Thesis (Ph. D.)--Syracuse University, 2005. / "Publication number AAT 3207107."

Thesis (Ph. D.)--Indiana University, Dept. of Chemistry, 2006. / "Title from dissertation home page (viewed July 16, 2007)." Source: Dissertation Abstracts International, Volume: 67-10, Section: B, page: 5739. Adviser: Kenneth G. Caulton.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3786. Adviser: Thomas B. Rauchfuss. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3788. Adviser: G.S. Girolami. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

Thesis (Ph. D.)--University of Illinois at Urbana-Champaign, 2006. / Source: Dissertation Abstracts International, Volume: 67-11, Section: B, page: 6396. Adviser: John R. Shapley. Includes bibliographical references. Available on microfilm from Pro Quest Information and Learning.

abstract: ABSTRACT Transition metals have been extensively employed to address various challenges related to catalytic organic transformations, small molecule activation, and energy storage over the last few decades. Inspired by recent catalytic advances mediated by redox noninnocent pyridine diimine (PDI) and α-diimine (DI) ligand supported transition metals, our group has designed new PDI and DI ligands by modifying the imine substituents to feature donor atoms. My doctoral research is focused on the development of PDI and DI ligand supported low valent first row metal complexes (Mn, Fe, Co) and their application in bond activation reactions and the hydrofunctionalization of unsaturated bonds. First two chapters of this dissertation are centered on the synthesis and application of redox non-innocent ligand supported low valent iron complexes. Notably, reduction of a DI-based iron dibromide led to the formation of a low valent iron dinitrogen compound. This compound was found to undergo a sequential C-H and C-P bond activation processes upon heating to form a dimeric compound. The plausible mechanism for dimer formation is also described here. Inspired by the excellent carbonyl hydrosilylation activity of our previously reported Mn catalyst, (Ph2PPrPDI)Mn, attempts were made to synthesize second generation Mn catalyst, which is described in the third chapter. Reduction of (PyEtPDI)MnCl2 furnished a deprotonated backbone methyl group containing Mn compound [(PyEtPDEA)Mn] whereas reduction of (Ph2PEtPDI)MnCl2 produced a dimeric compound, [(Ph2PEtPDI)Mn]2. Both compounds were characterized by NMR spectroscopy and XRD analysis. Hydrosilylation of aldehydes and ketones have been studied using [(PyEtPDEA)Mn] as a pre-catalyst. Similarly, 14 different aldehydes and 6 different ii formates were successfully hydrosilylated using [(Ph2PEtPDI)Mn]2 as a pre-catalyst. Encouraged by the limited number of cobalt catalysts for nitrile hydroboration, we sought to develop a cobalt catalyst that is active for hydroboration under mild conditions, which is discussed in the last chapter. Treatment of (PyEtPDI)CoCl2 with excess NaEt3BH furnished a diamagnetic Co(I) complex [(PyEtPDIH)Co], which exhibits a reduced imine functionality. Having this compound characterized, a broad substrate scope for both nitriles and imines have been investigated. The operative mechanism for nitrile dihydroboration has been investigated based on the outcomes of a series of stoichiometric reactions using NMR spectroscopy. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2018

Abstract not available.

<p> Several solvothermal synthetic methods have been developed to produce novel low-dimensional magnetic materials and determine their structure-properties relationships. Two main classes of compounds were investigated, including iron selenides and transition metal formate-chlorides.</p><p> Chapter 2 details the development of the first solution-based synthetic route to superconducting iron (II) selenide. Samples were found to retain superconducting properties only when air and water were rigorously excluded from the synthesis.</p><p> Chapter 3 presents the synthesis, structure, and magnetic properties of two new mixed-valence compounds with infinite &infin;¹(FeSe₂) tetrahedral chains separated by Fe-amine complexes. The use of different Fe-amine complexes allows for tuning of the magnetic properties without changing the general structural motif.</p><p> Chapters 4 and 5 report the first members of the transition metal chloride-formate family of compounds, which contain linear zig-zag chains of octahedrally coordinated metal atoms linked by &mu;₂-Cl and <i>syn-syn</i> formate bridges. These compounds order antiferromagnetically and exhibit metamagnetic transitions.</p><p> Chapter 6 describes a related set of transition metal formate-chloride compounds that are comprised of helical chains of edge-sharing M²⁺-centered octahedra. These compounds undergo 3D ferrimagnetic ordering at low temperature, and are rare examples of homospin topological ferrimagnets. </p><p>

Mixed valence compounds have been recognized over the past five decades as a unique class of chemical species. Their distinctive spectral, electrochemical, physical and magnetic properties arise from electron delocalization into the sites with uneven valence. A primary consequence of this electron delocalization phenomenon is the stabilization of high spin multiplicities in certain dinuclear synthetic and polynuclear biological clusters. Therefore, the subject of this dissertation is to extend the current knowledge of the analysis of synthetic mixed valence clusters by systematically altering the coordination chemistry and redox states at well-defined synthetic, polynuclear iron clusters. A central focus of this thesis is to investigate the effect of superexchange, direct exchange, and double exchange electronic coupling in dinuclear [Fe2], trinuclear [Fe3], hexanuclear [Fe6], and octanuclear [Fe8] clusters with the goal of better understanding the principles that govern their complex electronic structures. It is concluded that the resulting electronic structure in these polynuclear systems is highly dependent on the extent of electron delocalization which can be tuned by solvation, anation, or chemical redox changes. This finding is highlighted by the observation that small variations on the solvation coordination sphere and redox level one can transverse spin ground states from S = 0 to S = 11 by addition of 6e– into [Fe6]. / Chemistry and Chemical Biology

The electrochemical oxidation of Co2+ ions in the presence of a buffering species such as phosphate (Pi), methyl phosphonate (MePi), and borate (Bi) leads to the formation of amorphous cobalt oxide thin films that are capable of catalyzing the four electron-four proton oxidation of water to dioxygen. These cobalt oxygen evolving catalysts (Co–OECs) have been extensively studied by electrochemical techniques; however, the amorphous nature of these films means that garnering insights at the molecular and atomic level is difficult because electronic and structural characterization methods rely on measurements of bulk material. To address this challenge, polynuclear cobalt hydroxide and cobalt oxide compounds have been employed as platforms for understanding Co–OECs at the molecular level. In the first part of the thesis, we present the synthesis of a heptanuclear cobalt cluster in two different oxidation states, Co(II)7 and a mixed valence Co(III)Co(II)6. An anomalously slow self–exchange electron transfer rate as compared to that predicted from semiclassical Marcus theory was measured, supporting a charge transfer process that is accelerated by dissociation of the anion from the oxidized cluster. This mechanism sheds light on the inverse dependence of anions in the deposition mechanism of Co–OECs. Moreover, the results address a long-standing controversy surrounding the Co2+/3+ self–exchange electron transfer reaction of the hexaaqua complex. In the second part of the thesis, we report the synthesis and characterization of a dinuclear cobalt complex, which we use as an edge sites mimic (ESM) of the Co-OEC. A comparative investigation of the Pi and Bi binding of buffers to this ESM is provided. We find that the binding to the boric acid component of borate buffer is rapid, while binding to K2HPO4 is much slower, taking days to equilibrate at room temperature. These studies are used to provide a model for the interaction of Pi and Bi species with the active site of the Co-OEC. An inverse dependence on [Bi] of the electrochemical driven water oxidation activity by Co-OECs is demonstrated, which provides validation for the model and indicates that dinuclear cobalt edge sites are necessary for water oxidation catalysis. In the final chapter of the thesis, we use a series of spectroscopic and electrochemical methods to show that the observed water oxidation activity of the compound class Co4O4(OAc)4(py–X)4 emanates from a Co(II) impurity. This impurity is oxidized to produce Co-OEC, which is an active water oxidation catalyst. Differential electrochemical mass spectrometry (DEMS) is used to characterize the fate of glassy carbon at water oxidizing potentials, and demonstrate that such electrode materials should be used with caution for the study of water oxidation catalysis. We then investigate the electrochemical properties of Co4O4 cubanes in non-aqueous solvents, showing that the neutral cubanes may be oxidized by two electrons yielding a formal oxidation state of Co(IV)2Co(III)2. Finally, we show that these cubanes may be synthetically modified with tethered NMI photooxidants, which opens new avenues for exploring fixed-distance photoinduced ET using Co4O4 cubanes as the electron donor. Ultra-fast transient absorption experiments demonstrate that a charge separated state is formed following laser excitation. / Chemistry and Chemical Biology