Single electron transfer (SET) mechanisms are becoming ubiquitous in modern organic chemistry. However, it is often difficult to distinguish SET mechanisms from polar mechanisms. Kinetics, products and product distributions, and response to perturbation in solvent and substituents are often identical between the two mechanisms. Detection techniques such as EPR, CIDNP, and UV absorption can often detect "blind" pathways and thus cannot provide unambiguous evidence regarding the true mechanism of interest. In recent years mechanistic probes have been developed which can test for single electron transfer in the mechanism of interest in a more unambiguous manner, although a given probe is often applicable to a narrower range of reactions. In this work 1,1-dimethyl-5,7-di-t-butylspiro[2.5]octa-4,7-dien-6-one (6) is presented as a new "hypersensitive" probe for single electron transfer to conjugated carbonyl compounds. This new probe functions in a rather unique fashion, allowing interpretation of the mechanism at work on the basis of the regiochemistry of spirocyclic ring opening. This "regiodifferentiation" based probe was studied with a variety of nucleophiles (particularly Grignard reagents) and has been found to be effective in differentiating SET from polar processes, although surprising results indicative of polar pathways in the case of reaction of 6 with Grignard reagents other than methyl Grignard were found. Additional insight into the mechanism of the reaction of Grignard reagents with conjugated ketones is also presented. / Master of Science

Several new families of organic acceptors that are candidates as building blocks of molecule-based ferrimagnets were synthesized and characterized. These families include fluorodicyanostilbenes, a tetrachlorodicyanostilbene, naphthyltricyanoethylenes, bromophenyltricyanoethylenes, and an anthryltricyanoethylene. The magnetic networks were synthesized by reacting each acceptor with V(CO)6. The magnets synthesized in this study were characterized using a SQUID magnetometer, elemental analysis, and infrared spectroscopy. Although some combinations failed to yield magnetically ordered materials, others exhibited ordering temperatures in the range of 95 K – 260 K. The ordering temperatures and saturation magnetizations were compared among families of acceptors and correlated with individual properties of the acceptors such as reduction potential and structure. / Doctor of Philosophy / Several new families of organic molecules have been created and examined for use as building blocks of molecule-based magnets. These families include fluorodicyanostilbenes, a tetrachlorodicyanostilbene, naphthyltricyanoethylenes, bromophenyltricyanoethylenes, and an anthryltricyanoethylene. The 3-D magnetic scaffoldings were created by combining an individual organic molecule in one of the families listed above with vanadium. The magnets created in this study were examined using a SQUID magnetometer, elemental analysis, and infrared spectroscopy. Some of the combinations of the organic molecules with vanadium failed to result in a 3-D magnetic scaffolding and showed no magnetic properties. Others showed magnetic properties in the below certain temperatures in the range of 95 K – 260 K. The magnetic properties were compared among families of molecules and correlated with individual properties of each molecule such as electronic effects and structure.

During fabrication of integrated circuits, fluorocarbon plasma etching is used to pattern dielectric layers. As a byproduct of the process, a fluorocarbon residue is deposited on exposed surfaces and must be removed for subsequent processing. Conventional fluorocarbon cleaning processes typically include at least one plasma or liquid treatment that is oxidative in nature. Oxidative chemistries, however, cause material degradation to next generation low-dielectric constant (low-k) materials that are currently being implemented into fabrication processes. This work addresses the need for alternative fluorocarbon-residue removal chemistries that are compatible with next generation low-k materials. Radical anion chemistries are known for their ability to defluorinate fluorocarbon materials by a reductive mechanism. Naphthalene radical anion solutions, generated using sodium metal, are used to establish cleaning effectiveness with planar model residue films. The penetration rate of the defluorination reaction into model fluorocarbon film residues is measured and modeled. Because sodium is incompatible with integrated circuit processing, naphthalene radical anions are alternatively generated using electrochemical techniques. Using electrochemically-generated radical anions, residue removal from industrially patterned etch structures is used to evaluate the process cleaning efficiency. Optimization of the radical anion concentration and exposure time is important for effective residue removal. The efficiency of removal also depends on the feature spacing and the electrochemical solvent chosen. The synergistic combination of radical anion defluorination and wetting or swelling of the residue by the solvent is necessary for complete removal. In order to understand the interaction between the solvent and the residue, the surface and interfacial energy are determined using an Owens/Wendt analysis. These studies reveal chemical similarities between specific solvents and the model residue films. This approach can also be used to predict residue or film swelling by interaction with chemically similar solvents.

The chemistry of the radical anion generated from 1,I-dimethyl-5,7-di-tbutylspiro[ 2,5]octa-4,7-dien-6-one (<b>20</b>) was studied electrochemically using cyclic and linear sweep voltammetry (CV, LSV). The reduction potential of <b>20</b> was estimated to be -2.5 V VS. 0.1 M Ag⁺/Ag, similar to the reduction potentials observed for aryl ketones and enones. LSV results for the reduction of <b>20</b> are consistent with the occurrence of substrate reduction followed by a subsequent chemical step (an EC mechanism). The broadness of the reduction wave and variation of peak potential with sweep rate suggest that the rate limiting step is heterogeneous electron transfer. Ring opening of the radical anion generated from <b>20</b> results in a 9:1 ratio of the 3° and 1° distonic radical anions. The rate constant for ring opening has been estimated to be k ≥ 10⁷s⁻¹ with a calculated (AM1) enthalpy of ring opening of ΔH° > -15 kcal/mol. The facile nature of radical anion ring opening can be ascribed to the relief of cyclopropyl ring strain in conjunction with the establishment of aromaticity. On this basis, the regiochemistry of the ring opening of the radical anion derived from <b>20</b> suggests that polar and SET pathways can be differentiated based upon the regiospecificity of cyclopropyl ring opening. In reactions between <b>20</b> and nucleophiles known to react via SET with carbonyl compounds, 20 successfully produced products characteristic of SET pathways. However, subsequent studies of the reaction between <b>20</b> and thiophenoxide, a nucleophile purported to undergo SET, produced no evidence for a SET pathway. It was discovered that ring opened products may also be formed by competing polar pathways involving a carbocationic intermediate, especially in protic solvents. In dipolar aprotic solvents, ring opening occurs primarily via an S_N2 process, with nucleophilic attack occurring preferentially at the least hindered carbon. The strengths and weaknesses of <b>20</b> as a SET probe are discussed / Ph. D.