A nuclear magnetic resonance study of the critical region has been made in ethane which was chosen as the working substance for its convenient critical temperature and pressure. Standard radio frequency pulse techniques were used to measure the spin-lattice relaxation time T₁ and the self diffusion constant D by the method of spin echoes. A spectrometer having good stability and very flexible timing circuits was designed and constructed. An automatic temperature control system capable of holding the sample temperature constant to better than 0.01° C for long periods of time was also designed and constructed. The spin-lattice relaxation time in ethane has been measured along the vapor pressure curve over the entire liquid temperature range as well as in the equilibrium vapor from 0° C to the critical temperature (Tc =32.32° C) and in the dense gas from Tc to 60°C. In the liquid T₁ rises rapidly with increasing temperature and goes through a maximum at about 0°C after which it begins to fall. In the vapor T₁ is always less than in the liquid and increases with increasing temperature. In the dense gas above Tc the relaxation time decreases slowly with increasing temperature. These results are compared with the conventional theory for relaxation in liquids and dense gases. The theory gives the relaxation rate 1/T₁ in terms of three relaxation mechanisms: the dipole-dipole intermolecular interaction the dipole-dipole intramolecular interaction and the spin-rotational interaction. In view of the gross approximations made in the theory a very reasonable fit to the experimental data is obtained. For the low temperature liquid the dipole-dipole interactions are sufficient to account for the relaxation. At high temperatures the spin-rotational interaction seems to contribute significantly to the relaxation and near the critical point it is the dominant relaxation mechanism. No anomalous behaviour was observed in the relaxation near the critical point and to within the error of measurement it is adequately described in terms of changes in density and self diffusion constant. T₁ was also measured in dilute ethane gas over a temperature range of 180°K to 300°K. It was observed that T₁ is proportional to density ρ and the temperature dependence of T/ρ is about T⁻¹˙³⁷. Measurements of the diffusion constant reveal that for low temperatures the product Dρ for liquid ethane varies approximately as T³. As the temperature approaches the critical temperature there appears to be anomalous behaviour in D. For both the liquid and vapor the product Dρ begins to decrease and goes through a minimum and then increases rapidly as the critical point is reached. Oxygen has been added to these samples to decrease their relaxation time and this may well be an impurity effect. Particular attention was devoted to the question of the equilibrium state in the critical region and measurements were made on the time taken to achieve equilibrium. The approach of the ratio of liquid to vapor density to its equilibrium value was found to vary in a roughly exponential manner with a time constant of the order of several hours. Sufficient time was allowed after changing the sample temperature for equilibrium to be established and all measurements of diffusion constant and spin-lattice relaxation time reported here are thought to be equilibrium values. / Science, Faculty of / Physics and Astronomy, Department of / Graduate

A new method for measuring the nuclear hexadecapole interaction (HDI) in solids based on NMR quadrupole echoes is described. Theoretical values of the shifts of the quadrupole echo times caused by the HDI are given for two pulse and three pulse echoes in a nuclear spin 5/2 system. The method is applied to 1271 in an almost strain free crystal of KI and a hexadecapole coupling frequency (e2M16m16/h) of 630 Hz was found. Here e is the electronic charge, em16 is the fourth gradient of the external electric potential at the nuclear site, eM16 is the hexadecapole moment and h is the Planck constant. This HDI is smaller than previously measured values in solids (42.6 MHz for 1 81 Ta in TaF 5, 66.6 MHz for 175Lu in Lu(NO3 )3*4H 20), but not as small as an atomic beam result of 151 Hz for 165Ho in atomic Ho. The method described here may be used to search for the HDI in other cubic crystals. A double resonance (1151n, 31P) multiple pulse method was unsuccessfully used to search for the 1151n HDI in a single crystal of InP.

Abstract In this thesis, the classic Kurland-McGarvey theory for the nuclear magnetic resonance (NMR) chemical shift is presented in a modern framework for paramagnetic systems containing one or more unpaired electrons. First-principles computations are carried out for the NMR shielding tensors in paramagnetic transition-metal complexes. A combined ab initio/density-functional theory (DFT) approach is applied to obtain the necessary electron paramagnetic resonance (EPR) property tensors, i.e., the g-tensor, zero-field splitting tensor (D) and hyperfine coupling tensors (A). In DFT, both the generalised-gradient approximation and hybrid DFT are applied to calculate A. The complete active space self-consistent field theory (CASSCF) and N-electron valence-state perturbation theory (NEVPT2) are applied to calculate the g- and D-tensors. Scalar relativistic effects are included at the second-order Douglas-Kroll-Hess level for the g- and D-tensors and, for A, at the fully relativistic four-component matrix-Dirac-Kohn-Sham level. This methodology is applied to study ¹³C and ¹H chemical shifts and shielding anisotropies in a series of Co(II) pyrazolylborate complexes, a Cr(III) quinolyl-functionalised cyclopentadienyl complex, Ni(II) acetylacetonate complexes and various metallocenes. The results obtained from these calculations are generally in a good agreement with the experimental data, in some cases, for Ni(II) complexes, allowing to correct the experimental spectral signal assignment. CASSCF/NEVPT2 computations (especially for the D-tensor) are more accurate than DFT, which is useful for the purpose of obtaining the NMR chemical shifts. The computational results obtained are dependent on the choice of molecular geometry (experimental X-ray or computationally optimised), wavefunction used for g and D (CASSCF or NEVPT2), DFT functional for A, and the quality of the basis sets. The locally dense basis method used for the CASSCF/NEVPT2 computations is less expensive and gives equally good results for g and D as fully balanced basis sets. The scalar relativistic influences are usually small for g and D, but are large for A. Due to that, scalar relativistic effects are important for the chemical shift and shielding anisotropy, especially for carbon nuclei. These first-principles computations based on combined ab initio/DFT methodology are promising for the treatment of important electron correlation and scalar relativistic effects in the calculation of pNMR chemical shifts and shielding anisotropies. This work provides a straightforward platform for further development of pNMR shielding theory in terms of first-principles wavefunctions, as well as for applications in current problems in bio- and materials sciences, including low-temperature experiments. / Original papers The original papers are not included in the electronic version of the dissertation. Vaara, J., Rouf, S. A., & Mareš, J. (2015). Magnetic Couplings in the Chemical Shift of Paramagnetic NMR. Journal of Chemical Theory and Computation, 11(10), 4840–4849. https://doi.org/10.1021/acs.jctc.5b00656 Rouf, S. A., Mareš, J., & Vaara, J. (2015). ¹H Chemical Shifts in Paramagnetic Co(II) Pyrazolylborate Complexes: A First-Principles Study. Journal of Chemical Theory and Computation, 11(4), 1683–1691. https://doi.org/10.1021/acs.jctc.5b00193 Rouf, S. A., Jakobsen, V. B., Mareš, J., Jensen, N. D., McKenzie, C. J., Vaara, J., & Nielsen, U. G. (2017). Assignment of solid-state ¹³C and ¹H NMR spectra of paramagnetic Ni(II) acetylacetonate complexes aided by first-principles computations. Solid State Nuclear Magnetic Resonance, 87, 29–37. https://doi.org/10.1016/j.ssnmr.2017.07.003 Rouf, S. A., Mareš, J., & Vaara, J. (2017). Relativistic Approximations to Paramagnetic NMR Chemical Shift and Shielding Anisotropy in Transition Metal Systems. Journal of Chemical Theory and Computation, 13(8), 3731–3745. https://doi.org/10.1021/acs.jctc.7b00168 http://jultika.oulu.fi/Record/nbnfi-fe201801031039

The hydroxyl group functionality of a series of aquatic humic and fulvic acids was examined by methylating the samples with ¹³C-enriched reagents and looking at the ¹³C NMR of the resulting methyl esters and ethers. The methylation procedure entailed methylation with ¹³C-diazomethane followed by permethylation with ¹³C-methyl iodide/sodium hydride, DMF the solvent in both steps. The ¹³C NMR of diazomethylated samples allows one to distinguish between carboxylic acid OH, phenolic OH, and phenolic OH adjacent to two substituents. The ¹³C NMR spectra of permethylated samples shows that a significant amount of the hydroxyl group functionality can be methylated only when a strong base is used. The sources of the aquatic humic substances investigated included groundwater, lake, bog, and swamp waters. The ¹³C NMR spectra of the permethylated humic and fulvic acids revealed that the total hydroxyl group pattern--carboxylic acid OH, carbohydrate OH, phenolic and aliphatic OH--was very similar among these aquatic samples despite the fact that they represented biogeochemically different sources. Practical applications of this ¹³C NMR characterization technique are briefly illustrated. These include following the chemical changes in the Spirit Lake fulvic acid following the eruption of Mt. St. Helens, analyzing the chromatographic fractionation of a groundwater fulvic acid, and analyzing the residual products after chlorination of two commercial humic acids. Side reactions of the methylation procedure were also studied. A ¹⁵N NMR investigation of the 1,3 dipolar addition of diazomethane to a soil fulvic acid led to the tentative conclusion that the cycloadduct was an N-methyl pyrazoline. Evidence is presented that carbon methylation occurs to a large extent during the CH₃I/NaH step. The derivatization of ketone and/or quinone groups with methoxylamine for the purpose of viewing these groups as the N-OCH₄ derivatives in the ¹³C NMR was also examined. Solid state CP/MAS ¹³C NMR spectra of aquatic fulvic acids are presented and discussed. Structural features evident in liquid state ¹³C NMR spectra of samples permethylated with unenriched reagents and examined at high field are also discussed. Carbonyls of aromatic acid methyl esters are distinguishable from those of aliphatic and benzylic acid methyl esters in such spectra. The ²⁹Si NMR of a silylated humic acid did not yield much information on the hydroxyl group functionality.

No description available.

Submitted in partial compliance with the requirements of the Master’s Degree in Technology: Homoeopathy, Durban University of Technology, Durban, South Africa, 2016. / Aim The aim of this study was to compare the nuclear magnetic resonance spectra of Sulphur 12c samples produced by the traditional Hahnemannian method with Sulphur 12c samples produced using sonication as an alternative method of agitation. Sonication, while not widely employed as an agitating technique in the homoeopathic potentisation process, is a highly effective agitation process which produces effects on liquids that closely resemble the effect of traditional Hahnemannian hand succussion (Bhattacharyya et al. 2008). Thus, this study sought to reveal whether or not homoeopathic remedies produced by sonication bore a close enough physicochemical resemblance to traditional hand succussed remedies to be considered as a viable equivalent. Methodology Five sample groups were manufactured for analysis, all by means of serial dilution at the centesimal ratio (1:100) to the 12c potency, and with agitation between dilution levels where applicable. Three of the sample groups were experimental, namely the Sulphur 12c Hahnemannian, Sulphur 12c sonicated and Sulphur 12c both (succussion and sonication). The Sulphur 12c Hahnemannian samples were produced by hand according to the German Homoeopathic Pharmacopoeia (Benyunes 2005), which includes an agitation phase of 10 hand succussions. Sonicated samples were produced according to the Hahnemannian method as far as possible, however the agitation phase consisted of 30 seconds of sonication in a sonication bath at 40Hz in accordance with related studies (Sukul, Sinhabau, and Sukul 1999: 58-59; Sukul et al. 2001a: 187). Sulphur 12c both (succussion and sonication) samples underwent ten hand succussions and 30 seconds of sonication at 40Hz between dilution levels. Two of the sample groups were controls, namely Sulphur 12c unagitated and Lactose 12c unagitated, neither of which underwent agitation between dilution phases but were otherwise produced according to the German Homoeopathic Pharmacopoeia specification (Benyunes 2005). All samples were raised to the 12c potency level in 87% alcohol from a 3CH triturate. The Lactose 12c unagitated control was derived from a 3CH triturate of lactose, while the other samples were all derived from a 3CH triturate of Sulphur. The sample groups were sent for nuclear magnetic resonance (NMR) spectroscopy at the Department of Chemistry at Stellenbosch University. The NMR device used was the Varian UnityInova 600 NMR Spectrometer ®, with a Deuterated DMSO insert added as an instrument frequency lock. Samples were drawn and analysed by Dr D.J. Brand. One sample was drawn from each sample group. The chemical shift and relative integration values for the OH, H2O, CH2, and CH3 peaks of the NMR spectra were captured and tabulated using Microsoft Excel© 2013. The statistical analysis was performed with the aid of SPSS Version 22. The chemical shift and relative integration values for the H2O, OH, CH2 and CH3 peaks were used in the statistical analysis. The Kruskal-Wallis method was performed for the five sample groups to ascertain whether or not a statistically significant difference existed between the five sample groups. Comparisons between individual paired groups were conducted by means of the non-parametric Mann-Whitney test. The significance interval was set at α = Results The chemical shift values of the CH2 peaks of the samples showed a clear similarity between the samples produced by Hahnemannian hand succussion, sonication and both (succussion and sonication) as well as a clear difference between these three samples and the two controls. The relative integration values, however, showed no clear trends in support of or detracting from the hypotheses. Conclusion In terms of the CH2 peak chemical shift values it can be concluded that distinct similarities exist between 12c potency level of Sulphur produced by Hahnemannian hand succussion and sonication, and that the two methods of agitation produce similar structural properties in samples of the 12c potency level. Furthermore in terms of the chemical shift values, succussion and sonication develop remedies that are distinct from unagitated remedies of equivalent potency level. Thus, these findings support the use of sonication as a potentially viable alternative to hand succussion as a method of agitation in the potentisation process. Further studies need to be conducted however, with the inclusion of a greater variety of potency levels in order to possibly reveal more trends in terms of the relative integration values as these values were inconclusive in this study. / M

No description available.

Dissertation (PhD)--University of Stellenbosch, 2006. / ENGLISH ABSTRACT: The partial double bond character of the carbon-nitrogen bond of the (S)C-NRR’ moiety results in unsymmetrical dialkyl-substituted N-alkyl-N-alkyl(aryl)-N’-acylthioureas, R”C(O)NHC(S)NRR’ (HL) displaying E,Z configurational isomerism in solution. The isomerism manifests itself by the duplication of resonances of the N-alkyl groups in the 1H and 13C NMR spectra. In one class of these ligands where R and R’ groups are non-equivalent alkyl groups the isomerism is easily observable at 298 K in chloroform. In the other class where R’ is still an alkyl group and R is a para-substituted phenyl group the isomerism is only observable at much lower temperatures due to a lower barrier to rotation around the (S)C-N(alkyl)(para-X-Ph) bond (X = O-CH3, H and NO2). The electron-withdrawing nature of the nitro group in N-methyl-N-(4-nitro-phenyl)-N’-2,2-dimethylpropanoylthiourea, HL3A and N-pentyl-N- (4-nitro-phenyl)-N’-2,2-dimethylpropanoylthiourea, HL3D result in the E,Z isomerism of these ligands not observable even at 198 K in dichloromethane. The distribution of E and Z isomers of the unbound ligands vary depending on these R and R’ groups. Several E isomers of these ligands have been isolated and structurally characterised and the (S)C-NRR’ bond falls in the range [1.343(3) – 1.329(3) Å] which shorter than the average C-N single bond of 1.472(5) Å. The E,Z configurational isomerism in the unbound ligands is passed on to the Pt(II) chelates derived from these ligands. The presence of cis-[Pt(ZZ-L-S,O)2], cis-[Pt(EZ-L-S,O)2] and cis-[Pt(EE-L-S,O)2] is readily observable by means of 195Pt NMR spectroscopy which shows three well resolved resonances, and this can be confirmed by 1H and 13C NMR spectra of these complexes. The 195Pt nuclei are spatially linked to the 13C nuclei, four bonds away resulting in 4J(195Pt-13C) couplings with N-CH2- or N-CH3 carbons in a W pathway. The 195Pt NMR spectra are also linked to N-CH2- or N-CH3 proton resonances by means of the ZZ, EZ and EE isomer distributions. Assignment of these configurational isomers was then achieved by means of a combination of low magnetic field 13C NMR spectra and high-resolution gHSQC (1H/13C) NMR experiments. 1H NMR rotational dynamics study showed that the barrier to rotation, ΔG≠, around the (S)C-N(Me)(para-X-Ph) bond in cis-bis(N-methyl-N-(4-methoxy-phenyl)-N’-2,2-dimethylpropanoylthioureato)platinum(II), cis-[Pt(L1AS, O)2]; cis-bis(N-methyl-N-phenyl-N’-2,2-dimethylpropanoylthioureato)platinum(II), cis-[Pt(L2A-S,O)2] and cisbis( N-methyl-N-(4-nitro-phenyl)-N’-2,2-dimethylpropanoylthioureato)platinum(II), cis-[Pt(L3A-S,O)2] complexes was observed to follow the order: (electron-withdrawing group) NO2 < H < (electron-donating group) O-CH3. The ZZ isomer was observed to be favoured over the EZ and EE isomers in this order of the para-substituent on the Nphenyl group. The 1H dynamic NMR trends about the barrier to rotation, ΔG≠, around the (S)C-N(Me)(para-X-Ph) bond were also complemented by DFT linear transit calculations. The isomer distributions were also influenced by solvent polarity and the temperature at which the distributions are determined apart from the electronic influence of the para-substituent of the N-phenyl group. The ZZ, EZ and EE isomers of complexes derived from N-alkyl-N-(para-X-Ph)-N’-acylthioureas with varying Nalkyl substituent (methyl, isopropyl, cyclohexyl and n-pentyl) were determined from the 195Pt NMR spectra which were measured under identical conditions. The ZZ isomer was observed to be favoured over the EZ and EE isomers upon methyl group substitution with a bulkier alkyl group in the order: methyl < isopropyl < cyclohexyl < n-pentyl. Qualitatively it has been shown that a bulkier N-pentyl group increases the barrier to rotation around the (S)CN( alkyl)(para-X-Ph) bond over the N-methyl group and this leads to higher concentrations of the ZZ isomer over the EZ and EE isomers. The combined effects of the electron-donating substituent (X = O-CH3) on the N-(para-X-Ph) group and the bulkier N-alkyl group (n-pentyl) result in highest ZZ concentration (76 %) over EZ and EE isomers in the complex cis-bis(N-pentyl-N-(4-methoxy-phenyl)-N’-2,2-dimethylpropanoylthioureato)platinum(II), cis-[Pt(L1DS, O)2]. The lowest concentration ZZ (27 %) is obtained in the complex cis-bis(N-methyl-N-(4-nitro-phenyl)-N’-2,2- dimethylpropanoylthioureato)platinum(II), cis-[Pt(L3A-S,O)2] when the coordinated ligand has both N-methyl group and N-(4-nitro-Ph) group which both lower the barrier to rotation around the (S)C-N(alkyl)(para-X-Ph) bond. A crystal of the complex cis-bis(N-pentyl-N-(4-methoxy-phenyl)-N’-2,2-dimethylpropanoylthioureato)platinum(II), cis-[Pt(L1D-S,O)2] has been isolated and structurally characterised and was shown to be in the ZZ configuration, which is the major component (76 %) in chloroform. This is the first example of Pt(II) chelates with asymmetrically disubstituted ligands to be reported. / AFRIKAANSE OPSOMMING: Die gedeeltelike dubbelbinding karakter van die koolstof-stikstof-binding van die (S)C-NRR’-moieteit lei tot onsimmetriese dialkiel-gesubstitueerde N,N-dialkiel-N’-asieltioureums, R”C(O)NHC(S)NRR’ (HL) wat E,Zkonfigurasionele isomerie in oplossing besit. Die isomerie is sigbaar in die verdubbelling van die seine van die Nalkielgroepe in die 1H- en 13C-KMR spektra. In een so klas ligande waar R- en R’-groepe nie-ekwivalente alkielgroepe is, is isomerie duidelik sigbaar by 298 K in chloroform. In die ander klas waar R’ steeds ’n alkielgroep is, en R ’n para-gesubstitueerde feniel groep, is die isomerie alleenlik sigbaar by baie laer temperature as gevolg van ’n laer rotasieversperring om die (S)C-N(alkiel)(para-X-Ph)-binding (X = O-CH3, H and NO2). Die elektrononttrekkende aard van die nitrogroep in N-metiel-N-(4-nitrofeniel)-N’-(2,2-dimetielpropanoïel)tioüreum, HL3A en N-(4-nitrofenyl)-N-pentiel-N’-(2,2-dimetielpropanoïel)tioüreum, HL3D lei daartoe dat die E,Z-isomerie van die ligande nie eers by 198 K in dichlorometaan waargeneem word nie. Die verspreiding van die E en Z isomere verskil na gelang van die R en R’ groepe. Verskeie E-isomere van hierdie ligande is geïsoleer en struktureel gekarakteriseer en die (S)C-NRR’-bindingslengte is in ‘n gebied [1.343(3) – 1.329(3) Å] wat korter is as die gemiddelde C-N-enkelbindingslengte van 1.472(5) Å. Die Pt(II) chelate wat afgelei is van die ligande is blootgestel aan die E,Z-konfigurasie isomere van die ongebinde ligande. Die teenwoordigheid van cis-[Pt(ZZ-L-S,O)2], cis-[Pt(EZ-L-S,O)2] en cis-[Pt(EE-L-S,O)2] is maklik waarneembaar deur middel van 195Pt-KMR-spektroskopy wat drie goed geresolueerde seine toon, en dit kan bevestig word met 1H- en 13C-KMR spectra van hierdie komplekse. Die 195Pt kerne is ruimtelik geskakel met die 13C kerne deur vier bindings wat aanleiding gee tot 4J(195Pt-13C)-koppelings met N-CH2- of N-CH3-koolstofatome in ‘n Wkonformasie. Die 195Pt KMR spektra word geskakel met die N-CH2- of N-CH3-protonresonansies in al drie die moontlike ZZ, EZ en EE kompleksisomere. Toekenning van die konfigurasionele isomere is dan bewerkstellig deur middel van ‘n kombinasie van lae magneetveld 13C-KMR spectra en hoë resolusie gHSQC (1H/13C) KMR experimente. 1H-KMR-rotasiedinamiek studie toon dat die rotasiegrens, ΔG≠, om die (S)C-N(Me)(para-X-Ph)-binding in cisbis( N-metiel-N-(4-metoksifeniel)-N’-2,2-dimetielpropanoïeltioureato)platinum(II), cis-[Pt(L1A-S,O)2]; cis-bis(Nfeniel- N-metiel-N’-2,2-dimetielpropanoïeltioureato)platinum(II), cis-[Pt(L2A-S,O)2] en cis-bis(N-metiel-N-(4- nitrofeniel)-N’-2,2-dimetielpropanoïeltioureato)platinum(II), cis-[Pt(L3A-S,O)2] komplekse was met die volgende orde bepaal: (elektron-ontrekkende groep) NO2 < H < (elektron-skenkende groep) O-CH3. Die ZZ-isomeer blyk by voorkeur te vorm bo die EZ- en EE-isomere in dieselfde orde as hierbo wat betref para-substituent aan die Nfenielgroep. Die 1H dinamiese KMR tendencies ten opsigte van die rotasiegrens, ΔG≠, om die (S)C-N(Me)(para-XPh)- binding is gekomplimenteer met DFT-linêre organgs berekeninge. Die isomer verspreidings blyk ook beïnvloed te word deur die oplosmiddel polariteit en die temperatuur waarby die verspreidings bepaal is, buiten die elektroniese invloed van die para-substituent aan die N-fenielgroep. Die ZZ, EZ en EE isomeer verspreiding van komplekse wat afgelei is van N-alkiel-N-(para-X-Ph)-N’-asieltioureums met veranderlike N-alkiel substituente (metiel, isopropyl, sikloheksiel, en n-pentiel) is vasgestel deur middel van die 195Pt KMR wat opgeneem is onder identiese kondisies. Die ZZ-isomeer blyk die verkose isomeer te wees bo die EZen EE-isomere waar die metiel substituent vervang word met ‘n groter alkiel groep in die orde van: metiel < isopropiel < sikloheksiel < n-pentiel. Dit is kwalitatief getoon dat die groter N-pentielgroep die rotasiegrens verhoog vir rotasie om die (S)C-N(alkiel)(para-X-Ph)-binding bo dié van die N-metielgroep wat aanleiding gee tot hoër konsentrasies van die ZZ-isomeer relatief tot die EZ- en EE-isomere. Die gekombineerde uitwerking van die electron-skenkende substituent (O-CH3) op die N-(para-X-Ph)-groep en die groter N-alkiel groep (n-pentiel) gee aanleiding tot die hoogste ZZ-konsentrasie (76%) bo EZ- en EE-isomere in die kompleks cis-bis(N-pentiel-N-(4- metoksifeniel)-N’-2,2-dimetielpropanoïeltioureato)platinum(II), cis-[Pt(L1D-S,O)2]. Die laagste konsentrasie ZZ (27%) is verkry in die kompleks cis-bis(N-metiel-N-(4-nitrofeniel)-N’-2,2-dimetielpropanoïel)tioureato)platinum(II), cis-[Pt(L3A-S,O)2] waar die gekoördineerde ligand beide die N-metiel- sowel as die N-(4-nitro-Ph)-groep, wat albei die rotasiegrens van die (S)C-N(alkiel)(para-X-Ph)-binding verlaag. ‘n Kristalstruktuur van die kompleks cis-bis(N-pentiel-N-(4-metoksifeniel)-N’-2,2-dimetielpropanoïeltioureato) platinum(II), cis-[Pt(L1D-S,O)2] wat geïsoleer is, is struktureel gekarakteriseer en is in die ZZ-konfigurasie, wat die hoofkomponent (76%) is in chloroform. Hierdie is die eerste voorbeeld van Pt(II) chelate met asimmetriese digesubstitueerde ligande om geraporteer te word.

Thesis (PhD)--Stellenbosch University, 2005. / ENGLISH ABSTRACT: Pt(JV) complexes with S, 0-donating aroylthioureas have been synthesized by oxidative addition of elemental halogens to the Pt(JJ) precursors, leading to the first-reported crystal structures of Pt(JV) with this class of ligand. The treatment of Pt(II) complexes of N,N-diethyi-N'-benzoylthiourea with 12, Br2 and Cl2 leads to facile oxidative addition of the halogens to the platinum center, yielding several geometric isomers, as determined by 195Pt NMR; the products cis-bis(N ,N-diethyi-N' -benzoylthioureato )diiodoplatinum(IV), 26, and cisbis( N,N-diethyl-N'-benzoylthioureato)dibromo-platinum(IV), 27, have been isolated and structurally characterized. Reaction of cis-/trans-bis(N-benzoyi-N'-propylthiourea-kS)dibromoplatinum(II) with Br2, similarly results in oxidative addition of the dihalogen, yielding the product trans-bis(N-benzoyi-N'propylthiourea- kS)tetrabromoplatinum(IV), 29. lz, however, does not undergo oxidative addition to cis! trans-bis(N-benzoyi-N' -propylthiourea-kS)diiodoplatinum(II), instead the iodine inclusion compound trans-bis(N-benzoyl-N'-propylthiourea-kS)diiodoplatinum(II) diiodine, 28, was isolated. Short intermolecular I··· I interactions in crystals of compounds 26 and 28 lead to infinite chains of weakly linked molecules in the respective solids. 195Pt NMR reveals that the 3: 3 Pt(II) metallamacrocycle of 3,3,3',3'-tetra(n-butyl)-l,l'terephthaloylbis( thiourea) undergoes stepwise oxidative addition of 12 or Br2 to each of the Pt(II) centers, upon treatment with the dihalogens. Treatment of the 2: 2 Pt(II) complex of 3,3,3',3'-tetraethyl-1,1'isophthaloylbis( thiourea) with 12 also results in the oxidative addition of the halogen, yielding a 2 : 2 trans-Pt(IV)-iodo metallamacrocycle, 35. The corresponding trans-Pt(IV)-X (X= Br, Cl) complexes were synthesized by oxidative addition in an electrolytic cell containing the 2 : 2 Pt(II) precursor and an appropriate halide salt in dichloromethane. The 2: 2 trans-Pt(IV)-X (X= I, Br, Cl) metallamacrocycles, 36 an 37, were isolated and structurally characterized. Intermolecular 1···1 interactions between molecules of 35, in crystals of the compound, result in chains of weakly connectedmolecules in the lattice. 195 Pt NMR is used as a sensitive probe for studying the hydration/solvation spheres of the PtX/ (X = Cl, Br) anions, and to investigate the occurrence of {Na + [PtCl/"]}" contact ion-pairing in non-aqueous solutions. The 195Pt NMR chemical shifts of the Pt~2 • (X = Cl, Br) anions in D20 and in various organic solvents have been determined, and are discussed with regard to solvent polarities and donor and acceptor properties. The non-linear variations of bp1•195 for the anions with changing bulk composition in aqueous binary mixtures with the organic solvents, suggest that the anions are preferentially solvated by the organic solvents relative to water. The anion solvation sphere compositions with changing bulk composition, as well as preferential solvation equilibrium constants, K11 ", are determined from the NMR data. Significant non-linear variations of the 195Pt NMR chemical shift for methanol and acetonitrile solutions of PtXt (X = Cl, Br) ·with increasing NaCI04 concentrations indicate the occurrence of {Na+[PtX6 2_]}_ contact ion-pair formation in these solutions. By contrast, the variation of Dp1•195 for aqueous solutions of the halogenoplatinate anions with increasing sodium perchlorate concentration is slight, revealing that Na+···PtXe?- ion association is not favoured in the aqueous medium. The 195Pt chemical shift variations are used to estimate conditional ion-pair formation equilibrium quotients, Q (M"\ for {Na+[Ptxi·Jr contact ion-pair formation in water, methanol and acetonitrile. The estimated Q values illustrate that the extent of {Na+[Ptxi·Jr ion-pairing increases in these solvents in the order water< methanol< acetonitrile, which is in accordance with the solvent donor and acceptor properties. / AFRIKAANSE OPSOMMING: Pt(JV) komplekse met S, 0-donerende aroi"eltioiireum ligande is deur middel van die oksidatiewe addisie van halogene aan Pt(JJ) uitgangskomplekse gesintetiseer; die kristalstrukture van die Pt(IV) komplekse met hierdie tipe ligande word vir die eerste keer gerapporteer. Die behandeling van die Pt(II) komplekse van N,N-dietiel-N'-bensoieltioiireum met 12, Br2 en Cl2 gee geredelik aanleiding tot die oksidatiewe addisie van die halogene aan die platinum sentrum, en lei, volgens bepaling met 195Pt KMR, tot die vorming van verskeie geometriese isomere; die produkte cis-bis(N,Ndietiel- N' -bensoieltioiireato )di-jodoplatinum(IV), 26, en cis-bis(N,N-dietiel-N' -bensoieltioiireato )dibromoplatinum( IV), 27, is geisoleer en kristallografies gekarakteriseer. Reaksie van cis-/trans-bis(N-bensoiel-N'propieltioiireum- IGS)dibromoplatinum(II) met Br2, lei ooreenkomstiglik tot oksidatiewe addisie van die halogeen, met trans-bis(N-bensoiel-N' -propieltioiireum-IGS)tetrabromoplatinum(IV) as produk, 29. 12 ondergaan egter nie oksidatiewe addisie aan cis-ltrans-bis(N-bensolel-N' -propieltioiireum-IGS)dijodoplatinum( II) nie; 'n verbinding waarin h ingesluit word in 'n kristalstruktuur met trans-bis(N-bensoielN'- propieltioiireum-IGS)di-jodoplatinum(II), word geisoleer, 28. Kort intermolekulere 1···1 interaksies in die kristalstrukture van verbindings 26 en 28 lei tot die ontstaan van swak-gebonde molekuul-kettings in die kristalle. 195Pt KMR dui aan dat met behandeling van die 3 : 3 Pt(II) metallomakrosikliese kompleks van die 3,3,3' ,3 '-tetra(n-butiel)-1, 1 '-tereftaloielbis(tioiireum) ligand met 12 of Br2, daar stapsgewyse oksidatiewe addisie van die halogene aan die Pt(II) ione in die kompleks plaasvind. Behandeling van die 2 : 2 Pt(II) kompleks van 3,3,3' ,3 '-tetraetiel-1, 1 '-isoftaloielbis(tioiireum) met 12 gee ook aanleiding tot oksidatiewe addisie, met 'n 2 : 2 trans-Pt(IV)-jodo metallomakrosikliese kompleks as produk, 35. Die ooreenkomstige trans-Pt(IV)-X (X = Br, Cl) komplekse is gesintetiseer deur middel van oksidatiewe addisie in 'n elektrolitiese se! wat die 2 : 2 Pt(II) uitgangskompleks bevat tesame met 'n toepaslike haliedsout in dichlorometaan. Die 2 : 2 trans-Pt(IV)-X (X = I, Br, Cl) komplekse, 36 en 37, is geisoleer en kristallografies gekarakteriseer. lntermolekulere I··· I interaksies tussen molekule in kristalle van verbinding 35, gee aanleiding tot kettings van swak-gebonde molekule in die struktuur. 195 Pt KMR word gebruik om die hidraterings-/solvaterings-sfere van die PtX/" (X = Cl, Br) anione te ondersoek, asook om die voorkoms van {Na + [PtCIX/}F kontak-ioonparing in nie-waterige oplosmiddels te bestudeer. Die195Pt KMR chemise verskuiwing van die PtXl" (X= Cl, Br) anione in D20 en in verskeie organiese oplosmiddels is bepaal, en word bespreek met verwysing na die polariteite asook die donor- en akseptoreienskappe van die oplosmiddels. Die nie-lineere variasies van Op1_195 vir die anione met veranderende oplosmiddelsamestelling in waterige binere mengsels met die organiese oplosmiddels, dui aan dat die anione by voorkeur deur die organiese oplosmiddels gesolvateer word. Die solvateringssamestelling van die anione met veranderende oplosmiddelsamestelling, asook ewewigskonstantes vir die voorkeur-solvatering deur die organiese oplosmiddels, K11 ", word met behulp van die KMR data bepaal. Beduidende nie-lineere variasies van Op1_195 in metanol en asetonitriel oplossings van PtXl" (X = Cl, Br) met toenemende NaC104 konsentrasies, dui op die voorkoms van {Na +[PtClxl-]}- kontak-ioonparing in die oplossings. Die variasies van Op1_195 in waterige oplosings van die anione met toenemende NaC104 konsentrasies is egter minder beduidend, waaruit afgelei kan word dat ioonparing nie in die waterige medium bevoordeel word nie. Die 195Pt chemiese verskuiwings word gebruik om kondisionele ioonpaarvormings-ewewigskwosiente, Q (M-1 ), vir die vorming van {Na+[PtCIXtJr in water, metanol en asetonitriel af te lei. Die Q-waardes dui in ooreenstemming met die donor- en akseptoreienskappe van die onderskeie oplosmiddels aan dat die voorkoms van kontak-ioonparing toeneem vir die oplosmiddels in die volgorde water < metanol < asetonitriel.

published_or_final_version / Chemistry / Doctoral / Doctor of Philosophy