Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 240-150). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1997. / Typescript. Vita. Includes bibliographical references (leaves 240-150). Also available on the Internet.

Thesis (Ph. D.)--University of Washington, 2004. / Vita. Includes bibliographical references (leaves 196-209).

Thesis (Ph. D.)--University of Hong Kong, 2005.

Thesis (Ph.D.)--Baylor University, 2009. / Includes bibliographical references (p. 233-237).

Luminescent transition metal complexes have attracted tremendous interest in the analytical field. Most luminescent metal complexes possess long emission lifetimes in the visible region, and their phosphorescence can be readily distinguished from short-lived background auto-fluorescence. Moreover, their large Stokes shift can prevent self-quenching, while their modular synthesis allows their properties to be readily tuned without labor-intensive synthetic protocols. These properties render transition metal complexes as promising candidates for the development of biosensors. In this study, I aimed to explore different kinds of Ir(III) complexes that can be used as biosensors to monitor DNA secondary structures or protein conformations. Chapter 1 gives a brief introduction regarding the luminescence mechanism of transition metal complexes, and the properties, structures and preparations of Ir(III) complexes are also introduced. Chapters 24 report the syntheses and screening of Ir(III) complexes, and the use of these Ir(III) complexes to monitor the secondary structure of DNA, such as G-quadruplex, G-triplex and i-motif DNA. Chapter 2 reports the G-quadruplex-selective properties of two luminescent Ir(III) complexes 2.1 and 2.9 for the detection of ochratoxin A (OTA) and nicking endonuclease in aqueous solution, respectively; Chapter 3 explores a novel Ir(III) complex 3.8 which is highly specific for G-triplex DNA, and was thus employed for Mung Bean nuclease activity detection; Chapter 4 introduces the Ir(III) complex 4.1 that exhibited a high signal enhancement to i-motif DNA, and was therefore used for terminal deoxynucleotidyl transferase (TdT) activity detection. Chapter 5 describes the two novel cyclometalated Ir(III) complexes 5.1 and 5.21 that were used to monitor two kinds of proteins, human serum albumin (HSA) and beta-amyloid(140) (Aβ140), respectively.

No description available.

The use of two different chelating redox active ligands, 2,6-bis(6-methyl-1,2,4,5-3-yl) pyridine (BTZP) and 2,6-bis-(5,6-dialkyl-1,2,4-triazin-3-yl)-pyridine (BTP) in heterometallic first row and second row transition metal chemistry has yielded two new families of redox active metal complexes. These complexes were found to exhibit interesting electrochemical and magnetic properties. In this thesis, Chapter 1 lays the foundation for the research presented within. This section covers the fundamentals of the ligand design, ligand synthesis and related coordination chemistry literature review. Chapters 2 and 3 report the results of the current thesis. In Chapter 2, the synthesis and characterization of a family of discrete molecules and supramolecular arrangements, employing the ligand BTZP, is presented. All of the complexes presented in Chapter 2 are successfully synthesized and characterized with electrochemical and magnetic studies. According to the electrochemical data, it is found that the classic “terpy-like” complexes with [Co(BTZP) 2]2+ formula fosters more stability in the redox process. In Chapter 3, a family of transition metal complexes with [M(BTP) 2]2+ (M=Fe or Co) inorganic cores were obtained through the employment of the ligand BTP with various anions. In addition, dimeric molecules with [CoX4(BTP)2] formula were also obtained by solvothermal synthesis. The complexes were also electrochemically characterized, with all the complexes capable of being reduced, while only [CoII(BTP)2] (ClO4)2 showed reversible redox process. Similar with BTZP, the series of BTP based complexes are also characterized through magnetic measurement. Only cobalt-based BTP complexes are paramagnetic, with [CoII(BTP)2]2+ being spin crossover active when BF4- and ClO4- are present. However, the presence of NCS- and halides lead to either antiferromagnetic interactions and ferromagnetic interactions dominating at different temperature regimes.

Reaction of the tetracobalt cluster Co4(CO)10(t 4-PPh)2 with 1,2-bis(dimethylphosphino)ethane (dmpe) affords the bis-substituted cluster Co4(CO)8(dmpe)(t 4-PPh)2. The bidentate dmpe ligand is shown to bind to the cluster in a chelating fashion by IR, NMR, and X-ray diffractions analyses. The fluxional nature of the ancillary carbonyl groups has been studied by variable temperature 13C NMR measurements which reveal two distinct carbonyl scrambling pathways. The stability of the phosphine-ligated cluster has been examined using in situ Cylindrical Internal Reflection (CIR) Spectroscopy. The effect of the dmpe ligand on the cluster polyhedron will be discussed with respect to the observed crystallographic and spectroscopic results

Catalysts based on the first-row (3d) transition metals are commonly seen in chemical and biological reactions. To understand the role of the transition metal in the catalyst, the element specific technique core level spectroscopy is used to probe the electronic structure and geometric properties centered around the metal site. Different types of X-ray spectra can be applied to probe the metal 3d character orbitals involved in reactions, which make it possible to identify and characterize the reactive sites of samples in different forms. A detailed interpretation and understanding of the different X-ray spectra requires a unified method which can be used to model different types of X-ray spectra, e.g., soft and hard X-rays. In this thesis, theoretical investigations of the electronic structures of 3d transition metal complexes through X-ray spectroscopy are presented. The restricted active space method (RAS) is used to successfully reproduce different types of X-ray spectra by including all important spectral effects: multiplet structures, spin-orbit coupling, charge-transfer excitations, ligand field splitting and 3d-4p orbital hybridization. Different prototypes of molecules are adopted to test the applicability of the RAS theory. The metal L edge X-ray absorption (XAS) spectra of low spin complexes [Fe(CN)6]n and [Fe(P)(ImH)2]n in ferrous and ferric oxidation state are discussed. The RAS calculations on iron L edge spectra of these comparing complexes have been performed to fingerprint the oxidation states of metal ion, and different ligand environments. The Fe(P) system has several low-lying spin states in the ground state, which is used as a model to identify unknown species by their spectroscopic fingerprints through RAS spectra simulations. To pave the route of understanding the electronic structure of oxygen evolution complex of Mn4CaO5 cluster, the MnII(acac)2 and MnIII(acac)3 are adopted as prototypical Mn-complexes. The 3d partial fluorescence yield-XAS are employed on the Mn L-edge in solution. Combining experiments and RAS calculations, primary questions related to the oxidation state and spin state are discussed. The first application to simulate the metal K pre-edge XAS of mono-iron complexes and iron dimer using RAS method beyond the electric dipole is completed by implementing the approximate origin independent calculations for the intensities. The K pre-edge spectrum of centrosymmetric complex [FeCl6]n– ferrous state is discussed as s and a donor model systems. The intensity of the K pre-edge increases significantly if the centrosymmetric environment is broken, e:g:, when going from a six-coordinate to the four-coordinate site in [FeCl4]n. Distortions from centrosymmetry allow for 3d-4p orbital hybridization, which gives rise to electric dipole-allowed transitions in the K pre-edge region. In order to deliver ample electronic structure details with high resolution in the hard X-ray energy range, the two-photon 1s2p resonant inelastic X-ray scattering process is employed. Upon the above successful applications of one-photon iron L edge and K pre-edge spectra, the RAS method is extended to simulate and interpret the 1s2p resonant inelastic X-ray scattering spectra of [Fe(CN)6]n in ferrous and ferric oxidation states. The RAS applications on X-ray simulations are not restricted to the presented spectra in the thesis, it can be applied to the photon process of interest by including the corresponding core and valence orbitals of the sample.