SEMIEMPIRICAL SCF–LCAO–MO TREATMENT OF THIOPHENE, FURAN, AND PYRROLE

Abstract

The semiempirical SCF–LCAO–MO method of Pariser–Parr–Pople is utilized in the study of the π-electronic structures of thiophene, furan, and pyrrole. The core Hamiltonian expansion contains a Uz⁺⁺ term, the potential due to the ionized hetero-atom contributing two electrons to the π-system. The γzz, one-center coulomb repulsion integral for the hetero-atom is evaluated from the experimental spectroscopic data only. With the resonance integral βcz^c as the only variable parameter, the calculated π*–π electronic transitions are in a satisfactory agreement with the experimental data.