Theoretical studies of o-, m-, and p-benzyne negative ions
- Purdue Univ., West Lafayette, IN (United States)
A general theoretical description of `distonic` radical anions is presented, along with an account of an extensive series of ab initio molecular orbital and density functional theory calculations on the negative ions of o-, m- and p-benzyne. The performance of several different computational methods is evaluated with respect to artifactual symmetry-breaking. QCISD(T), CCSD(T), CASPT2N, and DFT(B3LYP) calculations employing double-{zeta} quality basis sets predict that o-, m- and p-benzyne anions all have high-symmetry, delocalized radical anion ground electronic states: {sup 2}B{sub 2} (C{sub 2v}), {sup 2}B{sub 2} (C{sub 2v}), and {sup 2}A{sub g} (D{sub 2h}), respectively. The meta and para isomers also exhibit low-lying, localized radical anion forms with distorted geometries that arise by pseudo Jahn-Teller interactions (vibronic coupling): {sup 2}A`(C{sub s}) for m-benzyne anion and {sup 2}A{sub 1} (C{sub 2v}) for p-benzyne anion. Broken-symmetry wave functions are obtained at symmetrical geometries from MCSCF and CISD calculations for p-benzyne anion, but not for o- and m-benzyne anions. The calculated potential energy surface for in-place distortion of m- and p-benzyne anions are found to be quite flat. An isodesmic reaction approach is used to calculate the electron, proton, and hydrogen atom-binding energies for each of the minimum energy states. Good agreement is achieved between the experimental estimates for these quantities and the calculated values for the lowest-energy anion states. 48 refs., 4 figs., 7 tabs.
- OSTI ID:
- 437397
- Journal Information:
- Journal of the American Chemical Society, Vol. 118, Issue 47; Other Information: PBD: 27 Nov 1996
- Country of Publication:
- United States
- Language:
- English
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