The Organic and Macromolecular Chemistry Program in the Chemistry Division at the National Science Foundation supports Professor Weston T. Borden of the University of North Texas who will perform research that will increase our understanding of the electronic structures and reactions of organic and organometallic molecules. Among the molecules on which Density Functional Theory (DFT) and ab initio calculations will be performed are: (a) tetrakis-annelated cyclooctetraene derivatives, in which the ground state is expected to be formed by transfer of a pair of electrons from high-lying sigma molecular orbitals (MOs) into one of the non-bonding MOs of the eight-membered ring, (b) substituted [2.2.2]propellanes, in which twelve fluoro, twelve methyl, and six carbonyl groups are all predicted to provide remarkable strengthening of the central C-C bond toward cleavage, (c) hexakis(trifluoromethyl)prismane, in which the six trifluoromethyl groups have been found experimentally to stabilize the molecule against ring opening to the corresponding Dewar benzene, and (d) a novel tetraradical in which the effect of geminal fluorines on the ordering of the low-lying electronic states (a quartet, three triplets, and two singlets) will be calculated, in advance of experiments to be performed by a collaborator at Hiroshima University in Japan.

Research by Professor Borden in the previous award period has produced quality publications and this is expected to continue. The broader impacts of Professor Borden's activities as an Associate Editor at the Journal of the American Chemical Society has contributed to maintaining the quality of the Journal as well as leading to Professor Borden editing a new online Journal called JACS Selects, featuring the best papers published in JACS in a particular area of chemistry. Being able to choose for JACS Selects not only the best papers published in JACS but also the experts best qualified to comment on each of these papers, would be impossible if the PI were not an active researcher himself. Professor Borden will also continue to mentor his post-docs and graduate students, to help them learn to (a) recognize unusual findings in both experimental and computational chemistry, (b) find explanations of these findings, (c) make predictions based on the explanations, and (d) communicate these explanations and predictions to other researchers, both orally and in writing. He will also pay special attention to mentoring members of his research group who belong to underrepresented groups to help them to become first-rate researchers.

Project Report

The research that was undertaken with support from NSF Grant CHE-0910527 had two major goals. The first goal was to carry out quantum mechanical calculations on the electronic structures of molecules that might, unlike most molecules, have two unpaired electrons. The second goal was to investigate computationally organic reactions that might occur by quantum mechanical tunneling through reaction barriers, rather than passage over these barriers. In both types of projects the purpose of our calculations was to make predictions that could be tested experimentally. In fact, we collaborated with experimentalists on performing such tests. These tests confirmed that the predictions that we had already published were, indeed, correct. The experimental confirmation of our predictions shows that the calculations we performed are accurate and that the qualitative reasoning that led us to perform these calculations is correct. Thus, the importance of the research that was completed under CHE-0910527 is really three-fold. First, the research identified specific molecules that have two unpaired electrons and specific reactions that proceed by quantum mechanical tunneling. Second, the research demonstrated the ability of quantum mechanical calculations to compute, with quantitative accuracy, the energy differences between the electronic states of molecules that have two unpaired electrons and the rates of reactions that proceed by quantum mechanical tunneling. Finally, and most importantly, the research validated the physical models that we used to make our qualitative predictions about which types of molecules will have two unpaired electrons and which types of reactions will proceed by quantum mechanical tunneling. The validation of the physical models that we used to make our predictions can be construed as being one of the broader outcomes of the research done under CHE-0910527. Another broader outcome is the training of the undergraduates and post-doctoral fellows who participated in the research supported by CHE-0910527.

National Science Foundation (NSF)
Division of Chemistry (CHE)
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Tyrone D. Mitchell
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University of North Texas
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