MSc (Chemistry) / Department of Chemistry / Surface water is used for domestic and agricultural activities in Musina region and other surrounding areas. This is because of the shortage of potable water. As a result, the people living in the region and its surrounding areas are potentially exposed to hazardous contaminants that may be present in the surface water. It is therefore important to ascertain the quality of the surface water in the region. Surface water samples were collected from Mutale, Nwanedi, Tshipise and Nzhelele rivers. The samples were analysed for anions such as fluoride (F-), chloride (Cl-), nitrate (NO3-), phosphate (PO43-), sulphate (SO42-); cations such as aluminium (Al), calcium (Ca), iron (Fe), potassium (K), magnesium (Mg), sodium (Na) and trace metals such as lithium (Li), vanadium (V), chromium (Cr), cobalt (Co), nickel (Ni), copper (Cu), zinc (Zn), arsenic (As), molybdenum (Mo), cadmium (Cd), thallium (Tl) and lead (Pb) by using analytical techniques such as IC, ICP-OES and ICP-MS. The same samples were also investigated for other parameters such as pH, temperature, EC, TH, TDS, Na % and SAR. The WHO (2008), SANS 241 (2006) and Canadian guideline (2017) were used as a water quality guideline for drinking purposes. Higher concentrations of Li, V, Cr, Ni, Cu, Zn, Al, Ca, Mg, K and Na in river water were detected in rainy season, whereas higher concentrations of As, Mo, K and Fe were recorded in dry season. The concentration of F-, Cd, Tl and Pb showed low contamination level in river samples. The results demonstrated that Tshipise river water was contaminated with high concentration of parameters: TDS (1864.0.8-3372.8 mg L-1), EC (2960.3-5270 mS cm-1), F- (6.403-8.419 mg L-1), SO42- (289.657-326.598 mg L-1), Na (836.690-922.810 mg L-1) and As (10.017-11.267 μg L-1) and relative to the (WHO) water guidelines. Nwanedi river also showed higher values of EC (298.0-699.0) mS cm-1 and TDS (190.3-447.5) mg L-1. In this study, the results indicated that water from Tshipise and Nwanedi river is not suitable for human consumption based on the guidelines of drinking water. The results also indicated that the soil sample had abundance of Ca, Al, Mn and Fe with concentration ranging from 0.13-10595, 0.0084-4.16, 0.0455-1116.5, 2.4-287404 mg Kg-1 respectively. / NRF

This work deals with the structural analysis of layered zirconium sulfophenylphosphonates and their intercalates with the use of the classical molecular simulation methods. The inner composition of both fully and partially sulfonated layers was determined in agreement with available experimental data, especially chemical analysis, thermogravimetric measurements and X-ray diffraction. The calculations revealed the positions of the water molecules in the planes of sulfo groups which strongly affect the resultant diffraction pattern. Within the zirconium sulfophenylphosphonate layered structure, the arrangements of intercalated species based on optically active dipyridylamine molecules and cations of sodium, copper and iron were solved with the respect to the agreement with experimental results and values of potential energy. In case of the dipyridylamine molecules and its derivatives, the resultant disordered partially row arrangements of the organic molecules in the interlayer were showed to influence the dipole moment of the intercalate. From this point of view, nitro-derivative has been picked out as the most suitable for potential applications. Regarding the intercalated cations, sodium cations take up the space of water molecules next to the sulfo groups while copper and iron cations are distributed in a...

No description available.

4 Title: Reactions of astrophysically important positive ions with molecules and atoms at low temperatures Author: Serhiy Rednyk Department: Department of Surface and Plasma Science Supervisor of the doctoral thesis: prof. RNDr. Juraj Glosík, DrSc, Ph.D., Department of Surface and Plasma Science Abstract: In the present work, the results of the experimental study of reactions of ions with atomic and molecular hydrogen are presented. Experiments were performed using a cold radiofrequency 22-pole ion trap apparatus in the temperature range, relevant for interstellar clouds (from 300 down to 15 K). The present study is devoted to experimental investigation of the reactions of NH+, NH2 + and NH3 + ions with H2. The reaction of NH+ with H2 has two channels, which lead to NH2 + (about 97 %) and H3 + (3 %) formation with nearly constant reaction rate coefficients. The reaction of NH2 + + H2 produces only NH3 + ions and the measured reaction rate coefficient is decreasing with increasing temperature from 6∙10−10 cm3 s−1 to 2∙10−10 cm3 s−1 . The measured reaction rate coefficient of NH3 + with H2, producing NH4 +, is increasing with decreasing temperature from 80 K down to 15 K, confirming predicted mechanism of tunneling through a potential barrier. Reaction of NH+ + H was studied using a combination of the 22-pole...

The synthesis of a rigid 4,5-bis(triphenylphosphinimino)-2,7-di-tert-butyl-9,9-dimethylxanthene (Ph3PN)2XT (1) ligand is outlined, along with a modified synthesis for previously reported 1,8-bis(triphenylphosphinimino)naphthalene (Ph3PN)2NAP (3). Reaction of neutral (Ph3PN)2XT with [Y(CH2SiMe3)3(THF)2] resulted in double cyclometallation, yielding the base-free monoalkyl complex, [({Ph2(C6H4)PN}2XT)Y(CH2SiMe3)] (2). Layering a concentrated THF solution of 2 with hexanes at −28 °C afforded THF-coordinated [({Ph2(C6H4)PN}2XT) Y(CH2SiMe3)(THF)]·2THF (2-THF·2THF), with a distorted pentagonal bipyramidal geometry and approximately meridional coordination of the pentadentate {Ph2(C6H4)PN}2XT dianion. Similarly, (Ph3PN)2NAP reacted with [Y(CH2SiMe3)3(THF)2] to afford a THF-coordinated monoalkyl complex, [{(Ph2(C6H4)PN)2NAP}Y(CH2SiMe3)(THF)] (4-THF). Layering a DME solution of 4-THF with hexanes at −28 °C afforded X-ray quality crystals of [{(Ph2(C6H4)PN)2NAP}Y(CH2SiMe3)(κ2-DME)]·hexane (4-DME·hexane), with a highly distorted pentagonal bipyramidal geometry and a facial coordination mode of the tetradentate {Ph2(C6H4)PN}2NAP dianion The synthesis of a rigid 4,5-bis(1,3-diisopropylimidazol-2-imine)-2,7,9,9-tetramethylacridan H(AII2) ligand (5) was achieved via a Buchwald-Hartwig cross-coupling reaction. Reaction of the proligand H(AII2) with [M(CH2SiMe3)3(THF)2] (M = Y(6), Sc(8)) yielded the base free dialkyl complexes [(AII2)Y(CH2SiMe3)2] (6) and [(AII2)Sc(CH2SiMe3)2] (8). The reaction of 6 with one equivalent of [CPh3][B(C6F5)4] yielded [(AII2)Y(CH2SiMe3)][B(C6F5)4] (7) in-situ. Complex 7 proved to be a potent intramolecular hydroamination catalyst for a variety of aminoalkane substrates. The attempted synthesis of 4,5-bis(1,3-diisopropylimidazol-2-imine)-2,7-di-tert-butyl-9,9-dimethylxanthene (XII2) via the Staudinger reaction resulted in the isolation of the triazene intermediate 4,5-bis(1,3-diisopropylimidazol-2-yliedene{triazene})-2,7-di-tert-butyl-9,9-dimethylxanthene XIA2 (9). Reaction of XIA2 with one equivalent of [Y(CH2SiMe3)3(THF)2] led to the isolation of [(XIA2)Y(CH2SiMe3)3] (10). Synthesis of XII2 (11) was achieved via a Buchwald-Hartwig cross-coupling reaction. Reaction of XII2 with one equivalent of YCl3(THF)3.5 resulted in the isolation of [(XII2)YCl3] (12). In contrast, the reaction of XII2 with one equivalent of [Y(CH2SiMe3)3(THF)2] led to several unidentified products. Reaction of XII2 with 1 equivalent of [H(Et2O)2][B(C6F5)4] led to the isolation of the precursor [H(XII)2][B(C6F5)4] (13). The reaction of 13 with 1.1 equivalents of [M(CH2SiMe3)3(THF)2] (M = {Y(14), Sc(15)} led to the isolation of the monocationic [(XII)2M(CH2SiMe3)2][B(C6F5)4] complexes. The reaction of [(XII)2Sc(CH2SiMe3)2][B(C6F5)4] with 1.1 equivalents of B(C6F5)3 led to the abstraction of a methyl anion from the silicon center, with concomitant migration of the remaining alkyl group to the positively charged silicon, forming a new CH2SiMe2CH2SiMe3 alkyl group. This process is accompanied by MeB(C6F5)3 anion formation, forming a contact ion pair to afford the dicationic species [(XII)2Sc(CH2SiMe3)][MeB(C6F5)3][B(C6F5)4] 16. In contrast, the reaction of 15 with 1.3 equivalents of [CPh3][B(C6F5)4] in the presence of 5 equivalents of toluene resulted in the synthesis of [(XII)2Sc(CH2SiMe3)(ɳx-toluene)][B(C6F5)4]2 17 in-situ. Complex 17 is a highly potent ethylene polymerization catalyst with an activity of 868 kg/mol·atm·h. The reaction of 15 with [HNMe2Ph][B(C6F5)4] led to the cyclometallation of the resulting NMe2Ph byproduct to yield [(XII2)Sc(C6H4NMe2)][B(C6F5)4]2 (18) in-situ. The synthesis of a rigid, asymmetric 4-(1,3-diisopropylimidazol-2-imine)-5-(2,6-diisopropylanilido)- 2,7-di-tert-butyl-9,9-dimethylxanthene XAI (19) ligand was achieved by a two step Buchwald-Hartwig cross-coupling reaction with initial cross coupling of 1,3-diisopropylimidazol-2-imine followed by the cross-coupling of 2,6-diisoproylaniline. The reaction of XAI with 1.1 equivalents of [Y(CH2SiMe3)3(THF)2] yielded [(XAI)Y(CH2SiMe3)2] (20). Subsequent reaction of [(XAI)Y(CH2SiMe3)2] with 1 equivalent of [CPh3][B(C6F5)4] in the presence of 10 equivalents of toluene resulted in the synthesis of the toluene coordinated [(XAI)Y(CH2SiMe3)(ɳx-toluene)][B(C6F5)4] (21) complex. Similar to 7, complex 21 was highly active for intramolecular hydroamination of various substrates. / Dissertation / Doctor of Philosophy (PhD) / Cationic group 3 alkyl complexes are underreported in comparison to analogous group 4 complexes. The scarcity of these complexes can be attributed to their propensity to engage in undesirable reactions such as ligand redistribution and cyclometallation. To increase the thermal stability of such complexes, design features, such as carefully positioned steric bulk and ligand rigidity are beneficial. Additionally, such ligands must also have considerable donor ability, in order to stabilize inherently electron deficient cationic metal centers. This work details the synthesis of a variety of neutral and monoanionic ligands that incorporate the aforementioned design features, which were utilized in the successful synthesis of a variety of neutral, monocationic and extremely rare dicationic group 3 alkyl complexes. The cationic monoalkyl complex in this work proved to be a highly potent intramolecular hydroamination catalyst. Furthermore, a rare dicationic scandium complex was highly active for ethylene polymerization

Mass spectrometry (MS) has become a widely used technique for the characterization of a wide range of substances in diverse fields. The selection of appropriate ionization techniques, source parameters, charge carriers based on the analyte’s polarity is essential in MS as only the ions are detected. When using a soft ionization technique, single stage-MS at best provides only chemical composition; thus, tandem MS is needed to determine structural information and dissociation pathways. This dissertation focuses on the characterization of various small molecules and ions using different ionization techniques, charge carriers, and collision-induced dissociation (CID). In Chapter II, commercially available ionic liquid (IL) cations, specifically imidazolium-based IL cations with different side-chain chemistries, were characterized by CID-MS. The imidazolium-based IL cations have diverse dissociations pathways depending on the nature of the side chain (aliphatic or aromatic) or the functional groups (allyl, vinyl, alcohol, methoxy, nitro) present on the side chain. Additionally, it was observed that some IL cations undergo thermal degradation under normal operating temperatures of electrospray ~275 °C. A variety of experimental and complementary computational chemistry results are presented. In Chapter III, cis-3-hydroxyproline (c3hPro) and cis-4-hydroxyproline (c4hPro) isomers were differentiated upon lithiation using CID-MS. The CID-MS of [c4hPro+Li]+ produces three primary fragmentation pathways, namely the neutral losses of H2O, CO, and CO2; whereas CID-MS of [c3hPro+Li]+ produces only loss of CO2 in this same region. These observations may have analytical utility, and in this work, the experimental observations were explored with thermodynamic and transition state calculations to better understand the processes. In Chapter IV, the accurate mass of synthetic monomers including PAH perfluorocycloalkene monomers and their precursors were measured and reported with a publication-quality mass accuracy using atmospheric pressure chemical ionization (APCI)-MS. Additionally, the effect of solution flow rate, ionization mode, source parameters (such as vaporization temperature, dry gas temperature and dry gas flow rate, nebulizer gas pressure), acidification, and different solvent systems on APCI-MS signal intensity were studied.

No description available.

No description available.

No description available.

No description available.