APPLICATION OF VESCF METHOD TO CALCULATION OF ELECTRONIC SPECTRA OF PYRIDINE, PYRROLE, AND FURAN

The partial neglect of differential overlap (PNDO) method has been applied to the heterocycles in the title to obtain total charge distributions. These have then been used to construct (semi-empirical) molecular cores, which have been used in the VESCF treatment of the π-systems. Configuration interaction treatments have then been carried out using the ground configuration, and all singly- and doubly-excited configurations. While the treatment is a semiempirical one, care has been taken to introduce no parameters which would be inconsistent with our earlier treatments of hydrocarbons and carbonyl compounds by the same methods. The results indicate that following this kind of scheme, it will probably be finally possible to calculate in a general a priori way the electronic spectra of π-systems of heterocycles, as well as hydrocarbons and carbonyl compounds, with an accuracy comparable with that of experiment. © 1969 Springer-Verlag.