On the Correlation between Ionization Potentials and Excitation Energies, part III: Pyrazine

✍ Scribed by Edwin Haselbach; Zuzanna Lanyiova; Michel Rossi

• Publisher: John Wiley and Sons
• Year: 1973
• Tongue: German
• Weight: 671 KB
• Volume: 56
• Category: Article
• ISSN: 0018-019X
• DOI: 10.1002/hlca.19730560826

✦ Synopsis

Abstract

A recently suggested scheme for relating ionisation potentials (IP) to excitation energies (E) has been applied to pyrazine and 2,6‐dimethylpyrazine. The results indicate that in these systems the energy gap (Δ__E__) between the two lowest lying ^1^n,π*‐states is significantly smaller than that (Δ__IP__) between the corresponding ^2^n‐states of the parent radical cations. The values estimated for Δ__E__ on the basis of Δ__IP__, measurable by photoelectron spectroscopy, disagree with those calculated theoretically but seem to be supported by the experimental evidence available.

Since Δ__E__ = Δ__IP__ would normally be expected, the relationship Δ__E__ < Δ__IP__ actually present in these systems is discussed and related to the different shape of the n‐MO's involved in the ionization and excitation processes.