No abstract

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