(A) Potential energy surface of benzene
in the S1 state
from S1 planar minimum (D6h symmetry) until the S1/S0 conical
intersection. The experimentally determined activation energy (∼8.6
kcal/mol) given in ref (69) is indicated by a line. (B) The NICS(1)zz at the various structures along the IRC. Geometries were calculated
at the SA4-CASSCF(6,6)/ANO-RCC-VTZP level, energies
were obtained at the MS4-CASPT2(6,6)/ANO-RCC-VTZP level,
and NICS(1)zz values were determined at
the CASSCF(6,6)/6-31++G(d,p) level. The plane defined
by the C1, C2, C4, and C5 atoms was used to define the central position
of the ghost atom located 1 Å below the plane (displayed as a
green dot in the inset) for NICS. For computational details and NICS
values in the opposite direction, see Figure S47.