SCF MO CALCULATIONS OF HETEROATOMIC SYSTEMS WITH VARIABLE BETA-APPROXIMATION .4. ELECTRONIC STRUCTURE AND SPECTRA OF PROTONATED N-HETEROCYCLES

In order to elucidate the electronic structure of protonated N-heterocycles, we have carried out SCF MO calculations, considering the σ-bond polarizations which are caused by the large net charge on nitrogen atom. Appropriate parametrizations of the valence state energies associated with the σ-bond polarization model have been proposed. Our calculations showed that a conventional covalent model for protonated N-heterocycles failed to explain the experimental electronic spectral data and an extremely polarized σ-core model gave quite good results in the whole. The present theory expected that the nature of electronic spectra of quinoline is considerably changed by the σ-bond polarization due to the protonation. © 1969 Springer-Verlag.