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Metal complexes of meso-dimercaptosuccinic (DMSA) acid were studied by potentiometric and infrared methods. The coordination sites were found to be metal dependent. In the cases of Pb²⁺ and Cd²⁺, one oxygen and one sulfur act as donors; in the case of Hg²⁺, two sulfur atoms act as donors. The solubilities of the chelates were found to be pH dependent. When the uncoordinated sulfhydryl and carboxylic acid groups dissociate, the chelates dissolve and remain in aqueous solution. In the case of racemic-DMSA, two types of Pb²⁺ chelates were isolated: one in which rac-DMSA is coordinated to Pb²⁺ via one oxygen and one sulfur atom and the other in which the Pb²⁺ is coordinated via two sulfur atoms. The monomethyl ester and the dimethyl ester of meso-DMSA (MoMeDMSA and DiMeDMSA, respectively) were synthesized and their metal chelates with Pb²⁺, Cd²⁺, and Hg²⁺ studied. Esterification of meso-DMSA was found to change its biological properties. Both compounds, MoMeDMSA and DiMeDMSA, increased the biliary excretion of cadmium, which strongly suggests that the two derivatives of meso-DMSA enter the hepatocyte. The acid dissociation constants of the chelating agents and the uncoordinated groups in its metal chelates were determined. The results suggested that these acid-base properties in addition to the polarity of the chelating agent contribute to the effectiveness in the mobilization of intracellular deposits of cadmium. The dimethyl ester of DMSA was found to compete effectively with metallothionein for Cd²⁺ and Zn²⁺ ions by ¹H NMR spectroscopy. The structures of the metal chelates formed upon interaction of DiMeDMSA and Cd²⁺, or Zn²⁺ in solution at physiological pH were determined by multinuclear magnetic resonance spectroscopy. Mononuclear complexes were found to be formed. In these complexes, the metal ions are tetrahedrally coordinated by four thiolate groups from two DiMeDMSA molecules.

Several surfaces chemically modified with a variety of surface modifiers have been studied using chromatographic, nuclear magnetic resonance, and computational techniques. The goal was to determine the effect of modifier structure on the solvation, selectivity, and efficiency of chemical interactions occurring at chemically modified surfaces. Oleyldimethylchlorosilane has been synthesized and bonded to silica to determine the effect of a conformational change at the center of the chain on the behavior of the entire surface. It has been shown with these studies that the configuration of the modifier plays an important role in determining the selectivity of chemical interactions at modified surfaces. By comparison with phospholipid bilayers, of the structure, solvation and dynamics of alkylmodified silicas has been achieved. Octyldimethylsilyl- and octadecyldimethylsilyl-modified silicas have been further reacted with t-butyltrichlorosilane, t-butyldimethylchlorosilane and trimethylchlorosilane to determine both the utility of t-butyltrichlorosilane as an end-capping reagent and the extent to which solvation of the near-surface region affects the performance of these surfaces. It was shown that the orientation and solvation of modifiers at the near surface has a profound effect on the selectivity and efficiency of chemical interactions at the surface. Sepharose gels modified with iminodiacetic acid have been studied by titrimetric and spectroscopic means. A model compound has been synthesized and characterized in solution. The results have led to a better understanding of the behavior of chelating agents at sepharose surfaces and the effects of immobilization on the behavior of ligands at a surface. Finally, quartz crystalline microbalances modified with physisorbed polymer layers have been studied by correspondence analysis. In this case, it has been shown that the polymer backbone of the modifying agent plays an important role in determining the selectivity of the modified surfaces. Together these studies have led to a more complete understanding of the effects of the structure and solvation of modified surfaces on the selectivity and efficiency of chemical interactions occurring at those surfaces. These observations apply to interactions occurring at chromatographic stationary phases and to interactions at chemically modified surfaces in general.

The metallacyclopentadiene (DIPp)₂CITa(CCMe₃=CHCH=CCMe₃) (α, α') (DIPP=2,6-diisopropylphenoxide) is isolated from the 2 electron reduction of Ta(DIPP)₂CI₃(OEt₂) in the presence of excess Me₃CC=CH. The α, α' isomer represents the kinetic product of this reaction since it can be thermolyzed to produce (DIPP)₂CITa(CCMe₃=CHCCMe₃=CH) (α, β’). The reactivity of these two isomers toward the addition of ethylene and alkynes has been investigated and found to be driven primarily by steric effects with the less hindered α, β’ isomer showing a more comprehensive chemistry. The rearrangement of α, α' to α, β’ was followed through several kinetic and mechanistic studies. This data support a mechanism involving dissociation of the a,a' isomer to the metallacyclopropene, (DIPP)₂CITa(HC=CCMe₃), and free Me₃CC=CH. These intermediates then recouple to form the thermodynamic product, the α, β’ isomer. The reaction of TA(DIPP)₃Cl₂(OEt₂) with quinoline or 6-methylquinoline (HC) produces the ligand exchange product (η¹-HC)Ta(DIPP)₃CI₂, the 2 electron reduction of either of these products yields [η²-(N,C)-HC]Ta(DIPP)₃ which can be isolated as the phosphine complex [η²-(N,C)-HC]Ta(DIPP)₃(PMe₃) upon reaction with trimethylphosphine. The reaction of either [η²-(N,C)-quinoline]Ta(DIPP)₃ or [η²-(N,C)quinoline] Ta(DIPP)₃(PMe₃) with hydrogen both in the presence and absence of Pd/C produces 1,2,3,4-tetrahydroquinoline and 2,2'-bisquinoline. The production of these compounds implicates the η²-(N,C) bonding mode in selective hydrogenation of heterocycles and ortho functionalization. The reaction of Nb(NEt₂)₂CI₃ with two equivalents of LiNHMes (Mes=2,4,6- C₆H₂Me₃) followed by addition of pyridine produces Nb(NMes)₂CI(py)₂. The reaction of Nb(NEt₂)₂CI₃ with 6 equivalents of LiNHMes produces the first tris imido complex of group 5, [(THF)₂Li][Nb(NMes)₃(NHMes)]. Comparable chemistry is seen with Ta. [(THF)₂Li][Nb(NMes)₃(NHMes)] reacts with lithium alkyls under kinetic conditions to produce [(THF)2Li][Nb(NMes)₃(R)] (R=Me, ⁿSu, ᵗSu, Me₃SiCH₂). Under thermodynamic conditions, however, the reaction of [(THF)₂Li][Nb(NMes)₃(NHMes)] with ᵗBuLi yields the first tetrakis imido complex of group 5, [(THF)₄Li₃][Nb(NMes)₄]

The overall goal of this research is a comprehensive characterization of self-assembled alkanethiol monolayer films at Ag and Au surfaces. A combination of surface Raman spectroscopy and electrochemistry is employed to study several important aspects of these films. Raman vibrational assignments for a series of n-alkanethiols (n = 4, 5, 8, 9, 10, 12, 16, and 18 for C(n)H(2n+1)SH) are determined in the spectral regions from 600 to 1300 cm⁻¹ and 2800 to 3000 cm⁻¹. Particular emphasis is given to the trans (T) and gauche (G) ν(C-S) and ν(C-C) bands and the ν(C-H) bands. Surface Raman spectra of n-alkanethiol films at electrochemically roughened and mechanically polished, polycrystalline Ag and Au surfaces are presented. Strong enhancements of surface Raman scattering are realized at roughened surfaces, while less enhancement is observed at the mechanically polished surfaces. The conformational order of these films at these surfaces is evaluated by the determination of T and G bands present in the spectra. The orientation of these films at Ag and Au is determined through the use of surface Raman selection rules. A method is developed for the determination of orientation of C-S and C-C bonds and methyl groups. The orientations deduced using the spectral results from each of these regions are found to be self-consistent. Different orientations are deduced for alkanethiol films at Ag and Au surfaces and are proposed to be influenced by metal-S bonding. The orientations can be altered in the electrochemical environment by control of the applied potential of these metal substrates. The potential-dependent behavior is correlated with the potential of zero-excess charge (PZC) of these metals. Defect structure of these films at Ag surfaces with various surface morphologies is evaluated with Pb deposition studies. Gross films defects are evaluated with Pb underpotential deposition and ion penetration is studied with bulk Pb deposition. Finally, surface Raman spectra of monolayer films at non-enhancing surfaces are presented. Spectra for butanethiol at single-crystal Ag surfaces and butanethiol and thiophenol at mechanically polished, polycrystalline Pt surfaces show the utility of Raman spectroscopy for studying films at a variety of surfaces.

In the analysis of solid samples, there are two distinct advantages to performing direct analysis on the solid: (1) minimal sample preparation and (2) avoids potential sample contamination from the reagents used in the dissolution process. The two most common optical techniques for direct solids analysis are arc and spark emission spectroscopy. The most important drawback associated with arc and spark spectroscopy is in the acquistion and interpretation of the spectrum. The development of a custom echelle spectrometer with Charge Injection Device (CID) array detection carried out in these laboratories should be particularly well suited for arc and spark emission spectroscopy. CIDs exhibit many of the best characteristics of photographic film and PMT detection while providing the added advantage of nondestructive readout and Random Access Integration (RAI). This thesis describes the work coupling a spark source to a CID/echelle spectrometer. When properly shielded, the sensitive electronics of the CID function normally in the presence of the spark discharge. The potential for this system to be able to handle the wide variety of spectroscopic situations resulting from the complex spectra typically obtained with this type of excitation is attributed to the flexibility of the instrument which allows the use of alternate line for analysis and internal standard calibration. Additionally, the use of multiple lines has been applied to comparative analysis, monitoring the background for changes in excitation, and determination of the optimum lines to be used for quantification. Effective utilization of the large database of spectral information has lead to the development of sophisticated expert systems such as automated qualitative and semiquantitative analysis routines. Preliminary work with an astigmatism free imaging spectrograph and a Charge Coupled Device (CCD) array detector has shown the ease with which spatial and spectral maps of emission source can be generated. Observation of the spark discharge process in a hope of gaining a clearer picture of the mechanisms of sample excitation seems to be the most rational approach to ultimately obtaining control over the spark process and alleviating the problems associated with sparks excitation.

Centrifugal Partition Chromatography (CPC) is a multistage liquid-liquid countercurrent distribution technique which utilizes rotating teflon cartridges to hold a liquid phase stationary while the other liquid phase is pumped at a constant flow rate. It has been demonstrated to be a valuable technique for the base line separations of families of metal ions such as the platinum group metals (PGM)--Pt, Pd, Rh and Ir. The separations of these metals as their anionic chloro complexes were achieved using the heptane-water phase pair with a stable and relatively inexpensive extractant trioctylphosphine oxide (TOPO) functioning as a ligand in its neutral form and as a cation in its protonated form. A striking feature of the chromatograms of the complexes and ion pairs were their much poorer efficiencies compared to the efficiency of an organic analyte like 3-picoline under identical distribution rations. The inefficiencies of the PGM separations were also a function of the concentrations of the aqueous and organic phase components. These inefficiencies could be attributed to slow kinetics of the back extraction of the complexes and ion pairs and could be used to derive the mechanisms of these slow chemical kinetic steps. A correlation was established for the Pd(II) system between the CPC inefficiencies and the half lives of the slow reactions measured independently by stopped flow in micelles. This correlation was utilized to derive the rate constants for the back extraction of the TOPO complexes and ion pairs of Pt and Ir. The mechanisms of the extraction reactions were derived using the principle of microscopic reversibility based on the mechanisms of the back extraction reactions. This was then used to obtain estimates for the rate constants for the extraction reactions as well. The PGM were thus separated and their equilibrium and kinetics (extraction and back extraction) completely characterized using CPC. This is a significant development with CPC because such complete equilibrium and kinetic characterizations are hard to achieve with conventional liquid chromatographic techniques.

Control of separation processes which occur at solid-liquid interfaces can be achieved by understanding the interactions which occur at these interfaces. Because of its many desirable bulk characteristics, silica is the solid support of choice for many separation applications. Utilizing various differential migration techniques, control of the separation at different silica surfaces was investigated through irreversible chemical modification of the surface, the use of a dynamic modifier, and through physicochemical alteration of the silica surface. A new bonded phase was prepared by reacting γ-(3,4 methylene dioxyphenyl) propyldimethylchlorosilane--synthesized from safrole and dimethylchlorosilane--with porous silica yielding a non-traditional bonded phase which maintained some similarity with traditional alkyl bonded phases while also possessing distinct differences. Through the use of diagnostic chromatography this surface was shown to demonstrate unique selectivity towards polar analytes when compared with an octyl and phenyl surface under the same solvation conditions. A thermal study utilizing diagnostic chromatography was also used to demonstrate the impact of orientation on retention at this surface. The large scale separation of C₆₀ and C₇₀ was accomplished using a batch process utilizing a traditional bonded phase under normal phase condiitons. Both the kinetics and thermodynamics of the separation were improved through the addition of a dynamic modifier to the running solvent. Macroscopic quantities of pure C₆₀ and C₇₀ are readily obtained using this approach. Control of electroosmotic flow in silica capillaries was demonstrated by chemically tailoring the surface with a series of novel silane modifiers. Although changes in electroosmotic flow velocity were observed, the ultimate goal of flow reversal was not achieved. Finally, a new ISRP surface was prepared by monoatomic oxygen treatment of large (63-90μm) irregularly shaped modified silica particles. This new ISRP was evaluated to determine if the more technically demanding but practically useful treatment of high efficiency particles for use in direct injection HPLC should be pursued.

The behavior of water at the modified silica interface was studied with Differential Scanning Calorimetry. A model for the interaction of water with the surface of silica was evolved to include the influence of the silica surface, the modification of the surface with hydrophobic and hydrophilic functional groups, and the presence of organic solvents. Initial studies involved the investigation of the melting behavior of water at the surface of unmodified silica. This was studied as a function of pore size, specific surface area, surface activity and specific pore volume. The perturbation of the water in the near surface region by interactions with the surface silanols and the curvature of the silica surface resulted in the observation of a melting peak was that was significantly different than the bulk water behavior. Changes to this peak were observed as a function of the modification of the silica surface with alkyl chains of varying chain length, and variations in the bonding density of these chains. As a consequence of the modification of the surface, the water was able to interact with only isolated silanol sites and this was reflected in a shift in the melting peaks. The deactivation of the silanol sites occurred both through the formation of the silyl ether linkage to the modifier, and the blocking of the surface by the hydrophobic alkyl chains. The changes in the behavior of water at the modified silica interface in the presence of organic solvents were also investigated. It was found that the ability of the organic solvent to hydrogen bond to the silica surface and with water was the greatest contributor to the changes in the melting behavior of the water. The behavior of water at the silica interface modified with hydrophilic functional groups was investigated. It was found that the functional groups that could hydrogen bond with the water could also influence its melting behavior. As a consequence the layer of water affected by the surface was extended further away from the surface than was observed with unmodified silica.

Studies of the mechanisms and energetics of a variety ion-molecule reactions involving organometallic and organic ions, have been performed using Fourier transform ion cyclotron resonance mass spectrometry (FTMS). The bond activation processes of V⁺, VO⁺, VOH⁺, and VOCH₃⁺ with water and methanol were investigated in detail. All ions are observed to preferentially activate the C-O bond in methanol, however C-H and O-H bond cleavage are also observed. The addition of the oxo, hydroxo, and methoxo ligands is found to significantly effect the intrinsic reactivity of the ions, relative to V⁺. The reactions of V(CO)₅⁻ with a wide variety of molecules have revealed mechanistic details of the oxidative addition and ligand switching reactions. Steric effects are proposed to account for the selective reactivity of V(CO)₅⁻ with alcohols and amines. Studies of ligand substitution reactions support an electron transfer initiated mechanism, implying that V(CO)₅⁻ has a triplet ground state and a trigonal bipyramidal structure. The chlorine atom transfer reactions of V(CO)₅⁻ with chloromethanes display a correlation with C-CI bond strength, suggesting the mechanism is initiated by oxidative addition of the C-C1 bond or involves a direct chlorine atom transfer. The decomposition of metallocarboxylate anions ([M(CO)ₓ₋₁CO₂]⁻) was studied in an effort to understand the production of CO₂ by metal carbonyl compounds, proposed as intermediates in the Water-Gas shift reaction. The nascent [M(CO)ₓ₋₁C0₂]⁻*, formed by nucleophilic addition of 0⁻ to M(CO)ₓ (M=Pe, Cr, V), is observed to undergo exclusive loss of CO₂ without subsequent decomposition of the product metal carbonyl anion (M(CO)ₓ₋₁⁻) The reaction of P AHs with O⁻ and O₂⁻ were studied, to investigate the potential of isomer differentiation by chemical ionization. These reactions are characterized by a number of reactive pathways, demonstrating the ability to distinguish isomers which cannot be differentiated by other ionization techniques. Kinetic energy release measurements of the S(N)2 reactions of F⁻ with CH3CI, C₆H₅CI, and CH₃COCl have been made using KEICR. The F⁻/CH₃Cl reaction results in a non-statistical energy disposal. The reaction is proposed to proceed by a direct mechanism.