Some graph-theoretic studies on aniline and p-phenylenediamine-like systems in HMO formalism

Abstract

By studying the signs of the terms in the characteristic polynomials (CP) and their derivatives of the molecular graph, energy-level patterns and the upper and lower bounds to the smallest and largest positive eigenvalues have been determined for aniline- and <em>p</em>-phenylenediamine-like systems. The dependence of the HMO energies of the highest occupied molecular orbitals on the heteroatom Huckel parameters, represented by h and k, has been ascertained. The results are in agreement with the trends in the actually computed energy values compiled by Coulson and Streitwieser. The derived modes of dependence of the HOMO energy on h and k correctly predict the trends in electron donor properties of the systems under study with variation in electronegativities of the hetero atoms.