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.

Metal-metal and metal-ligand electron delocalization in organometallic complexes, such as biferrocene, bis(mu-fulvalenediyl)diiron, CpM(CO)₄, (Cn*)RhMe₃, and (P₃)RhMe₃, (Cn* = 1,4,7-trimethyl-1,4,7-triazacyclononane and P₃ = CH₃C(CH₂PMe₂)₃ are examined by gas-phase photoelectron spectroscopy. Theoretical studies at various computational levels are also carried out to understand the delocalization. The metal-metal electron delocalization is studied using biferrocene and bis(mu-fulvalenediyl)diiron molecules. Compared with monometallic molecules, these molecules show a different degree of electron delocalization through a bridging ligand depending on the energy match between each ferrocene fragment. The extended π system of the ligand has greater impact on the ligand-based ionizations than on the metal-based ionizations. Further splitting and broadening of the metal-based ionization band is observed for the ring-tilted ferrocene. The metal-ligand electron delocalization is studied with two type of molecules. The first is (η⁵-C₅H₄R)M(CO)₄ (R = H, M = V, Nb, Ta; R = SiMe₃, M = Nb, Ta; R = COCH₃, M = Nb) which is used to probe the metal-carbonyl interaction. In general, these molecules exhibit both extensive delocalization of metal electron density and geometric sensitivity to the electron configuration. Such strong delocalization dampens the substitutent effect introduced onto the Cp ring or at the metal center. A consistent splitting of 0.4 eV is observed for the Cp-based ionization band for all of the molecules due to a dynamic Jahn-Teller distortion of the positive ions. The other type of molecule is (L)RhMe₃ [L = Cn* and P₃]. The amine molecule exhibits a negligible backbonding from the metal to the ligand while the phosphine molecule shows a strong metal-phosphine interaction provided by the electron donation from the metal to the phosphines. As a comparison, spectra of ligands Cn*, Cn, and P₃ show a similar band profile for the first ionization band. Theoretical studies demonstrate that the metal-phosphine backbonding accounts for the different band profiles in photoelectron spectra. A theoretical study of the relaxation energy of metal-based ionizations of CpM(CO)n (M = V, Nb, Ta, n = 4; M = Mn, Tc, Re, n = 3; M = Co, Rh, Ir, n = 2) in the Hartree-Fock formalism has been carried out. The results show that the electron relaxation energy of these molecules can be well understood in terms of Slater's concepts of electron shielding and effective nuclear charge.

One new dianion was prepared and many alkylation and oxidation reactions of this new dianion and several known dianions were carried out. These reactions provide the best synthetic routes to most of the compounds prepared. More specifically, many oxidation products were obtained when 3-methyl-1,4-pentadiene dianion was treated with alkyl bromides. A quantitative yield of substitution product was obtained by reacting this dianion with trimethylsilyl chloride. New compounds obtained by treating this dianion with 1,2-dichloroethane are shown below: The dianion shown below was prepared from 2,5-dimethyl-1,5-hexadiene and Lochmann's base. Many different 2,5-disubstituted 1,5-hexadienes and related compounds were made by treating this dianion with alkyl halides, sulfates and alkyl (alpha),(omega)-dihalides. Attempts to make a cyclic hexapyridyl by treating 2-methyleneallyl dianion with 6,6'-dicyano-2,2'-dipyridyl (see below) apparently failed.

The reversible phosphorylation of proteins plays a key role in nearly every aspect of cell life. This essential post-translational modification controls a myriad of cellular events from cell survival, differentiation, and migration to apoptosis. Two classes of enzymes, kinases and phosphatases, tightly control all phosphorylation events. Perturbation in the activity of any member of these classes of enzymes has been linked to numerous diseases including cancer, metabolic disorders, immune disorders and neurological disorders. Therefore, there is a great interest among the scientific community to develop methods to selectively modulate the activity of kinases and phosphatases not only for therapeutic purposes but also to understand the fundamental role of these enzymes in signaling events. The more than 500 kinases encoded in the human genome share a common catalytic fold and most inhibitors target the ATP binding site. Therefore selective targeting of a single kinase by an inhibitor at the highly conserved ATP binding site is one of the main concerns for designing probes or drugs. Our group has taken advantage of the potency and possible selectivity imparted by bivalent inhibitors and developed an in vitro selection approach to discover bivalent ligands. The strategy involves the use of an ATP-competitive small molecule warhead and a library of cyclic peptides displayed on phage that interact with the kinase of interest in a dynamic selection. The selection for a kinase binding peptide is carried out until consensus peptides are found and bivalent ligands are constructed by linking the selected cyclic peptide with the small molecule warhead through a synthetic linker. Using this approach a potent and selective bivalent inhibitor was found for PKA, a serine/threonine kinase. To interrogate the generality of this approach, a kinase closely related to PKA (PRKX) was used for which a very potent and selective bivalent ligand was found. The same selection strategy was further extended to the two kinases Lyn and Brk, which belong to the tyrosine kinase family. Though peptides were isolated that bound the desired kinase, potent bivalent inhibitors were not discovered. More generally, these experiments in sum are building a library of information regarding how to best design selections of potent and selective bivalent inhibitors. We further explored modulation of the activity of kinases and phosphatases by employing a ligand-gated split-protein approach. The small molecule gated spatial and temporal control of these enzymes should allow the study of signaling events in a controlled manner. The strategy employed consists in the identification of possible fragmentation sites within the catalytic domain of kinases and phosphatases by a sequence dissimilarity approach. Loop insertion mutants at the selected sites were tested for catalytic activity. Successful insertion mutants were further split into two catalytically inactive fragments, which were appended to two conditionally interacting protein domains. Upon addition of a small molecule, the two conditionally interacting domains reassemble the catalytic domain of the enzyme and restore catalytic activity. Using this approach we were able to modulate the activity of the tyrosine kinases Lyn, Fak and Src and the AGC kinase PKA. We also extended the approach to gate the activity of tyrosine phosphatases PTP1B, SHP1 and PTPH1. Finally, these ligand-gated split-kinases and phosphatases were validated in-cellulo. Thus, this work resulted in a new method for designing split-proteins and provided a palette of kinases and phosphatases that can be turned-on by small molecules. In total, these efforts describe two alternative routes that can be used to modulate phosphorylation events in a selective and controlled manner.

Very early in the history of atomic emission spectroscopy (AES) it was understood to be a powerful analytical tool. Until the 1930's the usefulness of atomic spectroscopy was not utilized very extensively even though its fundamental power was understood. The breakthrough that placed it in the standard chemistry laboratory was the discovery and implementation of the photoelectric effect. Since this discovery there has been a revolution in atomic spectroscopy which has brought it from the role of a humble servant used for primary elemental screening to an outstanding leader in applications of elemental analysis. Atomic emission spectroscopy of complex samples has long suffered from matrix effects which result in overlapping of spectral lines, fluctuating backgrounds and changing conditions in the source. Investigations employing an echelle polychromator with a two dimensional solid state array detector show great promise in minimizing the effects of these interferences on multielement analyses of complex samples. The Charge Injection Device (CID) detector used exhibits many characteristics which make it uniquely qualified for simultaneous, multielement detection in AES. With only slight modifications to the optics of a commercial spectrometer and the employment of a CID detector, detection limits for a number of elements are quite favorable. Dynamic ranges of over seven orders of magnitude are obtainable with this experimental system. The reduction of matrix effects by utilizing the huge wealth of information available from over 60,000 individual detector elements are demonstrated through results from several complex matrix standards. This CID-polychromator system was also employed for the element selective detection of gas chromatographic (GC) effluents. A microwave-induced plasma (MIP) based on the Surfatron design was built. A helium plasma from this device has shown to have resilience to organic samples and give good emission response to non-metallic atoms. A number of studies with this GC-AES-polychromator system are presented. This system is capable of monitoring atomic emissions from C, H, F, Cl, Br, I, O, N and S all simultaneously, and the selectivity of this system is unsurpassed. Elemental ratios for separated compounds are also presented as a precursor to empirical formula prediction.

The aim of this work was to study the solution conformation of dimeric and polymeric 1actams. In a first part of this work, the synthesis of bicyc1odi1actams as precursors of the polymers was explored. A new preparation for the 2, 5-diazabicyc1o [2,2,2] octa-3, 6-dione was developed. The dimers and polymers were obtained from the N-protected cis- and trans- 3-amino-6-carboxy-2-piperidone for which an improved synthesis was found. Base treatment of the trans activated ester led to the polymer. Using the methods of solution phase peptide synthesis, the four possible dimers were prepared. After transformation to the paranitrophenyl esters, they polymerized to oligomeric species under the same treatment. The solution conformation of the monomeric, dimeric and polymeric species was determined by 1- and 2-dimensional NMR techniques. The 1actam rings have a chair-like conformation in solution. The cis- 1actam is a powerful β-turn- inducer when incorporated in synthetic peptides. The cis- lactam was found, however, to have a very similar conformation in DMSO solution, without hydrogen bonding to stabilize the turn. No evidence was found for the β-turn in the dimers and polymers using 2-dimensional NMR techniques. The dimers were found to exist in an extended conformation in DMSO. The fact that every other amide bond is in the cis configuration, as well as the steric crowding due to the rings may not allow the existence of the β-turn.

Optoacoustic spectroscopy is a relatively old technique first described by Alexander Graham Bell in 1881. However, over the intervening years, little use was made of the technique due to its low sensitivity. This was due to low source intensities of available infrared light sources which limited the optoacoustic signal strength. With the advent of laser infrared light sources in the 1960's, there has been a resurgence of interest in optoacoustics. No longer is low source intensity a major limitation to successful optoacoustic spectroscopy. Although adequate infrared light sources are available, the large window background signal observed in all optoacoustic systems has been the major limitation in extending trace gas detection limits to the ppb or sub-ppb level. Similarly, there has been little demonstration of the use of the optoacoustic technique in environments where mixtures of gases are present which have severe spectral overlap. This work will discuss a new windowless cell design that largely eliminates the signal background problem ubiquitous to all presently available optoacoustic cells. New methodologies will be discussed that allow analyses of mixtures to be performed even in cases where spectral overlap is severe. Limitations to both the windowless cell and the various multicomponent analysis strategies are discussed.

Rhamnolipids are rhamnose-based glycolipids with strong biosurfactant properties. Because they are naturally occurring surfactants found in Gram-negative bacterial walls, rhamnolipids are biodegradable, low in toxicity and have the potential for bioremediation. However, rhamnolipids are biosynthesized as a large mixture of congeners, making purification poor and scalability difficult. The "green" properties of the compound make it a highly desirable alternative for the many carcinogenic and toxic synthetic surfactants on the market. A method for synthesizing rhamnolipids cost-effectively and at a large scale is highly desirable in a competitive surfactant industry. There is a large amount of literature for glycolipid synthesis, as well as literature for small-scale libraries of rhamnolipid congeners. However, many syntheses involve expensive reagents, dangerous procedures and low-yielding reactions. Therefore, many modifications are made in this dissertation in order to eliminate these problems and limitations. Modifications include standard reduction reactions, easily removable protecting groups and glycosylations utilizing minimally competent Lewis acid promoters. Other techniques involve enantiomer-to-diastereomer conversion for attaining all stereoisomers of the rhamnolipid congeners for comparison and analysis in an efficient manner. A general, cost-effective synthesis for monorhamnolipids is achieved and discussed in the following dissertation. The generality allows for synthesis of glycolipids with different carbohydrates and a variety of primary and secondary lipid alcohols, with varying hydrocarbon chain lengths. Additionally, the synthesis utilizes enantiomer-to-diastereomer conversion via glycosylation for the synthesis and purification of all rhamnolipid diastereomers in a single synthesis. This makes it possible to analyze surface properties and structure-activity relationships of the different congeners and their respective stereochemistry. The synthesis minimizes reaction steps, cost and time required of previously published rhamnolipid syntheses and is general for utilization in the future synthesis of rhamnose- and non-rhamnose-based derivatives, dirhamnolipids, and rhamnolipid polymers.