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Published July 1, 1976 | Published
Journal Article Open

The electronic structure of pyrazine. Configuration interaction calculations using an extended basis


Extensive ab initio double zeta basis set configuration interaction calculations have been carried out on the nπ^∗ and ππ^∗ states of pyrazine as well as on the low‐lying n and π cations. The calculations corroborate the validity of the valence bond (VB) model for the interaction of lone pair excitations proposed earlier by Wadt and Goddard. Good agreement (errors of ∼0.2 eV) with experiment is obtained (except for the higher‐lying 1ππ∗ states that possess significant ionic character). The calculations indicate that the order of increasing ionization potentials is ^2A_g(n), 2B_(1g)(π), 2B_(1u)(n), and ^2B_(2g)(π). The forbidden 1 ^1B_(2g)(nπ^∗) state is predicted to be 1.30 eV above the allowed 1^ 1B_(3u)(nπ^∗) state. Finally, the calculations indicate that the adiabatic excitation energies to the 1^ 3B_1(nπ^∗) and 1^ 3A_1(ππ^∗) states in pyridine should be nearly degenerate at ∼3.6 eV.

Additional Information

© 1976 American Institute of Physics. Received 6 November 1975. Online Publication Date: 28 August 2008. We thank Professor William R. Moomaw, Dr. Melvin B. Robin, Dr. Peter Esherick, and Professor Mostafa A. El-Sayed for communicating their experimental results to us prior to publication. Contribution No. 5221 from the Arthur Amos Noyes Laboratory of Chemical Physics, California Institute of Technology, Pasadena, CA 9ll25. NSF Predoctoral Fellow, 1970-1973; California Institute Research Foundation Fellow, 1973-1974 Partially supported by a Grant (MPS73-05132) from the National Science Foundation.

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