This grant in the Organic and Macromolecular Chemistry Program will support Dr. Dennis Dougherty's research into the properties of a group of organic chemical fragments known as biradicals. Biradicals can be thought of as molecules that contain a broken carbon-carbon bond. As such, they are excellent models for the transition states of reactions that involve bond-making and/or bond-breaking. In addition, their unusual electronic structures often lead to novel optical and magnetic properties. Biradicals also occur as intermediates in chemical reactions. Thus, their chemistry is an important part in developing an understanding of chemical structures and reactivity. The major tools of this study will be organic synthesis, matrix isolation spectroscopy and theoretical modeling. Fundamentally new structural types will be synthesized, often requiring the development of new synthesis methodologies. EPR, IR, and UV/VIS spectroscopies will be used to investigate the electronic structures of biradicals. Such spectroscopy will also allow the evaluation of the intrinsic reactivity patterns of biradicals by direct observation. A variety of theoretical tools will be used to guide and interpret the experimental studies. Specific targets include: a series of substituted cyclobutanediyls that will provide the first systematic study of the effects of substituents on the spectroscopy and reactivity of localized 1,3- biradicals; a new design for very high spin organic structures; the non-Kekule isomers of benzene and naphthalene and perturbed derivatives; and a new precursor of tetrahedrane.
