A Semi-empirical Theory of the Conjugated Systems I. General Formulation

A general semi-empirical theory of conjugated double bond systems, including those with non closed-shell structures and heteroatoms, is developed. The general formulation is similar with that of Pariser and Parr and that of Pople and others, but for non closed-shell structure our equations are somewhat different from those of Pople et al. The necessary parameters for hydrocarbons, which have previously been determined arbitrarily as the case may be, are estimated, in the present paper, by using the experimental data of the ethane and ethylene molecules. The theory is checked by some simple examples and found to be in satisfactory agreement with experiments.