High resolution (< 0.005 cm−1) electronic spectra of the diatomic molecular ions 70GeH+ and 74GeH+ have been recorded using a fast ion beam irradiated by a cw tunable dye laser. Over 150 transitions between the ground X1∑ + state and near-threshold levels of electronic states correlating to the lowest dissociation asymptotes Ge+(2P3/2) + H(2S) and Ge+(2P1/2) + H(2S) were observed in the range 16500 cm−1 to 18500 cm−1. The majority of the lines arise from a 1π-1∑ transition, where the predissociated excited state levels lie between the fine structure dissociation limits (Feshbach Resonances). The lifetimes of the rovibrational levels are found to increase, then decrease, with increasing rotational quantum number. Evidence for triplet (multichannel) mixing is revealed through the observation of additional lines and proton nuclear hyperfine splittings. Experimental results are compared with predictions of the vibrational and rotational energy levels obtained from a numerical solution of the Schrodinger equation. Least squares fitting yields molecular constants for the 1∑and the 1π states. A new apparatus used to create jet-cold molecular ions in a fast ion beam is detailed. Preliminary results have been obtained for the b4∑− g ← a4πu transition of O+ 2 which allow a rotational temperature for the source to be calculated.

The technique of electron spin resonance was used to study the magnetic properties of a number of complex salts of 7,7' ,8,8'-tetracyanoquinodimethane (TCNQ) in order to obtain a more complete understanding of the electronic states in these materials. All but one of the cations used in the preparation of these compounds were divalent and their TCNQ complex salts exhibit magnetic behaviour characteristic of thermally accessible triplet excitons. Three of these compounds, 1,2-di(N-p-cyanobenzyl-4-pyridinium)ethylene (DCBP)-(TCNQ)3' 1,2-di(N-methyl-4-pyridinium)ethane (DMPA)-(TCNQ)4 (I), and 1,4-di(N-pyridinium)butane (DPB)-(TCNQ)4' were available as single crystals and could be studied in detail. Four of these, however, were only available in polycrystalline form and these were DMPA(TCNQ)4(II) and 1,2-di(N-alkyl-4-pyridinium)ethylene (DRPE)-(TCNQ)S' in which R equals n-propyl (P), n-butyl (B), and cyclohexyl (H). The existence of two phases (I and II) of DMPA(TCNQ)4' first indicated by the electrical data, was supported by the different magnetic behaviour observed in this work. The absolute magnitudes of the signal intensity for DPPE(TCNQ)S' DHPE(TCNQ)S and DMPA(TCNQ)4 (II) ,were found to be well described by an approximate solution to the Heisenberg Hamiltonian, which indicates an exciton band is present in these compounds. The absence of dipolar splitting and the high d.c. conductivity supports this interpretation. However, DMPA(TCNQ)4(I), DPB(TCNQ)4' DBPE(TCNQ)S and DCBP(TCNQ)3 gave results indicative of localised triplet excitons. The latter compound exhibits dipolar splitting, and information concerning the exciton dynamics could be obtained. These results were consistent with the conductivity data and, where available, the crystal structure determinations. The complex salt TPT(TCNQ)4 was available in single crystal form and contained the only trivalent cation studied in this work. The temperature independent signal intensity indicated that triplet excitons were not present, and this behaviour was typical of Pauli paramagnetism. This observation was consistent with the semi-metallic d.c. conductivity observed and was explained in terms of the high degree of disorder present, as indicated by the crystal structure determination.

This may be interpreted as evidence that the profile of sub-structure of the lambda 6614 DIB is skewed towards the red in these three sightlines (Sk -68°135, Sk -69°223 and Sk -69°243) to a greater degree than that found in the Galactic ISM. Compared to Galactic trends, the LMC DIBs are found to be weak with respect to the reddening and neutral potassium column density towards Sk -67°2 and Sk -68°135. This may be attributable to a combination of the high UV flux and reduced shielding of interstellar clouds due to the low metallicity of the interstellar gas of the LMC, and results in the destruction of DIB carriers by photodissociation and/or photoionisation. Relative to N(H I) the lambda 6284 DIB observed in four LMC sightlines is shown to be approximately 1/5 to 1/2 of its average strength in the Milky Way. This supports the idea that the metallicity and/or dust-to-gas ratio of the ISM is closely linked with the chemistry that governs the abundance of DIB carriers relative to N(H I). Variations in the N(Ca II)/N(Ti II) ratio are found over at least an order of magnitude in the LMC ISM, and are taken as evidence for significant variation in the Ca n/Ca m ionisation balance. Derived logarithmic titanium depletions are found to be relatively low in the six LMC sightlines studied, with values between approximately -0.8 and -1.9, which are similar to the levels of depletion generally seen in the warm, shocked interstellar medium of the Galaxy.

<p> Metal containing complexes have been used to catalyze various organic transformations for the past few decades. The success of several mononuclear catalysts led to transition metal catalysts used in pharmaceuticals, environmental, and industrial processes. While mononuclear complexes have been used extensively, bimetallic systems have received far less attention. Bimetallic or polynuclear sites are commonly found in metalloenzymes that perform elegant transformation in biological systems, underlying their significance. Inorganic chemists take inspiration from nature and design model bimetallic complexes to further study this cooperativity effect. A bimetallic platform offers many structural and functional differences such as the identity of the metal atoms and the bonding interactions between metals, which have been reflected in their unique catalytic ability and reactivity. </p><p> This dissertation encompasses work related to the computational study of metal-metal interactions of bimetallic systems, the ¹H NMR study of stereochemical and conformational changes in solution of <i> N,N'</i>-diarylformamidines, the synthesis of dizinc formamidinate complexes, and the synthesis and catalytic ability of dicopper formamidinate complexes. </p><p> In the first part, DFT calculations are used to study factors that influence metal-metal bond lengths in various complexes. Several experimentally obtained X-ray crystal structures were used as the basis for the study. Differences in metal-metal separations were investigated through various functionals, indicating the importance of charge, orbital interactions, and formal bond order. BH&amp;HLYP SDD/aug-CC-PVDZ geometry optimizations of octahalodimetalate anions Tc₂X₈^n- (X = Cl, Br; n=2, 3), Re₂X₈^2- (X = Cl, Br), and Mo₂Cl₈^4- reproduced M-M bond distance trends observed experimentally. The study demonstrated that the increase in &sigma; and &pi; bond strength resulted in the shortening in Tc-Tc bond distance from Tc₂X₈^2- to Tc₂X₈^3-, which was further supported by the short Mo-Mo bond in the Mo₂Cl₈^4- ion. This study was expanded further through the inclusion of [M₂Cl₄(PMe₃)₄]ⁿ⁺ (M = Tc, Re, n = 0-2) and [Mo₂E₄]^n- (E = HPO₄ or SO₄, n = 2-4), allowing a systematic study on the role of charge on the metal atoms. PBEO SDD/aug-CC-PVDZ calculations revealed that both formal bond order and formal charge on the metal atoms dictate the trends in M-M bond strength. </p><p> The second half of this dissertation focuses on the synthesis and characterization of bimetallic Zn- and Cu-formamidinate complexes. The stereochemical exchange of substituted <i>N,N'</i>-diarylformamidines were studied through ¹H NMR in various solvents. Alkyl substituents placed on the ortho positions were found to shift the isomeric equilibrium in solution through destabilization of the hydrogen-bond dimer evident in X-ray crystal structures. The Z-isomer of substituted <i>N,N'</i>-diarylformamidines is observed in CDCl₃, C₆D₆, and DMSO-d₆ when the ligands feature significant steric hinderance. Similar ortho substituted <i> N,N'</i>-diarylformamidines were also used to enforce steric interactions to limit the nuclearity of Zn-formamidinate complexes. Various dizinc formamidinate complexes were synthesized through direct and transmetalation routes. NMR and mass spectrometry were used alongside X-ray crystal structures to fully characterize the dizinc complexes. Dicopper formamidinates formed through a transmetallation route were synthesized and feature distinct short Cu^&hellip;Cu separations thought to be brought about by metalophillic interactions. Preliminary results suggest catalytic ability of dicopper formamidinates in cyclopropanation and aziridination of styrene with various diazo compounds. The catalytic activity suggests the formation of dicopper carbene and nitrene intermediates, of which only few published experimentally observed examples exist in the literature.</p><p>

The domain sizes of a range of diblock polymers have been measured using solid-state NMR spin diffusion experiments carried out under fast magic angle spinning (MAS). 1H-1H exchange spectra were acquired at a range of mixing times and the results displayed effects due to both intra-domain and inter-domain spin diffusion. By fitting the data to an initial rate approximation domain sizes and spin diffusion coefficients were calculated. Simulations were also carried out to determine the impact of T1 relaxation during the experimental mixing time. The spin diffusion coefficient of polystyrene has also been studied under a variety of different conditions. Increasing MAS rate caused a decrease in the spin diffusion coefficient and at the fastest spinning speeds the rate of spin diffusion was much reduced. Temperature changes were shown to have little effect on the spin diffusion coefficient. The incorporation of recoupling sequences into the experimental mixing time was also studied. Solid-state NMR was also used to study a selection of hydroxyapatite nanoparticle/organic dispersant molecule composite materials with potential biomedical applications. 1H-31P correlation experiments were used to investigate the interaction between the dispersant molecules and the surface of hydroxyapatite nanoparticles. The spectra suggested that the dispersant molecules containing polylactic acid interacted with the surface of the nanoparticle via the polymer chain. Whereas dispersant molecules with an aliphatic chain appeared to interact with the particle via their head group. The results from DNP spectra, which selectively enhanced the surface regions, also supported this conclusion.

Made available in DSpace on 2014-06-11T19:29:08Z (GMT). No. of bitstreams: 0 Previous issue date: 2008-02-18Bitstream added on 2014-06-13T20:18:58Z : No. of bitstreams: 1 ferreira_rb_me_araiq.pdf: 771766 bytes, checksum: b69fe2b81286a33e730050f8930f9fab (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Foi desenvolvido um método para a determinação espectrométrica de fósforo em insumos agroindustriais. O método está baseado na determinação por Espectrometria de Absorção atômica com Fonte Contínua de Alta Resolução (HR-CS AAS) utilizando a linha atômica 213,618 nm e bandas de 246,400 nm e 324,616 nm. Foram estudadas as melhores condições para a análise via absorção pelas bandas de PO e da linha de P atômica. Para a primeira, a melhor forma de análise foi utilizar a chama oxidante ar / acetileno, já para a última situação a atomização foi pela utilização de uma chama oxidante de acetileno / óxido nitroso. As melhores condições de funcionamento, tais como altura do queimador, fluxo de gases e taxa de aspiração da amostra foram definidas, sendo seus valores ideais para cada comprimento de onda respectivamente: 246,400 nm (9 mm – 0,186 – 5 mL min-1), para 324,616 nm (8 mm – 0,170 – 5 mL min-1) e de 213,618 nm (4 mm – 0,450 – 5 mL min-1). Boa linearidade foinobtida para o intervalo de concentração 250 – 4000 mg L-1 P usando o modo de integração do sinal de absorbância CP ± 2 (5 pixels), utilizando-se os sais Na2HPO3.5H2O, NaH2PO4, NH4H2PO4 e H3PO4. Os resultados mostraram que era irrelevante a natureza dos compostos para obter um padrão de P. Quatro diferentes modos de integração de absorbância foram avaliados: CP ± 1 (3 pixels), CP ± 2 (5 pixels), CP ± 3 (7 pixels) e CP ± 4 (9 pixels). Foi observado que a sensibilidade (inclinação da curva e massa característica) melhoraram com o aumento do número de pixels. O método de determinação de P pelo HR-CS FAAS em insumos agroindustriais foi comparada com a titulação. A exatidão e precisão foram de acordo com 95% de confiança, o desvio padrão relativo (RSD) obtido foi de 2,0%. Boas recuperações, cerca de 98%, foi obtida a partir de testes de adição e recuperação. / It was developed a method for spectrometry determination of phosphorus in agroindustrial products. The method is based on the determination by high-resolution continuum source flame atomic absorption spectrometry technique (HR-CS FAAS) using the atomic line 213,618 nm and bands of 246,400 nm and 324,616 nm. It was studied the best conditions for the analysis, for the absorption by bands of PO and the line of P atomic. To the first the best form of analysis would be using an oxidizing air/acetylene flame for analyte atomization and the last an oxidizing acetylene/nitrous oxide flame. The best operating conditions was defined as the burner high, the gas flow rate and aspiration rate of the sample. The values for these operations conditions are respectively: to 246,400 nm ( 9 mm – 0,186 – 5 mL min-1), to 324,616 nm ( 8 mm – 0,170 - 5 mL min-1) and to 213,618 nm ( 4 mm – 0,450 - 5 mL min-1). Good linearity was obtained for the concentration range 250 – 4000 mg L-1 P using the wavelength integrate absorbance in CP ± 2 (5 pixels), using the salts Na2HPO3.5H2O, NaH2PO4, NH4H2PO4 e H3PO4. The results showed that the was irrelevant to the nature of the compound to obtain a standard of P. Four different wavelength integrated absorbance were evaluated: CP ± 1 (3 pixels), CP ± 2 (5 pixels), CP ± 3 (7 pixels) and CP ± 4 (9 pixels). It was observed that the sensitivity (slope and characteristic mass) improved with increased number of pixels. The method of analysis of P by HR-CS FAAS in agroindustrial products was compared with the titration. The accuracy and precision was agreement at 95% confidence level, the relative standard deviation (RSD) obtaneid was 2,0%. Good recoveries, about 98%, was obtained using test of addition and recovery.

The use of mass spectrometry for the analysis of petrochemical products and crude oils enables the generation of detailed molecular data essential for chemical characterisation and product development. However, the need for multistage sample preparation techniques can be time consuming and may result in the loss of information. Ambient ionisation in combination with mass spectrometry enables the direct analysis of compounds present on a surface with minimal or no sample preparation. The work presented in this thesis evaluates the application of mass spectrometry (MS) hyphenated with ambient ionisation and ion mobility for the analysis of chemical additives used in lubricant and petrochemical products and also crude oil. A technique called desorption electrospray ionisation (DESI) pioneered the ambient ionisation field. An in-house designed and constructed DESI source has been developed to enable hyphenation of DESI with MS and ion-mobility mass spectrometry (IM-MS) for the interrogation of chemical additives used in lubricant and petrochemical oils directly from multiple surface substrates. The approach has been successfully applied to the analysis of a range of chemical additives as standards and when present in a lubricating oil matrix. Data has also shown that DESI-MS can be used to map additive deposition on a surface. The quantitative capabilities of DESI-MS have been assessed using a lubricant antioxidant additive present in a lubricant oil matrix and deposited on a surface. The DESI-MS method showed good linearity with a limit of detection (LOD) for the antioxidant additive below that used in typical commercial formulations. The use of a suitable internal standard in the DESI-MS analysis has been shown to significantly improve the repeatability of the approach. Hyphenation of DESI with post ionisation separation methods, such as high field asymmetric waveform ion mobility spectrometry (FAIMS), can improve mass spectral response for targeted analytes through selective transmission. The analysis of a series of corrosion inhibitor additives in a base oil matrix has been carried out using electrospray (ESI) and DESI hyphenated with FAIMS-MS. FAIMS selection of target ions improved the sensitivity of ESI and DESI through enhanced analyte transmission and a reduction in the chemical noise resulting from the oil matrix. DESI-FAIMS-MS was shown to improve target analyte response compared to DESI-MS alone using the corrosion inhibitors as model compounds, showing how the combined technique can be used for the rapid analysis of analytes directly from surfaces with no sample preparation or pre concentration. Direct analysis in real time (DART) is an alternative ambient ionisation approach to DESI. The use of DART-MS for the direct analysis of lubricant and oil additives has been evaluated. All selected additives were successfully detected by DART-MS as standards and in an oil matrix. The surface material, DART helium gas temperature and the presence of an oil matrix were all shown to effect the desorption and ionisation of target analytes. The quantitative capabilities of DART-MS were assessed using the antioxidant additive in a lubricant oil matrix and in the presence of an internal standard. The technique showed good linearity and repeatability. The untargeted analysis of chemical additives present in a fully formulated lubricant oil has been carried out by DESI and DART ionisation techniques. The effect of DESI electrospray solvent and DART helium temperature were both shown to impact the observed mass spectral response for the sample. The analysis of crude oil is particularly problematic due to the high complexity of the sample. A crude oil sample has been analysed using ESI combined with high resolution MS, ESI-FAIMS-MS and DESI-MS. High resolution mass spectrometry enabled the identification of molecular ions that could be characterised using specialist software. The use of FAIMS resulted in shift in the observed chemical profile for the crude oil sample showing selective transmission of molecular species based upon the differential mobility of ions rather than factors such as polarity or solubility that are typically used for sample fractionation. Molecular species from within the crude oil sample were successfully desorbed and ionised by DESI-MS using a DESI solvent composition of 6:4 toluene:methanol.

<p> In light of their escalating exposure to possible environmental toxicants, there are many biological systems that need to be evaluated in a resource and time efficient manner. Understanding how toxicants behave in relation to their physicochemical properties and within complex biological media is especially important toward developing a stronger scientific foundation of these systems so that adequate regulatory decisions may be made. While there are many emerging methods available for the detection and characterization of these chemicals, nanotechnology has presented itself as a promising alternative toward creating more efficient assays. In particular, metallic nanoparticles and thin films exhibit unique optical properties that allow for highly sensitive and multiplexed studies to be performed. These plasmonic materials often preclude the use of molecular tags and labels, enabling direct characterizations and enhancing the throughput of biomolecular studies. However, their lack of specificity toward certain targets and potential toxicity has thus far precluded their widespread use in toxicity testing.</p><p> The cell membrane, a natural signal transducer, represents one of the fundamental structures for biological recognition and communication. These interfaces principally function as a selective barrier to exogenous materials, including ions, signaling molecules, growth factors, and toxins; therefore, understanding interactions at membrane interfaces is a vital step in elucidating how biological responses are effected. Supported lipid bilayers, which may easily be tailored in composition and complexity, are ideal interfaces for coupling to plasmonic assays since they may be supported in close proximity to metallic nanoparticles and thin films, where measurements are most sensitive. This research will focus on the coupling of plasmonic materials and biomimetic interfaces to increase the sensitivity, efficiency, and throughput of conventional toxicity assays. The fabrication of new plasmonic materials for membrane-based assays is presented, as well as method developments in membrane array formation and opportunities for hyphenation with complementary analytical techniques. </p><p>

Metal dication-ligand sandwich complexes have attracted intense attention recently for their widely use in catalysis, biochemistry and material science. The experimental techniques developed by our group have allowed forming, confining, cooling and investigating a wide range of metal dication complexes in the gas phase. In this thesis, the ultraviolet photofragmentation studies of Pb(II), Cu(II) and Ca(II) sandwich complexes with aromatic ligands are performed using a hybrid quadrupole ion trap instrument, followed by DFT/TDDFT calculations. The experimental results indicate that the complexes are capable of yielding structured, sometimes conformation resolved, UV spectra. The spectra of metal dication-benzene complexes exhibit features in the wavelength range 220-270 nm and a big raise as the wavelength decreases. The lead dication-bis(toluene) complex spectrum shows some well-resolved features arising from different conformers. The theory suggests that all of these complexes have excitations including significant contributions from the metal-based orbital. The adiabatic TDDFT methodology is able to give reasonable agreement between the calculated excitations and the experimental spectra for the close-shell complexes. But for some open-shell complexes, the calculated excitations are spin contaminated, which need to be discarded or corrected in the future. The degree of spin contamination for selected excitations is qualified by calculating the < S2 > values. For lead and calcium open-shell complexes, most of the excitations that can match the experimental features can be trusted. However, for the copper open-shell complex, only three states are ~90% doublet in their character which are responsible for some excitations that can match the spectra. Challenges such as developing the theory to describe the open-shell system and refining the experimental techniques to improve the resolution of the spectra, still remain.

Cyanotoxins are posing an increasing threat to the health of humans and wildlife. Cylindrospermopsin is a cyanotoxin that occurs in warm climates and is harmful when ingested. The toxic effects of CYN can affect multiple organ systems. The effects, coupled with the evidence of a mass contamination of a water supply in Australia, prove that CYN needs to be investigated further. Aptamers have become a desirable method for detection of CYN as a result of an aptamer’s high specificity and the ability to scale up experiments. Aptamers have been designed to bind with a variety of targets, including cyanotoxins. An aptamer for CYN was identified by Elshafey et al. This study aims to confirm the binding of the aptamer to CYN and the selectivity of the aptamer using fluorescent biosensing and circular dichroism. Aptamer affinity capture was used to investigate the possibility of a real world application of the aptamer.