Physical Chemistry: The Simple Hückel Method (Part V)

In the previous four parts of this series of articles on the SHM (the links to the other parts are reported at the end of the article), we learned how to apply the Hückel method to conjugated linear and cyclic molecules containing only carbon atoms. However, an unsaturated molecular system can contain hetero atoms that can conjugate their electrons. The contribution of different theoretical chemists has extended the method by including semiempirical terms for the overlapping integrals that consider the presence of non-carbon atoms in the conjugated system. This effort has been summarized by the American chemist A. Streitwieser providing a set of parameters to approximate both Columb and bond integrals in the Hückel determinant [1]. The derivation of these parameters has been discussed in detail by Streiweiser [2] or by Lowe [2]. This article will teach us how to use these parameters to build up the Hückel determinant for this conjugated molecular system.

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