Potential energy surfaces of fluorobenzene radical anions

Ab initio ROHF/6-31+G* and MP2/6-31+G*//ROHF/6-31+G* calculations were used to consider fluorination's effect on potential energy surfaces (PESs) of benzene radical anion's (RAs). The Hartree-Fock PESs of symmetrically fluorinated radical anions were found to be pseudorotation surfaces. Unlike the benzene anion PES, pseudorotation surfaces include nonplanar structures. A Mobius band may represent the pseudorotation scheme of C6H6- stationary structures. Cutting the band out, we may obtain a pseudorotation scheme peculiar to C6F6-. This way of PES scheme building is also applicable to partially fluorinated RAs. A complicated structure of fluorinated anions' PES results from the avoided crossing of pi states closed in energy together with the presence of a low-lying vibronically active excited sigma state. The number of stationary structures involved in pseudorotation varies in the series of anions, and may be changed at a higher level of calculations. (C) 2002 Wiley Periodicals, Inc.