The study of f-elements, the lanthanides and actinides, is a broad field that encompasses a wide range of disciplines, from materials science, to medical and biochemistries, radiochemistry, and nuclear physics. This breadth of inquiry is a result of a vast and unique set of properties and technological applications necessary for our modern civilization utilizing the f-elements. Improvements to these properties, or the discovery of new applications, continue to be active fields of research, motivated by a cognizance of material scarcity, environmentalism, and legacy nuclear weapons and energy waste. Researchers have approached the synthesis of novel f-element materials through two routes; applied techniques, such as novel synthesis processes and nanomaterial design, and fundamental exploration – electronic excited state energies, covalency and bonding, and investigating the minute details of structure-property relationships. It is through the vein of improvements via fundamental discovery that this dissertation has been prepared. Herein we present a series of studies that analyze the synthesis, structure, and properties of a varied set of f-elements – the lanthanides, uranium, and americium – through the application of specific material assembly criteria and focus upon the effects of those criteria on material properties.
The vast array of materials presented fall under the category of hybrid materials – those that contain both inorganic, in this case f-element metals, and organic moieties. Of the hybrid materials classifications, the one of most consequence to this dissertation utilizes noncovalent interactions, intermolecular forces that are not formal bonds, for assembly. Several established noncovalent motifs, e.g. halogen and hydrogen bonding, have been targeted by specific and judicious ligand choice to connect hybrid molecules together and coax them into the crystalline solid-state. Structures were determined by single crystal X-ray diffraction and density functional theory calculations, utilizing crystallographic models, generated electrostatic surface potentials to further explore noncovalent interaction pairings in hybrid molecular materials. The findings highlight noncovalent assembly, and the synthesis techniques thereof, as a means toward significant control over the formation of hybrid materials and thus influence over their chemical and solid-state structure.
Beyond the structural determination, spectroscopic analyses were performed via luminescence, vibrational, and electronic (absorption) spectroscopies. The f-element properties discussed hereafter are all influenced by local (the ligand environment of the f-element metal center) and global (supramolecular or intermolecular interactions) structural environments. Discussions focus on both local and supramolecular structural influences on spectroscopic signatures to analyze excited state, electronic structure, and behavior. Thus, utilization of noncovalent interactions in hybrid material assembly allows for increased control over structure, and thus structure-property relationships, toward a more thorough understanding of the fundamental properties of f-element structural and spectroscopic theory. Organizationally, this dissertation is presented in approximately chronological order and in order of f-element and spectroscopic complexity in regards to analyzing structure-property relationships.
|Advisor:||Cahill, Christopher L|
|Commitee:||King, Michael M, Miller, Houston, Voutchkova-Kostal, Adelina, Besson, Claire, Wilson, Richard|
|School:||The George Washington University|
|School Location:||United States -- District of Columbia|
|Source:||DAI 81/11(E), Dissertation Abstracts International|
|Subjects:||Chemistry, Materials science|
|Keywords:||Actinide, Americium, Crystallography, f-Elements, Lanthanide, Supramolecular|
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