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Kinetic studies are described for the activation of carbon monoxide, molecular hydrogen, and molecular oxygen by rhodium halide complexes in solution. Carbon monoxide reacts with bromorhodate(III) and bromocarbon-ylrhodate(III) complexes to produce the anionic species, [Rh(C0)2Br2]⁻. The reaction of [RhBr4(H2O)2]²⁻ in acid bromide solutions involves initial formation of a RhIII(C0) substitution product, which then undergoes reductive carbonylation: [Eqn 1 and 2] Further production of RhI is autocatalytic due to a more effective reduction via a CO independent path that involves a [RhIII…Br…RhI(CO)2I] bridged intermediate. Reductive carbonylation of the pentabromocarbonyl-rhodate(III) complex in aqueous HBr solution proceeds in a similar manner. Decomposition of RhIIICO) by water to produce Rh1 species (equations 1 and 2) results in the autocatalytic formation of [Rh(C0)2Br2]⁻ through a step that again involves a bromide-bridged intermediate, [(CO)RhIII…Br ---RhI(C0)2] . Carbon monoxide can be catalytically activated by rhodium(III) for the reduction of substrates such as ferric ion. Kinetic studies sug-gest a mechanism involving reduction of [Rh(C0)Br5]²⁻ by water. Data are consistent with the following scheme: [Eqn 3] Acid solutions of RhBr3•2H20 activate H2 for the reduction of FeIII . Formation of a metal hydride in the rate-determining step appears to involve substitution by an associative mechanism: [Eqn 4] Activation parameters for the reaction of [RhBr4(H20)2]⁻ with H2 are similar to those found for the corresponding reaction with CO (equation 1). The reaction of [Rh(C0)2Cl2]⁻ with 02 in 3M HC1 initiallyforms [RhIII(C0)C151]²⁻ by a path thought to involve formation of an oxygen complex: [Eqn 5] The observed kinetics indicate that further RhIII(CO) is autocatalytically produced according to the following sequence: [Eqn 6, 7, 8] Subsequent slower reaction to give chlororhodate(III) species 2-occurs via slow hydration of [Rh(C0)Cl5]²⁻. [Eqn 9,10] Studies on the oxidation of [Rh(CO)2C12]⁻ in LiCl/DMA by molecular 02 suggest the involvement of hydroperoxide free radicals for the production of RhII. Evidence for a carbonato intermediate formed during the oxidation process has been obtained. The RhII solutions were found to contain active, though inefficient, catalysts for the autoxida-tion of DMA. The presence of RhII - 02 has been detected by esr, and the superoxide species may be responsible for the autoxidation reaction. A paramagnetic chloride-bridged rhodium(II) anion [Rh0Clc(DMA)2]²⁻ was isolated from the oxygenated DMA solutions of [Rh(C0)2Cl2]⁻ containing excess chloride. / Science, Faculty of / Chemistry, Department of / Graduate

Kyle Heller, for the Master of Science degree in Mechanical Engineering, presented on October 2020, at Southern Illinois University Carbondale.MAJOR PROFESSOR: Dr. Kanchan Mondal Using powder X-ray diffraction, a material can have its crystalline structure identified. Powder X-ray diffraction alone is not enough if a material is unknown. Usually the exact chemical formula of the material is known, or a secondary analytical method is used to extract additional data in order to analyze the crystalline structure using Bragg’s law and the interplanar relationships. Secondary analytical methods are not as easy or inexpensive though. Generic values could be placed into the more basic structure types to obtain a rough idea of potential crystal types including space groups for the material based on its diffraction peaks. However, with a material that has an unknown spacing between its atoms (d-spacing) this is harder to implement. Thus, the use of a secondary software was employed to further analyze the possibilities. In this thesis, the software used for data extraction and refining were Expo 2014 and CrystalMaker X paired with CrystalDiffract and the final visualization was achieved using Endeavor. Two different titanium based organic inorganic halide perovskites (Dye 3 and Dye 4) prepared at different temperatures were evaluated to identify the crystallographic structure using only x-ray data available. The crystal parameters were calculated, and potential unit cells were visualized. Both the materials were found to be 4 (ABX3) type perovskites. The organic component for Dye 3 was methyl ammonium ion and that of Dye 4 was formamidinium ion. These perovskites have shown potential for use as sensitizers in visible light photovoltaic cells. It was concluded that Dye 4 was orthorhombic with a space grouping of C m c a (space group 64). The associated values were a = b =7.94 Å and c =11.55 Å. Dye 3 was also found to be orthorhombic with space grouping of P c c n (space group 56) being a better fit than C m c a. The associated values were a=b=16 Å and c=11 Å.

Over the last decade, impressive development in lead halide perovskites (LHPs) have made them leading candidate materials for photovoltaics (PVs), X-ray scintillators, and light-emitting diodes (LEDs). The success of LHPs NCs in lighting and display applications is mainly originated from their high photoluminescence quantum yield (PLQY), narrow emission, sizable bandgap, and cost-effective fabrication. Consequently, a comprehensive understanding of the design principles of LHP NCs will fuel further innovations in their optoelectronic applications. This dissertation centers on the synthesis and self-assembly of LHP NCs. At first, we investigate the capability of colloidal synthetic routine to engineer the shape, size, and dimensionality of the resulting LHPs NCs (chapter 2), including 0D nanospheres, 2D nanoplates, and 3D nanocubes. Starting from the LHPs NCs, nanoplates (chapter 3), nanowires (chapter 4), and superstructures (chapter 5) are successfully achieved via various self-assembly strategies. In chapter 3, we present a liquid-air interfaces-assisted self-assembly technique to obtain micro-scale CsPbBr3 nanoplates from as-synthesized nanoscale NCs. The AC-HRTEM offered an atomic-level observation during the structural evolution and revealed an oriented attachment-mediated assembly mechanism. The assembled CsPbBr3 nanoplates exhibited ultrahigh stability under X-ray energy dispersive spectroscopy (EDS) mapping conditions (300-kV electron beam), and the first atomic-resolution EDS elemental mapping data of LHP NCs were acquired. In chapter 4, we demonstrate an efficient green-chemistry approach for the self-assembly of CsPbBr3 NCs into 1D nanowires and nanobelts via the light induction. As an elegant and promising green-chemistry approach, light-induced self-assembly represents a rational method for designing perovskites. In chapter 5, we will explore the self-assembly of CsPbBr3 NCs into superstructures to overcome the ‘green gap’ to achieve a pure green emission with high PLQY for realizing next-generation vivid displays. In summary, we systematically investigated the mechanisms of LHP NC self-assembly, the kinetics of their morphological evolution and phase transitions, and driving forces that govern the self-assembly process. The assembled LHP NCs manifest desirable properties (e.g., superfluorescence, improved photoluminescence lifetime, enhanced stability against moisture, light, electron-beam irradiation, and thermal-degradation) that translate into dramatic improvements in device performance.

The infrared spectra of gaseous oxalyl fluoride, oxalyl chloride, and oxalyl chloride fluoride, and the Raman spectra of liquid oxalyl fluoride and liquid oxalyl chloride have been measured. A satisfactory analysis of these spectra has been obtained for all three molecules on the basis of the trans isomer. An I.B.M. 7040 digital computer has been programmed to calculate the fundamental frequencies, normal coordinates, Urey-Bradley force constants, and potential energy distributions in Urey-Bradley space. The two electronic band systems of oxalyl fluoride whose origins are located at 3082 Å and 3340 Å have been photographed in absorption under low resolution. These band systems have been assigned ¹Aᵤ←¹A_g and ³Aᵤ←¹A_g transitions respectively, and have been partially analyzed in terms of the vibrational energy levels associated with the combining electronic states. / Thesis / Doctor of Philosophy (PhD)

Semiconducting materials have emerged as the cornerstone of modern electronics owing to their extensive device applications. There is a continuous quest to find cost-effective and low-temperature compatible materials for future electronics. The recent reemergence of solution processable halide perovskites have taken the optoelectronics research to new paradigms. Apart from photovoltaics, the versatile characteristics of halide perovskites have resulted in a multitude of applications. This dissertation focuses on various properties and emerging applications particularly, photodetection and thermoelectrics of both hybrid and all-inorganic halide perovskites. It is important to understand the underlying properties of perovskites to further develop this class of materials. One of the major hurdles restricting the practical devices of perovskites is their sensitivity to moisture. A systematic investigation on the effect of humidity on hybrid perovskites revealed different degree of moisture uptake behaviour for micropatterns, films, and single crystals. Degradation pathways and processing limitations of hybrid perovskites are discussed which will aid in designing strategies to overcome these impediments for future large scale device integration. There is a recent surge of reports on doping hybrid perovskites to control its optoelectronic properties but in-depth understanding of these dopants and their ramifications remain unexplored. The effect of doping on the optoelectronic properties of hybrid perovskites is studied and a model is proposed for the observed behavior. Leveraging on the rapid growth of microcrystalline perovskite films, for the first time tunable bifacial perovskite photodetectors were fabricated, operating in both broadband and narrowband regimes. Furthermore, self-biased single crystalline photodetectors based on all-inorganic perovskite were developed with high on-off ratio and low dark current. Halide perovskites are emerging as a new class of materials for thermoelectric applications owing to their ultralow thermal conductivity and decent Seebeck coefficient. Here, halide perovskites are evaluated in terms of composition, stability, and performance tunability to understand their thermoelectric efficacy. Finally, as an alternative to Pb and Sn-based perovskites, a new hybrid was discovered with ultralow thermal conductivity and a general synthetic route to design such hybrids is proposed.

Many higher plants can synthesize methyl chloride gas via a common metabolic route, also known as the biological chloride methylation. The reaction is catalyzed by an S-adenosyl-L- methionine (AdoMet) dependent halide/thiol methyltransferase (H/TMT). It is speculated that plants use chloride methylation to remove excess chloride via volatilization and hence maintain homeostatic levels of cytoplasmic chloride ion, suggesting a role of H/TMT in salt tolerance. In this project, the effect of engineering a Brassica oleracea thiol methyltransferase (BoTMT) into tomato was studied to determine the physiological relevance of this enzyme in conferring salt tolerance. Transgenic tomato plants acquired the ability to release methyl chloride in response to NaCl treatment, but exhibited no greater tolerance to NaCl, based on several morphological and physiological measurements, as compared to the wild-type plants. The results indicate that AdoMet dependent chloride methylation is unlikely to contribute to an increase in salt tolerance in higher plants.

Many higher plants can synthesize methyl chloride gas via a common metabolic route, also known as the biological chloride methylation. The reaction is catalyzed by an S-adenosyl-L- methionine (AdoMet) dependent halide/thiol methyltransferase (H/TMT). It is speculated that plants use chloride methylation to remove excess chloride via volatilization and hence maintain homeostatic levels of cytoplasmic chloride ion, suggesting a role of H/TMT in salt tolerance. In this project, the effect of engineering a Brassica oleracea thiol methyltransferase (BoTMT) into tomato was studied to determine the physiological relevance of this enzyme in conferring salt tolerance. Transgenic tomato plants acquired the ability to release methyl chloride in response to NaCl treatment, but exhibited no greater tolerance to NaCl, based on several morphological and physiological measurements, as compared to the wild-type plants. The results indicate that AdoMet dependent chloride methylation is unlikely to contribute to an increase in salt tolerance in higher plants.

Ph.D. / The specific topic of this investigation is the crystal chemistry and thermotropic polymorphism of the inorganic mineral acid salts of the n-alkyldiamines. This series of compounds contain organic cations with a linear alkane backbone that ranges from short to long chains. As a result their properties changes according to chain length. As they are salts they have the ability to conduct current resulting in wide industrial applications, biological as well as in their use as surfactants and ionic liquids at relatively low temperatures. They also have promising properties for use as propellants, explosives and other pyrotechnic compositions. Their electrical and electronic properties are under investigation. Their ability to exhibit polymorphism has not previously been established. Polymorphism is the ability of a material to exist in more than one crystal form. Since long-chained materials are known to have flexible hydrocarbon chains, by chemical intuition it is reasonable to assume that these materials may have more than one type of molecular arrangement. Various investigations of the conformational and thermotropic polymorphism of the salts of the related n-alkylamines have previously been published in the literature but very little information is available for the polymorphism that may or may not exist in the salts of the n-alkyldiamines. This study is limited to the short and medium chain length n-alkyldiammonium halide salts; nitrate salts; sulphate and perchlorate salts where the general chemical formula for the materials under investigation is CnH2nN+H3X where n = 2 to 12 (except 11) and X = Cl-, Br-, I-, NO3 -, SO4 2- and ClO4 -. It was anticipated that within this range of materials both the hydrogen bonding interactions and the Van der Waal’s forces (as combined packing forces) will play a part in controlling the molecular packing. A large number of the materials were synthesized and their structural information was analyzed by the complimentary techniques of X-ray diffraction and thermal analysis. X-ray diffraction was used in this investigation as it is the best technique to study the crystal chemistry and the polymorphic behaviour of these materials. The results obtained from this method of analysis, the positions of atoms in the crystals, allows for the analysis of the three-dimensional packing in the crystal structure as well as the identification of the hydrogen bonding interactions. The technique of single crystal X-ray diffraction allows the determination of the crystal structures of polymorphs at specific temperatures resulting in information on the effect of change in temperature on crystal packing. Since the compounds investigated in this study were relatively easy to crystallize it was possible to obtain the large single crystals required to obtain single-crystal X-ray diffraction data, and accurate crystal structures could be obtained by this method. Out of a total of thirty-eight crystal structures compared in this investigation, sixteen were novel crystal structures and fourteen were rederminations of previously published structures deemed to be of inferior quality and not suitable for the comparative study. The remaining eight data sets were used as published. Two thermal analytical techniques, Differential Scanning Calorimetry (DSC) and Hot-Stage Microscopy (HSM), were employed to establish if thermotropic phase changes were evident in these materials. Phase transition temperatures at above ambient temperatures were determined by DSC methods while morphological and textural changes in crystals of the compounds under investigation were monitored by HSM methods. In many of the materials analyzed, multiple above ambient phases were identified and only one structure showed a unique below ambient solid-state phase transition.