Collaborative Research: Multireference Studies of Organic Polyradicals, Radical Reactions and Graphene Nanoribbons

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Carol Parish at the University of Richmond and Hans Lischka at Texas Tech University are supported by an award from the Chemical Theory, Models and Computational methods program to perform theoretical investigations of the structures, reactivities and excited states of di-, tetra- and poly-radical molecules important to understanding reaction mechanisms, pyrolysis and combustion of alternative fuels, anticancer antibiotics and graphene nanodevices. A fundamental understanding of the proper physical characterization of polyradicals is critically important for the further development of multireference (MR) electronic structure theory as well as understanding and controlling chemical phenomenon involving these open-shell intermediates. This proposal focuses on utilizing MR methods (MR-CI, MR-AQCC, CASPT2) to study 1.) model systems such as the geometries and excites states of o-, m- and p-benzyne, 2.) diradical intermediates found in the pyrolyis of asphaltene heteroaromatic compounds, 3.) novel electrocyclization reactions producing diradical intermediates that may function as anticancer antibiotics, 4.) reactions involving tetraradicals and the role that through-bond coupling plays in radical electron interaction, 5.) diradical and multiradical defects in graphene and to benchmark these MR methods against DFT results and 6.) developing input and analysis tools for the COLUMBUS package to facilitate the use of these highly correlated MR methods by the chemical community including undergraduate students. The ability to characterize properly open-shell polyradical species and the corresponding investigation of novel cyclization reactions holds significant promise for advancing the fields of MR theoretical chemistry, mechanistic organic chemistry, materials design and drug optimization. The proposal delineates several carefully conceived theoretical experiments designed to be performed by undergraduate researchers, graduate students and post-baccalaureate or post-doctoral fellows. This will create a community of scientists focusing on the proper characterization of interesting polyradical species using state-of-the-art electronic structure methods. Students at all levels will learn the details of computational quantum mechanics, spectroscopy and methods development.