Computational studies on the effects of heteroatom substitution in delocalized pi systems

Abstract

The effects of heteroatom (or group) substitution in several delocalized x systems are discussed. A brief review of the various types of heteroatom substitutions which preserve an isoelectronic valence space is presented. In the second chapter, a rationalization is presented for why silabenezene readily dimerizes, whereas the isovalent phosphabenzene does not. The next chapter is concerned with heteroatom substitution of the central carbon atom of trimethylenemethane radical cation and trimethylenemethane radical anion, both of which possess doublet ground states. The question addressed is whether an isovalent species with heteroatom substitution might have a quartet ground state. In the final chapter, it is predicted that the bishomoaromatic stabilization of several heteroatom-substituted semibullvalenes is quite small, despite the fact that these molecules have high-symmetry equilibrium geometries.