Multimeric ligands have the potential to be developed as targeted imaging agents and therapeutics for the diagnosis and treatment of cancer. Multimeric ligands consist of multiple binding residues tethered together by a linker and are capable of simultaneous binding to multiple receptors. This dissertation details the proof-of-principle experiments that establish that multimeric ligands bind with an increased affinity and cooperativity compared to their monomeric counterparts. We have chosen to evaluate combinations of ligands for the human melanocortin 4 receptor (hMC4R), human delta-opioid receptor (hdOR), cholecystokinin-B receptor (CCK-BR), and oxytocin receptor (OTR).Multivalent ligands can be homomeric, meaning that all ligands bind to the same receptor type, or they may be heteromeric, meaning that they bind to different types of receptors. We have evaluated homodimer and homotrimer binding to hMC4Rs, and heterodimer binding to hMC4Rs and hdORs. Ligands for the receptors were tethered together using backbones constructed of polyethylene glycol (PEG) units or different combinations of amino acid repeats. The effects of linker length and rigidity on the binding of multivalent ligands have been evaluated. Additionally, this dissertation details the development of a new lanthanide based binding method used to monitor receptor-ligand interactions. This assay makes use of lanthanide labels attached to a peptide that binds specifically to the receptor of interest. The amount of bound ligand is detected using time-resolved fluorescence (TRF). This assay produces results which are highly reproducible, require less setup time and reagents and do not require special waste disposal, all advantages over the traditional radioligand binding assays. This lanthanide based binding assay has been adapted to evaluate ligand binding to the hMC4R and hdOR.

This thesis will present the synthesis, characterization and magnetic measurements of lanthanide complexes with varying nuclearities (Ln, Ln2, Ln3 and Ln4). EuIII, GdIII, TbIII, DyIII, HoIII and YbIII have been selected as the metal centers. Eight polydentate Schiff-base ligands have been synthesized with N- and mostly O-based coordination environments which chelate 7-, 8- or 9-coordinate lanthanide ions. The molecular structures were characterized by single crystal X-ray crystallography and the magnetic properties were measured using a SQUID magnetometer. Each chapter consists of crystal structures and magnetic measurements for complexes with the same nuclearity. There are eight DyIII SMMs in this thesis which are discrete molecules that act as magnets below a certain temperature called their blocking temperature. This phenomenon results from an appreciable spin ground state (S) as well as negative uni-axial anisotropy (D), both present in lanthanide ions owing to their f electron shell, generating an effective energy barrier for the reversal of the magnetization (Ueff). The ab initio calculations are also included for the SMMs with high anisotropic energy barriers to understand the mechanisms of slow magnetic relaxation in these systems.

Paramagnetic lanthanide ions have been investigated as possible MIR phantom materials and contrast agents. The aim of this study is to determine if it is possible to apply the well known Solomon-Bloembergen equations to solutions of paramagnetic lanthanide ions that have fast electron spin relaxation times, compared to Gadolinium, the most widely used ion for NMR. Studies of the relaxivity, frequency and temperature dependence, show that there is a considerable difference in those properties over the series. Chelation of the ions to EDTA and DTPA resulted in a decrease in the relaxivity which was directly proportional to the decrease in the number of water molecules in the inner co-ordination sphere. The fit of the Solomon-Bloembergen equations to the variable frequency and temperature relaxation times showed that theory is valid for the fast electron spin ions and allowed the calculation of the electron spin relaxation times. This showed that there is a difference of 5 orders of magnitude between Gadolinium, the ion demonstrated to have a slow electron spin relaxation time, and the remaining ions. The addition of EDTA chelated forms of these ions to agarose gels produced NMR phantom materials with relaxation time characteristics that could be chosen to fulfil a desired application. The biodistribution of Gd-DTPA was investigated using ESR and NMR. The concentration of Gd-DTPA in excised rat tissue, 20 minutes after intraperitoneal injection, was determined, by the change in NMR water proton relaxation time from that of a control tissue, and by ESR from direct measurement of the microwave power absorbed by the sample, which is directly proportional to the number of unpaired electron spins in the sample. The results from these two methods of determining contrast agent concentration agree well with each other both in the order of biodistribution and on the absolute concentrations.

No description available.

Novel glass tracers, organic and inorganic polymers based on narrow band atomic fluorescence, have been developed for deployment as environmental tracers. The use of discrete fluorescent species in an environmentally stable host has been investigated to replace existing toxic, broad band molecular dye tracers. The narrow band emission signals offer the potential for the tracing of a large numbers of signals in the same environment; this has been investigated by examining multiple doped tracers which have the potential for coding to specific effluent sources or particulates. The concept of using lanthanide doped glasses as environmental tracers has been demonstrated. The spectral characterisation and concentration studies of the lanthanide doped tracer allow the selection of parameters to produce future tracers and detection systems for particular applications. Therefore by altering the chosen lanthanide dopant, number of dopants, dopant concentration and using selective excitation and emission wavelengths there are a huge number of possible unique tracer combinations. The significantly narrower bandwidth emission peaks of the lanthanide based tracers achieve more selective detection of multiple tracers without overlap interference and gives the potential to selectively and simultaneously monitor many different tracers in the same location. The spectral lifetime characteristics of the lanthanide tracers are very different from the lifetime of background fluorescence which is typically molecular in origin. This is an extra discrimination against background interference and is an important additional advantage of using lanthanide based tracers. Overall this work shows that a very large number of unique environmental tracers can be obtained by varying the concentration, the number of lanthanide ions in a glass and also the possibility of using organic and inorganic lanthanide chelate doped tracers.

This thesis will present the synthesis, characterization and magnetic measurements of lanthanide complexes with varying nuclearities (Ln, Ln2, Ln3 and Ln4). EuIII, GdIII, TbIII, DyIII, HoIII and YbIII have been selected as the metal centers. Eight polydentate Schiff-base ligands have been synthesized with N- and mostly O-based coordination environments which chelate 7-, 8- or 9-coordinate lanthanide ions. The molecular structures were characterized by single crystal X-ray crystallography and the magnetic properties were measured using a SQUID magnetometer. Each chapter consists of crystal structures and magnetic measurements for complexes with the same nuclearity. There are eight DyIII SMMs in this thesis which are discrete molecules that act as magnets below a certain temperature called their blocking temperature. This phenomenon results from an appreciable spin ground state (S) as well as negative uni-axial anisotropy (D), both present in lanthanide ions owing to their f electron shell, generating an effective energy barrier for the reversal of the magnetization (Ueff). The ab initio calculations are also included for the SMMs with high anisotropic energy barriers to understand the mechanisms of slow magnetic relaxation in these systems.

Conducting metallopolymers are a new and fascinating class of materials that incorporate metals into conducting polymer systems. These new materials combine the processing advantages of polymers with the electronic, optical and catalytic properties provided by the presence of metal centers. A large number of conducting metallopolymers have been synthesized and studied and have found applications in areas such as sensors, memory and light-emitting devices, solar cells, and catalysis. Among the various applications, conducting metallopolymers as emitting layers in high-efficiency polymer light-emitting diodes (PLEDs) attract great research interest. In order to get PLEDs with long lifetime, high quantum efficiency, and excellent color purity, we have developed an approach to synthesize well-defined conducting metallopolymers that incorporate lanthanide complexes in an inner sphere fashion. As such, we aim to take full advantage of the properties of both organic and inorganic components with high efficiency due to the direct electronic interface this configuration creates. Lanthanide complexes with polymerizable groups have been synthesized, characterized and utilized as precursors for conducting metallopolymers. These lanthanide monomers and corresponding metallopolymers display visible and near-infrared luminescence at room temperature that is consistent with efficient energy transfer from the organic polymer matrix to the lanthanide metal ion followed by lanthanide luminescence. As a second but closely related area, electrogenerated chemiluminescence (ECL) of polymers is attractive for light-emitting devices. Up to now, there are limited studies dealing with ECL from pure active materials deposited as solid films on electrodes. The operation theory and degradation mechanism are still under investigation. To advance the development of ECL of conducting metallopolymers, we prepared cyclometalated Pt(II) complexes with polythiophene system. Conducting metallopolymer films are prepared through controlled electropolymerization. ECL of the Pt(II) containing conducting polymers are observed for the first time. Finally, a preliminary study of magnetism and conductivity of conducting metallopolymers has been done. We incorporate Fe(II)/Fe(III) into our newly designed ligand systems with polymerizable thiophene derivatives. Three complexes show spin crossover (SCO) phenomena with the highest transition temperature at 265 K, which are further verified by variable temperature electron paramagnetic resonance spectra. / text

A series of kinetically stable chiral lanthanide complexes has been developed, with a view to developing responsive probes for use in analysis and in seeking chiral complexes exhibiting selectivity in their interaction with nucleic acids. Firstly a pH sensitive complex has been modified with the aim of tuning the pH range to which it responds to the physiologically useful regime. The synthesis was undertaken of relatively lipophilic 6-butylphenanthridinyl complexes. Their photophysical behaviour was investigated by absorbance and luminescence spectroscopy and the modulation of their emission examined in the pH range 4.5 to 7.5.In addition to their luminescent properties, enantiomerically pure chiral lanthanide complexes permit chiroptical techniques to be used, allowing their interactions with other chiral species to be addressed (e.g. nucleic acids, oligonucleotides).The first series of enantiopure lanthanide complexes has been devised that show several interesting features in binding to oligonucleotides and nucleic acids. These macrocyclic tris-and tetra-amide lanthanide (Eu, Tb or Yb) complexes contain an N-alkyl phenanthridinium unit that allows intercalation between the base pairs of the DNA. Their binding to [(AT)(_6)](_2), [(CG)(_6)](_2) and CT-DNA was monitored by changes in the ligand and metal based luminescence, and in the characteristic CD bands of the oligonucleotides. Binding affinities were assessed using intrinsic methods and the McGhee-von Hippel analysis. Marked differences have been observed in the binding of Eu and Yb complexes as a function of the A and Δ helicity of the complexes, which is itself determined by the configuration of the remote amide substituents. Binding of the A-Eu complex was over 50 times stronger to [(CG)(_6)](_2) compared to [(AT)(_6)](_2), while the left handed Δ-Yb complex showed a different pattern of selectivity. In the europium complex of a related heptadentate tris-amide ligand, the coordination of a DNA phosphate group to the lanthanide centre was suggested by emission and lifetime changes. Another series of chiral tetraamide complexes linked to the 6 position of the phenanthridine moiety was synthesised and studied. An additional stereogenic centre at carbon, alpha to the phenanthridine group was introduced with the aim of tuning the selectivity of binding. A set of four diastereoisomeric ligands was separated and their lanthanide complexes characterised. The binding of their Eu and Yb complexes was evaluated and differences between Eu and Yb complexes persisted. The additional chiral centre did not appear to modify the binding affinity of this series of complexes. Finally, a series of 6-phenanthridinyl complexes was investigated in which the phenanthridine N atom was directly bound to the lanthanide centre. Their affinity for DNA was found to be relatively low, which may be related to their rigid structure.

Complex lanthanide oxide systems are known to host novel phases of matter, while also providing functionality for practical applications. In this dissertation, the structural, magnetic and magnetocaloric properties of three families of lanthanide oxides have been studied with the dual aims of investigating the magnetic behaviour and identifying promising magnetic refrigerants for cooling to temperatures currently accessible using non-renewable liquid He. The thesis presents a two-part study of the magnetic and magnetocaloric properties of the geometrically frustrated lanthanide garnets, where the magnetic $Ln^{3+}$ form corner-sharing triangles. First, the family of garnets $Ln_3A_2X_3$O$_{12}$, $Ln$ = Gd, Tb, Dy, Ho, $A$ = Ga, Sc, In, Te, $X$ = Ga, Al, Li are investigated. Changes to the single-ion anisotropy of the magnetic ion as well as variations in the chemical pressure radically alters the nature of magnetic ordering, the degree of frustration and the magnetocaloric performance. In the second part, the garnets $Ln_3A$Ga$_4$O$_{12}$, $Ln$ = Gd, Tb, Dy, Ho, $A$ = Cr, Mn, are studied. Introducing additional spins significantly reduces the frustration in the garnet lattice. Low temperature powder neutron diffraction of Ho$_3$MnGa$_4$O$_{12}$ reveals concomitant ordering of Ho$^{3+}$ and Mn$^{3+}$ moments below the ordering temperature, $T_N$ = 5.8 K. The magnetocaloric performance of $Ln$_3CrGa$_4$O$_{12}$, $Ln$ = Gd, Dy, Ho, greatly surpasses that of the parent $Ln_3$Ga$_5$O$_{12}$ at $T$ = 2 K. The final results chapters in the thesis describe the magnetism and magnetocaloric effect in the lanthanide orthoborates, $Ln$BO$_3$ , $Ln$ = Eu, Gd, Tb, Dy, Ho, Er, Yb and the lanthanide metaborates, $Ln$(BO$_2$)$_3$, $Ln$ = Pr, Nd, Gd, Tb. The magnetic $Ln^{3+}$ form slightly distorted edge-sharing triangular layers in $Ln$BO$_3$. Unique magnetic features are observed, including short-range ordering and spin reorientation transitions depending on the single-ion anisotropy of the $Ln^{3+}$. The $Ln$BO$_3$ are also efficient magnetocalorics in the liquid helium temperature range. The lanthanide metaborates contain one-dimensional chains of magnetic lanthanide ions. Bulk magnetic measurements show features consistent with low-dimensional magnetism, such as magnetisation plateaux at one-third of the saturation magnetisation for Nd(BO$_2$)$_3$ and Tb(BO$_2$)$_3$ in a field of 14 T. This thesis provides insight into the fundamental magnetic properties of complex lanthanide oxide systems and also demonstrates strategies for identifying new magnetocaloric materials: both through chemical control of the structure of well-known magnetocalorics and by studying materials that have not been explored previously. The results pave the way for further in-depth investigations and finding new magnetic coolants based on complex lanthanide oxide systems.

xviii, 174 p. : ill. (some col.) A print copy of this thesis is available through the UO Libraries. Search the library catalog for the location and call number. / Hybrid nanoscale complexes incorporate the attributes of organic and inorganic components to yield novel multifunctional materials. Because the individual components themselves and the combinations used can be widely varied to tune the properties of the resulting complex, the potential for new properties and practical applications is nearly limitless. However, widespread use of these materials relies on appropriate design, synthesis and characterization strategies to ensure proper function and compositional integrity. This dissertation describes the chemistry of these hybrids, made possible by combining organic ligands, inorganic nanoparticles, and metal ions, and the interesting optical and spectroscopic properties associated with the hybrid nanomaterials. Organic ligands containing Bunte salt and acyclic malonamide functionalities were attached to gold nanoparticles to produce colorimetric sensors for lanthanide ion detection. Bunte salt functionality stabilizes the gold core and malonamide functionality offers selective and sensitive lanthanide ion binding. The binding interaction controls a nanoparticle cross-linking event that changes the color of the nanoparticle solution, resulting in visual, colorimetric lanthanide ion detection. Next, the concentration of malonamide ligand was diluted and replaced with a diluent ligand yielding nanoparticles stabilized with a mixed ligand composition. The mixed ligand environment makes the optical response of the colorimetric sensor reversible. Furthermore, the use of Bunte salt ligands during nanoparticle synthesis has allowed the investigation of the role of reducing agent on nanoparticle stability. In addition to exploring interactions pertaining to gold nanoparticle complexes, a new approach to sensitize europium ion luminescence was developed by fabricating a zinc oxide/europium complex. A molecular linker permits simultaneous zinc oxide nanoparticle functionalization and trivalent europium binding in order to tether the europium ion close to the nanoparticle surface. The zinc oxide nanoparticle can then act as an inorganic antenna, transferring energy to the europium ion and enhancing its luminescence. Finally, a strategy was developed to synthesize bifunctional bicyclic malonamides. Synthesis of these ligands allows the enhanced f-block ion binding affinity of bicyclic malonamides to be incorporated into functional materials to compare their performance to our previously prepared acyclic malonamide hybrid complexes. This dissertation includes my previously published and co-authored materials. / Committee in charge: Darren Johnson, Chairperson, Chemistry; James Hutchison, Advisor, Chemistry; Catherine Page, Member, Chemistry; Michael Haley, Member, Chemistry; Barbara Roy, Outside Member, Biology