The technique of X-ray diffraction has been used to investigate compounds which show charge-transfer properties in the solid state. It is shown how the results of structure determination can, under favourable conditions, give information about charge-transfer processes. Two sets of compounds have been studied, both of which contain metal-chloride bonds. The first is a series of mixed-valence cobalt hexammine chlorocuprates in which the average oxidation state of the copper can take any value between 1 and 2. The structure of the single-valence (copper (I)) compound, [Co(NH₃)₆]₄Cu₅Cl₁₇ was solved and data was also collected for a compound with Cu(I)/total Cu ~ 0.25. This was shown to have a structure to the single-valence copper (I) and copper (II) compounds and probable arrangements for the Cu(I) and Cu(II) ions are presented. It is shown that linear Cu-Cl-Cu bridges are almost certainly present and that these can account for the charge-transfer spectrum. A new chlorocuprate anion, [Cu₅Cl</sub>16</sub>]^11- was discovered, which has 23(T) symmetry.

Call number: LD2668 .T4 1984 G86 / Master of Science

Call number: LD2668 .T4 1986 D48 / Master of Science / Chemistry

Thesis (MSc)--Stellenbosch University, 2004. / ENGLISH ABSTRACT: Capillary electrophoresis (CE) has recently attracted considerable attention as a promising analytical technique for the separation of cations and anions in complex matrices. Determination of ions in aqueous samples using capillary electrophoresis can be accomplished with indirect UV detection. Most inorganic ions have weak absorption profiles in the UV-Vis wavelength range. These mostly non-absorbing species are commonly detected by indirect UV absorbance through addition of an absorbing co-ion (chromophore) into the electrolyte. Inorganic cations most often require an additional complexing agent to selectively alter their similar mobilities and proper separation. For optimal determination of alkali, alkaline, and transition metal ions, several electrolytes systems were studied. These include pyridine, imidazole and 4- aminopyridine as UV-absorbing species and glycolic acid, a-hydroxyisobutyric acid and their mixture were used as complexing reagents. A mixture of 10 metal ions (K+, Na+,Ca2+, Mg2+, Mn2+, Fe2+, Cd2+, Pb2+, Ni2+and Zn2+) was successfully separated. Detectionwas performed at 210,214 and 254 nm. In the anion determination chromate and 2, 6 pyridine dicarboxylic acids (PDC) were used as back ground electrolytes for inorganic ions (F-, CI- en SO₄² ̄ ) and organic acids (tartaric acid, malic acid, succinic acid and citric acid) separations respectively. Electroosmotic flow (EOF) was reversed in the direction of the anode by adding Cetyltrimethylammonium bromide (CTAB) to the electrolyte. Highly alkaline conditions were used to confer a negative charge on inorganic and organic anions to promote their migration towards the anode. The detection wavelength was 200 nm. All peaks were completely resolved and well separated. The limit of detection (LOD) of cations and anions were in the range of 0.5 - 3 ppm and 2 - 3.5 ppm respectively. The described methods were used successfully in routine analysis of real samples. This includes the qualitative and quantitative analysis of an environmental water samples from the areas surrounding Stellenbosch, beverages and orange juice. / AFRIKAANSE OPSOMMING: Kapillêre Elektroforese (CE) het in die onlangse verlede heelwat aandag getrek as "n belowende analitiese tegniek vir die skeiding van katione en anione in komplekse monsters. Die bepaling van ione in waterige medium met kapillêre elektroforese word gedoen deur indirekte Ultraviolet (UV) deteksie aangesien meeste anorganiese ione swak absorbsie in die die sigbare UV (UV-Vis) golflengtegebied toon. Deteksie van hierdie meestal nie-absorberende spesies word algemeen gedoen deur indirekte UV absorbansie deur die byvoeging van "n ko-ioon (chromofoor) tot die elektroliet. Anorganiese katione benodig dikwels "n addisionele komplekserings reagens om selektief hulle eenderse mobiliteite te verander en sodoende goeie skeiding te bewerkstellig. Vir die optimale bepaling van alkali-, alkali-aard- en oorgansmetaal ione is verskeie elektrolietsisteme bestudeer. Hierdie sluit in piridien, imidasool en 4-aminopiridien as UV absorberende spesies en glikoliensuur, a-hydroksie-isobottersuur asook "n mengsel van die twee as komplekserings reagense. "n Mengsel van 10 metaalione (K+, Na+, Ca2+, Mg2+, Mn2+, Fe2+, Cd2+, Pb2+, Ni2+ en Zn2+) is sukselvol op hierdie wyse geskei. Deteksie is gedoen by golflengtes van 210, 214 en 254 nm. Vir die anioon bepaling is chromaat en 2,6-piridiendikarboksielsuur gebruik as agtergrond elektroliete vir die skeiding van anorganiese anione (F-, CI- en SO₄² ̄ ) en organiese sure (tartaarsuur, malonsuur, suksiensuur en sitroensuur), onderskeidelik. Elektroosmotiese vloei (EOF) is omgekeer na die rigting van die anode deur byvoeging van setieltrimetielammoniumbromied (CTAB) by die elektroliet. Sterk alkaliese kondisies is gebruik om 'n negatiewe lading op die anorganiese en organiese anione te konsentreer en sodoende hul migrasie na die anode te bevorder. Die deteksiegolftengte hier gebruik was 200 nm. Volkome resolusie en goeie skeiding is gerealiseer vir al die pieke. Die deteksielimiete (LOD) vir die katione en die anione was 0.5 - 3 ppm en 2 - 3.5 ppm, onderskeidelik. Die metodes wat beskryf word is suksesvol aangewend vir roetiene analise van werklike monsters. Dit sluit in kwalitatiewe sowel as kwantitatiewe analise van omgewingswater monsters uit die Stellenbosch area, koeldranke en lemoensap.

This dissertation explores the use of anion photoelectron imaging to interrogate electronic dynamics in small chemical systems with an emphasis on photoelectron angular distributions. Experimental ion generation, mass selection, laser photodetachment and photoelectron imaging were performed in a negative-ion photoelectron imaging spectrometer described in detail. Results for photodetachment from the simplest anion, H⁻, are used to illustrate fundamental principles of quantum mechanics and provide basic insight into the physics behind photoelectron imaging from a pedagogical perspective. This perspective is expanded by introducing imaging results for additional, representative atomic and small molecular anions (O⁻, NH₂⁻ and N₃⁻) obtained at multiple photon energies to address the energy-dependence of photoelectron angular distributions both conceptually and semi-quantitatively in terms of interfering partial photoelectron waves. The effect of solvation on several of these species (H⁻, O⁻, and NH₂⁻) is addressed in photoelectron imaging of several series of cluster anions. The 532 and 355 nm energy spectra for H⁻(NH₃)n and NH₂⁻(NH₃)n (n = 0-5) reveal that these species are accurately described as the core anion solute stabilized electrostatically by n loosely coordinated NH3 molecules. The photoelectron angular distributions for solvated H⁻ deviate strongly from those predicted for unsolvated H⁻ as the electron kinetic energy approaches zero, indicating a shift in the partial-wave balance consistent with both solvation-induced perturbation (and symmetry-breaking) of the H⁻ parent orbital and photoelectron-solvent scattering. The photoelectron energy spectra obtained for the cluster series [O(N₂O)n]⁻ and [NO(N₂O)n]⁻ indicate the presence of multiple structural isomers of the anion cores, the former displaying sharp core-switching at n = 4, the latter isomer coexistence over the entire range studied. The photoelectron angular distributions for detachment from the O⁻(N₂O)n and NO⁻(N₂O)n isomers deviate strongly from those expected for bare O⁻ and NO⁻, respectively, in the region of an anionic shape resonance of N₂O, suggesting resonant photoelectron-solvent scattering. Partial-wave models for two-centered photoelectron interference in photodetachment from dissociating I₂⁻ is presented and discussed in the context of previous results. New time-resolved photoelectron imaging results for I₂⁻, for both parallel and perpendicular pump and probe beam polarizations, are presented and briefly discussed. Finally, new ideas and directions are proposed.

Layered double hydroxides (LDH) have been principally known as anion-exchanging, clay-like materials for several decades, and continues to be the main driving force for current and future research. The chemical interactions of LDH, with transition metallocyanides, have been a popular topic of investigation for many years, partly due to the use of powder x-ray diffraction and infrared spectroscopy as the main characterization tools. Each transition metallocyanide has a characteristic infrared stretching frequency that can be easily observed, and their respective sizes can be observed while intercalated within the interlayer of the LDH. The ability of LDH to incorporate metal cations or any ions/molecules/complexes, that have a postive charge, have not been previously investigated, mainly due to the chemical and physical nature of LDH. The possibility of cationic incorporation with LDH would most likely occur by surface adsorption, lattice metal replacement, or by intercalation into the LDH interlayers. Although infrared spectroscopy finds it main use through the identification of the anions incorporated with LDH, it can also be used to study and identify the various active and inactive bending and stretching modes that the metal hydroxide layers have.

This thesis is concerned with the synthesis and study of novel anion templated rotaxanes and catenanes for electrochemical anion sensing, as well as interlocked structures that possess different anion binding properties, higher-order topologies and the ability to undergo molecular motion. Chapter One provides an introduction to anion recognition and the preparation of interlocked structures. A short summary of fundamental aspects of supramolecular chemistry is followed by detailed surveys of current approaches to anion binding and sensing, as well as the templated synthesis of rotaxanes and catenanes. Chapter Two describes the preparation of rotaxanes and catenanes appended with ferrocene to allow for electrochemical anion sensing. The anion recognition properties of a [2]rotaxane and a [2]catenane, as investigated by ¹H NMR spectroscopy and electrochemical methods, are presented. The utilization of a ferrocene-appended macrocycle in the construction of surface confined anion templated rotaxanes and catenanes is also discussed. Chapter Three reports the work carried out to achieve electrochemical anion sensing by the incorporation of redox-active groups into the integral structures of interlocked structures. The syntheses of a bis-stoppered 1, 2, 3, 4, 5-pentaphenylferrocene [2]rotaxane and a ferrocene containing [3]rotaxane are presented, along with their subsequent anion recognition studies. In addition, attempts to incorporate ferrocene into the macrocyclic components of rotaxanes and catenanes are outlined. Chapter Four details further investigations into the use of interlocked structures to achieve anion recognition. Doubly-charged [2]catenanes able to bind anions in aqueous solvent media, as well as the incorporation of alternative anion binding motifs into interlocked architectures are reported. The exploitation of anion templated synthesis to allow for the construction of higher order structures (including [3]catenanes, a “handcuff” catenane and a Janus [2]rotaxane), as well as a [2]catenane system with anion controlled molecular motion is also described. Chapter Five presents the experimental procedures and characterization data relating to the compounds prepared in Chapters Two, Three and Four. Chapter Six summarizes the main conclusions of the work contained within this thesis. Supplementary experimental information relating to titration protocols, investigations into self-assembled monolayers (SAMs) and crystallographic data are provided in Appendices I, II and III.

Nitroglycerin and isoamyl nitrate have been used as nitrovasodilators since the nineteeth century. However, not until recently has it been known that these compounds were useful since they promoted the release of NO in the body. More recently, a new class of drugs, NO donors, has been developed. These include S-nitrosothiols (RSNO), sydnonimines, and nucleophilic NO adducts.

Appendix inside back cover. "June 2002" Bibliography: leaves 157-168. Experimental and theoretical studies were carried out on a number of unusual organic molecules of potential astronomical significance. The experimental work was corroborated by various theoretical approaches and by utilising computer-based quantum chemical calculations. Various covalently bound, anionic and neutral oxocarbon species were formed and studied. Additionally, two analogous heterocumulenic systems were investigated. Some isomers of either system, when energised, were shown to undergo gas-phase rearrangement processes.

Appendix inside back cover. / "June 2002" / Bibliography: leaves 157-168. / x, 168, [19] leaves : ill. ; 30 cm. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Experimental and theoretical studies were carried out on a number of unusual organic molecules of potential astronomical significance. The experimental work was corroborated by various theoretical approaches and by utilising computer-based quantum chemical calculations. Various covalently bound, anionic and neutral oxocarbon species were formed and studied. Additionally, two analogous heterocumulenic systems were investigated. Some isomers of either system, when energised, were shown to undergo gas-phase rearrangement processes. / Thesis (Ph.D.)--University of Adelaide, Dept. of Chemistry, 2002