<p> In this thesis I present the synthesis and characterization of materials exhibiting frustrated magnetism. In Chapter 1 I describe magnetic frustration and some of the magnetic states that can arise from it followed by the background on iridates and platinates with honeycomb structures and rare earth pyrochlores. </p><p> In Chapter 3 I discuss my work on the synthesis and properties of ternary sodium iridates with formulas Na_xM_2/3Ir_1/3O₂ and Na_xM_1/3Ir_2/3O₂ (M = Mn, Fe, Co, Ni, Cu, Zn). The ternary iridates are based on the honeycomb compound Na₂IrO₃ but show more disorder in the honeycomb layer than the parent. The six new compounds are all spin glasses but show distinct magnetic properties from one another. </p><p> In Chapter 4 I continue my work on honeycombs by exploring new ternary sodium platinates. These three new compounds with formulas Na₃MPt₂O_6+x (M = Mg, Cu, Zn) are structurally very similar to the iridates discussed in Chapter 2 but have non-magnetic Pt⁴⁺ in place of magnetic Ir⁴⁺. The Mg and Zn variants are non-magnetic while the Cu variant is paramagnetic at 2 K. </p><p> Chapter 5 is a synchrotron X-ray diffraction study of the magnetically frustrated rare earth pyrochlores Ho₂Ti₂O₇, Er₂Ti₂O₇ and Yb₂Ti₂O₇. Previous neutron scattering studies have shown reflections that are forbidden by the assigned space group <i>Fd-3m,</i> therefore high intensity, high resolution X-ray diffraction data was collected to determine if the reflections are present. Slight variations in sample stoichiometry were studied to account for possible sample variation. The forbidden reflections are absent from the X-ray diffraction patterns, providing strong evidence that the extra reflections in neutron scattering experiments are not structural in origin.</p>

<p> &beta;-Diketones are well known to form metal complexes with practically every known metal and metalloid. Metal complexes of fluorinated &beta;-diketones generally exhibit increased volatility and thermal stability compared to the non-fluorinated analogues, and thus are used extensively in various chemical vapor deposition (CVD) processes for the deposition of metal, simple or mixed metal oxides, and fluorine-doped metal oxide thin films. Furthermore, the electron-withdrawing nature of the fluorinated ligand enhances the Lewis acidity of a coordinatively unsaturated metal center which facilitates additional coordination reactions. The physical and structural properties of fluorinated &beta;-diketonate complexes are discussed in Chapter 1 and a few key application examples are given.</p><p> The focus of this work is the synthesis and single crystal X-ray structural characterization of unsolvated and coordinatively unsaturated metal complexes of bis(pentafluorobenzoyl)- methanide (L, C₆F₅COCHCOC₆F₅^-). In Chapter 2, we present the preparation and isolation of the unsolvated complex [Cu(L)₂] in pure crystalline form for the first time. We subsequently investigated the reaction of unsolvated [Cu(L)₂] with sodium hexafluoroacetylacetonate [Na(hfac)] in a solvent-free environment. This reaction allowed the isolation of the first heterometallic Na&ndash;Cu diketonate [Na₂Cu₂(L)₄(hfac)₂] structurally characterized by single crystal X-ray crystallography. Thermal decomposition of [Na₂Cu₂(L)₄(hfac)₂] was investigated for its potential application in MOCVD processes. In the final chapter, we present the first exploration of the anhydrous synthesis of Co(II) complexed with bis(pentafluorobenzoyl)methanide in order to produce a complex without ligated water. Single crystal X-ray crystallographic investigations revealed the isolation of the ethanol adduct, [Co₂(L)₄(C₂H₅OH)₂], and following the removal of ethanol, a 1,4-dioxane adduct, [{Co₂(L)₄}₂(C₄H₈O₂)]. </p><p> In this work, we have provided the first investigation of the synthesis, isolation and single crystal X-ray structural characterization of unsolvated and coordinatively unsaturated Cu(II) and Co(II) complexes of bis(pentafluorobenzoyl)methanide ligand. These studies demonstrate how the electrophilicity of a coordinatively unsaturated metal complexed to highly-fluorinated &acirc;-diketone ligands can be utilized for the formation of new adducts or new and interesting heterometallic complexes. This body of work provides a basis upon which future research into unsolvated and unligated bis(pentafluorobenzoyl)methanide metal complexes can expand.</p><p>

The unique electronic, magnetic, and optical properties of nanoparticles (NPs) make them useful building blocks for nanodevices and biofabrication. Site-selective immobilization/deposition of NPs on surfaces at desired positions is an important fabrication step in realizing the potential of nanomaterials in these applications. In this thesis, my research has focused on developing new strategies for mono- and multilayered-NP deposition on surfaces, increasing the stability of NP-assembles upon various surfaces for practical use of NP-based devices. Chemically directed dithiocarbamate binding of amine groups to NPs in the presence of CS2 was used for enhancing the robustness of NP assembles. Such patterning methodologies have allowed me to use site-directed NP immobilization in applications as diverse as microcontact printing, nanomolding in capillaries, nanoimprint lithography, and photolithography. Also, I have developed a simple and reliable one-step technique to form robust dendrimer-NP nanocomposites using dithiocarbamate-based chemistry. These composites are able to encapsulate and release various therapeutics, providing controllable sustained release and to separate small molecules and biomacromolecules.

The reduction of 1,2-catecholatochloroboron by lithium in liquid ammonia/dimethoxyethane produces a reactive mixture containing multiple products. Formation of complexes with 12-crown-4 allows the isolation of one of these, (12-C-4)LiB(O$\sb2$C$\sb6$H$\sb4)\sb2.$ This complex was characterized by chemical analyses, multinuclear NMR, and single crystal x-ray diffraction. Chemical and spectroscopic data suggest that the remainder of this mixture contains boron in an asymmetric electronic environment and a low oxidation state. Reaction of this mixture with TiCl$\sb4$ forms an air stable complex with the formula TiB$\sb2{\cdot2}$((12-C-4)$\cdot$Ti(O$\sb2$C$\sb6 $H$\sb4)\sb2$). $\sp{11}$B and $\sp{47,49}$Ti NMR measurements of this complex indicate that boron and titanium inhabit a highly asymmetric electronic environment possibly with a considerable B-Ti interaction. The complex TiB$\sb2{\cdot}$((dme)$\cdot$Ti(SC$\sb2$H$\sb5)\sb2$(NH$\sb2)\sb2\rbrack,$ was prepared in a similar way. Reaction of this complex with bidentate protic species produced a series of polymeric complexes. TGA of theses polymers showed that mass loss was essentially complete by 400-600$\sp\circ$C. Pyrolysis of this series to 1000$\sp\circ$C formed green ceramic products that were characterized by volatiles analysis, chemical analysis, $\sp{11}$B MAS-NMR, XPS and powder diffraction. Annealing the green products at 1650$\sp\circ$C caused a carbothermic reduction that removed oxide impurities and formed crystalline TiB$\sb2$/TiC. However, this reduction only occurred when the green ceramic contained $>$5% amorphous carbon. In all other cases, the annealed ceramics contained TiBO$\sb3$/TiC. Pyrolysis of TiB$\sb2{\cdot}2$((dme)$\cdot$Ti(O$\sb2$C$\sb6$H$\sb4)\sb2\rbrack$ in a fluidized bed reactor produced a green ceramic with a minimum particle size of 100 nm. For this product, formation of TiB$\sb2$/TiC by carbothermic reduction was complete by 800$\sp\circ$C, 450$\sp\circ$C lower that conventional preparations. Reaction of a boryl-titanium complex with solid supports containing surface hydroxide groups led to thin films of titanium boride.