Electric-arc vaporization of graphite rod/metal (or metal oxide) mixtures in an inert He atmosphere has been the method of choice for the production of endohedral metallofullerenes (Am@C2n). However, yields of endohedral metallofullerenes have been limited to only a few percent of the total fullerene yield, making the production and isolation of macroscopic quantities (grams) difficult. In the present study, fullerene/metal mixtures have been vaporized using a CO₂-laser beam. The sample pellets employed in the laser vaporization were prepared from empty-cage fullerenes (C60, C70, C76, C78, C84, ..• ) and small percentages, by weight, of metal or nletal oxide (La203, SC203, Y 203, Sc, Y, Er). In addition, a sample mixture of a scandium endohedral metallofullerene extract, prepared by electric-arc vaporization, was subjected to the laser. Vaporized samples were analyzed by negative-ion chemical ionization mass spectrometry and by normal phase HPLC. Inert atmospheres of helium, argon, and xenon were compared for optimization of yields of endohedral metallofullerenes, as well as for production of unique endohedral species not observed by production via electric-arc vaporization. Scandium, yttrium, and erbium endohedral metallofullerenes were synthesized by vaporization of fullerene mixtures and the appropriate metal. Optimum conditions were realized with pellet temperatures greater than or equal to 3000°C and inert gas pressures of -100 Torr. This method of CO₂ laser vaporization also served as a valuable tool to analyze the production mechanisms of fullerenes and endohedral metallofullerenes, such as production pathways (Le., C60 -> higher fullerenes -> endohedral metallofullerenes). / Master of Science

This dissertation elucidates a greater understanding of the vaporization and electrospray post-ionization mechanisms when using femtosecond laser pulses for desorption of surface molecules and electrospray ionization for capture and mass analysis of the gas phase ions. The internal energy deposition from nonresonant vaporization with femtosecond laser pulses was measured using dried and liquid samples of p-substituted benzylpyridinium ions and peptides. In the comparison of the experiments of using 800 nm and 1042 nm laser pulses, it was found that there are different vaporization mechanisms for dried and liquid samples. It was established that LEMS is a "soft" mass analysis technique as it resulted in comparable internal energy distributions to ESI-MS with one caveat; multiphoton excitation of dried samples results in extensive fragmentation at higher pulse energies. The quantitative aspects of the laser electrospray mass spectrometry (LEMS) technique were established using various multicomponent mixtures of small biomolecules. Experiments with LEMS resulted in similar quantitative characteristics to ESI-MS except that ESI-MS demonstrated a greater degree of ion suppression when using higher concentrations, particularly in the four-component mixture. The lack of ion suppression in the LEMS measurements was due to the ~1% neutral capture efficiency and most likely not a result of nonequilibrium partitioning. This was supported by the excess charge limit not being surpassed in the LEMS experiments and the quantitative analysis requiring the use of response factors. This dissertation also expanded upon the use of multivariate analysis for the classification of samples that were directly mass analyzed without any sample preparation using LEMS. A novel electrospray complexation mixture using cationic pairing agents, a lipid, and sodium acetate enabled the simultaneous detection of positive, neutral and negative charged features of inorganic-based explosive residues in a single experiment. This complexation mixture also enabled the detection of new features from an RDX-based propellant mixture. Principal component analysis (PCA) proved reliable for accurate classifications of the explosive mixtures. PCA was also used for accurate classification of eight phenotypes of Impatiens plant flower petals after mass analysis with LEMS. The PCA loading values were used to identify the key biomarkers in the classification. These important mass spectral features were identified as the biologically-relevant anthocyanins, which are phytochemicals that are responsible for the color of the flower petals. / Chemistry

In this dissertation, different approaches have been employed to address the quest of understanding the formation and growth mechanisms of carbon-containing molecular ions with relevance to astrochemistry. Ion mobility mass spectrometry and DFT computations were used to investigate how a second nitrogen in the pyrimidine ring will affect the formation of a covalent bond between the benzene radical cation and the neutral pyrimidine molecule, after it was shown that a stable covalent adduct can be formed between benzene radical cation and the neutral pyridine. Evidence for the formation of a more stable covalent adduct between the benzene radical cation and the pyrimidine is reported here. The effect of substituents on substituted-benzene cations on their solvation by an HCN solvent was also investigated using ion mobility mass spectrometry and DFT computations were also investigated. We looked at the effect of the presence of electron-withdrawing substituents in fluorobenzene, 1,4 di- fluorobenzene, and benzonitrile on their solvation by up to four HCN ligands, and compared it to previous work done to determine the solvation chemistry of benzene and phenylacetylene by HCN. We report here the observed increase in the binding of the HCN molecule to the aromatic ring as the electronegativity of the substituent increased. We also show in this dissertation, DFT calculations that reveal the formation of both hydrogen-bonded and electrostatic isomers, of similar energies for each addition to the ions respectively. The catalytic activity of the 1st and 2nd row TM ions towards the polymerization of acetylene done using the reflectron time of flight mass spectrometry and DFT calculations is also reported in this dissertation. We explain the variation in the observed trend in C-H/C-C activity of these ions. We also report the formation of carbide complexes by Zr+, Nb+, and Mo+, with the acetylene ligands, and show the thermodynamic considerations that influence the formation of these dehydrogenated ion-ligand complexes. Finally, we show in this dissertation, a novel ionization technique that we employed to generate ions that could be relevant to the interstellar and circumstellar media using the reflectron time of flight mass spectrometry.