The synthesis of a variety of new lanthanoid phosphine complexes has been achieved by complexing either one or two amido-diphosphine ligands to yttrium, lutetium or lanthanum. At room temperature, the seven-coordinate bis(amido- diphosphine) complexes, MCl[N(SiMe₂CH₂PR₂)₂]₂- are fluxional and display NMR spectra indicative of complexes where the phosphorus donors are rapidly exchanging, probably via a dissociation-reassociation pathway. It is possible to generate thermally unstable hydrocarbyl complexes of the type, M(R)[N(SiMe₂CH₂PMe₂)₂]₂, which undergo a clean first order elimination of R-H to generate cyclometallated complexes of the type, M[N(SiMe₂CHPMe₂)(SiMe₂CH₂PMe₂)][N(SiMe₂CH₂PMe₂)₂]; the yttrium derivative was crystallographically characterized. These thermally robust compounds will undergo a-bond metathesis with H₂ and D₂ at high temperature, but appear to be too sterically congested to react with larger molecules. The synthesis of a series of mono(amido-diphosphine) lanthanoid complexes, MCl₂ [N(SiMe₂CH₂PR₂)₂], (R = Me, Ph, Pr', Bu[symbol omitted]) has also been achieved. Complexes of the type, MCl₂[N(SiMe₂CH₂PMe₂)₂], are insoluble in hydrocarbon solvents, presumably because they are oligomeric in nature. They will however, dissolve in THF probably forming seven-coordinate bis(THF) monomers. Attempts to alkylate these compounds generally led to decomposition; the cyclometallated bis(ligand) complex, M[N(SiMe₂CHPMe₂)(SiMe₂CH₂PMe₂)] [N(SiMe2CH2PMe2)2], was identified as the major product. A route to a dimeric mono(amido-diphosphine) allyl complex, {YCl(allyl)[N(SiMe₂CH₂PMe₂)₂]}₂ (characterized by crystallography) was found via the reaction of allyl-MgCl or Mg(allyl)₂(dioxane) with YCl[N(SiMe₂CH₂PMe₂)₂]₂. The mono(ligand) complexes containing bulky phosphine donors (R = Ph, Bu[symbol omitted], Pr[symbol omitted]) are soluble in hydrocarbon solvents; YCl₂[N(SiMe₂CH₂PPr[symbol omitted]₂)₂] can be isolated as either a THF adduct or as the base-free dimer. A new reaction, mediated by a zirconium or hafnium amido-diphosphine complex, where allyl and butadiene moieties are coupled together to generate a coordinated [ɳ⁴:ɳ¹-CH₂=CHCH=CHCH₂CH₂CH₂]¹- fragment has been investigated. The process is very sensitive to the nature of the ancillary ligands at the metal. For MCl(ɳ⁴-C₄H₆)[N(SiMe₂CH₂PR₂)₂] complexes, after the addition of allylMgCl, the transformation takes about one hour when M = Hf & R = Pr[symbol omitted], two hours when M = Zr & R = Pr[symbol omitted], a week when M = Hf & R = Me, and results only in decomposition when M = Zr & R = Me. Similarly, for the zirconium mediated coupling of 1-methylallyl with butadiene, when R = Me, decomposition occurs and when R = Pr[symbol omitted], after two hours the coupling is complete. Two of the four possible coupled products are formed in unequal amounts, and the coupling occurs exclusively at the substituted end of the 1-methylallyl unit as determined by X-ray crystallography. Which diastereomer is formed in excess was not determined. The reduction of ZrCl₃[N(SiMe₂CH₂PR₂)₂] (R = Pr[symbol omitted] or Bu[symbol omitted]) with Na/Hg amalgam under nitrogen results in the formation of a binuclear zirconium dinitrogen complex, {ZrCl[N(SiMe₂CH₂PR₂)₂]}₂ (μ-ɳ²:ɳ²-N₂). X-ray crystallography (for R = Pr[symbol omitted]) reveals that the N₂ ligand is symmetrically bound in a side-on fashion to both metals. In addition, the N—N bond length of 1.548 (7) Å, the longest bond length ever reported for a dinitrogen complex, indicates that the dinitrogen has been reduced to a N₂⁴⁻ hydrazido ligand. Protonation of the complex with HCl results in a quantitative formation of hydrazine. / Science, Faculty of / Chemistry, Department of / Graduate

The absolute transition probabilities between the 3p⁵4s and 3p⁵4p configurations of neutral argon have been measured in a three part experiment. In the first experiment, a technique of absorption spectroscopy was used to obtain relative transition probabilities for spectral lines with a common lower level. Secondly, relative transition probabilities were obtained for spectral lines with a common upper level by measuring the relative intensities of suitable pairs of lines in an emission experiment. In the third experiment, the relative values were converted to absolute transition probabilities by obtaining the lifetime of the P₁-S2 transition at ʎ7503Å. The experimental techniques used in this experiment were developed by Robinson (1966) and van Andel (1966). / Science, Faculty of / Physics and Astronomy, Department of / Graduate

The columnar to equiaxed transition has been studied experimentally using accurate temperature measurements and with a heat transfer mathematical model in Pb-1.5%Sn and Sn-10%Pb alloys. The behaviour of the two alloys was markedly different. In the Pb-1.5%Sn alloy, the transition did not occur until a large portion of the liquid thermally supercooled. At this point the temperature gradient in the liquid is very low, approximately O℃/mm. For Sn-10%Pb, the transition occurred at a positive temperature gradient of approximately 0.12℃/mm which confirms earlier work by Mahapatra and Weinberg. Supercooling was also found to occur in this alloy but it is not certain whether the supercooling is constitutional or thermal. The difference in the behaviour of the two alloys is related to the density of nuclei prior to directional solidification. Altering the method to release latent heat by using the Scheil equation or the Lever rule instead of the traditional linear assumption in the mathematical model did not have a significant effect on the predicted temperatures or temperature gradients in the Pb-1.5%Sn alloy. The effect was seen when the Sn-10%Pb alloy was considered. The difference is attributed to the total amount of latent heat to be released by a particular alloy. / Applied Science, Faculty of / Materials Engineering, Department of / Graduate

The reaction of sodium pyrazolide or sodium 3,5-dimethyl-pyrazolide with trimethyl gallium followed by reaction of the resultant adduct with 'ethanolamine' produces novel asymmetric tridentate ligands which are capable of either meridional or facial coordination in transition metal complexes. Na⁺('pz')⁻ + Me₃Ga THF> Na⁺[Me₃Ga ('pz’) ] ⁻ Na⁺[Me₃Ga ('pz’) ] ⁻+ R’ ₂NCH₂CH₂OH₂ > Na⁺L⁻ + MeH With R' = H, these ligands react with divalent transition metal ions to give octahedral bis-ligand complexes. However with R’ = Me, reaction with divalent transition metal ions produced either trigonal bipyramidal (R = Me) or binuclear five-coordinate (R = H) complexes. The asymmetric chelating gallate ligands reacted with Mn(CO)₅Br to give LMn(CO)₃ and with appropriate Gp VI carbonyl derivatives to give LM(CO)₃⁻ ( M = Cr, Mo, W). The carbonyl anions were found to be stereochemically non-rigid in solution and a mechanism for the fluxional process is proposed. Reaction of LM(CO)₃⁻(M = Mo, W) with various three-electron ligands gave derivatives of the form, LM(CO)₂T (T = NO, N₂Ph, C₃H₅ C₄H₇, C₇H₇, and CH₂SMe). A similar fluxional process (to that found in the carbonyl anions) was found in the complex, [Me₂Ga(pz)(OCH₂CH₂NH₂)] Mo(CO)₂(n³ -C₄H₇). In addition, the cycloheptatrienyl derivatives were found to be fluxional as a result of a rapidly rotating C₇H₇ ring. Depending on the nature of T, the LM(CO)₂T derivatives can exhibit both positional and conformational isomerism and this subject is discussed in detail. Reaction of Na⁺L⁻ (R = R'= Me) with Ni(NO)I and Cu(PPh₃)Br gave LNi(NO) and LCu(PPh₃) respectively. Both of these molecules were found to be fluxional in solution and a similar mechanism to that proposed for the Gp VI carbonyl ions is invoked to explain these fluxional processes. The compounds, LMn(NO)₂ and LFe(NO)₂ (19-electron) were prepared by reaction of Na+L- (R = R'= Me) with appropriate metal dinitrosyl precursors.and are the first of their type to be synthesized. Finally, reaction of Na+L- (R = R'= Me) with Mo(NO)₂Cl₂ gave LMo(NO)₂Cl. In additon to studies involving the ligand L, the pyrazolyl bridged dimers [Ni('pz’)(NO)]₂, [Fe('pz')(NO)₂]₂ and [Co('pz')(NO)₂]₂ were prepared and their reactivity towards nucleophiles studied. The π-allyl compounds [Me₂Ga (pz" )₂]M (C₃H₅) (M = Ni or Pd) and [Ni (pz") (C₃H₅) ]"₂were also prepared. All the prepared compounds were systematically characterized with uv-vis, ir and XH nmr spectroscopy as well as mass spectrometry. In addition, x-ray studies were carried out (by Dr. S. Rettig) on several of the prepared compounds and these data are correlated with other physical measurements. / Science, Faculty of / Chemistry, Department of / Graduate

The aim of this studie is to explain possible factors that drive people to de-transition. The data was collected by observation of selfposted vidoes on youtube, where young women who are in the process of realizing a de-transition discuss reasons they think made them de-transist. The result produced by the inductive analysis show that the young women de-transit because of an insight that initial transition was not the correct path for them. Furthermore the results suggest that theres a risk that young people with general depressive symptoms, might wrongfully interpret these symptoms as gender dysphoria. This interpretation might be produced  and exist on the internet and might be socialy contagius. Further research on the topic is needed to ensure that young people who experience gender dysphoria gets the right healthcare.

The electronic and vibrational spectra of liquid chromium pentafluoride have been investigated. They were found to be consistent with a d1 system that is extensively fluorine-bridged at room temperature. The vibrational spectra were not consistent with C4v or D3h monomers.

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The perovskite solar cells have attracted much attention recently due to their low fabrication cost and high power conversion efficiency. However, the instability of such devices remained a serious challenge, which is yet to be resolved despite many attempts. In this thesis, the moisture degradation mechanism has been uncovered. It was found that the perovskite structure can be reconstructed when annealed at around 90℃, which leads to a reversible device of a much higher device lifetime. Following the experimental explorations, modelling work has also been conducted to simulate the water diffusion during the degradation and recovery. It was found that the moisture diffusion was initiated at the surface imperfection, where the activation energy for diffusion can be reduced. Based on these discoveries, a fresh structural negotiation method has been proposed to obtain a stable FAPbI3 phase of a suitable bandgap for photovoltaics, which showed a reduced Gibbs free energy of 0.12eV compared with the δ phase. In addition, the activation energy for such phase transition was calculated to be 0.45eV, meaning that the discovered phase is protected by both thermodynamics and kinetics. All this opens an unprecedented avenue in perovskite research, which will hopefully be of intrinsic interest to the broad materials research community as well. / Thesis / Doctor of Philosophy (PhD)