ABINITIO STUDY OF BENZENE RADICAL-ANION

Ab initio molecular orbital calculations with the STO-3G and 4-31G basis sets have been carried out for the radical anions of benzene (Bz-) and fluorobenzene (FBz-). In accordance with the Jahn-Teller theorem, Bz- is predicted to distort from regular hexagonal (D6h,) symmetry. The best structures of Bz- have D2h symmetry. Two quite different D2h structures are found, one with four longer and two shorter C-C bonds and the other with two longer and four shorter C-C bonds. Configuration interaction calculations suggest that these two structures have very similar energies. Interconversion of equivalent D2h structures requires little activation energy, a result consistent with the experimental ESR spectrum. The ring skeletons of FBz- and Bz- are similar suggesting that the Bz- structures might usefully serve as models in studies of radical anions of substituted benzenes. © 1978, American Chemical Society. All rights reserved.