Computational Studies of the 3-Dimensional. Structure of Cyclopenta Polycyclic Aromatic Hydrocarbons Containing a Gulf Region


Chemistry & Biochemistry

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Recently, some cyclopenta-fused polyaromatic hydrocarbons, an environmentally relevant subclass of chemicals, have been shown to have carcinogenic activity in animals. It has been suggested that benz[l] aceanthrylene (I), an active member of this subclass with a gulf region, has a trans dihydrodiol metabolite that is nonplanar and has two distinct spatial configurations. We have used MMP2(85) and AM1 to investigate the three-dimensional structure of this dihydrodiol and other similar derivatives of (I) and have found that although (I) is somewhat nonplanar the relevant derivatives are all nearly planar. Further, we have computed potential functions for the bending of the angular ring in the gulf region using MMP2(85), AM1, and ab initio computed energies for AM1 spatial configurations and find that these molecules all have only a single potential minimum. We have performed the same calculations for benzo[c]phenanthren and its 1,12 dimethyl derivative, molecules with a similar gulf region for which crystallographic data exists. In agreement with that data, we find that two distinct spatial configurations exist separated by significant barries. The differences between the results generated by the three different methods of computation will be discussed.