ANION PHOTOELECTRON SPECTROSCOPY: LESSONS LEARNED

A combination of various ion sources, a reaction cell, mass spectrometry, anion photoelectron spectroscopy and theoretical calculations has been utilized to study cluster anions belonging to a variety of categories. Emphasis has been placed on the rich information and potential applications that one can obtain from these techniques. Obtaining as much information as possible, pushing the boundary of chemistry, designing materials and studying reaction mechanisms are the aspects that one can learn from these experiments and calculations, which are discussed in the introduction and five chapters of this thesis. In Chapter 1, cluster anions showing very special bonding between TM and hydrogen are discussed. The interaction between transition metals (TM) and hydrogen has always been an intriguing research topic for such applications as hydrogen storage and catalysis of hydrogenation and dehydrogenation reactions. Special bonding features between TM and hydrogen other than the simple M-H σ bond are interesting not only because they are scarcely reported but also because they could help to discover and understand the nature of chemical bonding. In chapter 2, by inserting a reaction cell between the ion sources and the Wiley-McLaren region of the time-of-flight mass spectrometer, various reactions between cluster anions and neutral molecules have been studied. The oxidation reactions of aluminum hydride cluster anions and boron aluminum hydride cluster anions give insights about their potential applications as highly energetic materials. The reactions between aluminum hydride cluster anions and commonly used organic ligands shed light on the synthesis of never-existed low oxidation state aluminum containing materials. Chapter 3 discusses the mechanism of CO2 activation and fixation by coinage metal anions and platinum hydride cluster anions. Recycling CO2 is a hot topic by itself, however, our focus has been put on the mechanism of the interactions and reactions. Chapter 4 further stretches the material designing efforts into group 13 elements, aluminum and boron. Study on stable aluminum hydride cluster cations (4.1), o-carborane anions (4.5) and carbon aluminum hydride cluster anions (4.6) promises potential energetic materials. The derivative of AlH4-, AlH2Cp*Cl-, can be used as a building block for ionic liquid or salt (4.2). Li2Al3H8- in section 4.3 shows an unprecedented homocatenated chain, Al-Al-Al. By obtaining electron from Li, Al transmutates into C, and the Al3H83- kernel mimics propane. This discovery sheds light on the synthesis of a new salt, Li3Al3H8, an extension of an existing salt, LiAlH4. In section 4.4, a new precursor, Al+Ph2CO-, for synthesizing low oxidation state Al containing compounds is discussed. Al+Ph2CO- is similar to the famous monovalent AlCl, but the synthesis should be much simpler. Chapter 5 presents the very special chemical bonding features of LiOH2- cluster anion, known as the double Rydberg anion. In history, LiOH2- is the second experimentally observed double Rydberg anion only after the NH4-(NH3)n family. This finding, essentially a new type of chemical bonding, is viewed to have pushed the boundary of chemistry