In this award, Dr. Weber from University of Colorado at Boulder, will study transition metal complex ions with infrared and photodissociation spectroscopy. The ions will be generated by laser vaporization and supersonic expansion, or by electrospray ionization. Transition metal anion complexes with hydrocarbon molecules or CO and CO2 have significance in heterogeneous catalysis in general, and in CH and CO bond activation in particular. The study of halogen metalates in a solvent-free environment is expected to improve our understanding of their intrinsic properties. Frequently, these metalates are precursors for the formation of metal nanoparticles that play an important role in catalysis. In his education plan, Dr. Weber proposes to develop a new approach to teaching quantum mechanics, relying on student interaction and engagement. Dr. Weber will liaise with educational specialists and broadly disseminate the course plan via the internet for others to use.
Many industrial processes rely on heterogeneous catalysis. A famous example is the Haber-Bosch process in which ammonia is generated from hydrogen and nitrogen gases. Ammonia is the main feedstock for fertilizers upon which much of the world's food supply depends on. The gases interact with the solid surface of the catalyst that alters the reaction pathway such that less energy is required to make the reaction occur. In order to improve catalytic performance and the associated cost and resources required to run catalytic reactions, a detailed understanding of the chemical species that form intermittently in the reactions is imperative. Dr. Weber from University of Colorado at Boulder will use sophisticated equipment to generate species involved in catalytic reactions, and to study their structure in great detail. His work is unique in so far as he focuses on negatively charged species that are difficult to investigate, yet are expected to play an important role in these processes. These studies require a solid theoretical understanding on how to mathematically describe bonding interactions. This area of chemistry falls into the realm of quantum mechanics, a course that all chemistry undergraduate students have to pass. It often presents the greatest hurdle for graduation, as the material is mathematically challenging and drastically different from classical physics and chemistry. Dr. Weber plans to develop an interactive course that continuously gauges students' process, and to share this course with his colleagues via the internet.
Intellectual Merit: In this project, the Weber group investigated the structures and properties of complexes that contain transition metals, focusing on two different types of complexes. In one part of the project, so-called coordination complexes were studied. Such complexes are important in several areas of chemistry, from the synthesis of metal nanocrystals to catalysis. The properties of such complexes can be difficult to study in solutions, since the interaction of these molecules with the solvent can alter the properties of the complex itself. In addition, chemical reactions involving such complexes can happen so quickly that it is very difficult to gain any information on the intermediate steps that is necessary to fully understand the mechanisms involved. The Weber group can study these molecules in vacuum, which affords excellent control of the experimental parameters and allows detailed insight into molecular properties. Three of the studies in this area shall be highlighted here. Work on a gold complex that is commonly used to synthesize gold nanoparticles revealed how the photochemistry of the molecule depends on the wavelength of the light used. This can be important for photochemical approaches to synthesize gold nanoparticles. A study on the photochemistry of chromate esters provided evidence concerning the mechanism in which such molecules are degraded by interaction with light. This is important in order to understand the chemistry of toxic hexavalent chromium complexes. A study on the light absorption by permanganate ions showed how these molecules change their absorption spectrum due to different chemical environments. This study provides important benchmark data that can be used by theorists to evaluate the quality of their predictions for similar molecules and thereby improve the predictive power of their methods. In the second project area, the interaction of metal atoms with carbon dioxide was studied in the presence of an extra electron. In the interaction with some metals, this situation can represent a model for the one-electron reduction of carbon dioxide on catalyst surfaces. This process is one of the steps necessary for the conversion of carbon dioxide into feedstock to make useful chemicals and fuels. The Weber group found in these studies that gold and silver can form complexes in which the transfer of an electron onto a carbon dioxide molecule is very efficient. More importantly, the process is driven by the interaction with solvent molecules, which demonstrates that it is critical to take such effects into account in future theoretical models of these and similar catalysts. In contrast, cobalt and nickel formed complexes with carbon dioxide that have very different chemistry and are reminiscent of coordination complexes. The chemistry of copper atoms in this situation shows elements of both types of behavior. These studies provide important information that aid in the understanding of catalytic processes and ultimately may help to design new catalyst materials. Broader Impacts: A part of the CAREER Award has been used to transform the undergraduate Physical Chemistry II course taught at CU Boulder to improve student learning. In addition to learning goal definitions, a number of instruments (concept tests, surveys and student interviews) were developed to measure student learning. The students seemed to respond particularly well to in-class concept tests and to JAVA-applet based simulations that were used to visualize quantum mechanical phenomena and to facilitate inquiry-based learning. The learning goals, clicker questions and homework sets are available to any instructor on request. In addition, some of the concept tests have been modified and expanded upon in graduate courses taught by the PI. Seven graduate students were supported directly or indirectly through the award. Two former students who graduated with PhDs are now tenure-track assistant professors at four-year undergraduate institutions, and one will start in a similar position in 2015. Three former graduate students (two PhDs and one Master Student) are currently instructors at CU on the Boulder and Denver campuses. One former graduate student who graduated with a PhD is now a Foreign Affairs Officer and AAAS Fellow at the U.S. Department of State, concerned with science policy. As mentioned above, the funded work has advanced our fundamental understanding of transition metal chemistry of coordination complexes and carbon dioxide reduction catalysis. This has important consequences for the rational design of catalysts for industrial processes.
