The first chapter is an introduction to the f-elements, with a focus on the synthesis and chemistry of tetravalent cerium complexes. The synthesis, characterisation and reactivity of carbenes, particularly N-heterocyclic carbenes (NHCs), and anionic-functionalised NHC ligands is discussed. The synthesis and reactivity of s-block, Group three and fblock NHC complexes is reviewed. The synthesis of the alcohol-functionalised unsaturated imidazolium proligand, [H2L]I [H2L = HOCMe2CH2(1-CH{NCHCHNiPr})], is extended to saturated imidazolinium analogues, [H2LR]X, [HOCMe2CH2(1-CH{NCH2CH2NR})]X (R = iPr, abbreviated to P; R = Mes, abbreviated to M; R = Dipp, abbreviated to D, X = Cl, I). Mono-deprotonation results in the isolation of bicyclic imidazolidines HLR, which can be ring-opened and silylated by treatment with Me3SiI, to afford [HLR, OSiMe3]I, R = iPr and Mes. Further deprotonation of HLR with MN"2 (M = Mg, Zn; N" = N(SiMe3)2) affords LRMN" (M = Mg and Zn) and ZnLR 2. These complexes proved active for the polymerisation of raclactide at room temperature without the need for an initiator. The third chapter focuses on cerium chemistry. Repetition of the literature synthesis of CeIV tert-butoxide compounds affords the unsolvated Ce(OtBu)4 and also the cluster Ce3(OtBu)11. Treatment of Ce(OtBu)4 with HL did not yield a CeIV-NHC complex, but one bearing a tethered imidazolium group, (OtBu)3Ce( -OtBu)2( -HL)Ce(OtBu)3. The synthesis of a CeIII-NHC complex, CeL3, and the oxidation of this forms an unprecedented CeIV-NHC complex, CeL4, via ligand redistribution; the complex contains two bidentate ligands and two alkoxide-tethered free NHC groups. Functionalisation of the free NHCs with boranes affords the adducts Ce(L)2(L-B)2, where B = BH3 or 9-BBN (9-Borabicyclo[3.3.1]nonane). A number of cerium complexes of the saturated-backbone NHC, LR, LRCeN"2 and LR 2CeN", have been synthesised and their oxidation chemistry and reactivity investigated. The final chapter contains an NMR study of the synthesis of a series of yttrium LR adducts, LP xYN"(3-x) (x = 1, 2 or 3), and of the synthesis of uranium complexes LRUN"2, R = Mes or Dipp, including a range of small molecule reaction chemistry. The uranyl NHC complexes, UO2LR 2, R = Mes or Dipp, have also been synthesised and characterised; these possess very high frequency carbene carbon chemical shifts.

Les complexes luminescents d'ions lanthanides(III), de par leurs caractéristiques spectroscopiques, sont des alternatives intéressantes aux fluorophores organiques usuels pour des applications dans le domaine de la bioanalyse et de l'imagerie cellulaire. Les propriétés photophysiques de ces types de complexes sont notamment exploitées en tant que donneur de FRET en temps résolu permettant d'améliorer la sensibilité et la spécificité de la détection. Des développements récents ont aussi permis d'obtenir des sondes luminescentes pour le pH physiologique, pour divers analytes endogènes ou pour des compartiments cellulaires. Dans ce cadre, l'enjeu est d'obtenir des luminophores plus brillants pour une détection plus performante. Pour ceci, nous avons souhaité, par deux approches, apporter des modifications à une plateforme nonacoordinante pyridinophane présentant trois antennes pyridine et possédant trois bras acétate. D'une part, les bras complexants ont été diversifiés soit par d'autres motifs monodentes, soit par des motifs potentiellement bidentes, de manière à protéger l'ion lanthanide de la coordination de toute molécule d'eau qui limiterait l'efficacité de luminescence. La mesure des propriétés photophysiques des complexes d'europium ou de terbium a montré que l'introduction d'un bras coordinant phosphonate permettait de diminuer le degré d'hydratation des complexes, et que, par ailleurs, l'introduction d'un bras coordinant picolinate, portant la coordinance du ligand à 10, conduisait à des complexes exempts d'eau. D'autre part, il a été envisagé de modifier les chromophores pyridine de manière à rapprocher la longueur d'onde du maximum d'absorption de la fenêtre de transparence des milieux biologiques, et à augmenter le coefficient d'absorption molaire de l'édifice. Sur la base de travaux précédents, le motif chlorine a été choisi, synthétisé, et fonctionnalisé en vue de son couplage à un des noyaux pyridine du macrocycle pyridinophane. / Lanthanide luminescent complexes are, through their spectroscopic properties, interesting alternatives to organic fluorophores for bioanalyses or cell imaging. Their photophysical properties are in particular used as time-resolved FRET donors that can improve the detection sensitivity and specificity. Recent developments afforded luminescent probes for physiological pH, several endogenous ions or for cell compartments. In this context, developing brighter luminophores is a major stake for a more efficient detection. Following this goal, we envisioned two approaches in order to modify a nonacoordinated pyridinophane platform bearing three pyridine antennae and three acetate pendant arms. First, the pendant arms have been modified, either by other monodentate moieties or by potentially bidentate moieties, in order to shield the lanthanide ion from any water molecule that could limit the luminescence efficiency. Europium or terbium complexes photophysical measurements showed that the introduction of a phosphonate coordinating arm decreased the number of coordinated water molecules, and that the introduction of a picolinate arm, leading to a decacoordinated ligand, afforded a water-free complex. Second, the pyridine chromophores were targeted both in order to bring the maximum absorption wavelength closer to the biological tissue transparency window and to increase the absorption coefficient of the structure. According to previous results (Borbas group), a chlorin antenna has been chosen, synthesized, and functionalized in order to couple this antenna to the pyridinophane macrocycle.

A range of lanthanide compounds incorporating soft bridging ligands or alkoxide ligands have been synthesised and their magnetic properties investigated. These two classes of compound have shown promise as single molecule magnets but have not been widely studied; this thesis aims to expand on this area of research. Softer bridging ligands are found to slightly increase superexchange interactions between metal centres compared to harder bridging ligands. The introduction to this thesis covers the basic properties of the lanthanides, paying special attention to their chemistry with soft donor ligands and alkoxide ligands. Also included is an introduction to the field of single-molecule magnetism and the role of lanthanide complexes in the study of this behaviour. In Chapter 2, four complexes are reported: the phosphine adducts [Cp'3Ln(H2PMes)] and the phosphide-bridged trimers [(Cp'2)Ln(μ-PHMes)]3 (Ln = Er, Gd). Their structures and magnetic properties are characterised. In Chapter 3, the novel dodecametallic thiolate-bridged lanthanide macrocycles [(Cp'2Ln)3({μ-SCH2}3CMe)]4 (Ln = Dy, Y, Gd) are reported and characterised by X-ray crystallography, NMR spectroscopy and magnetometry. [(Cp'2Dy)3({μ-SCH2}3CMe)]4 is shown to be a single-molecule magnet with Ueff = 69 cm-1. In Chapter 4, the novel thiolate-bridged lanthanide dimers [Cp'2Ln(μ-SCH2{C4H7S2})]2 (Ln = Dy, Y, Gd) are reported, showing sulfur-sulfur bonding leading to ring cyclisation of the bridging ligand [MeC(CH2S)3]3-. These complexes are characterised by X-ray crystallography, NMR spectroscopy and magnetometry. Extra NMR spectroscopic studies were performed to investigate the mechanism of ring closure on the bridging ligand. [Cp'2Dy(μ-SCH2{C4H7S2})]2 is shown to be a single-molecule magnet with Ueff = 87 cm-1. In Chapter 5, four new lanthanide siloxide clusters incorporating alkali metals are reported: the trigonal bipyramidal [Dy2K3(OSiMe3)9]; the octahedral [Dy2K4(OSiMe3)10]; the bi-capped cuboid [Y4K6O6(OSiMe3)12]6-; and the [Dy3K8O3(OSiMe3)12]- 'burger' cluster. All clusters are structurally characterised by X-ray crystallography and [Dy2K4(OSiMe3)10] is magnetically characterised. The synthetic rationalisation for formation of these diverse structures is investigated.

Understanding the behaviour of actinide species is of importance when removing and processing all nuclear waste. Examples include the safe clean-up of contaminated waste ponds and aspects of the TALSPEAK (Trivalent Actinide-Lanthanide Separation by Phosphorus Reagent Extraction from Aqueous Komplexes) process. The chemistry of the ponds and the TALSPEAK process has been studied by probing the aqueous solution behaviour of Ln(III), Am(III), Cm(III) and Th(IV) ions in the presence of organic (EDTA4- (ethylenediamine tetraacetate), DTPA5- (diethylenetriamine pentaacetate) and lactate) and inorganic (CO32- (carbonate) and OH- (hydroxide)) ligands by a variety of techniques including Nuclear Magnetic Resonance (NMR), Ultra Violet-Visible (UV-Vis) and luminescence spectroscopies, as well as potentiometry. Various ternary complexes have been shown to exist, including [M(EDTA)(CO3)]3-(aq), (where M = LnIII, AmIII or CmIII) and [Th(EDTA)(CO3)2]4-(aq), which form approximately over the pH range 8 to 11, and also [M(EDTA)(lactate)]2-(aq) (where M = Ln(III) or Am(III)) and [Th(EDTA)(lactate)]-(aq), which predominantly occur over the pH range 4 to 6. The nature of lactate interaction with [M(DTPA)]2-(aq) complexes (where M = Ln(III) or Am(III)) is unclear, as it may be possible that lactate can coordinate directly to the metal ion or to the acetate groups of DTPA5- (via a H-bonding interaction). The knowledge gained in this research has given a deeper insight into the nature of lanthanide and actinide coordination chemistry in mixed-ligand environments. For example, the increasing solubility of actinide metal ions in the contaminated waste ponds is probably due to the ability of organic ligands present in the ponds to solubilise metal ions at high pH, and also under TALSPEAK conditions of pH 3.5, there is likely to be minimal interaction of lactate with the [Ln(DTPA)]2-(aq) complexes. The determination of metal ion speciation using a combination of NMR, UV-Vis and luminescence spectroscopies, coupled with potentiometry, could be applied to new characterisation challenges faced in the future of the nuclear industry.

An array of carbazole-bis(azole) (CzTR and CzTrR, Cz = carbazole, T = tetrazole, Tr = triazole, R = Me, iPr, Bz and CH2Mes) pincer ligands were synthesized and fully characterized by NMR, X-ray crystallography and high resolution mass spectrometry. The physical properties of these ligands, as well as their applications in metal coordination compounds, were extensively studied. Mono, bis- and tris-ligand lanthanide (Y, Yb, Er, Sm, and Ce) complexes were synthesized and the solid state crystal structures of these complexes revealed the unusual binding modes of these ligands. The capability of these ligands to distort from planarity and bind in a fac type fashion, as well as bidentate, rather than tridentate modes was unexpected. The reactivity of the mono-ligand lanthanide complexes was explored and showed modest activity in ring-opening polymerization of lactones, as well as some unusual one electron redox chemistry. Bis-ligand complexes of some first row transition metals (Fe, Co, Ni and Zn) were also explored. These air-stable complexes proved invaluable in studying the physical properties of the ligands themselves, as well as the metal complexes. The bis-ligand zinc complexes (CzTiPr)2Zn and (CzTriPr)2Zn showed reversible oxidation of the CzT and CzTr ligands at modest potentials, as well as ligand-based fluorescence. Two bis-ligand iron complexes were synthesised using sterically diverse ligands (CzTiPr)2Fe and (CzTCH2Mes)2Fe and while (CzTCH2Mes)2Fe showed temperature-independent paramagnetism, the similar (CzTiPr)2Fe complex showed a two-step thermally induced spin crossover phenomenon near room temperature in the solid state. The oxidation of (CzTiPr)2Fe yielded [(CzTiPr)2Fe]+ BF4-; we have speculated that this complex is initially oxidized at the ligand and then undergoes an electron transfer from the metal to the ligand to result in an Fe(III) complex. Mono-ligand iron complexes using the CzTiPr ligand were also synthesized. While ligand redistribution hindered initial progress, the use of a bulky phenoxide ancillary ligand arrested the redistribution pathway and allowed the synthesis of (CzTiPr)Fe(OAr)(THF). This iron complex proved to be the most successful in terms of isolating stable and reactive complexes with our ligands, and several adducts (THF, tBuNC, TPPO) were synthesized. Synthetic and DFT studies of these complexes demonstrated the tendency for the Fe to bind σ-donor ligands, but not π-acceptor ligands. This led to the isolation of a thermally sensitive four-coordinate iron complex (CzTiPr)Fe(OAr). The catalytic activity of these Fe phenoxide complexes in the hydrosilylation of styrene with phenylsilane was explored. These catalysts were able to selectively produce the Markovnikov hydrosilylation product with good activity. The apparent preservation of the Fe(II) oxidation state throughout the catalytic transformation suggests a possible ligand-assisted mechanism where the CzT ligand acts as a proton reservoir. / Graduate / 2021-11-23

<br> <p>The interest in understanding the <i>f</i>-block elements has been increasing because of the large applications of these elements across all fields of science and technology. The lanthanides are used in various technologies like car batteries and phone screens. The actinides are the basis of current nuclear fuel processes. The <i>f</i> -block has many interesting properties and has been proven to be fruitful in inorganic chemistry. Neodymium is redox inactive and was studied with a redox active ligand pyridine diimine to see if multielectron chemistry was viable. The neodymium chemistry is still in the preliminary stages of research, but there is possibility of fruitful reactivity. Recently neptunium chemistry was introduced to the Bart lab to study its rich redox chemistry. Neptunium’s fundamental properties have been investigated for the last 80 years with new bonding properties and behavior still being discovered today. Studies of neptunium began with investigating the trivalent oxidation state. Synthesis of new low valent trans-uranic starting materials is important because the fundamental chemistry of these trivalent compounds is not well studied. By creating Neptunium materials that are analogous to known uranium and lanthanide starting materials, <i>f</i>-block chemists will be able to apply their previously studied syntheses to a new element. </p>

Reported in Chapter 2 of this thesis is the reliable and tolerant synthesis of a small library of pyrazole and triazole heterocycles. This synthesis was achieved in two steps in good yields from the reaction of acetophenone and benzamide derivatives with dimethyl formamide-dimethyl acetal followed by a cyclization with hydrazine. Also reported is the synthesis and characterization of their corresponding scorpionate ligands. Preliminary co ordination chemistry was done with a variety of lanthanide metals and was studied by standard spectroscopic methods as well as variable temperature 1H NMR, which revealed that Curie-Weiss behaviour was followed for these complexes in solution. An X-ray crystal structure of a nine co-ordinate ytterbium metal centre with eight nitrogen atom (four pyrazole, four pyridine) donors and one chloride atom was obtained, which may have been a product of decomposition during crystal growth. The bond lengths of this structure were compared with other lanthanide complexes of similar structural motifs. This comparison supported the theory of decomposition as the pyridine nitrogen atom-ytterbium bond lengths were longer than the average ytterbium-nitrogen atom bond length. Reported in Chapter 4 of this thesis is the synthesis and partial characterization of a new organic dye named perinaphthindigo. Perinaphthindigo was synthesized with adapted iv Baeyer-Drewson reaction conditions for the synthesis of indigo which involved the treatment of 1,8-nitronaphthaldehyde with acetone under basic conditions, and was found to be an intense green colour in solution. Perinaphthindigo was produced in poor yields, so efforts were undertaken to improve the yields through an alternative two-step synthesis, first between 1,8-nitronaphthaldehyde and nitromethane in a Henry reaction followed by oxidative coupling. The synthesis of perinaphindigo was adapted so as to structurally modify the final compound, either through incorporation of solubilizing tert-butyl groups or bromine atoms for future cross-coupling chemistry. The brominated derivatives of perinaphthindigo were also synthesized in low yields so cross-coupling conditions were scanned on model precursor compounds. The brominated perinaphthindigo compounds were found to have a bathochromically shifted absorbance maximum from the parent perinaphthindigo. This bathochromic shift was more pronounced in our compounds than in the comparison of indigo and 6.6’-dibromoindigo which indicates our compounds are more sensitive to perturbation by substitution. Reported in Chapter 5 of this thesis is the study of the acid and base chemistry of Nindigo, a previously reported compound. The treatment of Nindigo with a series of strong acids led to an interesting “protoisomerization”, or trans to cis isomerization of the central olefin, with ultimate structural determination through X-ray crystallographic methods. This isomerization was studied through absorbance stopped-flow methods which identified a probable pathway of the isomerization through a neutral, cis species. The investigation of neutral Nindigo was undertaken to attempt to identify two peaks which are red-shifted from the π-to-π transition at 586 nm. These two peaks appear at 657 nm and 741 nm and are present in all solvents. The preparative acid chemistry allowed us to assign the first red shifted peak at 657 nm to the cationic species. Aggregation studies showed concentration dependent behaviour of the ratio between the peaks at 586 nm and 657 nm with little effect on the species at 741 nm. In order to probe whether an autoionization process was occurring, variable temperature NMR and UV-Vis experiments were performed which did not provide a definitive answer to the species at 741 nm. / Graduate

No description available.

The research described in this Dissertation is concerned generally with the exploration of the potential use of lanthanide elements in nanostructured materials for the purpose of modification of the magnetic and optical properties. This is explored through a focus on the development of lanthanide-containing iron oxide nanosystems. Our objectives of producing lanthanide containing nanostructured materials with potentially useful optical and magnetic applications has been achieved through the development of lanthanide-doped Fe3O4 and -Fe2O3 nanoparticles, as well as a unique core-shell magnetic-upconverting nanoparticle system.Necessary background information on nanomaterials, rationale for the study of lanthanide-containing iron oxide nanosystems and context for discussion of the results obtained in each project is provided in the Introduction Chapter. The syntheses of Fe3O4 nanoparticles doped with Eu(III) and Sm(III) are discussed, along with structural characterization and magnetic property investigation of products In Chapter 2. The following Chapter expands the study of lanthanide doping to -Fe2O3, a closely related yet distinct magnetic nanoparticle system. A completely different synthesis is attempted, and comparisons between the two systems are made.The development of novel synthetic methodologies used to create such products has yielded high-quality lanthanide-containing materials and are evidenced by TEM images displaying nearly monodisperse particles in each of our efforts. The modifications to the magnetic properties resulting from lanthanide doping include theobservation of ferromagnetism in the Fe3O4 system and increased magnetic saturation of -Fe2O3 nanoparticles, and are characterized by VSM and the visual observation of magnetic alignment of products. Our efforts towards developing a novel methodology capable of producing high quality Fe3O4 nanoparticles, and subsequent characterization of products, were published in the Journal of the American Chemical Society.Optically active, magnetic, core-shell nanoparticles are investigated in Chapter 4 for the potential uses in diagnosis and treatment of cancer. This multifunctional system uses Fe3O4 as a magnetic core, shelled by upconverting lanthanide-containing nanomaterials, and is rendered biocompatible through encapsulation of the core-shell structure by a silica shell. Added functionality is achieved through amine functionalization of the silica surface, with the goal of coupling the inorganic nanoparticle with drug targeting groups. TEM results indicate successful formation of the core-shell nanoparticles, and expected magnetic and optical properties are shown by visual observation and luminescence spectroscopy, respectively.

The research summarized in this dissertation is aimed at the design and exploratory synthesis, characterization, and property investigation of lanthanide-based functional materials. The substances prepared in this work, including small molecular complexes and nanostructured particles, are of fundamental scientific interest as well as practical significance due to the unique chemical and physical properties of the lanthanide elements. Envisioned applications include their uses as light-emitting materials in modern display technology, optical amplifiers, and high-density magnetic recording media. This research seeks to develop general methods for directing the formation of lanthanide materials, particularly as a means of influencing the physical properties of such materials. These efforts are elaborated in distinct yet related projects.In Chapter 2, exploratory synthesis, structural characterization, and photo-physical investigation of adducts of lanthanide &amp;#946;-diketonates with a tridentate neutral ligand, TPTZ are described.In Chapter 3, analogous studies utilizing p,p'-disubstituted bipyridine and phenathroline type bidentate neutral ligands are detailed. The structures of the complexes have been established by single crystal X-ray diffraction. Compositional and structural differences among the various complexes are caused by different structural and electronic properties of the ligands and overall steric compactness of the coordination sphere. Red and green luminescence characteristics of Eu(III) and Tb(III) ions are observed for the corresponding complexes, upon UV excitation, consistent with the well-established ligand-mediated energy transfer and light emission mechanism.In Chapter 4, the electroluminescence properties of various europium complexes are evaluated for their potential as emissive materials in organic light-emitting diodes.The synthesis and characterization of Er-doped LaPO4 nanoparticles are described in Chapter 5 together with the preparation and studies of hybrid nanocomposites composed of nanoparticle-doped sol-gels. A single-mode waveguide system was fabricated, wherein Er-doped nanoparticles solubilized in a sol-gel matrix has shown promising performance in propagating light signals (1.54 µm) without significant optical losses.In Chapter 6, synthesis, electron microscopic characterization and magnetic studies of crystalline Sm(III)- and Eu(III)-doped Fe3O4 nanoparticles are detailed. Magnetic studies suggest the ferromagnetic behavior of the lanthanide-doped Fe3O4 nanoparticles at room temperature and therefore, the significant effects of lanthanide doping.