Studies of gas-phase ionic clusters have become an integral component in understanding microsolvation and catalysis by transition metal cations. Further interest in this field is due to the possibility of bridging the gap between the condensed and gas phases by developing our understanding of clusters and the possibility that small clusters can have unique chemical and catalytic properties. Most gas phase studies have focused on singly charged ions. Electrospray allows for the production of multiply charged ions solvated by a few solvent molecules. Understanding smaller reactive species such as metal centered clusters with well-defined, gas phase conditions also allows for detailed comparison between theory and experiments. In these studies the main focus is to understand bond activation by transition metal cations and solvation of transition metal dications. The gas phase ions of interest are studied using an electrospray-ionization or laser-ablation dual time-of-flight mass spectrometer and are characterized using photofragment spectroscopy in the visible and ultraviolet regions of the spectrum. Photofragment spectroscopy is a powerful method that can be used in gas phase studies to gather a wealth of information on the ions’ bond strengths, spectroscopic constants, and dissociation kinetics and dynamics. The study of TiO+(CO2) spectroscopy (Chapter 3) was a result of study of CO2 bond activation by Ti+ that went on to provide a wealth of information on the spectroscopy and dissociation kinetics of this molecule. An electronic transition of the TiO+ chromophore was observed, 2Π←2Δ, revealing new information about the excited state and the effect of TiO + electronic state on the metal-CO2 ligand interaction. The photodissociation spectrum of this molecule is well resolved and shows progressions in the covalent Ti-O stretch and metal-ligand stretch and rock. The lifetime of electronically excited TiO+(CO 2) was measured, and depends strongly on vibrational energy. Calculations on TiO+ and TiO+(CO2) were combined with experimental results on TiO+(CO2) to predict spectroscopic transitions of TiO+, an astrophysically interesting molecule. The photodissociation dynamics of M2+(CH3CN)n(H 2O)m where M = Co and Ni, (Chapter 4) is important in understanding the gas phase microsolvation of metal dications. The coordination number and type of solvent affect the dissociation pathways. M2+(CH 3CN)n (n>2) primarily lose a solvent molecule. Electron transfer is a minor channel for n=3 and is the only channel observed for n=2. Mixed clusters M2+(CH3CN)n(H2O)m preferentially lose water. Loss of acetonitrile is a minor channel, as is proton transfer. Water is the proton donor. Replacing acetonitrile with water increases the proton transfer channel. Nickel and cobalt complexes show similar dissociation dynamics, with proton transfer more likely for nickel complexes. Methane activation by transition metal catalysts is industrially important as it can be used to produce gasoline from natural gas. We studied the products and intermediates of the reaction of laser-ablated platinum atoms with methane (Chapter 5). Photoionization efficiency curves were measured for PtCH 2 and the [H-Pt-CH3] insertion intermediate using tunable vacuum ultraviolet light. The resulting ionization energies were combined with bond strengths for the cations to derive bond strengths for the neutrals. These were used to construct a potential energy surface for methane activation by platinum atoms.

In this thesis, I describe the first exploratory experimental efforts probing light-matter interactions of chiral systems at the single molecule level. The dissymmetric single molecule chiroptical response in both excitation and emission polarization has been studied for different diastereomeric forms of bridged triarylamine helicenes. Fluorescence excitation circular dichroism (FECD), measuring the dissymmetric absorption with respect to excitation polarization, reports on the response to excitation polarization. The magnitude and distribution of chiroptical single molecule responses suggest both surface and orientation effects play a significant role. Computational modeling done to calculate the dissymmetry for specific orientations supports orientational dependence. Using a defocused imaging technique, which can be used to obtain orientation information for linear dipoles, emission patterns were obtained that lacked bilateral symmetry. These emission patterns were simulated using a semi-classical model that closely approximated the lack of bilateral symmetry. Refinement of the model and additional experiments using oriented molecules will allow for direct correlation of orientation and dissymmetry which is important for understanding the heterogeneities in the single molecule responses. In addition, dissymmetry in emission polarization has been studied using a novel imaging technique resolving polarization components on a frame-by-frame basis. The research into the intersection of single molecule spectroscopy and chiroptics has given new insight into the role of solvation and local environment in chiroptical interactions and may be useful for understand chiral-based photonics and advancing new technologies.

Direct, efficient oxidation of alkanes is a long-standing goal of catalysis. Gas phase FeO+ can convert methane to methanol and benzene to phenol under thermal conditions. Two key intermediates of these reactions are the [HO-Fe-R]+ insertion intermediate and Fe+(ROH) (R=CH3 or C6H5) exit channel complex. This work describes measurements of the vibrational spectra of these intermediates and electronic structure theory calculations of the potential energy surfaces for the reactions. They help to characterize the mechanism for these reactions. Chapter 1 describes previous studies of methane-to-methanol and benzene-to-phenol conversion by gas-phase transition metal oxide cations. Spectra of gas-phase reaction intermediates are obtained using photofragment spectroscopy, in which absorption of a photon leads to bond breaking. Utuilizing this technique to measure vibrational spectra is challenging, due to the low photon energies involved. Techniques used to measure vibrational spectra of ions - argon tagging, infrared multiple photon dissociation (IRMPD), vibrationally mediated photodissociation (VMP) and infrared laser assisted photodissociation spectroscopy (IRLAPS) are also detailed in chapter 1. The photofragment spectrometer and laser systems used in these studies are described in chapter 2, as is a multi-pass mirror arrangement which I implemented. This greatly improved the quality of vibrational spectra, particularly those measured using IRMPD. Chapter 3 describes studies of the O-H and C-H stretching vibrations of two intermediates of the FeO+ + CH4 reaction. These intermediates are selectively formed by reaction of laser ablated Fe + with specific organic precursors and are cooled in a supersonic expansion. Vibrations of the sextet and quartet states of the [HO-Fe-CH 3]+ insertion intermediate and Fe+(CH 3OH) exit channel complex are measured by IRMPD and Ar-tagging. Studies of the O-H stretching vibrations of the [HO-Fe-C6H5] + and Fe+(C6H5OH) intermediates of the FeO+ + C6H6 reaction are discussed in chapter 4. For Fe+(C6H5OH), the O-H stretch is observed at 3598 cm-1. Photodissociation primarily produces Fe+ + C6H5OH. IRMPD of [HO-Fe-C 6H5] + mainly produces FeOH+ + C6H 5 and the O-H stretch spectrum consists of a peak at ~3700 cm -1 with a shoulder at ~3670 cm-1. Chapter 5 compares three techniques - IRMPD, argon-tagging, and IRLAPS - in the quality of the measured vibrational spectra of Ag+(CH 3OH) ions produced under identical conditions. The sharpest spectrum is obtained using IRLAPS. The O-H stretch is observed at 3660 cm -1. Monitoring loss of argon from Ag+(CH3OH)(Ar) gives a slightly broader peak, with no significant shift. The vibrational spectrum obtained using IRMPD is shifted to 3635 cm-1, is substantially broader, and is asymmetrical, tailing to the red.

Hybrid quantum dot/organic semiconductor systems are of great interest in optoelectronic and photovoltaic applications, because they combine the robust and tunable optical properties of inorganic semiconductors with the processability of organic thin films. In particular, cadmium selenide (CdSe) quantum dots coordinated with oligo-(phenylene vinylene) ligands have displayed a number of hybrid optical properties that make them particularly well-suited to these applications. When probed on an individual particle level, these so-called CdSe-OPV nanostructures display a number of surprising photophysical characteristics, including strong quenching of fluorescence from coordinating ligands, enhanced emission from the CdSe quantum dot core, suppression of fluorescence intermittency, and photon antibunching, all of which make them attractive in the applications described above. By correlating fluorescence properties with atomic force microscopy, the effects of ligands on quantum dot luminescence are elucidated. In addition, recent studies on individual CdSe-OPV nanostructures have revealed a strong electronic coupling between the coordinating ligands and the nanocrystal core. These studies have shown that excitations in the organic ligands can strongly affect the electronic properties of the quantum dot, leading to linearly polarized optical transitions (both in absorption and emission) and polarization-modulated shifts in band edge emission frequency. These polarization effects suggest exciting new uses for these nanostructures in applications that demand the robust optical properties of quantum dots combined with polarization-switchable control of photon emission.

In the past decade, polyelectrolyte complexes (PECs) have received considerable attention as novel therapeutic agents for gene delivery technologies. The process of the gene delivery contains the formation of PECs, and the releasing of DNA from the PEC in the presence of longer polyanions inside the cells. These two aspects were studied, yet not completely understood so far. We made our contributions in these two aspects by studying two important questions in two chapters. In the first chapter, we studied the formation mechanism of single polyelectrolyte complex (PEC). The central question of chapter is the effective driving force between two polyelectrolytes during the complexation. This question was stated, studied and answered by Langevin dynamics simulation in both no salt and salty conditions. The conformation and degree of ionization change of chains were also systematically analyzed in this study. We found that a constant driving force between polyelectrolytes under certain circumstances in this process. In the second chapter, we investigated the mechanism of the DNA releasing by studying the substitution reaction of single PEC. The central topic in this chapter is the substitution efficiency, i.e., how hard/easy the substitution would happen. We answer this general question by discussing the minimum length of invader needed for an efficient substitution. We have concluded that the impetus of substitution reaction is the entropy gain due to counterions replaced by monomers in the formation of new complex. In the third chapter, motivated by the recent discovery of conductivity increase of PSS:PEDOT complex in ionic liquids(ILs), we investigated the effects of salt and ILs on PECs, and concluded that the stability of PEC is the result of the competition between the charge density of chains making the PEC and the concentration of salt around the PEC. Moreover, we studied the novel structure of PEC in the presence of ionic liquids (ILs), and suggested the direction of future theoretical study for this topic.

Includes bibliographical references. / Use was made of Nuclear Overhauser effects (nOe) and crystallography to determine the structure and packing in novel liquid clathrate systems. The stoicheiometry of the clathrates was investigated by various chemical methods including: thermogravimetric analysis, differential thermal analysis and proton nuclear magnetic resonance spectroscopy.

This thesis describes an investigation, by computer simulation, into the nature of the metal ion binding to low molecular weight ligands in blood plasma. A successful attempt is made to accommodate the effects of metal protein binding on the computed distribution that is obtained. An evaluation of the results is undertaken. The value and some applications of the knowledge arising from this kind of study are examined. The collection, assembly and processing of the data is described. A computer program is written to cope with the very large equilibrium systems that are simulated. The experimentally determined values for the formation constants of the metal ion ligand complexing reactions in the biofluid are found in the literature. These are corrected whenever they are not applicable to physiological conditions of temperature and ionic strength. Where no experimental values were available, formation constants for complexes that seemed likely to be important were estimated using certain types of chemical trend. The results of the blood plasma model may be summarized as follows. Copper and ferric iron are found to exist exclusively as ternary complexes except that the copper dihistidinato complex is important. With copper, these ternary complexes always involve histidine whilst citrate plays an analogous role in the ferric complex formation. Calcium, magnesium and manganese do not appear to exist as ternary complexes. With these three cations the bicarbonate species predominate although the binding is weak; as a consequence of the relatively high ligand concentration in plasma. Zinc and lead form both binary and ternary complexes. The ternary zinc cysteinate citrate complex is found to account for a significant percentage of the low molecular weight complex fraction of this metal. This result is in contrast to those of previous models.

Free radicals are reactive molecules, which makes them difficult to study. Learning more about free radicals is necessary since they are implicated in many diseases and conditions such as Alzheimer’s disease and aging. Spin traps are molecules that can be used to stabilize free radicals to allow time for the free radicals to be characterized. The purpose of this research was to examine four novel spin traps that combine the properties of existing spin traps to possibly create more effective spin traps. The four novel molecules in question were designed by taking the 4-methylfuroxanyl ring from the α(Z)-(3-methylfuroxan-4-yl)-N-t-butylnitrone spin trap and combining it with the 5,5-dimethylpyrroline-N-oxide, the 5-methyl-,5-(trifluoromethyl)pyrroline-N-oxide, the 5-acetamide,5-methylpyrroline-N-oxide, and the 5-carboxamide,5-methylpyrroline-N-oxide spin traps. These four novel spin traps were studied using the hydroxyl radical since it is an abundant free radical in biological systems. The computational methods Hartree-Fock (HF) and Density Functional Theory (DFT) were used to calculate the optimized geometries for the reactant species and the hydroxyl radical additions at the C-site, at the O-site, and for the diadduct, which is when two free radicals add, at the HF/6-31G*, HF/cc-pVDZ, DFT/B3LYP/6-31G*, and DFT/B3LYP/cc-pVDZ levels of theory. From these calculations, the thermodynamic stability of the final product versus the initial reactants was obtained. The C-site addition was found to be more thermodynamically favorable for all the molecules than the O-site addition. The diadduct radical addition for the four molecules was the most thermodynamically favorable. The next step in the research would be to explore the methylfuroxan-4-yl ring on other molecules to continue expanding the effectiveness of spin traps, so free radicals can be better understood.

The work of Hotz showed the lack of knowledge of the behaviour of electrolytes in acetone solutions as well as the uncertainty as to the possibility of preparing anhydrous acetone and the stability of this solvent, if it could be prepared. An extensive study was therefore undertaken in which the efficiency of various desiccants was studied in producing acetone as anhydrous as could be obtained. A very efficient still was designed and the average water content of the acetone produced was of the order of 0.006 per cent which is much lower than reported by any previous investigator. Moisture determinations were done using a modified Karl Fischer reagent.

Includes bibliographical references. / The contents of this thesis are essentially in two parts. The first deals with solution studies relating to the methyldopa-copper(II) system and its relevance to medicinal chemistry, a full abstract of which is given on page 1 of the main text. The second part describes five single crystal x-ray investigations into some interesting compounds isolated at this university. The abstracts to these topics may be found preceding the relevant sections as they appear in the text on pages 94, 118 and 146, respectively.