Quantum theory atoms in molecules charge-charge flux-dipole flux models for the infrared intensities of benzene and hexafluorobenzene.
The infrared fundamental intensities of benzene and hexafluorobenzene have been calculated at the MP2/6-311++G(3d,3p) level. The theoretical values are in excellent agreement with the averaged experimental C(6)H(6) results having a rms error of 15.3 km mol(-1). However, the theory badly underestimates the CF stretching and ring deformation intensities of C(6)F(6) having an overall rms error of 141 km mol(-1). The theoretical results confirm the dipole moment derivative signs previously attributed on the basis of the comparison of C(6)H(6) and C(6)D(6) derivatives and semiempirical molecular orbital results. A quantum theory atoms in molecules charge-charge flux-dipole flux interpretation of the theoretical results shows that electronic density changes for out-of-plane vibrations can be explained using a simple bond moment-rehybridization moment model proposed many years ago. However, these changes were found to be much more complicated for the in-plane vibrations involving important charge flux and dipole flux contributions for both molecules as well as contributions from the displacement of equilibrium atomic charges for hexafluorobenzene.
da Silva
João Viçozo
JV
Instituto de Química, Universidade Estadual de Campinas, CP 6154, 13084-970 Campinas, SP, Brazil.
Oliveira
Anselmo E
AE
Hase
Yoshiyuki
Y
Bruns
Roy E
RE