Synthesis and Study of Non-Kekule Molecules

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This proposal requests funds to examine a series of disjoint biradicals by chemical and spectroscopic methods. Molecular orbital calculations have predicted that disjoint biradicals will possess a singlet ground state. Previous work from this laboratory has resulted in finding a triplet ground state disjoint biradical. This contradiction of theory will be pursued further with new examples which have rigidly defined structures for comparison to theoretical calculations. Non-alternant biradicals will be explored, which contain in some fashion, cyclopentadiene rings. The interplay between structure and multiplicity of these biradicals will be explored, where lower membered systems are expected to be singlets and higher membered systems triplets. This grant from the Organic Dynamics Program supports the continuing work of Professor Paul Dowd at the University of Pittsburgh. The chemical and spectroscopic properties of a novel series of reactive intermediates known as biradicals will be examined. Biradicals are molecules where there are an odd number of electron at two sites. For example, in a hydrocarbon biradical, two carbon atoms will each be bonded to three other carbon atoms and have one unbonded electron. The two odd electrons may have spins paired (a singlet) or unpaired (a triplet). The lowest energy states (singlet or triplet) of the biradicals will be determined experimentally as a function of structure. These results will be compared to theoretical calculations.