Dissertation

Influence of Organometallic Actinide Systems on Bonding and Electronic Properties within the F-block

Long, Brian N

2022

Overview

The actinide series is of great importance, possessing applications in clean energy, space travel, medicinal use, and even household smoke detectors. Despite everyday applications, our knowledge of the actinides is severely limited compared to the rest of the periodic table. Low available quantities of these elements, in addition to hazardous radiotoxicity, presents a unique set of challenges when studying them. Nuclear energy presents grand opportunities for clean energy and is a leading source adopted by many countries; however, difficulties in recycling and separating these elements from nuclear waste proves to be a pervasive task. Furthering the limited understanding of bonding and electronic properties characteristic of the actinide series will present new opportunities for recycling and waste separation techniques. Historically, f-electrons were thought to be chemically inert, only participating in electrostatic interactions and displaying heavily localized behavior. Actinides were thought to act like their lanthanide counterparts; however, this is now known to be false. Actinide−carbon bonding showed the first evidence of covalency in the actinide series, differentiating their bonding properties from the lanthanides. Furthermore, recent studies have demonstrated how the greater radial extension of the 5f orbitals beyond the 4f orbitals results in greater reactivity and a lower degree of localization of the 5f electrons. Chapter 1 will provide background information on the actinide series, as well as its historical importance and applications. Information regarding the importance of organometallic actinide chemistry, intervalence charge transfer, and challenges in working with these elements is discussed. Chapters 2 and 3 build a baseline for intervalence charge transfer studies within the actinide series, presenting a series of dinuclear systems with neptunium, plutonium, and various lanthanide analogues. These complexes allow for flexible redox studies and will be applied for the synthesis of mixed-valent systems displaying the delocalization of f-electrons, pushing the boundary on our understanding of these fundamental properties.Chapter 3 transitions from the localized properties of f-electrons to their unique bonding properties by introducing an organometallic synthetic precursor. Metal−carbon bonding is a nearly untouched field in transplutonium elements, which is surprising considering the reported differences in covalency between the actinide−carbon and lanthanide−carbon bonding, as well as the prevalence of americium and curium in nuclear waste. Chapters 5 demonstrates how the addition of azine bridging ligands to these organometallic systems allows for the tuning of covalency in actinide−nitrogen bonding, a common target in improving separations techniques. Chapter 6 presents the first reported structural characterization of a curium−carbon bond, opening doorways to a new field of actinide chemistry: organocurium chemistry. In addition to unexpected bonding differences between curium and its samarium analogue, organometallic curium demonstrates never before seen optical properties, including significantly redshifted emission in a putative Cp′3Cm, as well as the quenched photoluminescence of (Cp′3Cm)2(μ−4,4′−bpy). This work introduces actinide systems that serve as a baseline for intervalence charge transfer experiments and the delocalization of f-electrons, as well as a series of transplutonium complexes possessing actinide−carbon bonding, possessing bonding and electronic properties never before observed with these elements.

• Publisher: ProQuest Dissertations & Theses
• Subject: Inorganic chemistry / Nuclear chemistry
• ISBN: 9798841771678