Source: Dissertation Abstracts International, Volume: 38-09, Section: B, page: 4231. / Thesis (Ph.D.)--The Florida State University, 1977.

The structures, physical properties, and reaction chemistry of molybdenum (V) and tungsten (V) porphyrin complexes are investigated. The four, five-coordinate nitrido molybdenum (V) and tungsten (V) complexes MoN(TMP), MoN(TPP), MoN(TTP), and WN(TPP) have been synthesized and characterized by mass, ESR, IR, and UV-Visible spectroscopic methods. Furthermore, one of the nitrido complexes MoN(TMP) and imido derivative (Mo(NMe)(TPP)(H$\sb2$O)) $\sp+$(I$\sb3$)$\sp-$ have been characterized by single-crystal X-ray diffraction techniques. MoN(TMP) has a square pyramidal structure in the solid state, with the Mo-nitrido bond length of 1.630 (4) A and nitrogen atom at the apical position. The terminal nitrido ligand is triply bonded to the metal. Nitrido complexes MoN(TMP) and MoN(TPP) form 1:1 adducts with Lewis acid, methylates at nitrogen atom upon reaction with methyl iodide, displaces one CO ligand from Mo(CO)$\sb6$, and react with HCl gas to produce (porph)MoN--BF$\sb3$, (Mo(NMe)(TPP)(H$\sb2$O)) $\sp+$(I$\sb3$)$\sp-$, (TPP)MoN--Mo(CO)$\sb5$, and ((porph)MoN--H) $\sp+$Cl$\sp-$, respectively. Also, nitrido complexes react with tertiary alkyl phosphines to form phosphineiminato complexes. (Mo(NMe)(TPP)(H$\sb2$O)) $\sp+$(I$\sb3$)$\sp-$ has a distorted octahedral structure in the solid state, with the Mo-imido bond length of 1.689 (6) A and the Mo-N-CH$\sb3$ angle of 175.34 (64)$\sp\circ$. Thus, the imido ligand in this compound acts as a four $\pi$-electron donor. / Quadruply bonded (W(TPP)) $\sb2$ and its reaction derivative WN(TPP) also have been synthesized. Diamagnetic tungsten dimer (W(TPP)) $\sb2$ shows the very similar spectroscopic patterns to those of (Mo(TPP)) $\sb2$. Temperature dependent $\sp1$H NMR spectra of this complex show two NMR distinct $\beta$-pyrrole protons at $-$48$\sp\circ$C due to the rotation about $\delta$ component tungsten-tungsten quadruple bond. The activation barrier was estimated 11.3 kcal/mole from the NMR line shape analysis. (W(TPP)) $\sb2$ reacts with p-tolyl azide to produce paramagnetic WN(TPP). / Source: Dissertation Abstracts International, Volume: 52-03, Section: B, page: 1425. / Major Professor: Virgil L. Goedken. / Thesis (Ph.D.)--The Florida State University, 1991.

As of 2014, there is an expected 69,000 metric tons of nuclear waste sitting in storage in the U.S. Little efforts have been made to deal with the radiotoxicity of the spent nuclear fuel (SNF). The problem arises from the complex mixture of the SNF and highly radioactive actinides. Due to the high radioactivity of the minor actinides (Pu-Cm), there is a lack of understanding the fundamental chemistry of the actinides. The focus of this work is to prepare coordination complexes that can be used as probes for elucidating changes in the structure and bonding across the actinides series Most coordination chemistry that has been studied with the actinide series has only utilized ligands stable to oxygen and moisture due to the difficulties of handling the transuranium actinides. The chemistry of non-aqueous ranium has made great progress, while, the non-aqueous chemistry of the transuranic elements is relatively unexplored and offers a wider platform for exploring methods of deducing electronic structure and information about the actinide-ligand bond. Such information can be very useful for discovering trends in the whole series. The beginning chapters focus on simple coordination compounds using soft N and S donor ligands for complexing Am-Cf. Since very little structure data is known for these elements and softer donor ligands have shown to have a preference over trivalent actinides than lanthanides, we focus on these systems to understand the trends in bonding across the 5f series. Chapter 4 focus on a series (U-Cf) of complexes using the redox active ligand 2,4,6,8-tetrakis(tert-butyl)-9-hydroxyphenoxanone (HDOPO) were synthesized in non-aqueous conditions under an inert atmosphere and have been fully characterized by X-ray, optical, magnetic, and computational techniques. Spectroscopic data reveals the An(DOPO)3 complexes of the earlier actinides being the tetravalent state, in contrast to the later actinides, they are in the trivalent state. Furthermore, the Cf(III) complex disrupts the tris-chelate trend due to radiolysis. It is also shown that the ligand undergoes redox transitions to stabilize the higher oxidation states of the earlier actinides. The results will help contribute toward gaining foundational knowledge of structure and bonding in non-aqueous transuranic chemistry as well as give insight into the participation of f-orbitals in bonding. The ending chapters are out of the scope of non-aqueous chemistry but projects that pertain to the nature of the actinide series. As the first focuses on the effects of radiolysis. As we go to the heavier actinides, radiolysis affects the crystallization of our targeted products. In this case, an aged thorium source produces peroxide over time changing the result of the product. Lastly, is an example of driven degeneracy covalency in an americium chromate system. It was thought the later actinides tend to be more ionic, however we are finding small amount of covalent character partakes in the bonding. Collectively, this body of work primary focus is elucidating the structure and bonding of the f-elements through coordination complexes utilizing various techniques. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2017. / November 13, 2017. / Includes bibliographical references. / Vladimir Dobrosavljević, University Representative; Kenneth Hanson, Committee Member; Michael Shatruk, Committee Member.

The current energy crisis is becoming more and more serious due to the industrial development and increasing population. Mimicking photosynthesis in plants provides a new way to solve this crisis. The goal is to harness solar energy and convert it into energy stored in chemical bonds such as methanol or hydrogen gas. Currently, most catalysts for proton reduction contain precious metals, such as palladium, platinum and ruthenium. The main goal of our research is to develop catalysts made of earth abundant metals. By incorporating organic ligands in our complexes, we can make catalysts that have similar catalytic activity as those made of rare metals. Herein, I report an iron and a nickel catalysts that can generate hydrogen from water.

Research on substituted polypyrazolylborate ligands could potentially lead to the development of useful compounds in the material sciences such as catalysis and metal ion extraction. A wide variety of substituents can be introduced to the pyrazole rings that modify the properties and reactivity of the complexes. Synthesis of 4-cyano-3-tolylpyrazole followed by the formation of a corresponding thallium(I) complex could allow one to examine the Tl-N bond length. When compared with other related complexes such as TlBpt-Bu, 4CN and TlBpPh, 4CN, the Tl-N bond length in the synthesized complex will help determine the effect of the new substituent.

No description available.

This dissertation seeks to determine the differences in the lanthanides and later actinides in non-aqueous media. Research in the f-elements is significantly understudied compared to the other metals of the periodic table. Even more so are the later actinides which were largely unstudied for an extended period as it was believed later actinides were identical to lanthanides. A review by Neidig et al, “The Covalency in f-element Complexes” has ignited significant interest in the bonding of the actinides.1 A tremendous amount of research in the f-elements, particularly the actinides, has been performed in aqueous conditions at high temperatures and pressures. Chemistry under these conditions limit the research possible for lower oxidation states. Additionally, non-aqueous techniques allow for the investigation of these elements in more organic environments. The goal of this work is to pave a greater understanding of knowledge for lanthanides and actinides by examining their redox and coordination chemistries in these environments that could lead to applications other than nuclear energy and weapons. The first portion of this dissertation examines the chemistry that is already heavily acknowledged about f-elements: coordination chemistry. When modeling later actinides, a common notion is to utilize the isoelectronic lanthanide as the surrogate. Although for electronic comparisons this is useful, it is often not the case for examining isostructural compounds. The isoelectronic lanthanide is often smaller in ionic radius, which is a factor that dominates the chemistry of the lanthanides. Despite this, isolation of isostructural coordination compounds was obtained for the isoelectronic and size analogs of americium; europium and neodymium. This seemingly mundane study showed that americium portrays a small amount of covalency in its bonds which is not observed in the lanthanides. These small differences lead to profound changes in chemical properties as observed later in this work. The second portion of this work focuses on analyzing the divalent oxidation state of f-elements with crown ethers. The divalent oxidation state has been obtained for all lanthanides using potassium and 2.2.2-cryptand. The next step was to determine the extent to which crown ethers and solvents have on the redox properties of f-elements. Because all the lanthanides had been obtained in the divalent oxidation state in a similar matter, it was expected that the redox chemistries would behave identically. To surprise, ytterbium behaves differently and shows greater reversibility than the most stable divalent lanthanide, europium. Additionally, it was found that californium also behaves like ytterbium electrochemically, even though it would be expected to behave like samarium. It was proposed that this may be attributed to the 5f orbitals. The last of this work involves obtaining californium in the divalent oxidation state as a molecular system. This was done by modeling with samarium which is the most similar to californium in its redox and coordination properties. Quick and simple routes to synthesizing divalent samarium structures were obtained in ordinary glovebox conditions for attempts with californium. Under identical reaction conditions, isolation of Cf(II) crystals in the solid state were unsuccessful. However, interesting spectroscopic properties where observed that portrayed divalent californium as having tunable luminescence similar to divalent europium compounds. To our surprise, even though samarium resembles californium, the chemistry between the two elements are very different, further broadening the gap between the 4f and 5f elements. / A Dissertation submitted to the Department of Chemistry and Biochemistry in partial fulfillment of the requirements for the degree of Doctor of Philosophy. / Fall Semester 2018. / September 28, 2018. / Actinides, Californium and Americium, Coordination Chemistry, Divalent Samarium, Lanthanides, Redox Chemistry / Includes bibliographical references. / Thomas E. Albrecht-Schmitt, Professor Directing Dissertation; Samuel L. Tabor, University Representative; Kenneth G. Hanson, Committee Member; Yan-Yan Hu, Committee Member.

Metal tetrapyrroles represent a large class of earth-abundant catalysts but are limited to naturally-occurring combinations. Chelatase enzymes are responsible for the catalyzed metal insertion into a specific tetrapyrrole. CfbA is a class II chelatase from Archaeaglobis fulgidus that catalyzes the insertion of nickel into sirohydrochlorin to give rise to Coenzyme F430 required for methanogensis. This archaeal chelatase was used to study the substrate scope of divalent metals and tetrapyrroles to probe various metal tetrapyrrole combinations. A spectroscopic study established that the CfbA is capable of binding to cobalt and nickel, in addition to various tetrapyrroles. Magnetic circular dichroism (MCD) established that the metal binding site of CfbA contains a labile high spin 6-coordinate cobalt species that is ligated to nitrogen- or oxygen- atoms. The two residues involved in metal binding is likely His10 and His74. Tetrapyrrole binding resulted in a shift in energy. Computational studies have shown that resultant red-shift in energy is due to slight ruffling upon binding to CfbA. The enzymatic capabilities of CfbA was probed with various metal and tetrapyrrole combinations. The rate of insertion was significantly impacted by identity of the metal and the position of the propionate and acetate side chains on the rings of the tetrapyrrole as compared to sirohydrochlorin. Modifications to these side chains resulted in changes in ruffling. An increase in the ruffling resulted in a decrease in the rate of the reaction. These results have shown a significant expansion of the tetrapyrrole substrate scope. Additionally, detailed insights into the proposed chelatase mechanism have been established. IsdG serves as the primary enzyme involved in iron acquisition from heme in Staphylococcus aureus. The active site contains a tryptophan residue at 67 that is expected to be involved in heme ruffling. Trp67 was substituted with a smaller amino acid, phenylalanine to determine the role it plays in heme ruffling and degradation. The optical spectroscopic characterization of W67F IsdG resulted in changes to the geometric and electronic structure. The absorbance spectrum of W67F blue-shifted in the Q- and Soret bands indicating a change in the heme ruffling. MCD, VTVH and 1H NMR spectroscopy have shown that the electronic ground state is indicative of a 2Eg state, consistent with reduced heme ruffling. The degradation of heme by W67F IsdG resulted in the formation of biliverdin, a product seen in canonical HOs. These data suggest that Trp67 significantly influences heme ruffling and degradation. Additionally, W67F IsdG follows a unique reaction mechanism compared to IsdG. These data provide information on the development of a selective inhibitor of IsdG to prevent pathogenesis.

The medicinal uses of gold date as far back as 2500 B.C. in China. In modern times, gold has been used in the treatment of a number of different human diseases including rheumatoid arthritis, cancer, and viral infections. This dissertation will focus on the development of gold complexes for the purpose of selective inhibition of HIV NCp7, a 55 amino acid zinc finger protein with two Cys3His zinc binding domains. NCp7 is involved in a number of viral life cycle processes including activation of reverse transcription, integration, DNA recognition, RNA packaging, and formation of the viral envelope. The diversity in the roles of NCp7 across the viral life cycle make it a highly attractive target for chemical intervention. Ejection of the tetrahedrally coordinated zinc atoms, modification or deletion of the zinc coordinating amino acids, or modification or deletion of the “essential” tryptophan residue can result in the loss of viral infectivity. This is due to the inability of NCp7 to recognize its “natural” substrate – polynucleic acids. Previous studies have investigated the differences in the manner in which platinum(II), gold(I), and gold(III) complexes interact with NCp7. The platinum(II) complex [Pt(dien)(9-EtGua)]2+ interacts with the C-terminal zinc finger of NCp7 in a non-covalent manner, through a π-π stacking interaction between the platinated 9-EtGua and the “essential” tryptophan residue. The isostructural and isoelectronic complex [Au(dien)(9-EtGua)]3+ ejects the tetrahedrally coordinated zinc atom and replaces it with a gold atom, forming “gold fingers”. This result is consistent with the interactions of the gold(I) complex [(PPh3)Au(9-EtGua)]+. In order to complete the series of isoelectronic and isostructural platinum(II), palladium(II), and gold(III) complexes with N-heterocyclic ligands and diethylenetriamine chelates, the complexes [Au(dien)(1-MeCyt)]3+ and [Au(N-Medien)(1-MeCyt)]3+ were synthesized. These complexes were found to dimerize the C-terminal zinc finger once the central zinc atom is ejected. This is likely the result of a charge transfer from the 1-methylcytosine ligand to the tryptophan residue, and is a product that was not seen as a result of interaction with the previously published 4-dimethylaminopyridine and 9-ethylguanine analogs. The 1-methylcytosine complexes also stabilize the gold(III) oxidation state and associate with N-acetyltryptophan in a manner consistent with the previously studied gold(III) analogs. Finally, in order to address concerns arising from the inner filter effect, a proof of concept study using 1H-NMR spectroscopy was utilized to show that the complex [Au(dien)(1-MeCyt)]3+ likely has a lower association constant with N-acetyltryptophan than the value determined by fluorescence quenching. The impact of the incorporation of additional steric hindrance on the gold(III) chelate was studied using the di-(2-picolyl)amine ligand. The gold(III) chlorides incorporating this ligand and the centrally methylated analog were found to eject zinc from the C-terminal zinc finger of NCp7, and the electronegativity differences between the gold(III) and platinum(II) metal centers were highlighted. The attempts to incorporate an N-heterocyclic ligand into these complexes were unsuccessful due to the steric and electronic demands of the chelate. The use of an organometallic chelating ligand led to the investigation of the ability of gold(III) complexes to catalyze the arylation of zinc-coordinating cysteine residues. The complex [AuCl2(dampa)], which had been formerly investigated as a chemotherapeutic agent due to its structural similarities to cisplatin, was found to arylate N-acetylcysteine, glutathione, and NCp7. The arylation was not found to be dependent on the cis- chloride ligand, as blocking that site with the ligand triphenylphosphine did not prevent the arylation of NCp7. The X-Ray crystal structure of the complex [AuCl(dampa)(PPh3)](PF6) was also solved. Using the advancement of the knowledge of how the electronic and structural properties of gold(III) complexes described herein impact interactions with NCp7, it is possible that a coordination complex that is a selective inhibitor of NCp7 may eventually be developed.

Source: Dissertation Abstracts International, Volume: 35-04, Section: B, page: 1559. / Thesis (Ph.D.)--The Florida State University, 1974.