CAREER: Development of Single-Molecule Fluorescence Imaging for Studying Inorganic, Organic, and Organometallic Reaction Mechanisms

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This award in the Inorganic, Bioinorganic and Organometallic Chemistry program supports work by Professor Suzanne Blum at the University of California, Irvine, to apply single-molecule fluorescence microscopy in the study of mechanisms of reactions which are of broad interest to the chemical community. Currently available techniques that study the properties of molecules en masse, e.g. ensemble spectroscopy, suffer from two major drawbacks: (1) instrument dynamic range that leads to an inability to detect minor (under ~1%) components in mixtures; and (2) lack of information on which components are responsible for reactivity and catalysis. The difficulty in observing catalytic intermediates is summarized by Halpern's Rule: "If you can observe or isolate an intermediate, it is unlikely to be catalytically relevant." Single-molecule approaches circumvent Halpern's Rule, because trace quantities of material can be probed spectroscopically, regardless of whether these intermediates accumulate to a level necessary for ensemble spectroscopy. Similarly, single molecule techniques permit direct observation of intermediates regardless of their position on the reaction coordinate (e.g., after the rate-determining step) and in part-per-billion quantities. Although a special issue of Science recently recognized the emerging power of single-molecule microscopy to answer biochemical questions, the potential of these techniques to answer chemical questions remains virtually untapped. The proposed research provides a general method to study a range of reactions, by attaching fluorescent tags to reagents and using total internal reflectance (TIRF) microscopy to monitor individual covalent bond forming events. Several different representative types of synthetically important organometallic reactions will be examined, including olefin polymerization and arene amination. Additionally, because TIRF is used, these single-molecule experiments will enhance our understanding of surface chemistry, and catalysis at the surface/solution barrier. Through a professional development program, graduate student teaching assistants work with the PI to participate in curriculum and lecture design at the highest levels. Discussion of pedagogy and assessment of impact play key roles. In the long term, the program improves the skills of community college, university, and K-12 teachers.Through a professional development program, graduate student teaching assistants work with the PI to participate in curriculum and lecture design at the highest levels. Discussion of pedagogy and assessment of impact play key roles. In the long term, the program improves the skills of community college, university, and K-12 teachers.