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This dissertation focuses on probing the fundamental chemistry of the actinide series, specifically the structure and bonding in complexes of transuranium elements. The actinides consist of the elements from actinium to lawrencium in the periodic table, best known for uranium and plutonium, which were used to develop nuclear weapons and power. Today, nuclear power is used to generate over 17% of the electricity across the world.[1, 2] Although an effective means of generating electricity, the waste generated from nuclear reactors is a major issue with relatively little progress being made to reduce the amount and radiotoxicity of the waste. Overall, this problem stems from the chemical complexity and highly radioactive nature of the actinides. Because of this the actinides are understudied, particularly beyond uranium, and as a result much of the fundamental chemistry is poorly understood. The goal of this work is to prepare coordination complexes that can be used as probes for elucidating changes in structure and bonding across the actinide series. Over the past couple decades, neutral nitrogen donating ligands have shown to have a greater affinity towards the actinides over the lanthanides.[1] The work discussed in this dissertation has focused on using nitrogen-containing carboxylates to explore periodic trends through the lanthanide and actinide series. The first step of this project was to explore structure and bonding differences between the lanthanide (4f) and actinide (5f) series. The early lanthanides, such as Ce and Nd are often used as surrogates for the actinides because they possess f orbitals and are relatively similar in size to that of their actinide analogs.[3] Depending on the coordinating ligand, the structure and bonding between the 4fs and 5fs can either mimic each other or diverge greatly. In some cases the structure of the actinides and lanthanides are very similar, but the electronic properties are vastly different. In chapters 3 and 4, unique structures and electronic properties of Pu and Ce complexes are explored. The second portion of this research was to investigate the differences in structure and bonding between of the transplutonium actinides, americium through californium (Am-Cf). Traditionally these later actinides were believed to mimic the lanthanides in both their structure and bonding characteristics, but as we explore the actinides more we find this might not be true. Our approach used a pyridine dicarboxylate derivative to make an isomorphous series of both the trivalent actinides and lanthanides. It was found that the late actinides, starting at Cf, have different electronic properties that are not paralleled by any of the lanthanides or early actinides. Much to our surprise, it seems that Cf represents a second transition in the actinide series, which is discussed in chapters 5 through 7. Overall, this dissertation focuses on exploring the structure and bonding of the f elements through solid-state chemistry utilizing a variety of characterization 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 2015. / July 14, 2015. / Actinide, Californium, Charge Transfer (CT), Lanthanide, Spectroscopy, XRD / Includes bibliographical references. / Thomas E. Albrecht-Schmitt, Professor Directing Dissertation; Bernd A. Berg, University Representative; John G. Dorsey, Committee Member; Albert E. Stiegman, Committee Member; Naresh Dalal, Committee Member.

<p> The events on September 11^th 2001 and subsequent attacks in America and around the world have brought a renewed interest in the nation&rsquo;s security including the concern over the use of a nuclear or a radiological dispersal device (RDD). Research utilizing NAA and ICP-MS has been done in two separate projects in order to help address some of these concerns. A research assistantship from Savannah River National Laboratory was granted in order to identify the impurities and isotope ratios of ¹⁹²Ir sources (chapters 2-4). An electrochemical dissolution method of the iridium was developed and used for sample preparation for ICP-MS analysis. ICP-MS analysis was then used to identify and quantify impurities and isotope ratios in iridium from various sources. The second research project has developed a series of lanthanide phosphate based nanoparticles for use as tagging and tracking agents (chapters 5-7). The composition of the nanoparticles were varied to provide a unique signature that can be rapidly and precisely measured in the field via neutron activation analysis. The nanoparticles could be used as a real-time in the field method for tracking and identifying materials such as explosives in a post detonation scenario.</p><p>

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The photochemistry and photopolymerisation activity of eight novel aromatic carbonyl photoinitiators have been examined. Five of these were t-butyl perester derivatives, three of 9-fluorenone and these were compared with fluorenone itself and the other two of benzophenone and this was used for comparison also. The remaining three compounds incorporated acetophenone type chromophores bound onto a polysiloxane backbone and these were compared to diethoxyacetophenone. The photochemistry was examined using UV/Vis absorption spectroscopy, luminescence, and flash photolysis, both conventional microsecond and laser nanosecond. The photopolymerisation activity was studied using different model monomers and concentration levels and analysis of the cure rate was measured using a gravimetric method. Investigation of the resulting polymers were undertaken using gel permeation chromatography, UV absorption spectroscopy and, where appropriate, fluorescence for end group analysis. For the t-butylperester derivatives differential photocalorimetry, real time FfIR and pendulum hardness testing was used. Spectroscopic and fluorescence data showed that the perester substitutions on the fluorenone chromophore had an electron withdrawing effect and increased the charge transfer content of the lowest excited singlet state. Absorption and phosphorescence spectra for the benzophenone derivatives compared to benzophenone itself were similar although the lower quantum yields and longer life times were indicative of the presence of an increase in charge transfer content of the lowest excited triplet state with increasing substitution. For the polysiloxane compounds the extinction coefficients and phosphorescent quantum yields tended to increase with increasing molecular weight. Photoreduction quantum yields were higher for the substituted fluorenones than fluorenone itself, that for the di substituted being twice that of the mono suggesting homolysis of the peroxyester groups to yield reactive benzoyloxy and t-butoxy radicals. For the benzophenone derivatives, the benzophenone had much higher values than the peresters indicating that benzophenone undergoes hydrogen abstraction more efficiently whereas the derivatives again undergo photoc1eavage about the peroxyester groups. Conventional microsecond flash photolysis showed that all the t-butylperester initiators were capable of forming a ketyl radical via hydrogen abstraction. For the benzophenone compounds this formation follows the order benzophenone>mono->tetraperester and is consistent with the phosphorescence measurements and other data. For the polysiloxanes conventional flash data indicated the formation of benzoyl radicals via photofragmentation and again the intensity of the transient absorption was proportional to the molecular weight of the photoinitiator. On nanosecond laser flash photolysis of the fluorenone derivatives in nitrogen saturated non-hydrogen donating solvents, transient absorptions corresponding to the triplet states were seen and residual absorption probably due to benzoyloxy radicals. Triplet-triplet absorption occurs for the benzophenone initiators under the same conditions but this is much stronger for benzophenone than the derivatives. In oxygenated solutions the triplet absorptions were effectively quenched but an interesting phenonemon occurs for all the t-butylperester derivatives in that a long lived transient growth was observed which is tentatively assigned to that of aromatic peroxy radical formation. On laser flash photolysis of the polysiloxane compounds very long lived transients were observed in both oxygenated and nitrogen saturated solutions. When nitrogen saturated, stable benzoyl radicals appear to have formed whereas when oxygen saturated some type of complexation seemed to occur with the oxygen. For all compounds the photopolymerisation activity was shown to be highly dependent on the structure of the initiator, the extinction coefficient in the relevant region of excitation and the degree of self termination reactions which can occur. All the tbutylperester derivatives and polysiloxane compounds were effective at photoinitiating the polymerisation of acrylate monomers. The derivatives of fluorenone initiated polymerisation without the use of a tertiary amine co-initiator unlike fluorenone itself. The derivatives of benzophenone also initiated polymerisation effectively without the presence of an amine co-synergist with the overall order being monoperester>tetraperester>benzophenone. Consistent with other results the efficiency of the polysiloxane compounds to initiate polymerisation was proportional to the molecular weight of the initiator.