Citrate-coated gadolinium trifluoride (Cit-GdF3) and poly(acrylic acid)-coated nanoparticles (PAA-GdF3 NPs) were synthesized, the former reproduced from literature (though using more refined conditions), the latter through a new, two-step, ligand exchange method. Diamagnetic nanoparticle analogs (Cit-YF3 NPs) were prepared to investigate citrate interactions with the nanoparticle surface using NMR. Citrate was found to bind in numerous conformations, with a total of between 29 – 46 % bound at 0 ºC. Exchange studies revealed short residence lifetimes of one and twelve seconds respectively for bound and free forms of citrate (0 ºC), perhaps explaining the colloidal instability of these nanoparticles. PAA-GdF3 NPs were synthesized by first producing their Cit-GdF3 counterparts, and then exchanging citrate for PAA. The impetus behind this latter synthesis was the relative enhancement in stability and relaxivity attainable by these nanoparticles. The displacement of citrate by PAA was verified using diffusion NMR studies.

Citrate-coated gadolinium trifluoride (Cit-GdF3) and poly(acrylic acid)-coated nanoparticles (PAA-GdF3 NPs) were synthesized, the former reproduced from literature (though using more refined conditions), the latter through a new, two-step, ligand exchange method. Diamagnetic nanoparticle analogs (Cit-YF3 NPs) were prepared to investigate citrate interactions with the nanoparticle surface using NMR. Citrate was found to bind in numerous conformations, with a total of between 29 – 46 % bound at 0 ºC. Exchange studies revealed short residence lifetimes of one and twelve seconds respectively for bound and free forms of citrate (0 ºC), perhaps explaining the colloidal instability of these nanoparticles. PAA-GdF3 NPs were synthesized by first producing their Cit-GdF3 counterparts, and then exchanging citrate for PAA. The impetus behind this latter synthesis was the relative enhancement in stability and relaxivity attainable by these nanoparticles. The displacement of citrate by PAA was verified using diffusion NMR studies.

Polyoxoniobates (PONbs) are a small family of highly electron-rich clusters. The development of new solids composed of these clusters have applications in green energy and electronics. However, the high charge environment of PONbs typically requires alkaline synthetic conditions that are unsuitable for introducing other metals and organic molecules, making synthesis of new systems difficult. To date, very few transition metals and organic ligands have been incorporated into these PONb solids, and lanthanide metal inclusion, which generally improves photoconductivity due to longlived f-orbital excitations, has not yet been fully realized. Here, the synthesis of a new class of lanthanide niobate cluster [Ln4(H2O)8(SO4)5(NbO3)2]·3H2O; Ln= Dy, Tb under acidic conditions is reported. Structures were determined by crystallography and time-dependent density functional theory (TD-DFT) was used to provide insight into photo-induced electronic transitions. Supporting computational methods that are currently being developed for modeling these emerging cluster systems are described.

Research in the fields of molecular conductors and magnets over the past four decades has involved collaborative efforts of chemists and physicists whose common goal is to design useful materials composed of molecular building blocks. Of particular interest are materials whose properties can be tuned by electronic or steric changes in the molecular sub-units. The research on TCNQ derivatives described in this thesis was inspired by the observation that, although a vast amount of research has been directed at understanding binary M(TCNQ•-) materials, analogous compounds based on substituted TCNQ acceptors are surprisingly scarce. Single crystals of a new structure type for the M+(TCNQ)•- binary family were isolated from reactions of two dihalogenated TCNQ derivatives with Cu(I) ions, namely Cu(TCNQX2) (X = Cl, Br). The new 3-D compound Cu(TCNQCl2) exhibits the highest conductivity of the M+(TCNQ)•- series to date, despite the greater separation of TCNQCl2 units as compared to other derivatives. Compounds of lower dimensionality were also obtained, namely the 2-D Cu(TCNQBr2)(CH3CN) and 1-D Cu(TCNQI2)(CH3CN)2 phases. Several 2p-3d heterospin molecular magnets were also synthesized. For example a “magnetic sponge” material based on a 2-D hexagonal framework of composition {[Mn2(TCNQF4)(CH3OH)7.5(H2O)0.5]-(TCNQF4)2•7.5CH3OH}∞, as well as molecular magnets based on first row metal ions and TCNQF4 ligands of composition MII(TCNQF4)-•(TCNQF42-)0.5(CH3CN) (M = Mn, Co) were prepared. In addition, unprecedented isostructural 2-D frameworks based on combinations of first row metal ions with TCNQBr2 radicals of composition [M(TCNQBr2)2(H2O)2]∞ (M = Mn, Zn) were synthesized. Lanthanide chemistry is also described in this dissertation. A series of mononuclear Ln-TCNQF4 heterospin complexes of composition {MIII[TCNQF4]2[H2O]x}(TCNQF4)(3H2O) (M = La, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er and Yb) was also obtained which exhibit remarkable properties. In this family of compounds there exists an unprecedented subtle interplay between single molecule magnetic behavior and phonon bottleneck effect behavior for the Tb analogue. Magnetic ordering was observed for the Sm analogue. A homologous series of 1-D materials based on alternating lanthanide ions and hexacyanometallates of formula {[Ln(tptz)(H2O)4Fe(CN)6]•8H2O}∞ (Ln = Pr, Nd, Sm, Eu, Gd, Tb) was obtained and a detailed magnetic study provided incontrovertible evidence that the SmIII-[FeIII(CN)6]3- compound exhibits ferromagnetic and not antiferromagnetic coupling as had been reported for related 1-D chains.

Les préoccupations énergétiques et environnementales actuelles ont fait du retraitement des déchets nucléaires un enjeu scientifique et économique majeur dans de nombreux pays. Une des voies de retraitement envisagée concerne l'extraction sélective des actinides mineurs trivalents An (Am3+, Cm3+) du reste des lanthanides Ln présents dans le combustible nucléaire usé. Pour cela, des ligands azotés sont actuellement testés: l'origine de leur sélectivité pour les actinides mineurs est encore mal identifiée mais pourrait venir de phénomènes de covalence accrus avec les actinides mineurs (III) par rapport aux lanthanides(III). Dans cette thèse, nous étudions la covalence dans la liaison actinide-ligand par des calculs de DFT (Théorie de la Fonctionnelle de la Densité), et ce en trois temps: étude avancée de la nature de la liaison métal-ligand, caractérisation spectroscopique de la covalence et premiers tests de dynamique moléculaire ab initio pour de futures études en solvant. Pour cela, nous appliquons des méthodes jusque là assez peu utilisées sur les complexes trivalents d'actinides (méthodes topologiques, TDDFT, LDDFT, dynamique moléculaire ab initio). Nous avons pu établir que la sélectivité de l'extractant BTP, le plus efficace pour la séparation An/Ln, provenait notamment d'un renforcement de la covalence dans la liaison An-BTP par rapport à la liaison Ln-BTP. Ceci n'avait jamais pu être montré auparavant, tant au niveau expérimental que théorique.

Afin d'accéder à des agents de contraste efficaces, il est essentiel d'optimiser simultanément les paramètres moléculaires influençant la relaxivité : nombre de molécules d'eau en première sphère de coordination, échange de l'eau, dynamique de rotation du complexe, relaxation électronique, distance Gd(III)-proton. Le but de ce travail est double. D'une part, il s'agit de concevoir et étudier des complexes possédant un nombre élevé de molécules d'eau coordinées et de comprendre l'influence de la sphère de coordination du métal sur la stabilité des complexes et la relaxation électronique. D'autre part, nous avons utilisé les ligands comme chromophores pour la mise au point de sondes luminescentes pour l'imagerie biomédicale.<br />Nous présentons la structure, la stabilité et la relaxivité de complexes de Gd(III) de deux séries de ligands tripodes dérivés du picolinate basés, soit sur le cycle 1,4,7-triazacyclononane, soit sur un pivot amine tertiaire. Ces complexes possèdent une relaxivité élevée dans l'eau et dans le sérum et peuvent former des interactions non-covalentes avec l'albumine sérique. L'interprétation de la relaxivité des protons de l'eau au moyen de nouvelles méthodes relaxométriques basées sur l'utilisation de solutés sondes nous a permis de montrer que la présence de groupement picolinate et du cycle 1,4,7-triazacyclononane pouvait conduire à des complexes de Gd(III) possédant des propriétés de relaxation électronique favorables.<br />Du fait de la présence de chromophores picolinate, les complexes d'Eu(III) et Tb(III) avec ces ligands donnent lieu à une luminescence intense dans le visible. D'autres complexes dérivés de l'unité 8 hydroxyquinoléine possèdent une luminescence élevée dans l'infrarouge et ont également été étudiés.

A new class of polymer coated lanthanide fluoride nanoparticle aggregates (NPAs) was developed as potential MRI contrast agents. The NPA synthesis has been perfected to control the size distribution and optimize relaxivities. Polyacrylic acid was used as a stabilizing polymer, and was conjugated to folic acid to improve targeting to SK-BR-3 breast cancer cells. Terbium was incorporated in the synthesis to study the passive and active targeting properties of NPAs. Through a series of microscopy experiments, a significant difference in uptake between NPAs with and without targeting moieties occurs after 48 hours of incubation. The relaxivity of the optimized nanoparticles was measured to be 56 s-1(mg/ml)-1 using a 1.5 T scanner, which may be compared to that of the commercially available Gd3+-DTPA [R1 = 7 s-1(mg/ml)-1]. Abdominal perfusion studies in rats also demonstrated that the NPAs provide better contrast of the vasculature than Gd3+-DTPA does at the same mass concentration.

The design of nonlinear optical (NLO) molecules has become a focus of current research in telecommunications, information technologies and optical data storage. Donor-acceptor substituted dipolar molecules have been the most investigated NLO chromophores. Dipolar molecules, however, have several limitations such as low optical transparency, low thermal stability and their strong tendency to adopt anti-parallel packing in the solid state. Recently, a new class of materials based on octupolar symmetries, which lack permanent dipole moments, has been proposed for NLO applications. At a structural level, it can be shown that the basic template for 3D octupolar molecules comes to a cube with alternating charges at the corners such as donor and acceptor substituent. Despite all the various structures reported, it is worth noting that no molecules actually representing the "real" octupolar cube have been obtained so far. In this thesis, we showed that the real octupolar cube can be demonstrated by lanthanide III complexes based on ABAB type phthalocyanine featuring alternating electron donor and electron acceptor groups. These structures are characterized by UV-NIR, X-Ray and exhibit highest quadratic hyperpolarizability ever reported for an octupolar molecule. Moreover, this work was extended to nonoctupolar lanthanide homoleptic double-decker complexes based on AB3, A4, B4, T4 type phthalocyanines. It was observed that these molecules present a quite large quadratic hyperpolarizability too, but smaller than the one obtained for the Ln(ABAB)2 series, as expected.

Les ligands β-diiminates sont des plateformes intéressantes utilisées en chimie de coordination en particulier pour la catalyse homogène, leurs paramètres électroniques et géométriques facilement ajustables les rendant particulièrement attractifs. Toutefois, ces modifications sont limitées à l'introduction de bases de Lewis neutres (éthers, amines tertiaires) sur les substituants portés par les atomes d'azote du squelette β-diiminate. L'objectif principal de ce travail de thèse porte sur le dépassement de telles limitations avec la synthèse de nouveaux ligands β-diiminates fonctionnalisés par un ou deux groupements phénolates anioniques et l'étude de leur chimie de coordination avec des ions lanthanides et actinides. Un intérêt particulier a été apporté à l'élucidation du mécanisme de formation de ces ligands, qui a mis en lumière la sensibilité des fonctions imines vis-à-vis des fonctions phénols, à l'origine des limitations décrites ci-dessus. Deux nouveaux ligands N-aryloxy-β-diiminates ont été synthétisés à l'échelle de plusieurs grammes avec de très bons rendements. Ces ligands diffèrent par leur encombrement stérique, qui influe sur leur coordination aux ions lanthanides et actinides. La réactivité de trois des complexes N-aryloxy-β-diiminate a été explorée. Un complexe du Ce(III) possède des propriétés de réduction intéressantes, sa sphère de coordination permettant un abaissement significatif du potentiel d'oxydation du couple Ce(III)/Ce(IV). La présence d'une lacune de coordination dans un complexe du Th(IV) a été mise àprofit pour stabiliser différents adduits de bases de Lewis. Deux types de réarrangement du complexe de thorium ont été mis à jour, qui sont contrôlés par la minimisation de répulsions inter-ligands. La réactivité rédox d'un complexe N-aryloxy-β-diiminate de l'U(IV) a été exploitée pour préparer un exemple rare de complexe monooxo terminal d'uranium. Cette espèce possède une chimie rédox riche et sa réduction a permis la synthèse des analogues de l'U(V) et de l'U(IV), formant ainsi la première série de complexes monooxo terminaux d'uranium stables à trois degrés d'oxydation successifs. Cette série représente une opportunité unique d'étudier l'influence des électrons f sur le phénomène d'influence trans inverse (ITI) observés dans les complexes oxo de l'uranium. Des calculs DFT préliminaires ont été réalisés pour rationaliser les comportements expérimentaux.

New 1,2,3,5-dithiadiazolyl (DTDA), 1,2,3,5-diselenadiazolyl (DSDA) radicals and their resulting metal complexes were synthesized and characterized. The overarching theme of this thesis is the utility of intermolecular interactions for facilitating previously unseen magnetic behaviours in thiazyl radical-metal complexes. This thesis contains the first examples of thiazyl radical metal complexes acting as molecule based magnets. The 4-benzoxazol-2′-yl-1,2,3,5-dithiadiazolyl (boaDTDA) radical and its selenium analogue 4-benzoxazol-2′-yl-1,2,3,5-diselenadiazolyl (boaDSDA) were coordinated to several paramagnetic metal ions including transition metal ions Mn(II), Co(II) and Ni(II). The Ni(hfac)2(boaDTDA) and Ni(hfac)2(boaDSDA) complexes are isomorphous and both demonstrate step like π-stacking leading to additional ferromagnetic (FM) intermolecular interactions. The Mn(hfac)2(boaDTDA) (hfac = 1,1,1,5,5,5-hexafluoroacetylacetonato) complex was the first DTDA metal complex to conclusively show that intermolecular S(DTDA)…O(hfac) contacts can lead to intermolecular anti-ferromagnetic (AF) interactions which, in turn, can lead to a large spin ground state. Based on the magnetic properties of the Mn(hfac)2(boaDTDA) complex, a new DTDA biradical ligand, 4,6-bisDTDApyrimidine (bisDTDApym), was developed and coordinated to Mn(hfac)2. The resulting dinuclear Mn(II) complex, [Mn(hfac)2]2(bisDTDApym), is arranged in the solid state by short S(DTDA)…O(hfac) interactions forming two dimensional ferrimagnetic sheets. These ferrimagnetic sheets AF couple to one another, giving rise to AF ordering below 4.5 K. The [Mn(hfac)2]2(bisDTDApym) is the first thiazyl metal complex to magnetically order and is a unique example of a molecular coordination complex which magnetically orders. This thesis also presents the synthesis and characterization of precursor materials of the form Ln(hfac)3(DME) (DME = dimethoxyethane) for coordination reactions to thiazyl radical ligands. The Dy(hfac)3(boaDTDA) and Dy(hfac)3(pyDTDA) (pyDTDA = 4-(2′-pyridyl)-1,2,3,5-DTDA) complexes demonstrate single molecule magnetism with energy barriers of 100 K and 70 K respectively. Ten-coordinate Ln(hfac)3(pyDTDA)2 (Ln = La, Ce, Pr) complexes demonstrate phase transition behaviour between dimerized and undimerized phases and were studied by X-ray crystallography and magnetometry. The aforementioned compounds are some of the over 50 new compounds which have been synthesized and fully characterized in this thesis.