophysical studies were also performed on [Cr(CN)6][Ln(DMF)4(H2 O)2] complexes, in which the lanthanide ion (Ln = Nd, Yb) acts as the energy acceptor from the hexacyanochromate chromophore. The structures of [Cr(CN)6][Ln(H2 O)2] (Ln = Gd, Yb) and K2[Ru(phen)(CN)4] (where phen = 1,10-phenanthroline) are also presented. Chapter Five gives a brief review of the field of X-Ray Crystallography with analysis of the history and theory of the technique, as well as an overview of its practical aspects used in this work. A few crystal structures solved by the author, and independent of the topics in this thesis, are also reported.

L’une des grandes directions de recherche dans la chimie moderne est la synthèse et l’étude denouveaux composés « commutables » capables de modifier leurs propriétés sous l’effet de stimuli extérieurs (température, lumière, champ magnétique ou électrique…). Ces systèmes peuvent stocker une information à l’échelle moléculaire. Dans ce contexte, parmi les systèmes les plus étudiés en chimie de coordination figurent les réseaux et les analogues moléculaires du bleu de Prusse. Cette thèse est dédiée à la synthèse et aux caractérisations de nouveaux analogues moléculaires du bleu de Prusse à transfert d’électron de type {Fe(µ-CN)M} (M = Fe, Mn, Co). Dans le premier chapitre sont présentées les familles de composés commutables à transfert d’électron par ordre décroissant de leur dimensionnalité, des systèmes 3D vers des systèmes discrets 0D. Le deuxième chapitre regroupe la synthèse et les caractérisations structurales, spectroscopiques, magnétiques, et électrochimiques de complexes-précurseurs de type [MII(LN5)]2+ et [FeIII(LN3/LN2)(CN)n]- (n = 2, 3) (LN5, LN3, LN2 étantdes ligands azotés penta-, tri- ou bidentes, respectivement) qui seront ensuite utilisés dans la synthèse des composés binucléaires. Le troisième chapitre présente la synthèse et les études structurales,spectroscopiques, magnétiques, optiques et électrochimiques de quatre nouveaux composés binucléaires paramagnétiques {FeIII(µ-CN)MII} (MII = Fe, Co). Enfin, le quatrième chapitre se focalise sur la synthèse et les propriétés spectroscopiques, magnétiques, photomagnétiques et électrochimiques de trois nouveaux complexes binucléaires diamagnétiques {FeII(µ-CN)CoIII} à transfert d’électron
One of the main research directions of modern chemistry is the synthesis and study of new switchablecompounds which can change their properties under external stimuli (temperature, light, magnetic orelectric field…). These systems can store the information at the molecular level. In this contextamongst the most studied systems in coordination chemistry are the 3D networks and the molecularPrussian blue analogs. This thesis deals with the synthesis and characterizations of new{Fe(µ-CN)M} (M = Fe, Mn, Co) molecular Prussian blue analogs. In the first chapter electrontransfer compounds are described in order of decreasing of their dimensionality, from 3D to thediscrete 0D systems. The second chapter describes the synthesis and structural, spectroscopic,electrochemical and magnetic characterizations of [MII(LN5)]2+ precursors (MII = Fe, Mn, Co) and[FeIII(LN3/LN2)(CN)n]- (n = 2, 3) (LN5, LN3, LN2 - nitrogen-based penta-, tri- and bi-dentate ligands,respectively), which are used in the synthesis of the binuclear complexes. Chapter three presents thesynthesis and structural, magnetic, spectroscopic and electrochemical studies of four binuclearparamagnetic {FeIII(µ-CN)MII} complexes (MII = Fe, Co). Chapter four is focused on the synthesisand spectroscopic, magnetic, photomagnetic and electrochemical properties of three binucleardiamagnetic {FeII(µ-CN)CoIII} electron transfer complexes

Ce mémoire est consacré à l'électrosynthèse, à la reactivite et à l'étude du comportement électrochimique de complexes organométalliques du niobium. La première partie de ce mémoire décrit le processus d'isomérisation du ligand nitrile pour des complexes du niobocène en fonction du degré d'oxydation du centre métallique. La seconde partie indique une nouvelle voie de synthèse de complexe imido du niobocène par action d'hydroxylamine aromatique sur le monochlorure de niobocène. La réduction monoélectronique de ces dérivés conduit à des complexes dimériques du niobium (IV) diamagnétiques. En présence de dioxyde de carbone ceux-ci évoluent vers la formation de dérivés carbonato du niobocène. La protonation du complexe imido conduit au complexe cationique amido dont la réduction électrochimique s'avère être catalytique. L'action d'amines aliphatiques sur les dihalogénures de niobocène conduit dans certaines conditions opératoires au complexe imido correspondant. La troisième partie de ce mémoire décrit l'étude de la réduction de dichlorure de niobocène vis à vis du groupe diazo (azobenzène et benzo(c)cinnoline). Si dans le premier cas on accède à des complexes du niobocène contenant le ligand azobenzène, en présence de benzo(c)cinnoline, on assiste à une élimination des deux ligands cyclopentadiényles avec formation d'un cluster a trois atomes de niobium. La dernière partie de ce travail traite de la réactivité de dichlorure de niobocène en présence de nitrobenzène et d'azoxybenzène. Dans le premier cas on démontre une propriété radicalaire non usuelle du complexe du niobium dont la réaction induit une modification du mode de coordination d'un des ligands cyclopentadiényles. Dans le deuxième cas le monochlorure de niobocène s'avère etre un agent de désoxygénation particulièrement efficace pour la transformation d'azoxybenzène en azobenzène.

Les œstrogènes sont des hormones stéroïdes, que circulent systémiquement chez les mammifères. Ils pénètrent dans leurs cellules cibles, interagissant avec les récepteurs des œstrogènes alpha et-ou bêta (REa REb : REs) ces interactions provoquent l'activation des REs régulant le système immun, la physiologie osseuse, le développement de certains cancers, entre autres. Les REs sont aussi activés sélectivement par d'autres molécules, l'objectif de ce travail est de concevoir et mettre au point une méthode de Criblage différentiel des ligands sélectifs et de haute affinité pour chaque RE (a et b). Cette méthode repose sur la synthèse de molécules d'œstradiol biotinylées, capables de se lier à la streptavidine immobilisée et d'interagir avec les REs. Pour les différencier, les REs ont été fusionnés en N-términal avec 2 protéines fluorescentes : la YFP « yellow fluorescent protein » pour les REa et la CFP « cyano fluorescent protein » pour les REb. Notre étude porte sur le choix de différentes positions de biotinylation de l'œstradiol, sur la longueur de bras entre la biotine et l'œstradiol. D'autre part nous avons aussi étudié l'efficacité de la liaison de différents ligands sur les récepteurs recombinants produits soit dans les cellules eucaryotes soit dans les cellules procaryotes.

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Coordena??o de Aperfei?oamento de Pessoal de N?vel Superior
The present work has as main objective to contribute to the coordination chemistry of the ligand kojic acid, with the synthesis and characterization of the homoleptic compounds [Al(kj)3], [Fe(kj)3], [Fe(kj)2], [Cu(kj)2] e [Ru(kj)3], and the new heteroleptic complexes, trans- K2[Fe(kj)2(CN)2] and trans-Na2[Ru(kj)2(CN)2]. The obtained compounds were characterized by vibrational spectroscopy in the infrared region (IV) and Electronic spectroscopy in the ultraviolet and visible region (Uv-Vis). The infrared results indicated the coordination of the bidentate ligand kojic acid, due to reductions in the values of the stretching frequencies of the carbonyl and double bonds, compared to the free ligand for all complexes obtained. The presence of new vibrational modes indicated the change of symmetry of the molecules in the new compounds synthesized. Additionally, the presence of vibrational modes assigned to metal-oxygen also contributed to confirm the ligand coordinating to the metal ions. Through this technique, was also possible to perform correlations of the numbers of vibrational modes, in the region 1400-900 cm-1 and the compounds geometry. The heteroleptic compounds exhibited υC≡N in 2065 and 2053 cm-1, respectively, for the trans-K2[Fe(kj)2(CN)2] and trans-Na2[Ru(kj)2(CN)2], indicating coordination of the cyano ligand to metal ions FeII e RuII. Comparing the obtained values with literature data was possible to identify the complex isomerism as trans. In relation to the results of electronic spectroscopy, studies of pH variation of kojic acid provided information on the distribution of electron density in the molecule, showing characteristic spectral profile of kojic ion and its protonated form (Hkj, kojic acid), with two bands at 215 and 269 nm, or deprotonated (kj-), with bands at 226 and 315 nm. The electronic spectra obtained for all complexes in aqueous medium, in the ultraviolet region, exhibited variations of the energies assigned to kojic acid intraligand transitions while in the visible region, only transitions assigned to charge transfer of iron and ruthenium complex have been identified
Com o presente trabalho tem-se como objetivo contribuir com a qu?mica de coordena??o do ligante ?cido k?jico, com a s?ntese e caracteriza??o de compostos homol?pticos [Al(kj)3], [Fe(kj)3], [Fe(kj)2], [Cu(kj)2] e [Ru(kj)3], assim como dos novos complexos heterol?pticos, trans-K2[Fe(kj)2(CN)2] e trans-Na2[Ru(kj)2(CN)2]. Os compostos obtidos foram caracterizados atrav?s da espectroscopia vibracional na regi?o do infravermelho e da espectroscopia eletr?nica na regi?o do ultravioleta e vis?vel (Uv-Vis). Os resultados de infravermelho comprovaram a coordena??o do ligante bidentado ?cido k?jico, devido ?s redu??es dos valores das frequ?ncias de estiramento da carbonila e das duplas liga??es, comparativamente ao ligante livre, para todos os complexos obtidos. Assim como a verifica??o de novos modos vibracionais, em decorr?ncia da altera??o de simetria da mol?cula na forma??o de novas estruturas para os compostos sintetizados. Al?m de modos vibracionais atribu?dos aos estiramentos metal-oxig?nio, evidenciando coordena??o dos ?ons met?licos ao ligante. Atrav?s dessa t?cnica, tamb?m foi poss?vel realizar correla??es dos n?meros de modos vibracionais, na regi?o de 1400 a 900 cm-1, com a geometria dos compostos. Adicionalmente aos complexos homol?pticos, os compostos heterol?pticos exibiram frequ?ncias de υC≡N em 2065 e 2053 cm-1, respectivamente, para o trans-K2[Fe(kj)2(CN)2] e o trans-Na2[Ru(kj)2(CN)2], indicando coordena??o do ligante ciano aos ?ons met?licos de FeII e RuII. Comparativamente com dados da literatura, foi poss?vel propor a isomeria, caracterizando os complexos em configura??o trans. E com rela??o aos resultados da espectroscopia eletr?nica, os estudos da varia??o do pH do ?cido k?jico forneceram informa??es sobre a distribui??o de densidade eletr?nica na mol?cula, apresentando perfil espectral caracter?stico do ?on k?jico na sua forma protonada (Hkj, ?cido k?jico), com duas bandas em 215 e 269 nm, ou desprotonada (kj-), com bandas em 226 e 315 nm. E os espectros eletr?nicos obtidos para todos os complexos em meio aquoso, na regi?o do ultravioleta exibiram varia??es das energias atribu?das ?s transi??es intraligantes do ?cido k?jico, e na regi?o do vis?vel, s? foram identificadas transi??es para os complexos de ferro e rut?nio, atribu?das em sua maioria as transfer?ncia de carga

La communication électronique dans des complexes dinucléaires du ruthénium peut être caractérisée soit par le couplage électronique Vab dans le système à valence mixte (RuII-RuIII), soit par le couplage magnétique J dans le système homovalent paramagnétique (RuIII-RuIII). L'objectif de ce travail était d'obtenir une famille de composés en faisant varier la longueur du ligand pontant et de mesurer les interactions électronique et magnétique afin d'établir une corrélation entre J et Vab.
Une première famille de complexes dinucléaires du ruthénium [{RuII(tpy)(acac)}2(µ-L)] (où tpy = 2,2'-6',2''-terpyridine, acac = acétylacétonate et L est un ligand pontant dicyanamide) a été synthétisée. Ces complexes, bien que prometteurs pour la mesure des couplages électroniques et magnétiques, n'ont pas pu être caractérisés et étudiés complètement en raisons des problèmes de solubilité rencontrés.
Une deuxième famille de composés [{RuII(tpy)(thd)}2(µ-L)] (où thd = 2,2,6,6-tétraméthylheptanedione), plus solubles de par la présence de groupements tert-butyles, a ensuite été synthétisée, la distance métal-métal variant entre 12,0 et 25,1 Å. Les formes à valence mixte RuII-RuIII de ces complexes ont été générées par électrochimie et le couplage électronique Vab déterminé par spectroscopie UV-Vis-Proche IR. On retrouve une décroissance exponentielle de ce paramètre avec la distance métal-métal. Les formes homovalentes paramagnétiques RuIII-RuIII ont été générées chimiquement et/ou électrochimiquement, des mesures de susceptibilité magnétique et des études RPE ont permis la détermination du paramètre de couplage magnétique J et la mise en évidence d'une loi de décroissance exponentielle de ce paramètre avec la distance métal-métal.
Le complexe le plus court de cette famille [{RuII(tpy)(thd)}2(µ-dicyd)] (où dicyd = dicyanamidobenzène) présente un comportement très différent. Des études électrochimiques, spectroscopiques (UV-Vis-PIR, RPE), magnétiques et cristallographiques complétées par des calculs DFT ont mis en lumière la non-innocence du ligand dicyanamidobenzène dans ce type de systèmes. En l'occurrence, celui-ci est oxydé avant les deux ions ruthénium (II).

Le sujet de cette these concerne l'etude de la reactivite d'un complexe aminocarbenique dinucleaire du fer (fe#2(co)#7(rccn(et)#2) comportant des fonctions carbeniques terminal et pontant vis-a-vis de ligands organiques insatures. Les resultats obtenus font ressortir l'attaque preferentielle de la fonction carbenique terminal: 1) les isocyanates et isothiocyanate reagissent sur le carbene terminal selon une cycloaddition engageant la liaison fe=c et c=n de ces ligands, pour conduire a l'obtention de complexes portant un cycle ferrapyrrolidone; 2) une insertion d'un atome de soufre dans la liaison fe=c est observee lors de la reaction du sulfure de carbone ou du sulfure d'ethylene sur le complexe aminocarbenique, d'ou l'obtention de complexes comportant un cycle ferrathioazete; 3) d'une maniere generale, les alcynes conduisent a la synthese de composes de type metallacycle resultant d'un mecanisme de cycloaddition entre la triple liaison acetylenique et la fonction carbenique fe=c. Enfin, les diazoalcanes reagissent sur les complexes carbeniques selon une reaction d'insertion de l'azote teminal du diazoalcane dans la liaison carbenique fe=c pour conduire a l'obtention de complexes portant un ferraazete

Le travail présenté dans cette thèse porte sur l'application de la spectroscopie RMN pour l'étude de matériaux magnétiques moléculaires. Une attention particulière est consacrée aux systèmes magnétiques possédant des cyanures : des briques de construction, des complexes de cyanure polymétalliques et des réseaux étendus (analogues bleu de Prusse) à faible dimension. Par le biais d’exemples spécifiques, nous essayons de montrer que la spectroscopie RMN peut être utilisée comme une puissante sonde magnétique et structurale des systèmes paramagnétiques (chapitre 2, 4, 5). De plus, la RMN est également utilisée pour étudier l’équilibre de spin, en solution, d’une famille de complexes à transition de spin Fe(II) (chapitre 3). En dehors de la spectroscopie RMN, différentes techniques comprenant la spectroscopie FT-IR et UV-Vis (à l'état solide et solution), l’analyse thermogravimétrique (ATG), la diffraction aux rayons X, la résonance paramagnétique électronique (RPE), la diffraction de neutrons polarisés (uniquement pour le composé [Fe(Tp)(CN)3]-) et la magnétométrie SQUID sont utilisées afin d’obtenir une caractérisation structurale et électronique fiable des matériaux magnétiques sondés. Ces techniques permettent également de rationaliser et de soutenir les résultats obtenus à partir de spectroscopie RMN. Par ailleurs, des calculs théoriques de certains composés ont été effectués à l’aide de la méthode DFT (en collaboration avec les théoriciens) afin de soutenir les observations expérimentales. Le premier chapitre de la thèse revient sur quelques concepts de base de la spectroscopie RMN, à l'état solide et en solution, et expose brièvement quelques exemples d'études de systèmes paramagnétiques en RMN. La partie expérimentale de ce même chapitre met l'accent sur l'utilisation de la spectroscopie RMN 13C et 15N à l'état solide pour sonder les propriétés magnétiques locales, estimer la densité de spin et sa répartition sur les ligands cyanures. Une question fondamentale pour les magnéto-chimistes est ainsi soulevée : comment l'électron non apparié, délocalisé de la source paramagnétique sur le ligand pontant, donne t-il naissance à l'interaction magnétique d'échange? Dans le troisième chapitre de la thèse, la spectroscopie RMN 1H paramagnétique en solution a été utilisée pour étudier des complexes mononucléaires Fe(II) commutables, c’est-à-dire pouvant subir un changement de leurs propriétés magnétiques (et optiques) sous l’influence de stimuli externes. L’équilibre de transition de spin thermo-induit des complexes [FeII(R-bik)3]2+ a été étudié par RMN 1H, à température variable, et les résultats ont été comparés à ceux obtenus avec des techniques différentes. Le quatrième chapitre traite de la caractérisation magnéto-structurale de certains complexes polynucléaires fondé sur la nouvelle brique de construction cyanurée [CoIII(Me2Tp)(CN)3]-. La spectroscopie RMN du noyau quadripolaire 59Co est employée comme sonde pour suivre à différente température, le comportement magnétique des systèmes moléculaires contenant du Co(III). La RMN 59Co permet par ailleurs, l’étude du mécanisme d'extension de spin sur le pont cyanure
The work presented in this Ph.D. dissertation focuses on the application of NMR spectroscopy for studying molecular magnetic materials. A particular attention is devoted to cyanide-contaning magnetic systems: cyanide building blocks, low-dimensional polymetallic complexes and extended networks (Prussian blue analogues). Basically, we try to show through selected examples that NMR can be used as a powerful structural and magnetic probe to address a variety of questions related to paramagnetic materials (chapter 2, 4, 5). Besides, we also use here NMR to study spin equilibrium in solution in a family of Fe(II) spin-crossover complexes (chapter 3). Apart from the use of various NMR techniques, different physical techniques including FT-IR and UV-Vis spectroscopy (in solid-state and solution), TGA, X-ray diffraction, EPR spectroscopy, Polarized neutron diffraction (only for [Fe(Tp)(CN)3]- compound), and SQUID magnetometry are used to obtain reliable structural and electronic characterization of the probed magnetic materials and to rationalize and support the results obtained from NMR spectroscopy. Theoretical DFT calculations (in collaboration with theoreticians) are also performed on some selected compounds to support the experimental observations. The first chapter of the dissertation provides a short overview of some basic concepts of NMR spectroscopy in solid state and in solution and gives very briefly some few examples of NMR studies on a variety of paramagnetic systems. The first experimental chapter of the thesis focuses on the use of 13C and 15N solid-state NMR spectroscopy to probe local magnetic properties and to estimate the spin density and its distribution onto the cyanide ligands. It thus addresses a fundamental question for magnetochemists: how the unpaired electron delocalized from the paramagnetic source onto the bridging ligand to give rise to the magnetic exchange interaction? In the third chapter of the thesis, the solution state paramagnetic 1H NMR spectroscopy has been used to study Fe(II) mononuclear switchable complexes, which undergo a change of their magnetic (and optical) properties upon external stimuli. More specifically, the thermally-induced spin-crossover equilibria of the [FeII(R-bik)3]2+ complexes has been studied by variable temperature 1H NMR and the results are compared to those obtained by other techniques. The fourth chapter deals with the magneto-structural characterization of some polynuclear complexes based on the new cyanide-based [CoIII(Me2Tp)(CN)3]- building block. NMR spectroscopy of the quadrupolar 59Co nucleus is used as a probe for following the magnetic behaviour of these Co(III) containing molecular systems at different temperature. It also allows to investigate the spin extension mechanism over the cyanide bridge. Finally the chapter 5 intends to explore the use of 113Cd NMR spectroscopy as both a local structural and magnetic probe for studying Fe-Cd based molecular materials

The cyanide ligand has frequently been used to prepare clusters with novel magnetic properties due to its ability to provide an efficient pathway for superexchange between metal centers that are bound in an end-to-end fashion. One of the common synthetic approaches in this chemistry is to design suitable cyanide containing precursors and then to react such building blocks with metal complexes consisting of accessible sites. The triphos ligand (triphos: 1,1,1-tris(diphenylphosphinomethyl)ethane) has been employed in this vein to prepare metal complexes, one of which is a five coordinate paramagnetic complex (S = 1/2) with a square pyramidal metal center, [CoII(triphos)(CN)2]. A family of molecular squares, [{MIICl2}2{CoII(triphos)(CN)2}2] (M= Mn (2), Fe (3), Co (4), Ni (5), and Zn (6)), has been synthesized by the reaction of CoII(triphos)(CN)2 and MCl2 (M= Mn, Co, Ni, Zn) or Fe4Cl8(THF)6 in CH2Cl2/EtOH mixture. A series of cyanide-bridged trinuclear complexes, {[Co(triphos)(CN)2]2 [M(MeOH)4]}(ClO4)2 ( M = Mn (7), Fe (8), Co (9), and Ni (10)) and tetranuclear complexes, {[Co(triphos)(CN)2]2[M(MeOH)4]2}(ClO4)4 ([Co2M2] M = Mn (11) and Ni (12)) have been synthesized in a similar fashion by the reaction of CoII(triphos)(CN)2 and M(ClO4)2.6H2O (M= Mn, Fe, Co, Ni) in methanol. The trinuclear compounds (7-9), and tetranuclear complexes (2-6, 11, 12), are characterized by antiferromagnetic coupling between metal centers while magnetic behavior of 10 indicates the presence of ferromagnetic interactions between the paramagnetic metal centers. Interactions between magnetic orbitals of Co(II) and M(II) ions were also investigated by means of the density functional theoretical (DFT) calculations. Another triphos containing building block, [(triphos)Re(CN)3] anion (13), has been employed to prepare derivatives of a cubic SMM cluster with four octahedral Re(II) ions and four tetrahedral Mn(II) sites bridging through cyanide ligand. The reactions of Re(II) precursor with MnI2 and solvated Mn(II) ions resulting in derivatives of Re4Mn4 cube with different ligands attached to the Mn center other than the chloride atom were reported. Our efforts on linking these cubes using organo cyanide ligands such as dicyanamide (dca) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) to form extended networks were also discussed.

Although fluoride is used at low concentrations in drinking water as a means of promoting dental health, it poses a danger at high exposure levels where it can lead to skeletal fluorosis or other adverse effects. Cyanide is notoriously toxic, and its large scale use in industrial processes warrants the need for close monitoring to remain aware of potential contamination of water sources and other environmental resources. Based on these considerations, it is critical to continue to develop improved methods of monitoring fluoride and cyanide concentrations in water. However, molecular recognition of these anions in water poses considerable challenges. For fluoride, this is due largely to its high hydration enthalpy (Ho = -504 kJ mol-1), which drastically reduces its reactivity in water. Additionally, the strong basicity of cyanide (pKa of (HCN) = 9.3) may obscure its detection in neutral water due to protonation. In addition to achieving detection of these anions in water, it is most desirable to have information of the detection event relayed in the form of a positive, rather than negative, response (i.e., turn-on vs turn-off). The general strategy of appending cationic groups to triarylboranes imparts beneficial Coulombic, inductive, and sometimes chelate effects that have allowed a number of these Lewis acidic receptors to sense fluoride and cyanide in aqueous environments. With the goal of developing new triarylborane-based receptors that show enhanced affinities for these anions, as well as turn-on responses to detection, a series of pyridinium boranes were synthesized and studied. Having recognized that the inherent Lewis acidity of antimony(V) species might be exploited for anion sensing, we also describe initial studies on the ability of tetraorganostibonium ions (R4Sb+) and cationic transition metal-triarylstibine complexes (R3SbM+) to complex fluoride. Finally, the electropositivity of antimony and its ability to form stable compounds in both the +3 and +5 oxidation states have led us to begin investigations into the bonding and redox reactivity of novel metal stibine/stiborane complexes.

This thesis is presented in two parts. The first part, Chapter 2, 3, and 4, offers a series of studies on noncovalent interactions in Ligand Gation Ion Channels (LGICs). The second part describes a series of studies involving the synthesis and characterization of cyanine dyes. The common thread in this work is the use of Density Functional Theory (DFT) to study chemical-scale phenomenon. Chapter 1 offers a brief introduction to DFT and a comparison with other traditional computational chemistry methodology; Hartree-Fock (HF). Summaries of the use of DFT to study both noncovalent interations and electronically excited states are also presented. In addition, the author comments on the correct application of DFT.

Chapter 2 details a computational study of the cation-π interaction of complex cations to substituted benzenes and indoles. The cation-π interaction is the electrostatic interaction between a cation and the negative electrostatic potential on an aromatic ring originating from its large permanent quadrupole moment. This chapter, in addition to establishing the correct computational parameters, establishes a large set of substituent effects with which to study cation-π interactions in vivo. These binding energy values are compared to previous applications of cation-π binding energies from our lab, and it was found that the derived binding energies are sufficiently accurate.

Chapter 3 applies the foundational knowledge from the previous chapter to study cation-π interactions of cationic ligands to multiple aromatics. This is a common motif in vivo known as the aromatic box. Using this methodology, it is established that cation binding in this form is cooperative. Further, many aromatic boxes from crystal structures were evaluated energetically.

Chapter 4 describes work to develop a new amino acid to study hydrogen bonds in Xenopus laevis oocytes. These fluorinated aliphatic amino acids inductively attenuate the hydrogen bond accepting ability of the carbonyl. This new strategy was used to probe for a hydrogen bond between the indole NH α4 TrpB and a backbone carbonyl associated with L119 on the β2 subunit of the α4β2 nicotinic acetylcholine receptor (nAChR). The fluorinated amino acids were validated computationally and with NMR studies. This new strategy showed that the α4-β2 interfacial hydrogen prediction was false.

Chapter 5 describes the synthesis and characterization of a series of meso-aromatic-acetylene cyanine dyes which feature a very large Stokes shift. Synthesis of the dyes features a key Sonagashira reaction. These dyes are investigated photophysically and computationally using time dependent DFT (TDDFT). The mechanism for this Stokes shift is an excitation to the S2 state, relaxation to the S1 state, and normal cyanine fluorescence.

Chapter 6 describes three separate strategies to construct a cyanine-based photocage to release drugs in vivo using an ortho-quinone methide strategy. One strategy utilized an acetylene-aromatic cyanine dye much like those described in Chapter 5, the second utilized an ethynyl-trimethylphenyl cation dye, and the third a photoinduced electron transfer cyanine dye. None of these strategies produced a usable photocage. The failure of these strategies are ascribed to both the short excited state lifetime of cyanine dyes and the direction of the transition dipole moment.

Finally, three appendices are presented. Appendix A describes early work to synthesize and characterize a meso-hydroxy substituted Cy5 dye. Appendix B offers many of the same computations as Chapters 2 and 3 using HF instead of DFT. Appendix C describes orbital mixing of cyanine dyes from Chapter 5 using HF instead of DFT.