RUI: Spectroscopic and Computational Studies of Alpha, Beta-Unsaturated Carbonyl Compounds in Triplet Excited States

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Professor Stephen Drucker, Department of Chemistry at the University of Wisconsin - Eau Claire is funded by the Chemical Structure, Dynamics and Mechanisms A (CSDM-A) program for "Spectroscopic and Computational Studies of Alpha, Beta-Unsaturated Carbonyl Compounds in Triplet Excited States." Triplet states (species having two unpaired electrons) play a central role in many reactions that occur in the presence of light. Prof. Drucker and his group are investigating the nature of the triplet states of a series of organic molecules and aree exploring the differences between the triplet states and their singlet (the species that has no unpaired electrons) counterparts. These studies give fundamental insights into light induced chemical reactions. In addition, the experiments provide benchmark spectroscopic information for testing or refining computational treatments of chemical species. In this project, undergraduate group members will conduct in-depth research. Such opportunities add substantial value to the undergraduate education program, and can also foster rich opportunities for advanced study. Ongoing collaborations with investigators at Purdue will enable Prof. Drucker's undergraduates to participate in a range of activities. In turn, graduate students in the collaborating research group will be able to explore faculty careers at undergraduate institutions as they interact with Prof. Drucker and his students from UW-Eau Claire.The cavity ringdown (CRD) spectra of acrolein and isotopically substituted derivatives under the cooling conditions of a free-jet expansion, using a slit nozzle source are being recorded. These experiments afford high-precision inertial constants that will be used to determine a substitution structure for the T1 state. Experimental geometrical parameters will be compared with predictions of equilibrium geometry from high-level calculations. In a second component of the project, CRD at room temperature or in a planar free-jet expansion is used to characterize the lowest triplet states of monocyclic alpha,beta-unsaturated carbonyl compounds. Studies on cyclic enones, including cyclic lactones, provide information on the relative energies of the triplet (n,pi*) and (pi,pi*) states, the propensity for configuration mixing, and hyperconjugation between these molecules. The ability to reproduce such differences will constitute a stringent test of TDDFT or other computational methods.