Search

Uranium is a toxic heavy metal, causing biochemical harm to humans and other living organisms if present in significant concentrations. The mechanisms behind this toxicity have been the subject of considerable investigation since the days of the Manhattan Project and remain important today with respect to the safe management of contamination arising from the nuclear energy industry. It is widely acknowledged, however, that there are gaps in understanding, particularly relating to the behaviour of uranium species in complex biological environments and the precise molecular interactions with proteins and other biomolecules. Chapter 1 introduces some fundamental uranium chemistry and photophysics, alongside a brief survey of the current analytical techniques available to monitor uranium in the environment, and of the current understanding with regards to uranium-protein interactions. Chapters 2 and 3 present the successful application of upconverting nanoparticles (UCNPs) to the quantitative detection of aqueous UVIO22+ ions. To the best of our knowledge, this is the first time that such a system has been reliably demonstrated with UCNPs, and likely one of the first UVIO22+ sensors to employ excitation within the near infrared 'biological window'. A brief introduction to the photophysics of upconversion and the wider UCNP field is presented in Chapter 2, alongside results characterising the design and synthesis of suitable nanoparticles. Chapter 3 describes the results of UVIO22+ sensing studies which combine UCNPs with one of three organic dyes: arsenazo-III, Br-PADAP and Br-PAPS. An appendix at the end of this thesis briefly investigates the possibility of luminescence energy transfer between UCNPs and uranyl(VI), in response to literature published during the course of the PhD. Chapters 4 and 5 present complementary studies investigating the interactions of UVIO22+ with a range of de novo coiled coil peptides, synthesised in collaboration with the Peacock group (University of Birmingham). In Chapter 4, the suitability of analytical techniques is assessed with an initial library of peptides; one peptide system (CS1-2) is found to exhibit remarkably bright uranyl emission at room temperature and is therefore subject to further detailed characterisation, with a focus on luminescence spectroscopy. In Chapter 5, two further studies are described, prompted by the results from Chapter 4. The first explores the impact of phosphorylation on peptide-uranyl affinity and luminescence; the second explores the selective complexation of UVIO22+ and Eu3+ within a heterobimetallic coiled coil scaffold, and the possibility of intermetallic energy transfer therein.

Recycling rare-earth metals from end-of-life products such as hard-drive magnets is of critical importance particularly in the face of growing demand for consumer goods and other applications. Liquid-liquid extraction is the preferred method of separation utilising organic extractants owing to their scalability and commercial potential. The use of volatile diluents is a major safety concern in these large separation processes. Task-specific ionic liquids have been developed in response, benefiting from their negligible vapour pressure offering an alternative for liquid-liquid rare-earth metal separation. The work presented in this thesis aimed to develop the multifunctional amide ionic liquid, [MAIL][NTf2], for extraction of rare-earth metals from waste magnet feeds, specifically separation of dysprosium(III) and neodymium(III). In addition to designing and synthesising new generations of extractants with the hope of developing superior extractants.

Interdisciplinary research combining Chemistry and Physics has given countless inventions and remains an essential benefactor of material science studies. Single-molecule magnets (SMMs) is one such discovery proving to be of great interest for future technologies. SMMs are molecules that can retain magnetisation below a certain temperature. These nanoscopic magnets can be utilised in the development of ultra-high-density storage devices and quantum computers (via their Quantum tunnelling of magnetisation property). They were discovered three decades ago but have remained technologically impractical; some recent remarkable advancements have re-ignited the research field with new ideas towards making high-temperature SMMs. The latest design approach of high-performing SMMs requires a single Dy centre surrounded by uniaxial anionic ligands (ideally two coordinate Dy complex). Herein, the role of ligands and the resultant crystal field on the physical properties of SMMs is surveyed, and the characteristic advantages of alkoxide and aryloxide ligands in realising low-coordinate high-performing Ln SMMs is investigated. The synthesis and detailed magnetic studies of families of Ln SMMs of coordination number (CN) 5, [Ln(OMes*)2(THF)2X] (Mes*=2,4,6-tBu-phenyl; Ln = Dy, Y; X = Cl, Br, I), CN6, [Ln(OPh*)2(THF)3X] (Ph*=2,6-CHPh2-4-tBu-phenyl; Ln = Dy, Y; X = Cl, Br), and CN4, [Na(THF)6][Ln(OAd*)2Cl2] (Ad*=2,6-Ad-4-tBu-phenyl; Ln = Dy, Y) and [Na(THF)6][Dy(OMes*)3X] (Mes*=2,4,6-tBu-phenyl; X = Cl, BH4), are presented in Chapters 2, 3 and 4, respectively. These results provide meaningful correlations and proof of concepts about low-coordinate Ln SMMs, such as the halide influence on quantum tunnelling of magnetisation in Chapter 2, the effect of a meridional arrangement of anionic ligands on the crystal field and magnetic properties in octahedral Dy complexes in Chapter 3, and interesting magnetic behaviour of distorted tetrahedral Dy SMMs in Chapter 4.

Cyclopentadienyl ligands (Cp) and their derivatives have been used throughout the Periodic Table since the 1950s. They have provided landmark complexes across the s-, p-, d- and f-block elements, including the first metallocenium f-element complexes and the first complete series of non-traditional Ln2+ complexes. Herein, this work utilises bulky substituted cyclopentadienyl ligands, including Cpttt {C5H2(tBu)3-1,2,4}, Cptt {C5H3(tBu)2-1,3}, Cp'' {C5H3(SiMe3)2-1,3}, to prepare novel f-block complexes in low oxidation states. Chapter 1 reviews the literature on cyclopentadienyl ligands as used on rare earth and actinide metals, which sets the context of the thesis. Additionally, chapter 1 also reviews bulky substituted Cp ligands that have stabilised low oxidation states for rare earth and actinide metals. In Chapter 2, the Cpttt ligand was employed to stabilise the early lanthanide metallocenium complexes [Ln(Cpttt)2{(C6F5-k1-F)B(C6F5)3}] (Ln = La, Ce, Pr, Nd) and [Sm(Cpttt)2][B(C6F5)4], which were synthesised by halide abstraction of the heteroleptic precursors [Ln(Cpttt)2(Cl)] using [H(SiEt3)2][B(C6F5)4]. In Chapters 3 and 4, the Cptt ligand was employed to prepare homoleptic early lanthanide complexes in both +2 and +3 oxidation states. Treatment of LnCl3 with KCptt gave a series of trivalent complexes [Ln(Cptt)3] (Ln = La, Ce, Pr, Nd, Sm), which were reduced by KC8 in the presence of 2.2.2-cryptand to yield a series of divalent complexes [K(2.2.2-cryptand)][Ln(Cptt)3] (Ln = La, Ce, Pr, Nd). In Chapter 5, a phospholyl ligand Htp (Htp = 2,5-di-tert-butylphosphoyl), which is similar to Cptt, was employed in the synthesis of the heteroleptic complexes [Ln(Htp)2(u-BH4)]2 (Ln = La, Ce, Nd, Sm) and [Ln(Htp)2(u-BH4)2K(S)2] (Ln = La, Ce, S = DME; Ln = Ce, S = Et2O and THF) to investigate differences between substituted phospholyl ligands and their corresponding CpR ligands. Chapter 6 (also known as appendix) contains results that did not form a coherent part of the overall story in this thesis. In this chapter, the Th4+ alkyl complex [Th(Cp'')3(Me)] was obtained by the reaction of [Th(Cp'')3] with the N-heterocyclic olefin H2C=C(NMeCH)2.

The work contained in this thesis focusses on magnetic exchange interactions in lanthanide (Ln) dimetallic molecules, and the investigation of novel high-performance single-molecule magnets (SMMs). It combines a range of experimental techniques (Far-IR, SQUID magnetometry, and EPR and INS spectroscopies) to obtain a comprehensive picture of the magnetic properties of such molecular materials. Due to the complexity of describing exchange interactions between pairs of strongly spin-orbit coupled spin systems, the goal is to build a reliable experimental dataset before comparisons against model Hamiltonians. To this end, herein we study an asymmetric dimetallic molecule [hqH2][Dy2(hq)4(NO3)3]-MeOH (hqH = 8-hydroxyquinoline) and a symmetric molecule [Ln2(HMeQ)4(NO3)6] (HMeQ = 2-methyl-8-hydroxyquinoline). Describing the exchange interaction of two Kramer's Ln ions using an effective Seff = 1/2 model proved successful in reproducing the highly detailed experimental spectra for both systems. Therefore, the resultant exchange coupled spectrum is representative of the true exchange coupled system. These results, along with previous work within the group,1 build a data-base of spectroscopically verified exchange coupled Ln systems. As more molecules are studied in this way, it is hopeful that trends in magnetic interactions can be identified and synthetic targets can be designed with specific magnetic interactions in mind. This work also provides detailed data sets which can be used in the development of new theoretical models for complicated exchange-coupled molecules. Concurrently, work on new high-performance SMMs prepared at Manchester was undertaken, performing magnetic investigations of [Dy(DiMeQ)2(H2O)Cl3] (DiMeQ = 5,7-dimethyl-8-hydroxyquinoline) and several [Dy(SCS)2]- variants. These studies allowed the identification of trends in literature SMMs and revealed the importance of the Raman relaxation process in influencing SMM blocking temperatures. I present a detailed study of high performing literature SMMs, with the assignment of t_switch as a new parameter which correlates with SMM blocking behaviour.

This project was focused on the synthesis and reactivity of rare-earth nbutyl complexes of the formula [CpMe2M(μ-nBu)]2 (where M = Y, Dy). Dysprosium was used as it has a large magnetic moment which is favourable for producing single molecule magnets (SMMs). Yttrium was used as a diamagnetic analogue to examine the reactivity of [CpMe2Y(μ- nBu)]2 in solution, and provide further characterisation of isolated complexes with NMR spectroscopy. Another goal of the project was to establish the reactivity of [CpMe2M(μ- nBu)]2 with respect to the commonly used alkylating reagent nbutyllithium (nBuLi). It was found that the nbutyl complexes are remarkably stable in solution and the solid state, allowing for the synthesis to be scaled up and for the nbutyl complexes to be used as starting materials. The reactivity of [CpMe2M(μ- nBu)]2 towards ferrocene was investigated. The product was a ferrocenyl-bridged dimer of the formula [CpMe2M(μ-(C5H4)FeCp)]2 resulting from a single deprotonation of ferrocene. The reactivity of [CpMe2M(μ- nBu)]2 towards N-heterocyclic carbenes (NHCs) was also investigated. No reaction occurred between [CpMe2Y(μ- nBu)]2 and 1,3-bis-(2,6-diisopropylphenyl)imidazol-2-ylidene (IPr), a reaction did occur between [CpMe2Y(μ- nBu)]2 and 1,3-bis-(tert-butyl)imidazol-2-ylidene (ItBu) but no crystalline product could be obtained. [CpMe2M(μ- nBu)]2 reacts with 1,3-bis(2,4,6-trimethylphenyl)imidazol-2-ylidene (IMes) to form a monomeric, benzyl tethered carbene complex [CpMe2M(IMes’)]. An ortho-methyl group on one of the mesityl substituents is deprotonated generating an asymmetric functionalised carbene. A control experiment between CpMe3M (M = Dy, Y) and IMes resulted in the formation of the abnormal, rearranged carbene complexes [CpMe3M(aIMes)]. C6H6. Structural analysis revealed a very short C-H---π interaction between neighbouring molecules. The mechanism of carbene rearrangement was probed by 1H NMR spectroscopy (M = Y). Magnetic susceptibility measurements revealed that [CpMe2Dy(μ- nBu)]2, [CpMe2Dy(μ-(C5H4)FeCp)]2, [CpMe2Dy(IMes’)] and [CpMe3Dy(aIMes)]. C6H6 are not SMMs. [CpMe2M(μ- nBu)]2 activates sulfur and selenium to form hexanuclear clusters of the formula [CpMe10M((E3)2E2] (M = Dy, Y; E = S, Se). [CpMe10M((S3)2S2] is an SMM with an energy barrier to magnetisation reversal, Ueff, of 73 cm-1. The analogous selenium cluster could be characterised by single crystal X-ray diffraction however separation from unreacted selenium proved difficult without using coordinating solvent. Extraction of [CpMe10Y((Se3)2Se2] with THF resulted in the crystallisation of the ion pair [CpMe2Y(THF)3][{CpMeY(Se2)}6Se] and [{CpMe2Y(THF)}(µ-Se2)]. A trimetallic dysprosium coordination complex containing a hexaazatrinapthalene (HAN) bridging ligand is reported. Magnetic measurements on [{(thd)3Dy}3HAN] (Dy3HAN) show that it is an SMM in zero field and two magnetic relaxation mechanisms are present. An optimised DC field of 1 kOe allowed for better resolution of the two relaxation processes and an energy barrier for each process could be extracted. The Ueff barriers are 42 and 52 cm-1. Ab initio theoretical analysis revealed the magnetic anisotropy axes are nearly collinear precluding the presence of a toroidal magnetic moment. The ground state of Dy3HAN was found to be frustrated.

In this thesis, three main chapters are discussed, including an Er3+-doped Y2O3 system, a Yb3+-doped NaYF4 nanoparticle system and a Yb(F-TPIP)3 co-evaporated with a Zn(F-BTZ)2 organic system. The main discussion is about the underlying physics of lanthanides, sensitisation of lanthanide ions by using the time resolved spectroscopy method. The up- and down-conversion processes between Er3+ ion pairs in the Y2O3 system was systematically investigated using the time resolved spectroscopy method regarding different Er3+ doping concentrations. The measured lifetime gives direct evidence for differentiating the excited state absorption (ESA) and energy transfer (ET) mechanisms during up-conversion processes. Also, the looping mechanism is found by measuring the NIR luminescence lifetime. Most importantly, the red to green emission ratio change during up-conversion processes with doping concentration is explained by a combination of up-conversion route change and concentration quenching effect. A novel sensitisation of Yb3+-doped NaYF4 nanoparticles is demonstrated by capping a 1,2,3,4,5,6,7-heptafluoro-8-hydroxyanthracene-9,10-dione (HL) ligand to the nanoparticle surface. The HL ligand acts as an antenna which can absorb visible light (400 nm to 600 nm) and then transfers the excited energy to Yb3+ ions encapsulated in the NaYF4 host. Interestingly, the energy transfers from the HL ligand to Yb3+ ions near the surface and then migrates to the Yb3+ ions inside the core of nanoparticles and is proved by a systematic time resolved spectroscopy study. The integrated organic chromophore based-excitation is almost 300 times higher compared with the Yb3+ intrinsic absorption band based-excitation. The last main discussion is given to the sensitisation of Yb3+ ions in a co-evaporated organic system as the co-evaporated organic system is more optically desirable than either the Y2O3 or the nanoparticle system. Compared with the intrinsic sensitisation, two orders of magnitude times sensitisation of Yb3+ ions is demonstrated by co-evaporating Yb(F-TPIP)3 and the Zn(F-BTZ)2 chromophore, making it a suitable material for a waveguide amplifier. In summary, an Er3+-doped Y2O3 system is investigated as the fundamental study to understand the underlying physics, and then HL ligand and Zn(F-BTZ)2 chromophore are investigated as potential sensitisers for Yb3+-doped nanoparticles and organic systems separately. The study in this thesis should be useful not only for fundamental physics but also as a reference for the applications of lanthanides.

This thesis describes the synthesis of interlocked anion host systems which exploit hydrogen bonding, halogen bonding, and lanthanide-coordination for anion recognition and sensing in aqueous solution. Chapter 1 introduces the field of anion supramolecular chemistry, with particular focus on areas of particular relevance to this thesis, namely anion recognition and sensing, anion templation and the synthesis of interlocked structures. Chapter 2 describes the synthesis of hydrogen bonding rotaxane and catenane hosts for recognising and sensing oxoanions in aqueous solvent media. The novel use of nitrate anion templation for the synthesis of interlocked molecules is reported, and the unprecedented selective recognition of nitrate in aqueous solvent media is demonstrated. Chapter 3 details the preparation of water soluble permethylated β-cyclodextrin-stoppered rotaxane hosts that utilise halogen bonding and hydrogen bonding interactions to bind anions in pure water. The first thermodynamic investigation into halogen bonding in water is reported, and the relative capabilities of halogen and hydrogen bonding for anion recognition in water are compared. Chapter 4 investigates the incorporation of lanthanide cations into rotaxane hosts for optical anion sensing. The seminal use of lanthanide cation templation for interlocked molecule synthesis is described, before anion templation approaches towards the synthesis of lanthanide-based rotaxanes are discussed. The luminescence anion sensing capabilities of these interlocked hosts are investigated. Chapter 5 describes the experimental procedures used in this work, and details the characterisation of compounds presented in Chapters 2–4. Chapter 6 summarises the conclusions of this thesis.

Lanthanides are critical elements used in numerous modern technologies, but their mining and purification pose significant environmental challenges. This thesis describes the development of synthetic biology tools to enable more sustainable extraction of lanthanides using engineered microbes. In Chapter 1, I engineer LanTERN, a first-of-its-kind fluorescent biosensor that directly transduces lanthanide binding into a fluorescent signal. LanTERN enables direct fluorescent detection of lanthanide binding, overcoming the limitations of previous sensors. Chapter 2 details early work on generating small, stable lanthanide-binding peptides through de novo design. Finally, Chapter 3 places this work in the broader context of synthetic microbiology for sustainability applications. I present a framework categorizing sustainability efforts based on their level of environmental containment and discuss research priorities for responsibly deploying engineered microbes. Together, the tools and perspectives provided help lay a foundation for engineering microbes to extract, concentrate, and separate lanthanides in a more environmentally friendly manner.

In this thesis, the chemistry of lanthanide and actinide complexes of Schiff-base, polypyrrolic macrocyclic ligands has been evaluated. Chapter one introduces some general chemistry of uranium before focussing on uranium(III) and (IV) coordination complexes of nitrogen donor ligands. The surface chemistry of uranium metal is also briefly discussed along with the synthesis of uranium borohydride, hydride and alkyl complexes. Chapter two describes the synthesis and characterisation of the monometallic complexes [M(L)] or [M(HL)], where M = Y, Ce, and U, of the octadentate Schiffbase pyrrole macrocycle H4L. In particular, these complexes display a new binding mode of the macrocycle which leads to the formation of the unique trinuclear supramolecular complexes [M(HL)]3, (M = Ce, Y). Reactions of these materials towards hydrolysis, oxygen sources and other metal reagents are also exemplified. Chapter three details the synthesis and characterisation of the bimetallic complexes, [(MX)2(L)], where M = Ce, U, and Np and X = I or Cl, and [(MX2)2(L)], where M = U, and the attempts to transform these complexes into metal hydrides via their borohydrides. The solid state variable temperature magnetism of the binuclear U(III) and Np(III) complexes was recorded and was found to be consistent with the formation of iodide-bridged, polymeric structures. Chapter four explores the synthesis and reactions of adducts between UI3 and neutral macrocyclic ligands that incorporate either oxygen or nitrogen donors such as crown ethers and cyclam, respectively. The new synthesis of the key starting material, unsolvated UI3 is also outlined, along with the full characterisation of UI4(OEt)2.

While copper is an essential micronutrient in all living organisms, copper misregulation in humans is associated with neurodegenerative disorders such as Menkes and Wilson’s diseases, amyotrophic lateral sclerosis and Alzheimer’s disease. Furthermore, copper is a widely-produced pollutant and thus the detection of Cu(II) and Cu(I) has received much attention in recent years. Copper can be detected in a number of ways including; quenching of fluorescence upon the binding of paramagnetic Cu(II) (a "turn-off" response); augmentation of fluorescence upon Cu(II) binding due to PET modulation (a "turn-on" response); and selective Cu(II)- or Cu(I)-catalysed reactions where the luminescence of the product is distinctly different to that of the starting material. A review of Cu(I) and Cu(II) sensors is described herein. The Hulme group has previously developed a sensor for ligand-bound copper(I) utilising the copper(I)-catalysed [GS-−Cu(I)] variant of the Huisgen 1,3-dipolar cycloaddition reaction. Cu(I)-catalysed alkyne-azide cycloaddition (CuAAC or “click”) was carried out between an alkynyl Eu(III)-DOTA complex and a dansyl azide yielding a 1,4-triazole with a modest turn-on response (10-fold increase in luminescence). The project described herein aimed to achieve a more significant increase in lanthanide luminescence intensity through alteration of the donor moeity, lanthanide ion, and linker length between donor and acceptor moiety. The synthesis of several lanthanide-DOTA complexes, azido fluorophores and the formation of novel Cu(I)-sensors via CuAAC is described herein. All Cu(I) sensors were excited at their individual λex and their lanthanide luminescence intensity was measured using a timedelayed phosphorimeter. The DOTA structural motif has the ability to complex a plethora of potentially useful radionuclides including; yttrium, indium, gallium, lutetium and gadolinium. In general, DOTA-complexes doped with gadolinium are utilised for the identification of tumour sites while yttrium or indium complexes are used for tumour treatment. Biotin-DOTA conjugates have previously been used for pretargeted cancer imaging and radiotherapy. Biotinidase degradation of the amide bond in some biotin constructs has been reported, rendering them unable to bind to the pre-targeted antibody-(strept)avidin site. A novel biotinyl azide lacking this vulnerable amide bond is reported, with potential for bioconjugation to a variety of biomolecules via “click” chemistry. The synthesis of two novel biotinylated Gd-DOTA complexes, with prospective application as pretargeted MRI contrast agents, are also described.

The (trivalent) lanthanides exhibit a common sequence of phases upon the application of pressure: hcp → dhcp → fcc → “distorted-fcc”. The “distorted-fcc”’ phase (d-fcc), observed in the light lanthanides is known to be related by geometric distortions to the fcc unit cell, yet the d-fcc phase has been reported to comprise of one or two structures, with no prevailing consensus as to the solution(s). This thesis contains a detailed study of the d-fcc phase of the light lanthanides Pr and Nd. High-pressure angle-dispersive powder-diffraction techniques were employed to systematically study the phases adopted by Pr (up to 25GPa) and Nd (up to 44GPa). Particular attention was paid to solving the d-fcc of each of these elements, the structure of which is very unclear in published work. In Pr, the d-fcc between 7 and 20GPa is shown to comprise of two phases, the solutions of which are shown to be hR24 (R¯3m) and oC16 (Ibam) for the regions 7-14GPa and 14-20GPa, respectively. The pressure dependence of each of these structures over their stability range is presented. Revisions to previously-published volume vs. pressure data are made, with a different value for the volume collapse at the 4f electron delocalisation transition reported. Similarly, the d-fcc phase of Nd, stable over the pressure range 16-40GPa, is studied in detail. Nd differs from Pr by undergoing a further transition, to a hP3 (P63) structure, on pressurisation above 40GPa, before transforming to a α-Uranium phase. The distorted-fcc phase is shown, like that of Pr, to comprise of two phases, hR24 (R¯3m) and oC16 (Ibam) for the pressure regions 16-26GPa and 26-40GPa, respectively. Data on Nd are presented up to the maximum pressure achieved, 44GPa. Data from a preliminary study of La are also presented, along with a brief report on attempts to prepare a single crystal of Pr within a diamond anvil cell, by laser annealing of a powder of Pr.

Contrast agents are used in over 35% of MRI scans today and their use is increasing as they become ever more sophisticated. The challenge for researchers in this field is to synthesise smart imaging agents, which can be addressed using more than one imaging modality. The ultimate goal of these types of contrast agents is to be able to increase the contrast between normal and diseased tissue with smaller amounts of the agent being administered. This thesis describes the synthesis of complexes that are designed to have increased hydration numbers and rapid solvent exchange. The key to designing clinically effective contrast agents of this type is to minimize the affinity the contrast agent for endogenous anions such as phosphate that can exclude water from the inner coordination sphere, inhibiting exchange and reducing the relaxivity. A hexaanionic ligand was synthesized by tri-alkylation of cyclen with the dimethyl ester of N-isophthaloylchloroacetamide and subsequent hydrolysis. Lanthanide complexes of the ester and acid form of the ligand were synthesized and were shown to be luminescent. Relaxometric and time-resolved studies were used to establish that phosphate binding is not significantly inhibited in the anionic complex, suggesting that proximate negative charge is essential to inhibition of anion binding. Lanthanide complexes of DO3P and a bisDO3P analogue containing a bipyridyl bridge were also prepared, and shown to be more effective at inhibiting phosphate binding, though their properties exhibit dependence on pH. The bipyridyl derivative was used to prepare rhenium containing d-f hybrid complexes. These exhibited luminescence from both the rhenium MLCT and the lanthanide, though sensitized emission from the ytterbium is inefficient as a consequence of poor spectral overlap, Routes towards preparation of ligands bearing pyridylphosphinate pendent arms have also been explored.

This study investigates the photoluminescence (PL), cathodoluminescence (CL), radioluminescence (RL) and ionoluminescence (IL) of natural and synthetic minerals. The natural minerals (fluorapatite, leucophanite, meliphanite and zircon) are mostly from Ilímaussaq Alkaline Complex in South Greenland, Langesundsfjord in Norway and from different localities within Scotland. Synthetic fluorapatite (manufactured as part of the present study) and zircon doped with rare earth elements (REE) were used to compare single and multidoped materials. This study has shown that many of the generally accepted applications of luminescence are not as straightforward as often suggested by the current literature. For example, the study demonstrates how site distribution of REE, based on luminescence, is greatly affected by the dopant level and structural changes, and that different conclusions can be drawn on the same sample depending on method applied. Furthermore, it is clearly demonstrated that using luminescence as a tool for quantitative trace element determination is not going to be a standard technique in the near future if ever. The two main findings supporting this conclusion are the non-linear intensity decrease between different REE activators in the same sample and a large variation between activators at the concentration at which self-quenching starts. In contrast to the general perception that luminescence related to REE is mostly independent of the host, this study has shown a strong interaction between host and REE activators. This conclusion is supported by the change in the activator’s coordination polyhedron observed with single-crystal and powder X-ray diffraction combined with full chemical characterisation. When combining the weak interaction between some REE with the strong host interaction this study has shown the potential for designing new types of colour tuneable and “white light” LEDs based on natural minerals. This study also reveals that zircon doped with Gd³⁺ and Eu³⁺ can potentially have quantum-cutting properties.

Luminescent complexes of lanthanide ions are of growing interest because the long lifetime of emission allows time-resolved detection procedures to be employed. A key step in the development of such systems lies in the preparation of highly luminescent complexes which display high stability in aqueous solution. A series of ligands based on 1,4,7,10-tetraazacyclododecane have been prepared, in which the nitrogen atoms are appended with coordinating phosphinate or amide groups, or a combination of both. The compounds obtained are octadentate ligands which form water-soluble lanthanide complexes of high stability. Complexes incorporating aryl groups in the pendent arms have been prepared and some display intense metal luminescence following excitation into the organic chromophores. A back energy transfer process occurs in the terbium complexes containing naphthyl or quinohnone groups. Measurements of the luminescence lifetimes in H(_2)O and H(_2)O show diat diere are no metal-bound water molecules in the tetrabenzylphosphinate complexes. Those incorporating one amide and three phosphinate groups display hydration states between 0 and 1. An attempt has been made to correlate this information with that obtained from an analysis of the nuclear magnetic resonance dispersion profiles of related gadolinium complexes. The complexes incorporating secondary amide groups display an additional deactivation pathway for the metal excited state involving energy transfer into N-H bonds. The luminescence behaviour of four macrocyclic tetraamide ligands incorporating naphthyl fluorophores has been studied. These compounds exhibit distinctive changes in luminescence in the presence of quenching (eg. Pb(^2+), Cu(^2+) and Ni(^2+)) and non- quenching ions (eg. Cd(^2+) and Zn(^2+)). This behaviour extends to non-aqueous solution. The protonated tetranaphthyl ligand forms an intramolecular excimer in which the excimer emission displays a sensitive dependence on the polarity of die solvent.

Competing magnetic interactions between magnetic ions in triangular or hexagonallattice systems can create exotic magnetic ground states of interest for quantum computing and high temperature superconductivity. These triangular/hexagonal structural motifs have been studied extensively within several material systems, but one material system that has remains underexplored is the phosphide family LnCd3P3 (Ln = Lanthanide). LnCd3P3 compounds possess well-separated Ln3+ ions set in a triangular lattice, which makes this system another avenue to study frustrated magnetism and the resulting exotic magnetic ground states. Previously, the properties of the LaCd3P3 and CeCd3P3 have been examined in detail, and the crystal structure of PrCd3P3 has been studied with X-Ray Diffraction. In this work, a new method for synthesizing high quality polycrystalline samples of these LnCd3P3 compounds is presented. This new method was used to synthesize polycrystalline samples of NdCd3P3, which is a new member of the LnCd3P3 material system. We then conducted resistivity, heat capacity, and magnetization measurements of NdCd3P3 samples, which revealed magnetic transitions at temperatures below 20 K. Next, a flux growth method for synthesizing single crystals of heavier LnCd3P3 compounds was developed. PrCd3P3 single crystals were then grown using this method and studied with magnetization and heat capacity measurements.

Rare earth elements are found in relative ubiquity within the earth’s crust and have a multitude of application to both everyday life and military defense. On the periodic table, rare earth elements consist of all 15 lanthanides, along with scandium and yttrium. These elements have a wide variety of application, spanning from private and public sector applications, all the way to military defense, thus making them highly desirable metals for eventual utilization. Current methods of rare earth element extraction and purification involve environmentally harmful processes, leading to North America’s decision to not mine for rare earth elements within its territories. This decision has created a distinct lack of self-sufficiency in rare earth element production, currently resulting in a complete reliance of rare earth element imports from other countries, namely China. Due to the current processes of rare earth element extraction and purification posing large detriment to environmental stability along with a decrease in U.S. autonomy, determination of new, safer routes of rare earth element processing is of utmost priority. Specific proteins are known to bind metal ions, which has provided the scientificfoundation for a protein-based extraction and purification method targeting rare earth elements. Previous research has identified a protein which is known to bind lanthanides, providing a high potential prospect for the solution to this problem. The protein of interest, named lanmodulin (LanM), contains four regions, denoted as EF hands, with three of which being involved in lanthanide binding. Building upon the previously mentioned solution is a thioredoxin protein found in the extremophile Pyrococcus furiosus. P. furiosus thioredoxin has shown the ability to stably accept newly introduced peptide sequences within its native amino acid sequence. The area of insertion possesses closely located cysteine residues which show potential to form a disulfide bond, effectively increasing rigidity to the binding site’s structure. The Air Force Research Labs have successfully cloned the lanthanide binding loops from LanM to the thioredoxin protein, possibly allowing for a one step extraction/purification process of rare earth elements. The focus of this research is to build upon previous findings using computational chemistry tools and designed simulation experiments. Molecular modeling simulations have provided accurate calculations of energy requirements for both lanthanide ions binding to the proteins along with the energy required to remove the lanthanides from their respective binding pockets. Simulations are also being used for determination of binding loop selectivity and overall effects of the proteins’conformational changes upon ion binding and ultimate removal. Conclusions drawn from this research will provide a stable foundation to build upon in the coming years within this field.

In a world where clean water predictability is challenged by both global warming and the contamination of our natural resources, it is our responsibility to advance water separation technologies into more efficient processes and to lessen their environmental footprint. Pore and surface functionalization of membranes can enhance the separation of ions from water and even help overcome intrinsic challenges that some current separation technologies possess. If we begin with a complete fundamental understanding of the nanoscale interactions that occur in the process of separating ions from water, then we can engineer new functionalized composite membranes to provide alternative processes keeping life cycle aspects, lowering energy consumption, and keeping minimum supply needs in consideration. This research evaluated the synthesis and performance of three new membrane platforms: a positively charged nanofiltration (NF) membrane, a dual-functional NF and adsorptive membrane, and a set of adsorptive/ion exchange membranes. The application of these technologies include: the recovery of valuable lanthanide ions (rare earth elements) from water, and the removal of organic and inorganic ions and pollutants, such as per- and polyfluoroalkyl substances (PFAS) and arsenic, among other ions being studied. A comprehensive study that involved the synthesis of the membrane technologies, thorough materials characterization, analysis of the separation performance, and modeling of the solute transport through these membranes, was performed for each one of these three materials/applications. First, positively charged nanofiltration membranes were created by adding commercially available polyallylamine hydrochloride (PAH, primary amine) to the conventional interfacial polymerization technique. The NF membranes with added PAH had high and stable lanthanides retention rates, with values around 99.3% in mixtures with high ionic strength (100 mM, equivalent to ~6000 ppm), 99.3% rejection at 85% water recovery (and high Na+/La3+ selectivity, with 0% Na+ rejection starting at 65% recovery), and both constant lanthanum rejection and permeate flux even at pH 2.7. The Donnan steric pore model with dielectric exclusion elucidated the transport mechanism of lanthanides and sodium, proving the potential of highly selective separation with acceptable water permeability using positively charged NF membranes. Second, the rejections of ionogenic compounds by nanofiltration (NF) membranes at pH values near the membrane isoelectric point were compared to the size-transfer-dependent and mass-transfer-dependent modeled rejection rates of these compounds in an ionized state. This provided new insight on the transport mechanism of PFAS through the NF layer. The synthesis of an additional support barrier with thermo-responsive adsorption/desorption properties (quantified by water permeance variation) was proposed. This allowed for enhanced separations of PFAS and preventing other compounds, such as NOM, to enter the backing adsorption domain. The synthesis was made possible by successfully adding an NF layer on top of a poly-N-isopropylacrylamide (PNIPAm) pore-functionalized microfiltration support structure. The support layer adsorbed organics (178 mg perfluorooctanoic acid (PFOA) adsorbed/m2), and the simultaneous exclusion (50-70%) from the NF layer allows separations at a high water flux of 100 L/m2-h at 7 bar. Finally, three types of adsorptive polymers comprised of strong/weak acid, strong base, and iron-chitosan complex groups were synthesized in the pores and on the surface of microfiltration (MF) membranes. These were tested for removal of organic and inorganic cations and anions from water, including arsenic, per- and polyfluoroalkyl substances (PFAS), and calcium (hardness). An increase in the relative adsorption capacity by up to eight times when compared to beads and crushed-down resins, as well as up to two orders of magnitude faster adsorption kinetics were found. This research includes an analysis of the simple synthesis approach, consideration for how to apply the results of this research on a larger scale, and comparison against commercial adsorptive/ion exchange technologies, ultimately quantifying the gap in adsorption capacities between adsorptive membranes and adsorptive resins.

This dissertation describes efforts to expand the area of low oxidation state chemistry for the rare-earth metals and the actinides. The use of the spherically encapsulating 2.2.2-cryptand (crypt) for the isolation of new complexes of +3 and +2 ions of these metals was explored. In addition, X-ray photoelectron spectroscopy (XPS) was used to evaluate the electron configurations of Gd(II) complexes by comparison with Gd(III) analogs. Specifically, Chapter 2 describes the isolation of complexes of Sm(III) and Nd(III) with crypt, [Sm(crypt)(OTf)2][OTf] and [Nd(crypt)(OTf)2][OTf], and their reduction chemistry. The [Ln(crypt)(OTf)2][OTf] complexes reacted with KC8 in THF to form the LnII(crypt)(OTf)2 counterparts. Chapter 3 describes the synthesis and attempted reduction of [Ln(crypt)(OTf)2][OTf] complexes for Ln = La, Ce, and Pr. Unlike their Sm and Nd counterparts, neither chemical nor electrochemical reduction was observed for La and Ce. Chapter 4 describes the extension of the crypt ligand to actinides in collaboration with Dr. Andrew Gaunt and Dr. Conrad Goodwin at Los Alamos National Laboratory (LANL) for An = U, Np, and Pu. Small scale reactions with uranium to make [U(crypt)(OTf)2][OTf] were conducted and used as a method to extend this chemistry to Np and Pu, which are of limited availability. Chapter 5 describes methods using liquid ammonia and sodium metal to attempt reductions of smaller Ln metals encapsulated in the cryptand ligand. This method was explored because Ln-in-crypt complexes of the smaller lanthanides later in the series are not soluble in THF. Chapter 6 describes the exploration of borohydride, (BH4)1-, and thexylborohydride, (H3BCMe2CMe2H)1-, ligands to make THF-soluble LnII-in-crypt complexes. These ligands were used for both Sm and Dy. While evidence suggests that a THF-soluble SmII(crypt)(H3BCMe2CMe2H)2 can be generated, Dy-in-crypt complexes with borohydrides were still not THF-soluble. Chapter 7 describes the isolation of a SmII ion encapsulated in a 2.2.1-cryptand (221crypt) ligand environment, [Sm(221crypt)(OTf)][OTf]. A cryptand with a smaller pocket was explored to see if this could affect the solubility of these cryptand complexes. Instead of making complexes more soluble in THF, the opposite was observed. Chapter 8 describes the isolation of a [TmII(crypt)(OTf)][OTf]2 complex. In comparison to the reductions described in Chapter 2, this complex was not isolated by chemical reduction of a TmIII-in-crypt complex, but rather the reduction of TmIII(OTf)3 with KC8 followed by the addition of crypt. Chapter 9 describes X-ray photoelectron spectroscopy (XPS) measurements made on Gd complexes in different coordination environments, specifically, Gd[(NSiMe3)2]3, Cptet3Gd, [K(crypt)][Gd[(NSiMe3)2]3], and [K(crypt)][Cptet3Gd] and a comparison with cyclopentadienyl analogs.

Herein the syntheses and characterization of model actinide and lanthanide complexes bearing phosphorus-based ligands are reported. High-symmetry molecular models featuring phosphorus-based ligands are very advantageous for experimental metal-ligand covalency studies because phosphorus-31 nuclear magnetic resonance spectroscopy and phosphorus-Kβ X-ray emission spectrometry can be used to study the electronic structure and orbital interactions of metal-phosphorus bonds. Furthermore, high-symmetry models simplify spectral interpretation, and reduce the complexity of computational studies of the actinides. The quantum chemistry of the actinides is very complex because relativistic effects and spin-orbit coupling are very important influences on the electronic structures of these elements. Low-symmetry and high coordination numbers are very common in actinide coordination chemistry, which further complicates actinide computational chemistry. The creation of molecular models with high-symmetry and low coordination numbers greatly reduces the complexity of empirical electronic structure studies. Using a combination of advanced spectroscopy and advanced computational methods, details about the metal-ligand orbital interactions in actinide and lanthanide complexes can be obtained. Herein reactions of advanced f-element amide complexes with phosphorus-based compounds are reported, with the intention of creating high-symmetry, low-coordinate f-metal complexes for empirical electronic structure investigations.

With the ever increasing availability of computational resources, more challenging chemical systems can be studied. Among these challenges are the rotational and vibrational spectra of diatomic molecules within spectroscopic accuracy, the environmental perturbations induced on a rotating water molecule, the prediction of free binding energies of lanthanide complexes using machine learning, and the study of catalytic mechanisms through a theoretical framework. High levels of electronic structure theory were combined with a rigorous treatment of either the anharmonic vibrational wave functions to study diatomic molecules or the rotational wave functions to study H2O-pH2 interactions. The former was initially applied to the CF+ cation and excellent agreement was observed between theoretical and experimental spectroscopic constants. Likewise, the H2O-pH2 interactions were utilized to identify satellite peaks in the infrared spectra of a H2O-doped, pH2 crystal lattice. These peaks most likely occur due to a vacancy site directly around the H2O molecule. The study of lanthanide complexes is challenging due to their unique electronic structure. Specifically, the study of lanthanide-tris-β-diketone complexes was studied to calculate their respective free binding energies. Machine learning was utilized in this instance to act as the function which mapped the structure of the β-diketone ligands to the free binding energies. Predictions were made and several β-diketone ligands were identified which maximized the separation between lanthanide and lutetium. Finally, the study of catalytic mechanisms using theoretical methods is not without challenge due to the complex electronic structure of such systems. The hydrogen evolution reaction, the dehalogenation of CH2Cl2, the hydrogenation of small, unsaturated hydrocarbons, and the hydroformylation reaction were studied using either molecular electrocatalysts or transmetalated forms of the HKUST-1 metal-organic framework.

Selective host‒guest interactions are relevant for advancing molecular sensing, catalytic, or pharmaceutical applications. However, characterizing solution dynamics of inorganic supramolecular complexes can be complicated by paramagnetism, ligand exchange processes, and complex speciation. The work presented in this thesis first describes development of methods to study lanthanide-containing metallacrowns (MCs) by nuclear magnetic resonance (NMR). Using these tools, solution stability of 12-MC-4 dimers (LnGa8(shi)8(OH)4), and guest-induced dimerization equilibria of 15-MC-5’s (LnCu5(pheHA)5) are analyzed. Subsequently, the development of a solution-stable dimeric metallacrown nanocapsule, derived from amphipathic 15-MC-5 structures, is presented. T1 relaxation times of proton resonances of LnGa8(shi)8(OH)4 and LnCu5(pheHA)5 were measured by NMR, and the ability to use a pulsed gradient spin echo sequence to perform diffusion ordered spectroscopy (DOSY) was assessed. In general, resonances with T1 greater than the defined diffusion delay were typically observed in DOSY (excepting broad peaks). Hydrodynamic radii, calculated from diffusion data incorporating an internal standard, were assessed for various metallacrowns of differing molecular weights and shapes. Solution stability of LnGa8(shi)8(OH)4 was examined by DOSY and mass spectrometry (ESI-MS) to determine that the complex remains intact as a dimer in methanolic solution, although some exchange of hydroxide for methoxide occurs. The guest-induced supramolecular dimerization of LnCu5(pheHA)5, which acts as a host for the dicarboxylate guest muconate, was found to be dependent on the lanthanide identity using calorimetric methods and DOSY. Metallacrowns with intermediate-sized lanthanides (Eu, Gd, Dy) formed dimeric complexes of host2‒guest (2:1) in solution that were in equilibrium with host‒guest (1:1) and unbound monomeric MCs. Larger and smaller lanthanides (La, Nd, Sm, Ho) only formed 1:1 complexes (in equilibrium with free MC). The driving force for dimerization across the series is thought to be a competition between higher stability of MCs (larger lanthanides) and more favorable geometry for bridging guests (smaller lanthanides). In the interest of freeing space in the interior cavity for alternative guests, enhancing solution stability, and attaining dimers for Ln’s that could not form the 2:1, synthetic efforts were undertaken to obtain a dimer of 15-MC-5’s that was covalently linked via a “hinge” formed by a pair of ligands on opposing MCs, herein termed MC2-clam. MC2-clam complexes attempted directly using dihydroximate ligands as the hinge ligand were found either to produce insoluble complexes or generate only monomeric MCs. Instead, mixed-ligand MCs were synthesized using a ratio of ligands L and L’ to bias statistical formation toward LnCu5L5 and LnCu5L4L’1, and away from greater proportions of L’. Since Cu5L4 is a known intermediate in formation of LnCu5L5, ligand exchange dynamics were examined for copper(II)/alpha-amino hydroximate-based 12-MC-4’s and 15-MC-5’s in efforts to utilize the intermediate to increase yield of LnCu5L4L’1. Whereas 15-MC-5’s are thermodynamically and kinetically stable, Cu5L4 12-MC-4’s were found to exchange ligands within minutes, which precluded high yielding transformation of Cu5L4 into LnCu5L4L’¬1. Ethynyl- and azido-functionalized ligands were incorporated as L’ into LnCu5L4L’1 in the statistical distribution, and were cross-reacted via copper-catalyzed cycloaddition to achieve the hinged MC2-clam. Samples of MC2-clam, which contained excess monomeric LnCu5¬(pheHA)5, were enriched by size-based purification methods, characterized by ESI-MS and DOSY, and shown to bind dicarboxylate guests. These studies demonstrated that lanthanide identity can be critical for supramolecular assembly and motivated the development a new subset of supramolecular host molecules for guest recognition. The investigation elucidated fundamental information relevant for the manipulation of metallacrown complexes in solutions.

The interactions between proteins and metals drive a myriad of processes in biology. Understanding the specifics of these interactions can lead to applications such as identifying disease targets and developing tools for industry waste recovery, among others. Vibrational infrared spectroscopy is a powerful tool for the analysis of protein structure and dynamics. In particular, subtle changes in the protein’s metal binding site geometry are directly accessible through the intrinsic vibrational modes of common coordinating amino acids. The first chapter of this thesis is a book chapter written with the goal of equipping any scientific researcher with the skill set necessary for this sort of investigation. Both fundamental theory of IR spectroscopy and practical protocols of data collection are included, so that anyone who wishes to take a spectrum of a protein can. The second chapter is a manuscript currently in preparation that describes a specific case in which IR spectroscopy and MD simulation has been invaluable in understanding metal coordination by proteins. Lanmodulin (LanM) is a newly characterized protein that contains EF hands, a canonical calcium binding motif. However, LanM coordinates lanthanides with a remarkably high affinity, and the structural basis for this specificity is still not understood. We use IR spectroscopy and MD simulation to characterize changes in the LanM’s binding dependent on coordinated ion and binding site sequence, with particular emphasis on the unique proline in each binding site. We find that removal of this proline confers a higher degree of flexibility to the binding site as a whole, suggesting that LanM may have evolved this particular sequence specific for the biologically relevant early lanthanides.

The electrodeposition process has been the standard method for producing actinide and lanthanide thin films for decades. The major benefits of the technique include high reproducibility, simple equipment set up, and high material utilization. The latter is important when producing actinide thin films of rare materials, which is the case for many actinide thin film targets for Super Heavy Element (SHE) research. Many techniques besides electrodeposition have been used for non-radioactive lanthanides and have shown to be most useful for radioactive lanthanides as well as enriched stable lanthanides due to the amount of available material. Despite its use for several decades, there is still a significant amount that is unknown about the actinide electrodeposition process. Consequently, it has become apparent that a deeper understanding of the electrodeposition process is necessary to produce films with improved properties. For example, greater adhesion could increase the lifetime of thin film targets irradiated on high current particle accelerators. For this reason, there are ongoing efforts to gain an understanding of the actinide electrodeposition process utilizing in-situ characterization techniques of lanthanide depositions. For rare actinide thin films, a lanthanide surrogate is desired to understand the morphology of the deposited material without depleting the amount of the rare actinide desired. This master’s thesis project will focus on the development of optical spectroscopy techniques for online monitoring of the electrodeposition process as well as address the proposed chemical form for the deposition of a lanthanide, and in turn, actinide electrodeposition

This thesis focuses on defining the electronic structure of molecular lanthanide complexes. Dy(III)/Ga(III) metallacrowns in three general coordination geometries (C4v, D4d, and C1) were isolated to examine the effects on Dy(III) emission. The ligand energy levels were tuned by making chemical substitutions onto the salicylhydroxamate or isophthalate backbone ligands. The spectral profile corresponded with the geometry in each case, despite ligand singlet and triplet energy levels ranging in the series from 25870-28860 cm-1 and 21550-22680 cm-1, respectively. Blue ligand fluorescence was also found to modify the compounds’ emission profile because variation in ligand energy levels led to shifts in the peak of blue ligand emissions (ranging 360-403 nm), as well as different ligand-Dy(III) interactions leading to a variety of ligand/Dy(III) quantum emission ratios (ranging 0.0035-0.455). Incorporation of ligand emissions leads to a wide tunability of Commission Internationale de l'éclairage coordinates ranging from x=0.29-0.40 and y=0.28-0.43, with coordination geometry and ligand emission contribution being the most important effects. The effect of shifting ligand energy levels on the thermal dependence of lanthanide emissions was examined to develop new molecular nanothermometers. Working with Ga8Ln2L8L’4 compounds (where Ln=Sm(III) or Tb(III), L’=isophthalate, L=salicylhydroxamate, 5-methylsalicylhydroxamate, 5-methoxysalicylhydroxamate, or 3-hydroxy-2-naphthohydroxamate), ligand-centric singlet energy levels ranged from 23300-27800, while triplet levels ranged from 18150-21980 cm-1. Comparison with relevant excited Sm(III)* and Tb(III)* energy levels (17800 and 20400 cm-1, respectively), showed that the excited Ln(III)*-ligand triplet gap was most important in dictating thermal dependence of emission intensity via back energy transfer, however, when the singlet-triplet ligand energy gap was especially small (3760 cm-1), energy transfer across this gap is also important. This also applies to designing imaging probes, with room-temperature, visible emission quantum yields ranging 2.07(6)-31.2(2)% for Tb(III) and 0.0267(7)-2.27(5)% for Sm(III). Maximal thermal dependence occurred over a wide thermal range (ca. 150-350 K), based on the ligand-lanthanide energy gaps. By mixing two of the Sm(III) and Tb(III) compounds, an optical thermometer was created based on the emission ratio of these two ions. For (1:1 Sm2L8:Tb2L8, [L=5-methoxysalicylhydroxamate]) in the solid state, peak temperature sensitivity greater than 3 %/K at 225 K was found. When (1:1 Sm2L8:Tb2L8, [L=salicylhydroxamate acid]) was placed in polystyrene nanobeads and examined as an aqueous suspension, maximum sensitivity of 1.9 %/K was found at 328 K, thus these materials may be useful in biological applications such as cellular thermal imaging. Finally, magnetic field-dependent luminescence was used to extract g-factors from Zeeman splitting patterns for ground and excited states of Yb(III). Extraction of the relevant parameters was performed by fitting the Zeeman response of resonant energies via luminescence. For the four states of the ground manifold for the crystal in the B/parallel/C3 orientation it was found g/par/1=4.47(0.27), g/par/2=3.69(0.39), g/par/3=2.97(0.43), and g/par/4 = 0.98(0.28). In the B/perpendicular/C3 orientation it was found g/perp/1=2.50(0.19) and g/perp/2=1.33(0.23). Meanwhile the emitting state’s g-factor could also be extracted, with g/par/E=2.70(0.27) and g/perp/E=0.52(0.19). These properties are difficult to measure by other experimental techniques and provide direct experimental insight into wavefunction mixing in the complex. In summary, this thesis used synthesis and spectroscopy to evaluate the impact of the ligand field on lanthanide physical properties while also developing technologies to probe the electronic structure more fully. These studies should assist in the design of future lanthanide based materials that exploit ligand field effects.

Throughout human history, the nature of life’s origin has been a prominent question seen with much philosophical importance. Our best scientific model for the origin of life is the RNA world hypothesis, which describes the earliest forms of life as having RNA as the only genome and the only genome-encoded catalysts, as opposed to the DNA-RNA-protein world of modern biology. Research into geology and prebiotic chemistry, however, describe a complex chemical environment in which the ribozymes would have had many catalytic possibilities to explore. In this dissertation, I present the results of two in vitro selections which examined the utility of peptides and lanthanides as cofactors for triphosphorylation ribozymes. These ribozymes utilize trimetaphosphate, a prebiotically plausible polyphosphate source, to triphosphorylate their own 5’-ends as a simpler analog for studying nucleoside activation. The first selection was done in the presence of ten octapeptides of varying prebiotic plausibility, and two ribozymes were examined in detail. Ribozyme 20 displayed a strongly beneficial relationship with one specific peptide, which increased the RNA’s activity by 900 (+/- 300)-fold, providing an example of a ribozyme that could benefit from a primitive translation system. In contrast, the mild (2-10 fold) benefit for ribozyme 23 interacting with six of the ten peptides provides an example of a ribozyme that could possibly benefit from random, abiotically assembled peptides. The other selection, using ytterbium as a metal ion cofactor instead of the standard magnesium, yielded many active sequences. One sequence, ribozyme 51, was studied in detail and was very sensitive to the ionic radius of the lanthanide. It required a lanthanide for activity and seemed to only be able to bind trimetaphosphate as a complex with the lanthanide, but still seemed to prefer other metal cations for folding. These results provide insight into the relationships of peptides and lanthanides with the development of catalytic RNAs, as well as opening doors for future study for understanding both the origin of life and the general principles of their interactions.

This dissertation focuses on the expansion of ligand sets available to isolate new +2 ions of the rare earth metals, i.e., Sc, Y, and the lanthanides. In addition to their isolation, their reactivity and physical properties have also been investigated. Chapter 1 describes the basis of this dissertation research, i.e., the initial isolation of new Ln(II) ions using the (C5H4SiMe3)33− ligand set and the characterization of these new Ln2+ ions. Chapter 2 describes the use of the (C5Me4H)33− ligand set to isolate a new series of Ln2+ complexes and compares their properties to the (C5H4SiMe3)33− complexes. In the (C5H4SiMe3)33− ligand set, Dy adopts a 4f95d1 electron configuration while in the (C5Me4H)33− ligand set, Dy adopts a 4f10 electron configuration. Chapter 3 describes efforts to isolate the first C5Me5 complex of a new Ln2+ ion in heteroleptic Y2+ complexes of the form, [CpX2Y(NR2)]1−, where CpX = C5Me5 and C5Me4H, and study their properties. Chapter 4 describes the reactivity and reductive chemistry of rare earth metal allylcomplexes with benzoxazole. Appendix A describes the reactivity of the [(C5Me4H)3Ln]1− complexes for Ln = La and Ce with tert-butyl isocyanide including EPR spectroscopy. Appendix B describes efforts to synthesize and reduce other heteroleptic rare earth metal complexes by investigating the dynamic between ligand choice and the identity of the rare earth metal.

Computational work was performed to support several synthetic projects in the Doerrer lab. The new luminescent cerium complexes [K(THF)6][Ce(OC4F9)4(THF)2] (20) and [K(THF)2][Ce(pinF)2(THF)3] (22) were structurally optimized in the gas phase, and their uncommonly blue-shifted absorption spectra were simulated by TD-DFT. Electronic structure analysis elucidated the 4f→5d transitions responsible for the absorption peaks, showing the involvement of the fluorinated alkoxide ligands in the composition of the donor orbitals. The [pinF]2− ligand was also coordinated to Sn(II) and Sn(IV). The structures of the new compounds [K]2[Sn(pinF)2] (31) and [K]2[Sn(pinF)3] (32) were optimized by DFT and their electronic structures examined, revealing a sterically exposed lone pair in the case of 31, and for 32 showing that its unusually twisted six-coordinate geometry (azimuthal angle ~30°) is maintained in the absence of counterions. Metal-metal interactions were investigated in the diamagnetic lantern compounds [PtM(SOCR)4(OH2)] (R = CH3, M = Mg (1), Zn (56); R = C6H5, M = Mg (2), Ca (3), Zn (4)). 195Pt NMR spectra calculated for these lanterns and the precursor ion [Pt(SAc)4]2− (42) demonstrate the electronic effect of coordinating these Lewis acidic metals to the electron-rich Pt(II) center. Canonical and NBO analyses show that the {PtZn} lanterns 41 and 56 possess dative bonds between Pt and Zn, while Ca and Mg feature purely ionic interactions with Pt. A new class of heterobimetallic lantern complexes of the form [PtM(pipCOS)4(py)] (M = Mn (43), Co (44), Ni (45), and Zn (46)) were synthesized. These species exhibit strong absorption in the visible range that was investigated by DFT. Structural and electronic analyses reveal donation from the lone pair on the piperidine N atom into the delocalized ligand system in the ground state, indicating the potential for LMCT to occur upon excitation. A new bidentate ligand, a condensed thioamide, was bound to a Pt(II) center in the complexes [Pt(ctaPhMe)2] (57) and [Pt(ctaPhMe)2]2− (59). DFT analysis of these and the hypothetical ion [Pt(ctaPhMe)2]− (58) showed that reduction occurs on the ligands themselves, with the added electron density concentrated on carbon atoms in the ring, and that the doubly reduced species exists in the high-spin state.

Pincer ligands attract great current interest because they bestow exceptional stability on their metal complexes. Modification of the pincer scaffold can be used to tune the electron density at the metal ion and, therefore, the physical and chemical properties. This thesis reports studies of 2,5-di(2-pyridyl)pyrrolide (dpp–) NNN-pincer ligands and their transition and rare-earth metal complexes. Homoleptic complexes were prepared and screened for useful physical (e.g., magnetic or photophysical) or chemical (e.g., redox or reactive) properties. Predictable control of the properties through the substitution of the pyrrolide ring was a particular goal, and was achieved. The critical review of the literature on the chemistry of dpp– ligands and related pyridine-pyrrolide pincers, Chapter 1, concluded that a range of dpp– derivatives with flexible coordination modes was accessible, but with underdeveloped coordination chemistry. Chapter 2 provides a theoretical quantification (B3LYP-GD3BJ/6-31G** calculations) of the internal stain (ΔEL(strain)) that builds when a dpp– or related pyridine-pyrrolide pincer ligand binds a metal ion. A relationship was discovered correlating ΔEL(strain) and the change in interatomic separation of the two terminal donor atoms when bound (ρL(coord)) and metal-free (ρL(relax)). The relationship was employed to explain, a posteriori, the occurrence of spin crossover activity in Fe(II)-pincer complexes. A series of five structurally similar cobalt(II) complexes, [Co(dppR1,R2)2], bearing different pyrrolide 3,4-substituents are discussed in Chapter 3. The oxidation and spin states of the cobalt ion were switched by appropriate external stimuli, with the CoIII/CoII couple predictably sensitive to the Swain-Lupton electronic parameters for the pyrrolide substituents. Chapter 4 describes the first lanthanide(III) complexes of dpp– ligands. Ligand-sensitised, lanthanide-centred emission was observed for [Eu(dppCO2Me,Me)3] (red emission) and [Yb(dppCO2Me,Me)3] (near-infrared emission). Chapter 5 reports enhanced reactivity for [Ru(dpp)2] complexes compared to the ubiquitous [Ru(tpy)2]2+. Hemilability of the dpp– ligand results from its large ρL(relax), and this was exploited for catalytic transformations of small molecules bound at the ruthenium(II) centre. Four small preliminary studies are included in Chapter 6, each providing an entry point into more detailed future investigations. Chapter 7 provides a summary of the results, highlights advances made and suggests how these could be used into the future.

This dissertation details investigations into ligand effects on the non-traditional rare-earth(II) ions, i.e., those with 4fn5d1 electron configurations (as well as 3d1 Sc(II) and 4d1 Y(II)) instead of 4fn+1. Specifically, effects on kinetic stability and the reducing ability of complexes of these ions are explored as a function of ligand set and metal. Chapter 1 describes the synthesis and characterization of rare-earth(II) complexes of the aryloxide ligand 2,6-tBu2-4-Me-C6H2O and sets forth the hypothesis that kinetic stability of rare-earth(II) compounds depends on the steric saturation of the metal center. Chapter 2 expands on the steric argument made in Chapter 1 by synthesizing Y(III) and Y(II) complexes of the bulky aryloxide 2,6,-(1-adamantyl)2-4-tBu-C6H2O; the crystallographically-characterized Y(II) complex is kinetically stabilized compared to the thermally unstable Y(II) complex with 2,6-tBu2-4-Me-C6H2O in Chapter 1, which is detected only spectroscopically. Chapter 3 reports the synthesis of rare-earth(III) compounds of the asymmetric amide ligands N(SiMe3)R, where R = phenyl or cyclohexyl, which prove to be insufficiently sterically-saturating ligands for rare-earth(II) compound isolation. Chapter 4 compares the reducing power of Th(II) and U(II) complexes to Y(II) and La(II) complexes using EPR spectroscopy. Chapter 5 continues these comparisons with a wider range of rare-earth (II) compounds, varying the metal involved as well as the ligand set, and also describes ligand exchange reactivity leading to EPR evidence for heteroleptic rare-earth (II) compounds.

This dissertation describes strategies for the synthesis of low valent f element complexes, isolation of f element cryptate complexes using 2.2.2-cryptand, and the analysis of the electronic structures of (C5H4SiMe3)3Ln and [K(2.2.2-cryptand)][(C5H4SiMe3)3Ln] complexes (Ln = Sm, Eu, Gd, Tb) using X-ray photoelectron spectroscopy (XPS). The primary motivation of this research sought to expand the number of f element complexes in the +2 oxidation state by modifying counterions and ligand environments to investigate the chemical properties that help enable the isolation of these low valent ions. Several new complexes were isolated and strategies for the isolation of these ions will be discussed throughout this dissertation. In addition to developing synthetic strategies, the electronic structure of Ln(II) ions were examined using XPS to probe the electronic structure of both core electrons and valence electrons of these unusual ions with mixed-electron configurations. In Chapter 1, lithium reduction of Cp′3Ln (Cp′ = C5H4SiMe3; Ln = Y, Tb, Dy, Ho) under Ar in the presence of 2.2.2-cryptand (crypt) is discussed. Examples of crystallographically-characterizable Ln(II) complexes of these metals are isolable, [Li(crypt)][Cp′3Ln]. In each complex, lithium is found in an N2O4 donor atom coordination geometry that is unusual for the cryptand ligand. Lithium reduction of Cp′3Y under N2 at −35 °C forms the Y(II) complex (Cp′3Y)1−, which reduces dinitrogen upon warming to room temperature to generate the (N2)2− complex [Cp′2Y(THF)]2(µ-ƞ2:ƞ2-N2). In Chapter 2, the synthetic options for generating complexes of the actinide metals in the +2 oxidation state are discussed. Reduction of Cp″3U [Cp″ = C5H3(SiMe3)2] and the lanthanide analogs, Cp″3La and Cp″3Ce with lithium in the absence of crown ether and cryptand chelates is described. In each case, crystallographically-characterizable [Li(THF)4][Cp″3M] (M = La, Ce, U) complexes were obtainable. Reductions using Cs were also explored and X-ray crystallography revealed the formation of an oligomeric structure, [Cp″U(μ-Cp″)2Cs(THF)2]n, involving Cp″ ligands that bridge "(Cp″UII)1+" moieties to "[Cp"2Cs(THF)2]1−" units. In Chapter 3, the synthesis of crystallographically-characterizable Ln(II) complexes of Tb and Ho by reducing CpMe3Ln(THF) (CpMe = C5H4Me) with KC8 in THF in the presence of 18-crown-6 (18-c-6) is described. X-ray crystallography revealed that these complexes are isolated with a methylcyclopentadienide inverse sandwich countercation: [(18-c-6)K(µ-CpMe)K(18-c-6)][CpMe3Ln] (Ln = Tb, Ho). In Chapter 4, the reactivity of Cp′2Ln(THF)2 metallocenes with crypt to form Ln(II)-in-crypt complexes, [Ln(crypt)(THF)][Cp′3Ln]2 (Ln = Sm, Eu) and [Yb(crypt)][Cp′3Yb]2, is discussed. In each of the complexes, a ligand rearrangement occurs to form a Ln(II) dication with two [Cp′3Ln]1– counteranions. In Chapter 5, the facile encapsulation of U(III) and La(III) by crypt using simple starting materials is described. Addition of crypt to UI3 and LaCl3 forms the crystallographically-characterizable complexes, [U(crypt)I2]I and [La(crypt)Cl2]Cl. In the presence of water, the U(III)-aquo adducts, [U(crypt)I(OH2)][I]2 and [Ucrypt)I(OH2)][I][BPh4], can be isolated. In Chapter 6, the reactivity of LnI2(THF)2 (Ln = Sm, Eu, Yb) with crypt is discussed to examine if these readily accessible precursors could provide new examples of lanthanide-in-crypt complexes. The crystallographically-characterized Ln(II)-in-crypt complexes [Ln(crypt)(DMF)2][I]2 (Ln = Sm, Eu) and [Yb(crypt)(DMF)][I]2 were synthesized by reacting LnI2(THF)2 (Ln = Sm, Eu, Yb) with crypt in THF and recrystallizing from DMF. Crystallographic data were also obtained on the Ln(II)-in-crypt complex [Ln(crypt)(DMF)2][BPh4]2 which was synthesized by addition of two equivalents of NaBPh4 to [Ln(crypt)(DMF)2][I]2. In Chapter 7, the synthesis of Ln(III)-in-crypt complexes using Ln(OTf)3 (Ln = Nd, Dy) starting materials is discussed. In MeCN, the Dy(III)-in-crypt complex formed is [Dy(crypt)(OTf)][OTf]2 and in DMF, the Nd(III)-in-crypt complex formed is [Nd(crypt)(DMF)2][OTf]3. A Nd(III)-in-crypt complex, [Nd(crypt)(OTf)2][OTf], can also be formed in THF and subsequently reduced using KC8 to form the Nd(II)-in-crypt complex [Nd(crypt)(OTf)2]. In Chapter 8, the electrochemical properties of U(III)-in-crypt complex [U(crypt)I2]I were examined in DMF and MeCN to determine the oxidative stability offered by crypt as a ligand. Cyclic-voltammetry revealed a U(IV)/U(III) quasi-reversible redox couple of –0.55 V (vs Fc+/0). In the presence of [CoCp2][PF6] in MeCN, a reversible U(III)/U(II) redox couple of –1.84 V (vs Fc+/0) was observed. U(III)-in-crypt complexes were also and was found to be robust to water. Additional examples of a U(III)-in-crypt complex with a DMF, MeCN and water adducts have also been crystallographically-characterized. In Chapter 9, reduction of Th(OC6H2tBu2-2,6-Me-4)4 using either KC8 or Li in THF forming crystallographically-characterizable Th(III) complexes in the salts [K(THF)5(Et2O)][Th(OC6H2tBu2-2,6-Me-4)4] and [Li(THF)4][Th(OC6H2tBu2-2,6-Me-4)4] is discussed. In each structure the four aryloxide ligands are arranged in a square planar geometry, the first example of this coordination mode for an f element complex. The Th(III) ion and four oxygen donor atoms are coplanar to within 0.05 Å. EPR spectroscopy reveals an axial signal consistent with a metal-based radical in a planar complex. DFT calculations yield a C4-symmetric structure which accommodates a low-lying SOMO of 6dz2 character with 7s Rydberg admixture. In Chapter 10, using X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) calculations are discussed to evaluate the electronic structure of molecular Ln(II) complexes [Cp′3Ln]1– (Cp′ = C5H4SiMe3; Ln = Sm, Eu, Gd, Tb) formed by reduction of the Ln(III) precursors, Cp′3Ln. DFT calculations suggest that Eu(II) has a 4f7 and Gd(II) has a 4f75d1 electron configuration, whereas Tb(II) could not be unambiguously assigned due to its possible multiconfigurational ground state.

Utilizing nuclear energy to combat climate change is rapidly becoming necessary to mitigate major disruptive events. However, nuclear technology has an inherent dual use concern which creates a challenge to the legitimacy of some nuclear energy programs. Ergo, nuclear energy must be expanded with care of region and country-specific threats to maintain long-term prosperity. One such avenue is implementing spectroscopic on-line monitoring for tracking special nuclear material in close to real time. Using UV/Visible spectrum absorbance implements a barrier to nefarious tampering of a recycling system by utilizing physical properties unique from existing safeguards. In this thesis, optimization of a partial least squares regression model built on UV/Vis absorbance was explored, along with probing of a power analysis to better understand modeling parameters, and the speciation of neodymium with citrate as may be found in advanced nuclear fuel recycling. The models were optimized to maximize accuracy while minimizing susceptibility to deception. Ultimately, an accurate on-line model for special nuclear material will make nuclear recycling a more globally achievable goal, ergo increasing the prevalence of nuclear energy and contributing to climate change abatement.

The wide use of the f-elements, including nuclear weapons, nuclear energy and radiopharmaceuticals, has led to the growing unwanted accumulation of the lanthanides and actinides in the environment. The removal of these metals requires the design of highly selective ligands that take advantage of their complex chemistry (wide degree of covalency and high coordination numbers). Additionally, the environments these metals are typically being removed from involve a complicated mixture of other metals and strong counterions. Ligand design for the f-elements requires high selectivity and the formation of stable complexes in a wide range of environments. Ethylene diamine tetraacetic acid (EDTA) is one of the most well-known and widely utilized ligands in coordination chemistry, and hydroxamate-containing ligands are some of the most common in biological chemistry, suggesting a natural combination of EDTA-like backbones with hydroxamate arms. Specifically, the increase from the hexadentate EDTA to the decadentate hydroxamate analog would address the larger coordination numbers of the f-elements. EDTA, however, is too small even for Fe(III), leaving a coordinated water on the Fe, and is far too small for Ln/An(III) ions. Consequently, I synthesized a hydroxamate EDTA analog where the arms are longer by one carbon (ethylenediamine tetrapropionyl hydroxamic acid, EDTPHA). Potentiometric titrations of EDTPHA with La(III), Eu(III), and Lu(III), and a comparison with a synthetic all-carboxylate analog (EDTP) reveal that EDTPHA is powerful ligand for lanthanides competitive with EDTA. During the course of the work I developed a new protecting group for use in hydroxamate synthesis, and the straightforward synthesis of the EDTPHA ligand (utilizing highly pure aza-Michael chemistry) enables future work with additional ligands including EDTA-like ligands as well as siderophore-like peptide ligands to optimize their selectivity for f-element chemistry.

Rare-earth metal complexes are of interest in the use of new technologies such as single-molecule magnets (SMMs). New SMMs containing rare-earth metals can expand the limits of modern technology, but must first be made and studied before implementation. The synthesis of the new complexes (C5Me5)2Ln(μ-S)2M(μ-S)2Ln(C5Me5)2 (Ln = Y, Gd, Tb, Dy; M = Mo, W), Ln2M, and the subsequent reduction of the molybdenum compounds with Co(C5Me5)2 to form radical-bridged species [(C5Me5)2Ln(μ-S)2Mo(μ-S)2Ln(C5Me5)2][Co(C5Me5)2], (Ln2Mo)1− is described. An undetected ammonia impurity in the starting material led to the synthesis of asymmetric complexes [(C5Me5)2Ln(NH3)](μ-S)2M(μ-S)2Ln(C5Me5)2, Ln2MNH3, and the reduction of these complexes with KC8 in the presence of 18-crown-6 yielded [K(18-crown-6)](μ-S)2M(μ-S)2Ln(C5Me5)2, KMLn. Further exploration of the ammonia impurity led to the synthesis of the new yttrium metallocenes, (C5Me5)2Y(NH2)(THF), YNH2, and [(C5Me5)2Y(NH3)(THF)][BPh4], YNH3. Ammonia reactions with other lanthanide metallocenes (C5Me5)2Ln(THF)x (Ln = Sm, Yb; x = 0–2) and Cp′′3Ce (Cp′′ = C5H3(SiMe3)2) were pursued to create ammonia-containing complexes which could not be definitively characterized due to instability. In situ addition of the 2,4,6,-tri-tBu-phenoxyl radical yielded evidence for oxidation and hydrogen abstraction, but the complexes have not yet been crystallographically characterized. Finally, 89Y NMR spectroscopy was employed to obtain another method of characterization for yttrium compounds and the advantages of 1H89Y HMBC experiments over traditional 89Y NMR experiments are highlighted.

The efficient conversion of low-energy, near-infrared (NIR) photons to higher energies promises advancements across a range of disparate fields, from more efficient solar energy capture to advanced biologic studies and therapies. At the forefront of this effort, upconverting nanoparticles (UCNPs) contain an array of lanthanide ions alloyed into a ceramic matrix, most commonly NaYF4. These lanthanide ions possess a 4f orbital manifold with a series of ladder-like, long-lived electronic states, allowing the sequential absorption of NIR photons at relatively low photon flux. The electrons climb the 4f Stark levels, absorbing multiple photons from the excitation source before relaxing back to the ground state upon emission of a photon with an energy higher than those from the source. While UCNPs are among the most efficient systems for converting NIR light to visible, they still hold key limitations, namely, they only weakly absorb incoming photons, hindering their external quantum efficiencies and overall performance. This thesis presents studies designed to enhance the efficiency and brightness of UCNPs. One method to circumvent the inherently weak absorption in UCNPs involves attaching organic dye antennae to the surface of the nanoparticles to absorb incoming light and funnel the absorbed energy into the UCNP. However, a detailed understanding of the energy transfer mechanism between dye and UCNP is required to fully realize the potential of this system. We propose, using a series of spectroscopic and kinetic measurements, that this energy transfer is mediated via the absorbing dye triplet state, and further that the intersystem crossing rate within the dye is enhanced by interactions with the heavy nuclei of the lanthanides within the UCNP. We then design a highly efficient dye:UCNP hybrid system utilizing this new understanding. Lastly we present a study highlighting the power and potential of using UCNPs for biological applications. Together these studies will advance the utilization of photon upconversion towards realizing its promise in applications.

Lanthanides, known as the “vitamin of industry”, have been playing a pivotal role in a wealth of advanced materials and modern technologies including catalysts, magnets, lasers, economical lighting, and solar-energy conversion. With the development of nanoscience, lanthanide nanoparticles have been attracting increasing research interest as a new form of the old materials since 2000. These nanoparticles not only bring properties previously thought impossible in bulk lanthanide materials, but also raise concerns and challenges (e.g. quenching) that were not considered towards practical applications. This dissertation is dedicated to understanding and tackling these challenges with designed colloidal lanthanide nanoparticles. Particularly, the first theme explains how the dopants in the nanoparticle matrix contribute to the size and shape of nanoparticles (doping). The second theme explores the growth behavior of core-shell nanoparticles with controlled interfacial strains (epitaxy). The third theme introduces how to address the quenching challenges and enhance the photoluminescence on nanoparticles with the optimized doping and epitaxy (photon management). We show that the optimized lanthanide nanoparticles have record-high emission efficiency, provide insight for future nanoparticle designs, and can be used as a promising toolset for a wide ranges of research topics including bioimaging, therapeutics, photocatalysis, and optical energy conversion.

The rare earth elements (REE), composed primarily of the fifteen lanthanides, find broad application in many modern devices making them indispensable and important to the sustainable, green world approach prevalent these days. Liquid-liquid extraction for the separation of lanthanides using a calix[4]arene scaffold with coordinating ligands on its lower rim has been studied for many years. New solid phase materials capable of coordinating metals are important to the field of rare earth metal separation and isolation as they will not only minimize solvent wastes but have the potential to be reused, thereby making the separation and recovery of rare earth metals economical. In the first part, the synthesis and characterization of new chlorine terminated 2-alkyl-p-tert-butylcalix[4]arenes with different coordinating ligands such as phosphine oxides, ketones, CMPO, and esters on the lower rim were investigated. Here, the extraction efficiencies of these new calix[4]arenes for rare earth metals in liquid-liquid extraction was investigated in order to confirm that functionalization at the 2-position of the calix[4]arenes does not interfere with the extraction properties of the coordinating ligands on the lower rim.In the second part of this project, further modification of the 2-position was carried out by converting the chlorine terminated end to the highly desirable amino group, which was then utilized in coupling reactions to immobilize these 2-position/tail modified calix[4]arenes bearing lower rim coordinating ligands on solid supports covalently via the attached linker group. These newly synthesized solid phase extractants were characterized using solid state NMR spectroscopy, FT-IR spectroscopy, elemental analysis and EDS and their thermal stability was further determined using TGA. This represents the first report of attachment of calix[4]arene ligands to solid supports via their 2-positions to the best of our knowledge. These new materials were further investigated in the separation of lanthanides.

My dissertation is composed of two projects. The first area of study was the conclusion of a six-year project to determine the neutron-induced fission cross-section of Am-240. This cross-section is difficult to study due to the 50.8 hour half-life of Am-240 but is important for the evaluation of neutron signatures to establish the history of plutonium-containing materials.Such a study is relevant for the fields of nuclear stockpile stewardship and nuclear forensics. Prior to the study outlined here, much of the ground work for this determination had already been provided, including the identification of the Pu-242(p; 3n)Am-240 reaction for the production of approximately 100 nanograms of Am-240 and the development of a preliminary separation procedure to isolate the Am-240 from the unreacted Pu-242 and the undesirable fission and decay products generated from other reactions with the target. However, many variables in the separation procedure needed further investigation. Therefore, a series of column chromatography experiments was performed to determine which of the two previouslydesigned procedures would provide the best purification of 240Am while minimizing the losses. Once the general outline of the procedure was determined, a collaboration with Idaho National Laboratory (INL) made it possible to further refine and test it. Of the four steps in the originally designed procedure, the final step was among the most difficult to accomplish as it involved the separation of the light trivalent lanthanides from americium. Americium/lanthanide separations are dificult due to their identical oxidation states and very similar ionic radii of americium and the lanthanides. The original step utilized a columncomposed of TEVA® extraction chromatography resin and a mobile phase composed of ammonium thiocyanate and formic acid. Due to the complexity of this procedure, several alternative procedures were tested at INL with the TRU® resin and a mixture of fission products more representative of those that would be found in the actual target. A gas pressurized extraction chromatography (GPEC) system was used to automate the separation andachieve greater resolution between the lanthanide and americium elution peaks. Ultimately, it was demonstrated that the original TEVA® resin procedure was more reliable than the TRU® resin procedure, however the TRU® GPEC experiments may be relevant for future target material separations. The culmination of this project was the testing of the first stepof the procedure with one-tenth of the amount of Pu-242 that will be in the actual target. This experiment, in conjunction with the americium/lanthanide separation steps that were tested, prompted a re-evaluation and abbreviation of the overall separation procedure, decreasing the required number of total separation steps from four to two. Therefore, the purification of Am-240 could be accomplished much more quickly and easily than originally anticipated,making the determination of the neutron-induced fission cross-section of Am-240 more of a reasonable possibility in the future.Part II of my dissertation describes the investigation of the adsorption and complexation properties of silica-anchored carbamoylmethylphophine oxide (CMPO)-calix[4]arenes. In Part I, it was demonstrated that the difficulty encountered when separating trivalent lanthanides and actinides can be a severe impediment to accomplishing even fairly straightforward benchtop radiochemical procedures. Much greater motivation for developing newtechnologies to achieve this are encountered when considering the mixtures of trivalent actinides and lanthanides produced when irradiated nuclear fuel is reprocessed. CMPO, a ligand that binds indiscriminately with both the trivalent actinides and lanthanides, was attached to a calix[4]arene scaffold, which was then attached via two different methods to a silica surface. In previous studies, it has been shown that the CMPO-calix[4]arene has a greater affinity for americium than europium. The experiments in this work aimed to establishwhether this relationship held for CMPO-calix[4]arenes anchored in two new ways to the silica surface. It was found that, for a very particular set of conditions - high salt concentration and an aqueous solution pH of 3 - that a CMPO-calix[4]arene very rigidly anchored to the surface of the silica displayed extremely high uptake for Eu(III)when sites outnumbered the number of Eu(III) atoms by at least 10 to 1. This was not found when the same material andconditions were tested with Am(III) nor when the more flexibly anchored CMPO-calix[4]arene material and conditions were tested, leading to the conclusion that both the aqueous solution conditions and the rigidity of the grafted site affect the affinity of the CMPO-calix[4]arene toward cations of interest. The optimization of the CMPO-calix[4]arene system could havebeen potentially useful for Part I of this dissertation for separating americium and the lanthanides, had it existed at the time, and could eventually be applied to the separation of trivalent actinides and lanthanides at the conclusion of nuclear fuel reprocessing.Part I and Part II contribute to two different areas of actinide/lanthanide separation research, with Part I focused on optimizing existing resin systems to achieve separation and Part II focused on testing new materials specifically intended for separating trivalent actinides and lanthanides. Part I shows that existing resin systems can be used to rapidly purify a very small amount of americium from much greater amounts of plutonium, the lanthanides, and other elements. Part II demonstrates that the affinity of a grafted CMPO-calix[4]arene site for either trivalent actinides or lanthanides can be tailored based on the rigidity of the grafting to the solid and the aqueous phase conditions. Separately, it is hoped that these studies can be applied to work focused on detailed actinide target material purification and new innovations in actinide/lanthanide separations, respectively. However, it is also hoped that, cumulatively, these studies contribute to a broader understanding of actinide and lanthanide interactions with ligands designed to effect their separation, both for benchtop laboratory separations and nuclear fuel reprocessing.

Since their discovery two decades ago, single walled carbon nanotubes (SWNT) have created an expansion of scientific interest that continues to grow to this day. This is due to a good balance between presence of bandgap, chemical reactivity and electrical conductivity. By interconnection of the individual nanotubes or modulation of the SWNT’s electronic states, electronic devices made with thin films can become candidates for next generation electronics in areas such as memory devices, spintronics, energy storage devices and optoelectronics. My thesis focuses on the modulation of the electronic structure, optical properties and transport characteristics of single walled carbon nanotube films and their application in electronic and optoelectronic devices.Individual SWNTs have exceptional electronic properties but are difficult to manipulate for use in electronic devices. Alternatively, devices utilize SWNTs in thin films. SWNT thin films, however, may lose some of the properties due to Schottky barriers and electron hoping between metal-nanotube junctions and individual nanotubes within the film, respectively. Until recently, there has been no known route to preserve both conjugation and electrical properties. Prior attempts using covalent chemical functionalization led to re-hybridization of sp2 carbon centers to sp3, which introduces defects into the material and results in a decrease of electron mobility.As was discovered in Haddon Research group, depositing Group VI transition metals via atomic vapor deposition into SWNT films results in formation of bis-hexahapto covalent bonds. This (η6–SWNT)Metal(η6–SWNT) type of bonding was found to interconnect the delocalized systems without inducing structural re-hybridization and results in a decrease of the thin films electrical resistance. Recently, with the assistance of electron beam deposition, we deposited atomic metal vapor of various lanthanide metals on the SWNT thin films with the idea that they would also form covalent interconnects between nanotube sidewalls. In the case of highly electropositive lanthanides, the possibility of hexahapto bonding combined with ionic character can be evaluated and theorized.We have reported the first use of lanthanides to enhance the conductivities of SWNT thin films and showed that these metals can not only form bis-hexahapto interconnects at the SWNT junctions but can also inject electrons into the conduction bands of the SWNTs, forming a new type of mixed covalent-ionic bonding in the SWNT network. By monitoring electrical resistance and taking spectroscopic measurements of the Near-Infrared region we are able to show the correlation between enhanced conductivity and suppression of the S11 interband transition of semiconducting SWNTs.Potential applications of SWNT thin films as electrochromic windows require reversible modulation of the electronic structure. In order to fabricate SWNTs devices which allow for this behavior it is necessary to modulate the electronic structure by physical means such as the application of an electrical potential. We found that ionic solutions can assist with maintaining complete suppression of two Van Hove singularities in the Density of States of semiconducting SWNTs which results in optically transparent windows in the Near-Infrared region, similar to the effect seen with the incorporation of atomic lanthanide metals in thin films. We demonstrate this behavior to provide a route to nanotube based optoelectronic devices in which we use electric fields to reversibly dope the SWNT films and thereby achieve controllable modulation of optical properties of SWNT thin film.

Computational chemistry lies at the intersection of chemistry, physics, mathematics, and computer science, and can be used to explain the behavior of atoms and molecules, as well as to augment experiment. In this work, computational chemistry methods are used to predict structural and energetic properties of small molecules, i.e. molecules with less than 60 atoms. Different aspects of computational chemistry are examined in this work. The importance of examining the converged orbitals obtained in an electronic structure calculation is explained. The ability to more completely describe the orbital space through the extrapolation of energies obtained at increasing quality of basis set is investigated with the use of the Sapporo-nZP-2012 family of basis set. The correlation consistent Composite Approach (ccCA) is utilized to compute the enthalpies of formation of a set of molecules and the accuracy is compared with the target method, CCSD(T,FC1)/aug-cc-pCV∞Z-DK. Both methodologies are able to produce computed enthalpies of formation that are typically within 1 kcal mol-1 of reliable experiment. This demonstrates that ccCA can be used instead of much more computationally intensive methods (in terms of memory, processors, and time required for a calculation) with the expectation of similar accuracy yet at a reduced computational cost. The enthalpies of formation for systems containing s-block elements have been computed using the multireference variant of ccCA (MR-ccCA), which is designed specifically for systems that require an explicit treatment of nondynamical correlation. Density functional theory (DFT) has been used for the prediction of the structural properties of a set of lanthanide trihalide molecules as well as the reaction energetics for the rearrangement of diphosphine ligands around a triosmium cluster.

Particles with specific energies of ~1 MeV/u or greater interact with matter primarily through the excitation of electrons. Swift heavy ions, with high masses and velocities in this electronic excitation regime, are encountered by materials in the form of nuclear fission fragments, cosmic rays, and ion accelerator beams. The dense ionization resulting from ion-solid interactions in this regime produce diverse, material-dependent structural and chemical modifications in insulators. This dissertation reports investigation of swift heavy ion-induced phase and valence modifications to oxides of the f-block (lanthanide and actinide) elements. Dependence of these modifications on the variations in ionic radius (due to the lanthanide/actinide contraction) and accessible oxidation states (due to the effects of f¬-orbital localization) characteristic of elements in this system is discussed. Lanthanides typically exhibit a single trivalent oxidation state, such that they form sesquioxides. The phase systematics of these compounds varies across the lanthanide series due to the influence of lanthanide ionic radius on phase stability. In response to swift heavy ion irradiation, transformations to polymorphic and non-equilibrium phases were observed. These transformations were caused by atomic displacement and point defect formation during relaxation of an irradiation-induced electron-hole plasma, such that their composition-dependence could be attributed to the influence of cation size on the associated collective atomic reorganization mechanisms. In contrast to the lanthanides the light actinide elements have more itinerant ¬f-electrons and are typically multivalent. Swift heavy ion irradiation of several actinide and lanthanide dioxides resulted in no phase transformations, but caused cation valence reduction in those materials incorporating cations with stable trivalent oxidation states. Coupling between these chemical modifications and structural distortions, due to associated changes in the ionic radii and bonding of cations, were observed. In trioxides, this valence reduction caused changes in stoichiometry, with accompanying redox-coupled phase transformations. Ternary lanthanide stannate complex oxides exhibited both amorphization and disordering in response to irradiation. Their susceptibility to irradiation-induced amorphization decreased with the ionic radius of the lanthanide cation. Compounds that were resistant to amorphization instead exhibited disordering in the form of mixing of the two cations (Ln and Sn) onto a single sublattice, via cation antisite formation.

Dinitrogen can be reduced by photochemical activation of the trivalent rare earth bis(pentamethylcyclopentadienyl) allyl complexes (η5-C5Me5)2Ln(η3-C3H4R) (Ln = Y, Lu; R = H, Me) to form the (N=N)2− complexes, [(C5Me5)2Ln]2(μ-η2:η2-N2). This demonstrates that productive organolanthanide photochemistry is not limited to complexes of the unusual (η3-C5Me4H)1- ligand found in the heterometallic complexes (C5Me5)2(C5Me4H)Ln and (C5Me5)(C5Me4H)2Ln (Ln = Y, Lu, Dy). Photolytic activation of (C5Me5)2Ln(C3H5) (Ln = Y, La) in the presence of isoprene provides a rare photopolymerization route to polyisoprene. Irradiation of (C5Me5)2Y(C3H4Me) in the absence of other substrates results in the isolation of the corresponding ‘tuckover’ complex, (C5Me5)2Y(μ-H)(μ-η1:η5-CH2C5Me4)Y(C5Me5).

Rare earths and actinides are of great interest given their varied applications in energy conversion and storage, such as in catalysis and batteries, and for advanced technological applications related to optical and magnetic properties (including electronics and automotive), amongst others. Many of the rare earth elements are considered endangered species due to their unique properties which have no clear alternatives that will maintain performance for important applications. The optimal approach is to find readily available alternatives for critical materials to ensure a certain standard of living and quality of life for future generations, but it is very likely that reusing and recycling of endangered elements will be required. Computational methods are a key component in the search for less costly separation processes and in optimizing known separation methods, which could ultimately lead to reusing and recycling endangered elements, and for finding alternatives for critical materials. Optimization of separation processes is needed not only for separations of rare earths, but also for separations of actinides. Separating uranium from seawater has recently become an area of interest due to the large amount of uranium found in seawater, which exceeds the amount found on the Earth’s crust. Actinide separation is also required in the processing of radioactive waste, and is therefore necessary to fully realize the contribution of nuclear energy to an economy based on clean energy. Computational techniques can be enormously helpful in optimizing and designing separation agents to aid in the separation process of lanthanides and actinides. The chapters included in this dissertation seek to contribute to the understanding of complexation of lanthanides and actinides with different complexing agents, through in-depth computational studies. The material presented in Chapter II focuses on contributing to the understanding of the mechanism involved in solvent extraction of lanthanides with carboxylic acids. In particular, Chapter II studies possible conformations involved in the formation of the coordination shell and the determination of preferred coordination numbers. Chapter III studies effects of beta diketones with different substituents as extracting agents. Chapter IV focuses on providing better understanding of selective extraction of uranium, neptunium, plutonium, and americium with imide dioximes.

Diimine rhenium(I) tricarbonyl complexes are known as phosphorescent emitters and electro- and photocatalysts for the reduction of CO₂ to CO. Conducting metallopolymers containing this rhenium(I) moiety should not only retain the photoluminescent and catalytic properties of the complex but also gain the conductivity, processability, and mechanical flexibility typical of [pi]-conjugated polymers. A series of tricarbonyl rhenium(I) diimine-type monomers and metallopolymers have been prepared. Appended to the ligands are thiophene and 3,4-ethylenedioxythiophene (EDOT) groups for electropolymerization of the metal complexes. UV-Vis absorption and emission spectroscopy studies of the monomers indicate that light emission originates from triplet ligand-centered (³LC) [pi] [right arrow] [pi]* and triplet metal-to-ligand charge transfer (³MLCT) excited states. Additionally, both the monomers and metallopolymers show electrocatalytic activity towards the reduction of CO₂ to CO. Furthermore, the EDOT-functionalized diimine-type ligand (EDOT₂-BPP) also serves as a good sensitizing ligand for luminescent lanthanide emission. A series of lanthanide complexes that utilize tris([beta]-diketonates) and EDOT₂-BPP ligands have been synthesized and studied using X-ray crystallography and photophysical techniques. Large quantum yields and microsecond lifetimes were found for the EuIII and SmIII complexes. Complexes of TbIII were found to have weak luminescent emission due to the less-than-optimal energy gap between the sensitizing ligands and the excited state of the TbIII ion. Oligothiophenes are models for polymeric systems because of solution processability, controlled chain length, and a well-defined structure. We have synthesized a library of alkyl and polyfluoroalkyl-substituted oligothiophenes to study how molecular structure, long-range order, spatial orientation, and varying degree of electronic coupling between molecules influences charge separation in photovoltaics. These oligoalkylthiophenes have been characterized by X-ray diffraction, photophysical methods, electrochemistry, and UV-Vis and EPR spectroscopies. Although the electronic properties of these oligoalkylthiophenes do not vary with alkyl group, aggregates of oligooctylthiophene, made through solution processing, have distinct morphologies with varying amounts of electronic disorder. The extent of electronic disorder within the aggregate is determined by comparing the suppression of the 0-0 vibronic band in the fluorescence spectra to that of the non-aggregated parent molecule. This extent of electronic disorder was correlated with the local contact potential of individual aggregates through Kelvin probe force microscopy (KPFM) measurements.

Luminescent lanthanide complexes have been widely studied for various biotechnology and materials science uses, however, the application of these luminescent systems in metallopolymers has been relatively limited, especially when compared to those incorporating transition metal complexes. The unique and interesting photophysical properties of lanthanide complexes (i.e., high color purity and long radiative lifetimes) make these systems ideal for the development of luminescent metallopolymers, which are a unique class of hybrid materials that synthetically incorporate metal centers into organic polymers, thereby taking advantage of the beneficial properties of both traditional inorganic (i.e., catalysis, optics, electronics) and organic (i.e., easy to process, flexible, low weight) materials. A new class of lanthanide complexes exhibiting metal-based visible and near-IR photoluminescence has been designed, synthesized and fully characterized by melting point, ESI-MS, elemental analysis and single crystal and powder X-ray diffraction (when possible). The photophysical properties of these luminescent monomer complexes were studied in solution and the solid state, with the emission spectra displaying the characteristic line-like emission peaks of the trivalent lanthanide ions. This indicates efficient energy transfer from ligand centered excited states to the emissive excited states of the lanthanides. The monomer complexes have been electropolymerized, resulting in conducting metallopolymers that display metal-based photoluminescence. Because these hybrid materials retain the desirable properties of both inorganic semiconductors and organic polymers, such as near metallic electrical conductivity, ease of processing, flexibility and light weight, they are promising for applications in solid-state lighting.

The rare-earth elements Y and La-Lu share many similar physical and chemical properties. These similarities are reflected by the difficulty in the complete separation of the rare earths, often requiring hundreds to thousands of stages for the production of pure rare earths. Yttrium, traditionally known to be separated with Ho, has also been observed to be separated with other elements within the lanthanide series, and even outside the bounds of the lanthanide series itself. Previous publications by several authors have indicated that steric factors could influence the position of Y in solvent extractions of the rare earths using carboxylic acid extractants, and steric parameters such as Es′ could be used to rationalize the position of Y versus the overall steric bulk of these extractants. The purpose of this research project was to build upon the primary findings of these previous investigations and to gain further insight into the structural characteristics that influence the position of Y in solvent extraction systems. Solvent extraction experiments were performed on nine-element rare-earth solutions using a total of 29 carboxylic acid extractants. Rare-earth concentrations were determined using inductively-coupled plasma-optical emission spectrometry (ICP-OES). The results of these experiments showed that -Es′ values less than 2 placed Y in the light rare-earth region (La-Eu), while -Es′ values greater than 2 placed Y in the heavy rare-earth region (Gd-Lu). Additionally, substitutions at the α-carbon atom relative to the carboxyl group in these extractants were found to have the greatest influences on the position of Y. It was found that extractants which posessed an α-carbon atom which was not a component of a phenyl or cyclohexyl ring placed Y in three distinct locations—Ce-Pr, Gd-Tb, and Ho-Er, depending on the number of hydrogen atoms located at the α-carbon. Extractants which had an α-carbon atom that was contained within a cyclohexyl or phenyl ring placed Y into two possible regions—Ce-Pr and Gd-Tb.

Part 1. The effective use of f-element complexes as catalysts for reactions such as hydroamination and hydrophosphination has been demonstrated in many recent reports. Unfortunately, the homoleptic starting materials underpinning this chemistry are generally derived from only a handful of ligands. That is, of the homoleptic lanthanide complexes that exist, the majority make use of alkylsilane (-CH2SiMe3), silylamide (-N(SiMe3)2), or benzyl (-CH2C6H5) derivatives. The paucity of tri-alkyl lanthanide complexes can be attributed to the required extended coordination sphere and high Lewis acidity or electrophilicity of these metals. While these properties make lanthanum alkyl complexes very reactive, in turn they also make their synthesis and manipulation quite challenging. Our efforts have focused on the development of unexplored homoleptic tri-alkyl rare-earth metal complexes utilizing simple ligands that fulfill both the electronic and steric requirements of these metal centers. Herein, we report our findings of a new class of homoleptic tri-alkyl rare-earth metal complexes using alpha-metallated N,N-dimethylbenzylamine ligands as stable benzyl ligand derivatives to form lanthanide complexes free of coordinating solvent.We have also expanded the reactivity scope of these homoleptic lanthanide complexes to include stoichiometric insertion and catalytic hydrophosphination reactions involving heterocumulenes. The tris alpha-metallated N,N-dimethylbenzylamine lanthanum and yttrium complexes [¿¿-La(DMBA)3, ¿¿-Y(DMBA)3] have proven to be capable starting materials that undergo triple insertion reactions with a variety of carbodiimide ligands. In addition ¿¿-La(DMBA)3 demonstrated excellent catalytic activity for the room temperature hydrophosphination of a wide array of heterocumulenes. Part 2. Another current focus of the Schmidt group involves development of a class of lower rim functionalized calix[4]arenes containing ligands that have been previously shown to selectively separate lanthanides. These calix[4]arenes will be attached to a solid support through an alkyl linker at the methylene position and separation will be based primarily on the ionic radius of the metal cation. In summary, we report the synthesis and derivatization of a series of 2-(¿¿-(alkyl))tetramethoxy-p-tert butylcalix[4]arenes. These calix[4]arenes represent intermediates in a multi-step synthesis for the design of lower rim modified calix[4]arenes that will be evaluated for the separation of lanthanide ions with the future goal of attachment to a solid support.

The separation of americium from curium in spent nuclear fuel (SNF) has important implications for spent nuclear fuel reprocessing. Removal of curium from SNF reduces the heat load in newly refabricated fuel elements and minimizes the buildup of heavier actinides (Cf-252) caused by repeated recycle of curium in reactors. Unfortunately, this separation has historically been difficult to accomplish due to their similar chemistries without resorting to chromatographic or precipitation techniques. However, a size-based approach to separating these two elements has been proposed that could easily be incorporated into solvent extraction-based separations schemes like the TALSPEAK process. In this approach, the formation of aqueous-phase ternary complexes (i.e., complexes of a metal with a large primary and smaller secondary ligand) with Am(III) - but not with Cm(III) - would increase the thermodynamic stability of Am(III) relative to Cm(III), making Am(III) less extractable. As there are few reports of ternary complexes in the literature, the objective of this work was to investigate the factors that influence their formation. Factors such as ligand size, basicity, and steric constraints influence whether or not ternary complexes form and how strong such complexes will be. Spectroscopic, calorimetric, and thermometric techniques were used to investigate how these factors affect the formation of ternary complexes containing a large polyaminocarboxylate and a smaller dicarboxylate ligand bound to americium, neodymium, samarium, holmium, terbium, or erbium. Results from investigations with diethylenetriamine-N,N,N',N',N"-pentaacetic acid (DTPA), which is the octadentate ligand used in the TALSPEAK process, and lactate as the secondary ligand indicated that inner sphere complexes were not formed under the conditions used because the DTPA ligand is too large to accommodate lactate. Outer-sphere ternary complexes may form but they were estimated to be too weak to significantly affect the TALSPEAK extraction thermodynamics. Ternary complexes were readily formed with the septadentate DO3A (1,4,7,10-tetraazacyclododecane-1,4,7-triacetic acid) and hexadentate CDTA (trans-1,2-diaminocyclohexanetetraacetic acid) ligands, whose binary complexes (e.g., Ln(CDTA)-) have at least one residual water of hydration that can be displaced by a small secondary ligand. The results of thermodynamic investigations of Ln(CDTA)- complexes with the secondary ligands oxalate, malonate, and iminodiacetate revealed that the strength of the ternary complexes with CDTA generally increased with decreasing ionic radius when steric hindrance was minimal, indicating that the bonding with these ligands was primarily ionic. In addition, secondary ligands that formed five-membered ring complexes were more stable than those that formed six-membered rings, and more basic ligands formed stronger complexes. Similar ternary complexes with DO3A showed little increase in thermodynamic stability compared to analogous CDTA complexes, which is likely due to increased steric hindrance in the DO3A complexes.

The major topics discussed are the phosphorescence sensitization in the lanthanides via energy transfer and in the organics by heavy atom effects. The f-f transitions in lanthanides are parity forbidden and have weak molar extinction coefficients. Upon complexation with the ligand, ttrpy (4'-p-Tolyl-[2,2':6',2"]-terpyridine) the absorption takes place through the ligand and the excitation is transferred to the lanthanides, which in turn emit. This process is known as "sensitized luminescence." Bright red emission from europium and bright green emission from terbium complexes were observed. There is ongoing work on the making of OLEDs with neutral complexes of lanthanide hexafluoroacetyl acetonate/ttrpy, studied in this dissertation. Attempts to observe analogous energy transfer from the inorganic donor complexes of Au(I) thiocyanates were unsuccessful due to poor overlap of the emissions of these systems with the absorptions of Eu(III) and Tb(III). Photophysics of silver-aromatic complexes deals with the enhancement of phosphorescence in the aromatics. The heavy atom effect of the silver is responsible for this enhancement in phosphorescence. Aromatics such as naphthalene, perylene, anthracene and pyrene were involved in this study. Stern Volmer plots were studied by performing the quenching studies. The quenchers employed were both heavy metals such as silver and thallium and lighter metal like potassium. Dynamic quenching as the predominant phenomenon was noticed.