Dans cette thèse, le développement de nouveaux matériaux organiques-inorganiques pour deux enjeux technologiques majeurs est présenté : (1) le développement de phosphores sans métal pour l'éclairage ; (2) l'évaluation du potentiel de matériaux hybrides contenant des lanthanides comme concentrateurs solaires luminescents. En outre, un autre objectif, de nature fondamentale, est de comprendre l'effet de modifications légères dans le fragment organique de matériaux hybrides (changements de régioisomère, utilisation des thiourées à la place des urées) et de les mettre en forme (des poudres vers les films) pour moduler leurs nanostructures et photoluminescence. Ce manuscrit est divisé en 4 parties : (I) une introduction bibliographique décrivant les concepts de base de cette thèse : les mécanismes de luminescence et les réactions sol-gel sont d'abord décrits. La photoluminescence des sels de lanthanides est introduite. Finalement, les organosilices contenant des sels de lanthanides sont étudiées. (II) La synthèse, les caractérisations et les applications potentielles de différents silsesquioxanes pontés provenant de différents isomères (n,n'-diuréido-2,2'-bipyridine) et contenant des sels de lanthanides ou en l'absence complète de métal, sont décrits. Les propriétés des matériaux provenant des différents isomères sont comparées afin de mieux comprendre la coordination des ions lanthanides. (III) Cette partie s'intéresse à la mise en forme des précurseurs utilisés précédemment pour obtenir les matériaux correspondants sous forme de films minces. Les propriétés de ces dépôts sont comparées à celles des poudres précédentes. (IV) La substitution systématique des groupements urées par des thiourées dans des silsesquioxanes pontés bien connus a été réalisé : (1) Les propriétés structurales de matériaux synthétisés sous différentes conditions et à base de groupements thiourées sont étudiées ; (2) Les propriétés de photoluminescence des matériaux des isomères n,n'-dithiouréido-2,2'-bypiridine sont présentées. / In this thesis, the development of new organic-inorganic materials for two technological challenges is presented : (1) developing metal-free phosphors for solid state lighting ; (2) investigating the potential of lanthanide-containing materials as luminescent solar concentrators. Moreover, a fundamental objective is to understand the effect of minor modifications in the organic fragment of the hybrid materials (changing the regioisomer, using urea or thiourea crosslinks) and of the processing (from powders to films) to modulate their nanostructure and pholuminescence. This manuscript is divided in four parts : (I) a bibliographic introduction describing the basic concepts of this thesis : the luminescence mechanisms and the sol-gel reactions are first described. The photoluminescence of lanthanide salts is introduced ; finally, the organosilicas containing lanthanide salts are studied. (II) The synthesis, characterisations and potential applications of different bulk pristine and lanthanide-containing bridged silsesquioxanes derived from different n,n'-diureido-2,2'-bipyridine isomers are described. The properties of the material derived from the different isomers are compared to get insights into the coordination of the lanthanide ions. (III) The third part deals with the processing of the former sols to obtain the corresponding materials as thin films ; the properties of these coatings and of the formerly obtained powders are compared. (IV) The systematic substitution of urea by thiourea groups in the composition of well-known urea cross-linked bridged silsesquioxanes is performed. This fourth part is divided in two parts : (1) the structural features of simple thiourea-based materials synthesised under different conditions are investigated ; (2), the photoluminescence properties of n,n'-dithioureido-2,2'-bypiridine isomers are studied.

L’imagerie médicale a permis à l’Homme de mieux connaitre son anatomie, le fonctionnement de son corps, et de diagnostiquer ses pathologies à des stades de plus en plus précoces, à partir de techniques peu invasives. Au cœur de cette discipline, l’imagerie moléculaire permet d’observer les processus biologiques qui participent au fonctionnement du vivant à des fins exploratoires, diagnostiques, thérapeutiques et aujourd’hui théranostiques. L’activité enzymatique étant à l’origine d’une grande part du métabolisme, la plupart des pathologies implique le dérèglement de celle-ci. L’observation par imagerie moléculaire de cette activité constitue alors un outil prépondérant de l’arsenal médical. Parmi les techniques d’imagerie les plus adaptées à cet enjeu, l’Imagerie par Résonnance Magnétique (IRM) permet d’observer les tissus et organes de façon non invasive, en s’appuyant couramment sur l’administration au patient d’agents de contraste. Ces molécules destinées à renforcer la qualité des images acquises peuvent également être utilisées pour réagir à la présence de cibles biologiques d’intérêt, notamment des enzymes, accompagnant ainsi les clichés obtenus d’informations biologiques et physiologiques. Parmi les nombreux outils pharmacologiques destinés à l’IRM, les complexes de lanthanides ont déjà prouvé leur efficacité en imagerie clinique, et peuvent potentiellement être détectés par trois modalités d’imagerie complémentaires : l’IRM à effets T₁ et paraCEST, et l’imagerie optique. Notre équipe travaille à la conception d’une plateforme modulable permettant de détecter une grande variété d’enzymes. Elle est constituée d’un « déclencheur » qui peut être activé par une enzyme ciblée, relié par l’intermédiaire d’un bras « auto-immolable » à un « rapporteur » assurant la détection de la sonde. Ce dernier se compose d’un chélate de lanthanide qui confère à la sonde des propriétés magnétiques détectables par IRM à effets T₁ et paraCEST. Par ailleurs, une antenne de type pyridine assure l’excitation du lanthanide conduisant à sa luminescence, qui peut être détectée par imagerie optique. L’activation enzymatique de l’agent de contraste conduit à la dégradation du bras « auto-immolable », qui s’accompagne d’une modification détectable des propriétés magnétiques et optiques du rapporteur ainsi libéré. Une plateforme de ce type a été conçue lors de travaux précédents ce projet de thèse pour la détection de l’activité de la β-galactosidase. Cependant le processus de dégradation du bras « auto-immolable » déclenché par l’activité de l’enzyme ne permet pas de libérer le rapporteur sous forme activée. En effet, la cascade électronique à l’origine de ce processus est considérablement ralentie par la coordination du bras « auto-immolable » au lanthanide. Aussi, l’objectif de ce projet de thèse consiste à modifier la structure de ces agents de contraste afin de lever ce blocage cinétique, tout en conservant une détectabilité par les trois modalités d’imagerie citées précédemment.Pour ce faire, six nouveaux analogues ont été synthétisés sous forme de modèles de sondes dénués de leur partie déclencheur, afin de s’assurer de la conservation de leurs propriétés magnétiques et optiques tout en s’affranchissant des difficultés synthétiques liées à la présence de celui-ci. A l’issue de la caractérisation physicochimique de ces derniers, deux structures ont été retenues pour la conception de sondes activables par la β-galactosidase. Une première permettant la détection trimodale de l’activation enzymatique, et une seconde dont la détection par IRM à effets T₁ et paraCEST est pH-dépendante. Enfin, à l’issue de leur synthèse, des tests enzymatiques nous ont permis de suivre les cinétiques d’activation des agents de contrastes obtenus par les modalités d’imagerie prévues pour ces composés. / Medical imaging has allowed Mankind to reach a good knowledge in human anatomy, body operation and to diagnose pathologies earlier and earlier, through minimally invasive techniques. Molecular imaging at the heart of this science enables the sight of biological processes standing in the operation of life for both exploratory, diagnostic, therapeutic and even theranostic means. As a wide part of metabolism is provided by enzymatic activity, its imbalance can mean pathological context. Thus, monitoring enzymatic activity through molecular imaging could become a new power weapon in medical arsenal. Among best adapted imaging techniques to this stake, Magnetic Resonance Imaging (MRI) permits to picture tissues and organs non-invasively, widely through contrast agent prescription. These molecules designed to sharpen acquired images quality can also be used for reaction with biological targets of interest, especially enzymes, thus binding those pictures with biological and physiological data. In the many pharmacological tools associated with MRI, lanthanides complexes have already proven efficiency in clinical imaging, and are likely to be detected through three complementary imaging modalities: T₁-MRI, paraCEST-MRI and optical imaging.Our team achieves the design of a tunable platform that can detect a wide range of enzymes. It is composed of a “trigger” that can be activated by a targeted enzyme, bound through a self-immolative linker to a “reporter” moiety that enables the probe to be detected. The latter is endowed with a lanthanide chelate that gives the probe magnetic and optical properties that can be monitored by T₁-MRI or paraCEST-MRI. In addition, a pyridine antenna enables lanthanide sensitization and luminescence, that can be detected by optical imaging. Upon enzymatic activation, self-immolation of the linker causes the release of the reporter moiety, and the modification of its magnetic and optical properties.Previous work in our team has achieved the synthesis of a probe following these concepts and aiming at β-galactosidase activity detection. However, enzyme-triggered self-immolation of the probe did not release the activated reporter moiety, due to the linker’s coordination to the lanthanide. This PhD project is thus intended to modify the chemical structure of this platform to enhance its activation kinetics, while keeping it detectable by MRI and optical imaging. To reach this goal, six novel analogues have been synthetized as models without trigger moiety to check the preservation of magnetic and optical properties while making synthesis easier and faster. Following probes’ magnetic and optical characterization, two structures were selected for the design of a probe aiming at β-galactosidase activity detection. The first one could enable trimodal detection of its activity, and the second one showed pH-dependency of T₁ and paraCEST effects. After synthesis, enzymatic tests allowed us to monitor enzyme activation kinetics for both probes by the previously scheduled imaging modalities.

Les nanoparticules luminescentes sont particulièrement étudiées pour leur application dans les systèmes d’éclairages ou comme sondes en bio-imagerie. Parmi elles, les nanoparticules anisotropes de matrices cristallines dopées par des ions lanthanides présentent une émission polarisée, qui dépend de la symétrie des sites des ions émetteurs. Le lien entre direction de polarisation et axes cristallins des nanocristaux permet de déterminer leur orientation, et peut donc être exploité pour suivre l'orientation d’objets ou pour caractériser la déformation de milieux hôtes.Les objectifs de ce doctorat ont été de s’intéresser aux origines fondamentales de l’émission polarisée de nanobâtonnets de phosphate de lanthane dopés par des ions europium trivalents (LaPO4:Eu) et d’utiliser la luminescence polarisée à des mesures d’orientation.Dans une première partie, les nanobâtonnets de LaPO4:Eu ont été synthétisés puis alignés sous forme des films orientés. La luminescence de ces films a permis de suivre avec précision la transition de phase de la matrice hôte, de sa structure hexagonale à une structure monoclinique ; et de mettre en évidence la présence de défauts structuraux. La polarisation des spectres de luminescence a ensuite été étudiée. Les taux de polarisation mesurés sont plus élevés pour la phase monoclinique que pour la phase hexagonale. La sensibilité du spectre de polarisation au milieu diélectrique qui les entoure a été mise en évidence.La seconde partie de cette étude porte sur l’utilisation de la polarisation des nanobâtonnets de LaPO4:Eu pour déterminer leur orientation. La connaissance des spectres polarisés des films parfaitement alignés a permis de déterminer le paramètre d’ordre d’une suspension de nanobâtonnets désordonnés en écoulement dans un canal microfluidique puis d’estimer le taux de cisaillement de cet écoulement. Notre étude a permis de préciser quantitativement les conditions dans lesquelles l’utilisation de la luminescence polarisée comme sonde locale du taux de cisaillement d’un écoulement est valide. / Luminescent nanoparticles have been studied for their applications in lighting devices or as probes in biology. Among these nanoparticles, the anisotropic crystals doped with lanthanides ions emit linearly polarized light. The relation between the polarized directions and the crystallographic axis of the nanocrystals allow determining their 3D orientation, which could be an asset to track objects or to characterize flows.The purposes of this thesis were to investigate the origin of the polarized light of nanorods of lanthanum phosphate doped with europium ions (LaPO4:Eu) and to apply this polarized light to determine their orientation.First, nanorods of LaPO4:Eu are synthesized and aligned to prepare oriented films. The phase transition of the LaPO4 matrix is investigated, from the hexagonal to the monoclinic structure. The luminescence is used to track precisely the transition and show the presence of structural defects. Then the polarized spectra are observed. The polarization degrees of the monoclinic phase are higher than those of the hexagonal one. The sensitivity of the polarization with the dielectric medium is also shown.Then, the polarized light is used to determine the orientation of the nanorods. The knowledge of the polarized spectra along he nanorods axis and perpendicularly to it is used to calculate the order parameter of disoriented nanorods in a microfluidic channel and then to estimate the shear rate of the flow. Our study allows quantifying the conditions in which the nanorods can be used as probes to measure the local shear rate.

Longtemps la chimie des lanthanides divalents a été limitée par le nombre et la qualité des précurseurs disponibles. Ce travail s'intéresse donc à la préparation de nouveaux précurseurs et à leur application en activation de petites molécules dans l'optique de préparer de nouveaux matériaux.Des précurseurs peu encombrés de type triflates ont ainsi été préparés et leur comportement en solution a été étudié. L'anion triflate présentant l'avantage de favoriser les assemblages en raison de ses différents modes de coordination.Un autre type de précurseur a été synthétisé et étudié : il s'agit des lanthanidocènes. Alors que la chimie organométallique des lanthanides se heurte souvent à un contrôle difficile des symétries, un ligand à neuf chaînons a permis d'isoler les premiers ytterbocènes et samarocènes divalents.La synthèse de ces nouveaux précurseurs pose la question de leurs propriétés électroniques. Ces-dernières ont donc été étudiées sur plusieurs précurseurs de thulium divalents illustrant ainsi l'influence de la symétrie des complexes. Un choix judicieux de chimie de coordination a notamment permis d'isoler les premières molécules-aimants de lanthanides divalents.Enfin, dans un troisième temps, la réactivité vis-à-vis de petites molécules des précurseurs préparés a été étudiée montrant ainsi qu'il était possible de construire des assemblages variés par réactivité des lanthanides divalents. L'accessibilité d'un assemblage Sm/S présentant des molécules coordinées échangeables a permis de progressivement passer de la molécule au matériau par de la chimie supramoléculaire. / Divalent lanthanide chemistry has long been hampered by the lack of adapted precursors. This work is therefore focussing on the preparation of new divalent lanthanides precursors and their use in small molecule activation for building new materials.Triflate precursors were prepared and their solution properties were studied. ith their multiple coordination modes, triflate anions were shown to favour assemblies growth.Another type of precursor was also prepared: the lanthanidocene. Although organometallic chemistry of lanthanide is often known for the poor control of the complexes symmetry, a 9-membered ligand allowed the preparation of the "true" divalent ytterbocene and samarocene.The electronic properties of divalent lanthanides complexes are poorly known. The prepared thulium (II) precursors were therefore extensively studied. The influence of the symmetry on electronic properties was caracterised and a well-chosen set of ligands was proven to enable interesting magnetic properties such as single-molecule-magnet behaviour.The last part of this work focused on the reactivity of these precursors towards small molecules. Assemblies were grown from the reactivity of divalent samarium with carbon dioxide or yellow sulfur. On one of the obtained assemblies, supramolecular chemistry was carried out, progressively bridging the gap between molecules and materials.

No description available.

This research explores the synthesis of anthracene and stilbene-based metal-organic framework (MOF) structures as potential scintillating (radioluminescent) materials for use in the detection of gamma radiation. The organic molecules 9,10-anthracenedicarboxylic acid (ADCH2) and trans-4,4’-stilbenedicarboxylic acid (SDCH2), were each used as a linker, in combination with a range of lanthanide metal ions, to synthesize novel three dimensional MOF structures under hydrothermal conditions. With ADCH2, the early period lanthanides yield isostructures with the metal ion in higher coordination (nine) than for those with late period metals (seven). The ADC-MOFs show linker-based photoluminescence properties with well defined vibronic peaks in their emission profile and their emission (λmax~435 nm) blue shifting from that of the ADCH2 powder (~500 nm) and closer to the organic molecule in monomer arrangement (λmax ~ 420 nm). The structures also show photoluminescence lifetimes between 1 and 2 ns, which is similar to the reported value for monomeric anthracene units. The blue-shift and reduction in lifetime, compared to ADCH2, are indicative of minimal π-π interactions amongst the aromatic moieties, thereby limiting the non-radiative relaxation pathways. On exposure to ionizing radiation (protons and g- rays), the ADC-MOFs demonstrated scintillation properties, with a radioluminescence lifetime of ~ 6 ns which is similar to that of the ADCH2 powder. A combination of SDCH2 and lanthanide metal ions produced two isostructured MOFs containing Tm3+ and Er3+, under the hydrothermal synthesis conditions explored. The 3-D structure contained ultra large diamond-shaped pores with dimensions of 16 Å x 30 Å. A blue-shift of fluorescence spectra was observed for the SDC-MOF structures (λmax ~ 425 nm) compared to that of bulk SDCH2 powder (λmax ~475 nm), and closely resembling that of monomeric isolated SDC units (λmax~475 nm). Their photoluminescence lifetime is ~0.76 ns, about half of that observed for SDCH2 powder. The blue shift and reduction in lifetime (compared to SDCH2) is attributed to minimal π-π interactions between SDC units in the MOF structure, thus minimizing associated non-radiative relaxation pathways. The isolation of anthracene and stilbene in MOF structures therefore has the potential to improve their performance as scintillators.

The evolution of the present work began with the syntheses of novel bis(alkylimino)acenaphthene (BIAN) ligands. At the outset of this research, despite the presence of dozens of aryl-BIAN ligands in the literature, there were as of yet no reported BIAN ligands bearing alkyl substituents. Given the nearly ubiquitous use of transition metal complexes of alkyl diazabutadiene (DAB) ligands for e.g. catalysis and as ligands for carbene chemistry, interest was generated in developing this emerging field of synthetic chemistry. Initial studies focused on the synthesis of alkyl-BIAN ligands since the traditional synthetic approaches that had been developed for aryl-BIAN ligands were unsuccessful for the alkyl analogues. As an alternate synthetic route, it was decided to employ amino- and imino-alane transfer reagents which had previously proved successful for the conversion of C=O into C=N-R functionalities. While this transfer route had proved successful to synthesize moderate yields of highly fluorinated DAB ligands, it was unknown how or whether this methodology would apply in the case of alkylated BIAN systems. Over the past decade, there has been a surge of interest regarding lanthanide complexes that are capable of undergoing spontaneous electron transfer processes. There are several reports in the literature that describe the ability of Ln(II) ions to undergo spontaneous oxidation, thereby causing one-electron reduction of the coordinated ligand and generally resulting in the corresponding Ln(III) complex. The present work focused on an enhanced understanding of the electronic communication between the lanthanide and the attached ligand. Particular emphasis was placed on defining the resulting oxidation states and the manner in which delocalized electrons of the radical anion species travel over a conjugated system. This fundamental information was gleaned from single-crystal X-ray diffraction studies and magnetic moment measurements that were obtained using the Evans method. Additional insights stemmed from the use of more classical techniques such as IR and NMR spectroscopy. In favorable cases, the presence or absence of spectral peaks can permit assignment of the lanthanide oxidation state. Accordingly, the research plan was to synthesize a series of BIAN-supported decamethyllanthanocene complexes with the goal of learning how to control the spontaneous charge transfer that had been reported in the literature. A longer term goal was to develop a bifunctional ligand of the BIAN type that was capable of accommodating two lanthanide or main group element moieties. Systems with tunable electronic interactions between lanthanide or main group elements are of interest because they offer the prospect of extended delocalization of electron density. Systems of this type have potential applications as e.g. molecular wires and single-molecule magnets. Indeed, such systems have been investigated by using bis(bipyridyl) and bis(terpyridyl) ligands to support two redox-active moieties. However, in the present work, it was recognized that a bifunctional BIAN-type ligand might be of considerable interest as the supporting structure for studying the communication between lanthanide or main group element moieties. A synthesis of variously substituted tetrakis(imino)pyracene (TIP) ligands was therefore undertaken. The flat, rigid nature of the TIP ligands rendered them ideal scaffolds for studying the redox behavior and electronic communication between lanthanide or main group element centers. The new TIP ligand class also proved to be useful for the assembly of the first example of a metallopolymer based on a BIAN-type ligand. / text

Lanthanide-based nanoparticles can be used in a variety of applications, including biomedical work such as imaging and cancer therapies, and in solar cells. This thesis presents two different potential applications for lanthanide-based nanoparticles and a possible new method for single nanoparticle analysis. Each of the projects presented in this thesis starts from the colloidal synthesis of the nanoparticles and then explores their varying properties, such as size and size distribution, crystallinity, elemental composition, and optical properties. Chapter 1 presents a short introduction to lanthanides and explores their ability to luminesce and upconvert. These optical properties make lanthanide-based nanoparticles attractive in both the visible and near-infrared (NIR) range. Chapter 2 explores the possibility of using β-LaF3:Nd3+ (5%) nanoparticles in a colloidal laser to overcome some issues that solid state lasers face due to thermal effects. A colloidal laser requires small nanoparticles that can emit a useful wavelength and that are dispersed in a high boiling point liquid. In Chapter 3, a cation exchange of ytterbium for yttrium and erbium in water-dispersible β-NaYF4:Er3+ nanoparticles across a polyvinylpyrrolidone (PVP) surface coating was tested as a possible synthesis route for radioactive nanoparticles. Incorporating radioactive materials at the end of a therapy preparation would limit the number of synthesis steps in an isotope laboratory. Chapter 4 presents single-particle analysis of β-NaYF4:Er3+ (50%) nanoparticles using X-ray absorption spectroscopy (XAS) at the Canadian Light Source (CLS). Electron beams in scanning electron transmission microscopes (STEM) can damage the samples, making quantification of nanoparticles challenging. Finally, Chapter 5 discusses some conclusions and suggests possible future work. / Graduate / 0494

The research work reported in this dissertation is focused on exploring the systematic syntheses and characteristics of lanthanide-containing functional materials. Lanthanides have interesting properties that arise as a consequence of f-electrons, namely, magnetism, luminescence, and flexible coordination sphere. These studies were extended further into heterometallic systems containing transition metal ions, specifically Ni(II) and Co(II), to further explore the behavior of lanthanides in functional materials with addition of transition metal ions. The results include the high nucleraity lanthanide hydroxide clusters and metal-organic frameworks which showed potential applications in catalysis, separations, solid-state light-emitting devices and magnetism. Chapter 1 provides background on lanthanides and different types of lanthanide-containing materials, their properties, and potential applications followed by a synopsis to the research work in each chapter. In Chapter 2, the synthesis, structure characterization, magnetic studies and solution stability studies of a novel class of high-nuclearity lanthanide hydroxide cluster complexes {Ln54} with Chromogen I, a ligand transformed from in situ N-Acetyl-D-glucosamine are summarized. Attention is focused on this ligand transformation since it shows a possible pathway for selective and efficient transformation of biomass into useful chemicals with the unique coordination chemistry of lanthanides. The remainder of this chapter is focused on using hydroxylcarboxylic acids for the formation of high-nuclearity lanthanide hydroxide clusters with the aim of expanding the array of ligands that can be utilized for developing these systems. Chapter 3 discusses the synthesis, structural characterization and photoluminescence properties of a novel series of lanthanide metal-organic frameworks utilizing iminodiacetic acid as bridging ligand. The possibility of luminescence color tuning employing mixed metal system containing Eu and Tb was shown. The lifetimes for the luminescence systems were evaluated based on photo decay studies in order to understand the energy transfer processes in the mixed-metal system. An energy transfer from Tb to Eu was evident based on the data. Chapter 4 focuses on a 3d-4f heterometallic system based on Ni(II) that has been synthesized using a metalloligand approach. A metalloligand containing Ni was first synthesized and then used for further lanthanide coordination. The result of this effort was a bi-porous metal-organic framework (MOF) which contains both hydrophilic and hydrophobic pores. The magnetic studies showed weak antiferromagnetic interactions between the Ni centers and confirmed the absence of single-molecule magnet behavior. Chapter 5 explores another 3d-4f heterometallic system which contains Co(II) using a different synthetic approach than that reported in Chapter 4. A 2-D layer type MOF containing both Ln(III) (Ln= Pr, La, Nd) Co(II) was obtained with the use of iminodiacetic acid as the supporting ligand under solvothermal conditions which further extends to a 3-D network with extensive hydrogen bonding. Magnetic studies were carried out to explore the magnetic interactions between the metal ions and results were not conclusive due to the complicated intrinsic magnetic characteristics possessed by both Ln(III) and Co(II).Chapter 6 describes results on another lanthanide-containing MOF that assembles as a layered material creating channels between the layers. The structural analysis of the MOF of interest and other MOFs obtained under the controlled conditions were discussed. This work has potential applications as an advanced material for proton conductivity, intercalation, and ion exchange. Chapter 7 summarizes the body of work by examining the results and significance of the results presented in Chapters 2-6 and discusses the future directions possible for each project. Appendix A provides all the crystallographic information including bond lengths and angles.

This project was focused on the synthesis and reactivity of rare-earth nbutyl complexes of the formula [CpMe2M(μ-nBu)]2 (where M = Y, Dy). Dysprosium was used as it has a large magnetic moment which is favourable for producing single molecule magnets (SMMs). Yttrium was used as a diamagnetic analogue to examine the reactivity of [CpMe2Y(μ- nBu)]2 in solution, and provide further characterisation of isolated complexes with NMR spectroscopy. Another goal of the project was to establish the reactivity of [CpMe2M(μ- nBu)]2 with respect to the commonly used alkylating reagent nbutyllithium (nBuLi). It was found that the nbutyl complexes are remarkably stable in solution and the solid state, allowing for the synthesis to be scaled up and for the nbutyl complexes to be used as starting materials. The reactivity of [CpMe2M(μ- nBu)]2 towards ferrocene was investigated. The product was a ferrocenyl-bridged dimer of the formula [CpMe2M(μ-(C5H4)FeCp)]2 resulting from a single deprotonation of ferrocene. The reactivity of [CpMe2M(μ- nBu)]2 towards N-heterocyclic carbenes (NHCs) was also investigated. No reaction occurred between [CpMe2Y(μ- nBu)]2 and 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr), a reaction did occur between [CpMe2Y(μ- nBu)]2 and 1,3-bis-(tert-butyl)imidazol-2-ylidene (ItBu) but no crystalline product could be obtained. [CpMe2M(μ- nBu)]2 reacts with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) to form a monomeric, benzyl tethered carbene complex [CpMe2M(IMes’)]. An ortho-methyl group on one of the mesityl substituents is deprotonated generating an asymmetric functionalised carbene. A control experiment between CpMe3M (M = Dy, Y) and IMes resulted in the formation of the abnormal, rearranged carbene complexes [CpMe3M(aIMes)]. C6H6. Structural analysis revealed a very short C-H---π interaction between neighbouring molecules. The mechanism of carbene rearrangement was probed by 1H NMR spectroscopy (M = Y). Magnetic susceptibility measurements revealed that [CpMe2Dy(μ- nBu)]2, [CpMe2Dy(μ-(C5H4)FeCp)]2, [CpMe2Dy(IMes’)] and [CpMe3Dy(aIMes)]. C6H6 are not SMMs. [CpMe2M(μ- nBu)]2 activates sulfur and selenium to form hexanuclear clusters of the formula [CpMe10M((E3)2E2] (M = Dy, Y; E = S, Se). [CpMe10M((S3)2S2] is an SMM with an energy barrier to magnetisation reversal, Ueff, of 73 cm-1. The analogous selenium cluster could be characterised by single crystal X-ray diffraction however separation from unreacted selenium proved difficult without using coordinating solvent. Extraction of [CpMe10Y((Se3)2Se2] with THF resulted in the crystallisation of the ion pair [CpMe2Y(THF)3][{CpMeY(Se2)}6Se] and [{CpMe2Y(THF)}(µ-Se2)]. A trimetallic dysprosium coordination complex containing a hexaazatrinapthalene (HAN) bridging ligand is reported. Magnetic measurements on [{(thd)3Dy}3HAN] (Dy3HAN) show that it is an SMM in zero field and two magnetic relaxation mechanisms are present. An optimised DC field of 1 kOe allowed for better resolution of the two relaxation processes and an energy barrier for each process could be extracted. The Ueff barriers are 42 and 52 cm-1. Ab initio theoretical analysis revealed the magnetic anisotropy axes are nearly collinear precluding the presence of a toroidal magnetic moment. The ground state of Dy3HAN was found to be frustrated.