MO-Berechnungen an Heterocyclen. XXV. Zur Elektronenstruktur des Pyridin-N-Oxids

MO-Calculations on Heterocycles. XXV. On the Electronic Structure of Pyridin-N-Oxide MO calculations with different levels of sophistication (ab initio, HAM/3, INDO-, CNDO- and PPP-typ) are reported. The eigenvalues of the different methods are correlated with the experimentally known assignment of the PE spectrum on the basis of HeI/HeII intensities. The pattern of the PE spectrum and also the large dipole moment make this compound a very useful test molecule for quantumchemical calculations. Comments are made concerning the calculation of dipole moments within the point charge model especially in the PPP-approximation.