Spectroscopic Studies of Microsolvation, Hydrogen Bonding, and Proton Transfer

Through this award, funded by the Chemical Structure, Dynamics, and Mechanisms - A Program of the Division of Chemistry, Prof. Kenneth R. Leopold will elucidate fundamental aspects of microsolvation, hydrogen bonding, and proton transfer through microwave spectroscopy of small gas phase clusters. Toward this goal, a new chirped-pulse microwave spectrometer will be constructed. The new instrument will run in tandem with the existing cavity-type Fourier transform microwave spectrometer at the Minnesota laboratory and will reduce data acquisition time by two to three orders of magnitude. Accurate moments of inertia and nuclear hyperfine constants will be obtained from spectra and used to determine the structures of the complexes studied as well as the nature of the electron distributions within the monomer units. The fundamental science will be explored, in many cases, using molecules that are active in the Earth's atmosphere, producing a blend of basic and applied science. The ability to collect data rapidly will permit the sharing of resources with faculty and undergraduates at primarily undergraduate institutions, thus expanding both the scientific and educational impact of the new spectrometer.

Molecules have distinct preferences for how they interact when they approach each other, and these preferences have important effects on the macroscopic world as we know it. This research involves detailed studies aimed at understanding how these intermolecular interactions in the microscopic world relate to the properties of bulk matter. By studying how molecules absorb microwaves, the distances between atoms and the angles between bonds can be determined. Then, by forming small clusters (small groups of molecules), it is possible to learn about the geometric features of intermolecular interactions and how these features evolve as the molecules assemble. Such information constitutes foundational knowledge for a wide variety of disciplines. For example, small molecular clusters can play several roles in the chemistry of the Earth's atmosphere, as they are involved in processes leading to atmospheric acids and aerosols. Moreover, small molecular clusters offer microscopic insight into the molecules dissolve in solutions, whose properties can determine the efficacy of synthetic and industrial processes. Intermolecular interactions also play an important role in biology through their influence on the shapes (conformations) of molecules important in life processes. Thus, this work will have broad impact in areas ranging from environmental chemistry, to industrial chemistry, to molecular biology. The participation of graduate students, undergraduates, and postdoctoral fellows adds a significant educational component to the broader impact of this work.