The introductory Chapter to this thesis outlines fundamental aspects of 4f lanthanide(III) coordination chemistry, in particular compounds that possess the intriguing properties of slow relaxation of magnetisation, (or the ability to behave as single-molecule magnets, SMMs). The recent renaissance into the study of the magnetic behaviour of 4f-coordination complexes has led to the consideration of utilising organometallic precursors for the development of novel lanthanide containing compounds, which may possess interesting magnetic properties, subsequently forming the basis of Chapter Two. In Chapter Two, the syntheses and structures of the novel lithiated thiolate ligand, lithium triphenylsilylthiolate, (Ph3SiS-Li) (2.1), and the sulfur-bridged, dimetallic dysprosium(III) and gadolinium(III) complexes [(MeCp)2Dy(µ-SSiPh3)]2 (2.2) and [(MeCp)2Gd(µ-SSiPh3)]2 (2.3), are described in detail. The structural and physical properties of these compounds are analysed through NMR, elemental analysis and SQUID magnetometry, alongside supporting theoretical calculations to reveal that compound 2.2 is the first dimetallic, sulfur-bridged SMM reported, giving an energy barrier to the reversal of magnetisation of Ueff = 192 ± 5 K.56bChapter Three reports on the structural development of a series of lanthanide monomers, exhibiting the general motif [Ln(OSiPh3)3(THF)3] (where Ln = Dy(3.4), Er(3.5), Ho(3.6), Gd(3.7), Tb(3.8)), exploiting the siloxide ligand Ph3SiOH through two novel synthetic routes. This Chapter also provides new analytical insight to these complexes by exploring their magnetic properties through a series of SQUID measurements and through the analysis of their electronic properties using air sensitive, variable temperature optical absorption spectroscopy. Compounds 3.4 and 3.5 were revealed to be SMMs, with 3.5 having a much higher thermal barrier to the reversal of magnetisation, Ueff = ~ 28 K, than 3.4, which are supported by theoretical analysis. Chapter Four describes the utility of ligand 2.1 and Ph3SiOH in the context of 3d transition metal cyclopentadienyl chemistry, outlining the syntheses and structures of three distinct compounds; the trimetallic, [Cp2Mn3(µ-OSiPh3)4](4.7), the hetero-cubane tetramer [CpMn(µ-SSiPh3)]4 (4.8) and the dimetallic thiolate-bridged [CpCr(µ-SSiPh3)]2 (4.9) compound. These compounds were formed in reactions exploiting organometallic manganocene and chromocene precursors. Magnetic susceptibility measurements were conducted on these compounds to gain further insight into their structural properties. The magnetic exchange coupling constants for Mn(II) compounds 4.7 and 4.8 were J = - 4.4 cm-1 and J = - 3.0 cm-1 respectively. Furthermore, having demonstrated the use of metal-cyclopentadienyl building blocks in the synthesis of novel SMMs, Chapter Five discusses the possibility of further advancement on the development of this class of magnetic molecules.

Conselho Nacional de Desenvolvimento Científico e Tecnológico / In this work is presented the hydrothermal synthesis, the structural studies and spectroscopic properties of three coordination polymers based on lanthanides ions (Eu3+, Tb3+ and Gd3+) and DPA as ligand (DPA= 2,6- dipicolinate). Structural study of [Eu(DPA)(HDPA)(H2O)2.4H2O] displayed the presence of self-assembled dimeric and hexameric water clusters fit in the linear chains and the respective role on the stabilization of supramolecular strucuture. The spectroscopic investigations show the low quantum efficiency (η = 12.7%) caused by large contribution of non-radiative decay rates governing the relaxation process due to vibronic coupling with water molecules. The coordination polymers [Tb(DPA)(HDPA)] and [Gd(DPA)(HDPA)] are isostructurals and allowed the investigation about energy transfers processes. In the case of [Tb(DPA)(HDPA)] compound, the photoluminescence data shown the high quantum yield of emission (≈ 50%) due tho the DPA ligand to be a good sensitizer and the lack of water molecules coordinated directly to metal. / Nesse trabalho é apresentado a síntese hidrotermal, estudo estrutural e as propriedades espectroscópicas de três polímeros de coordenação baseados nos lantanídeos (Eu3+, Tb3+ e Gd3+) e o DPA como ligante (DPA= 2,6- dipicolinato). A determinação estrutural do [Eu(DPA)(HDPA)(H2O)2.4H2O] evidencia a presença de clusters de água auto organizados com dímeros e hexâmeros intercalando as diferentes cadeias e o respectivo papel na estabilização da estrutura supramolecular tridimensional. Através dos estudos espectroscópicos foi evidenciado a baixa eficiência quântica (η = 12.7%) como reflexo da larga contribuição das taxas não-radiativas que controlam o processo de relaxação, devido ao acoplamento vibrônico com as moléculas de água. Os polímeros de coordenação [Tb(DPA)(HDPA)] e [Gd(DPA)(HDPA)] são iso-estruturais e permitiram a investigação do processo de transferência de energia. No caso do composto [Tb(DPA)(HDPA)], os dados de luminescência mostraram elevado rendimento quântico da emissão (≈ 50%) devido ao ligante DPA se um bom sensibilizador e a ausência de moléculas de água coordenadas ao metal.

Experimentally measuring how ligand modifications affect metal-ligand bonding and electronic structure is an important goal with relevance to diverse fields such as transition metal catalysis and f-element separations. X-ray absorption spectroscopy (XAS) is an excellent technique for investigating structure/function relationships in metal complexes because it can be used to quantify variations in covalent metal-ligand bonding and electronic structure. Here I describe a series of XAS investigations aimed at elucidating how ligand and structural changes affect chemical bonding and properties in transition metal and uranium complexes. The synthesis and characterization of several new classes of f-element complexes are also discussed. Diphosphines are very important ligands in homogeneous catalysis because they can be used to tune reaction rates, the electronic properties of transition metals, and the stereochemistry of catalytic products. P K-edge XAS studies on solid Ni and Pd diphosphine compounds have shown that M-P covalency is not exclusively dependent on the P-M-P angle (i.e. bite angle), which changes as a function of differing linker groups on the diphosphine backbone. Building on these studies, I show how changes in diphosphine bite angle influence Pd-P covalency in solution and when phenyl substituents attached to phosphorus are replaced with alkyl substituents. This work required the development of an improved solid energy calibration standard for routine energy referencing of P K-edge XAS spectra. I discuss the limitations of P K-edge XAS energy standards used previously and propose tetraphenylphosphonium bromide as a new energy calibration standard for future P K-edge XAS work. The use of nuclear power has resulted in critical challenges surrounding the long-term storage and remediation of nuclear waste. Advanced nuclear fuel cycles can address the scientific challenges of nuclear waste, but require the difficult separation of minor actinides and lanthanides. A multi-donor ligand containing a thioether appendage was prepared to determine if it would bind differently to lanthanide and actinide metals, thereby resulting in metal complexes that could be separated due to differing solubilities. In a related study, a new class of homoleptic lanthanide and actinide borohydride complexes called phosphinodiboranates were prepared. I discuss how the differing solution structures of f-element phosphinodiboranates may offer potential for f-element separations. A series of polyoxovanadate alkoxide clusters was synthesized to investigate the underlying electronic properties that make them useful in catalysis and small-molecule activation. The clusters can access four discrete pseudo-reversible one-electron transfer reactions. V K-edge XAS studies were performed to elucidate variations in electronic structure and bonding in the clusters as a function of redox events, and the results indicate that covalency plays a significant role in the one-electron transfer reactions. These results inspired the synthesis and characterization of an actinide polyoxovanadate compound. Activation and functionalization of the oxo bond in UO22+ is important for understanding the fundamental chemistry of uranium and for developing metal separation processes. A novel uranyl polyoxovanadate compound was studied with V K-edge XAS to determine if covalent interactions between the uranium and vanadium metal centers exist (similar to those observed for the polyoxovanadate alkoxide clusters), and if such interactions could be exploited for activation of the oxo bond in the uranyl dication. Results indicate, however, that the U-O bond remains inactivated.

The focus of this thesis is to develop lanthanide (Ln) luminescent materials through the exploration of coordination polymers and nanomaterials. Herein, dimethyl-3,4- furanedicarboxylate acid undergoes hydrolysis under hydrothermal conditions to form coordination polymers with lanthanide ions. The resulting coordination polymers exhibited luminescent properties, with quantum yields and lifetimes for the Eu-and Tb-CP of 1.14+-0.32% and 0.387=-0.0001 mx, and 3.33=-0.82% and 0.769=-0.006 ms, respectively. While the incorporation of lanthanides was not achieved in this work, progress toward the production of pure phase InP in the nanoregime has been made, using a low-cost, hydrothermal method. Through SEM and PXRD conflict, it is believed that pure INP particles with a size range of 58-81 nm were successfully synthesized. / by Natalie E. Greig. / Thesis (M.S.)--Florida Atlantic University, 2012. / Includes bibliography. / Mode of access: World Wide Web. / System requirements: Adobe Reader.

This thesis includes NMR studies of free base meso-tetra(otolyl) porphyrin (TTP) and meso -tetraphenylporphyrin (TPP) and their dications protonated by trifluoroacetic acid (TFA). The chemical shift changes of the -NH resonance are very unusual and have never been reported. At the beginning of the titration, the N-H resonances broaden considerably but do not shift; when the ratio of [TFA]/[TTP] or [TFA]/[TPPf are over 2, the N-H resonances shift markedly to lower field by as much as 1.6 ppm. At acid levels well above the equivalence point, the NH resonances moves back to higher field. Moreover upon protonation the NH line of TTP becomes a complex multiplet which changes as a function of [TFA]/[TTP]. The NH line of TPP remains a singlet at all acid levels. We also report here a way of isolating atropisomers of mesotetra( o -tolyl)porphyrin through HPLC by using an analytical C-18 bond pack reverse phase column eluted by a 1 %THF + 99%Me0H solvent combination. A preliminary study by HPLC was also carried out on ZnTTP(II) with aliquots of 2,6-dimethylpyridine, and the retention time of the separation decreased markedly, but this study needs to be repeated and improved. TTP and TPP dications at two different acid levels were studied by VT-NMR, and the downfield shift of -NH resonance of TTP dications was more pronounced at higher temperatures than those of TPP dications.

Dreiwertige Actinide (An(III)) und Lanthanide (Ln(III)) stellen im Falle ihrer Inkorporation eine ernste Gefahr für die Gesundheit des Menschen dar. An(III) sind künstlich erzeugte, stark radioaktive Elemente, die insbesondere bei der nuklearen Energiegewinnung in Kernkraftwerken entstehen. Durch Störfälle oder nicht fachgerechte Lagerung radioaktiven Abfalls können sie in die Umwelt und die Nahrungskette des Menschen gelangen. Ln(III) sind hingegen nicht radioaktive Elemente, die natürlicherweise vorkommen und für vielfältige Anwendungen in Technik und Medizin abgebaut werden. Folglich kann der Mensch sowohl mit An(III) als auch Ln(III) in Kontakt kommen bzw. sie inkorporieren. Es ist daher von enormer Wichtigkeit, das Verhalten dieser Elemente im menschlichen Körper aufzuklären. Während makroskopische Vorgänge wie Verteilung, Anreicherung und Ausscheidung bereits sehr gut untersucht sind, ist das Wissen hinsichtlich der chemischen Bindungsform (Speziation) von An(III) und Ln(III) in Körperflüssigkeiten noch sehr lückenhaft. In der vorliegenden Arbeit wurde daher erstmals die chemische Bindungsform von Cm(III) und Eu(III) in natürlichem menschlichem Urin (in vitro) spektroskopisch aufgeklärt und die gebildeten Komplexe identifiziert. Hierzu wurden auch grundlegende Untersuchungen zur Komplexierung von Cm(III) und Eu(III) in synthetischem Modellurin sowie mit den urinrelevanten organischen Modellliganden Harnstoff, Alanin, Phenylalanin, Threonin und Citrat durchgeführt und die noch unbekannten Komplexbildungskonstanten bestimmt. Abschließend wurden alle experimentellen Ergebnisse mit Literaturdaten und Vorherberechnungen mittels thermodynamischer Modellierung verglichen. Auf Grund der hervorragenden Lumineszenzeigenschaften von Cm(III) und Eu(III) konnte insbesondere auch die Eignung der zeitaufgelösten laserinduzierten Fluoreszenzspektroskopie (TRLFS) als Methode zur Untersuchung dieser Metallionen in unbehandelten, komplexen biologischen Flüssigkeiten demonstriert werden. Die Ergebnisse dieser Arbeit liefern damit neue Erkenntnisse zu den biochemischen Reaktionen von An(III) und Ln(III) in Körperflüssigkeiten auf molekularer Ebene und tragen zu einem besseren Verständnis der bekannten, makroskopischen Effekte dieser Elemente bei. Darüber hinaus sind sie die Grundlage weiterführender in-vivo-Untersuchungen.

In this report we studied the properties of the dye IR806 and possible mechanisms of the dye sensitization effect on ytterbium-erbium co-doped upconversion nanoparticles. We found that the dye IR806 has two primary emission peaks in the NIR spectral range at around 850 nm and at around 950 nm. The intensity of these peaks were observed to be affected by the concentration of the dye and the addition of Gadolinium(III) chloride and Yttrium(III) chloride. Specifically increases in the intensity of the 950 nm peak relative to the 850 nm were of interest since ytterbium readily absorbs 950 nm and transfers this energy in the upconversion process. Our hypothesis is that the change in the intensity of the 850 nm and the 950 nm peak is associated with aggregation of the dye IR806 and the amount of monomers and dimers. Results from adding ytterbium-erbium co-doped upconversion nanoparticles in IR806-ethanol solution points to the picture of dimers being formed on the surface on the nanoparticles. This analysis is however based on the assumption that the 850 nm emission peak of IR806 is associated with monomers and that the 950 peak is associated with dimers, which is yet to be confirmed and further studies are therefore needed.

Despite not being a tangible substance, light is becoming an increasingly valuable tool in numerous areas of science and technology: the use of laser excitation of a fluorescent probe can generate incredibly detailed images of cellular structures without the need for large amounts of dissection; new types of solar cells are being produced using organic dyes to harvest light; computer data can be stored by inducing a chemical change in a compound through irradiation with light. However, before any of these materials can be applied in such a way, their properties must first be analyzed for them to be deemed viable. The focus of this dissertation is the photophysical characterization, linear and nonlinear, of a several novel organic compounds, and a europium complex, as well as using quantum chemical calculation techniques to understand some of the phenomena that are witnessed and begin to develop predictive capability. The nonlinear characterization of compounds utilizes wavelengths outside of their linear absorption range, where a focused beam can achieve the same excitation as one at half the wavelength, though this effect has a quadratic dependence on power. The potential for nonlinear excitation, or two-photon absorption (2PA), is becoming of increasing interest and importance for organic chromophores. Exciting only a small volume of material at a focal point makes it possible to nondestructively image samples in 3-dimensions, record data in multiple layers, and fabricate intricate structures through photopolymerization reactions. Lanthanides such as europium are known to exhibit sharp emission bands when excited, typically through an antenna effect due to the low probability of achieving direct excitation. This emission is long-lived, and through gating systems can readily be separated from background noise and autofluorescence (often observed in biological samples) that have much shorter lifetimes. Thus, one of the foci of this dissertation is the photophysical investigation of a series of novel lanthanide complexes, with particular attention to a europium complex.

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