Calculations for photoelectron spectra of azoles by the AM1 method using a green's function approximation for the outer valence molecular orbital

Abstract

We have carried out nonempirical (4–31G) and semiempirical (MNDO and AM1) calculations for pyrazole, imidazole, and their 1-vinyl derivatives. The SCF calculations significantly overestimate the value of the orbital energy for n-type MO's. For the 1-vinylpyrazole molecule, all the methods incorrectly give the sequence of energy levels. The best agreement with experimental ionization potentials is obtained when using a Green's function approximation for the outer valence MO's together with the AM1 method.