The optimized geometries for the S0 and S1 states of dibenzo-p-dioxin and eight polychlorinated dibenzo-p-dioxins (PCDDs) were obtained by using HF, B3LYP, or CIS methods. Calculated results were in good agreement with available X-ray crystallographic structures. The effects of substituent chlorine atoms and electronic excitation on the molecular geometries are discussed. The correlation energy was estimated by a comparison of (0-0) transition energies, calculated using HF and CIS methods, with observed energies. It was confirmed that the correlation energy of PCDD was primarily caused by the electrons belonging to the benzene and central rings, and that substituted chlorine atoms made a relatively small contribution to the correlation energy. The correction for the correlation energy demonstrated that it was possible to make (0-0) transition energies agree with experimental energies within an error of 2%. Electronic spectra were also studied on the basis of INDO/S calculations.
All Science Journal Classification (ASJC) codes
- Condensed Matter Physics
- Physical and Theoretical Chemistry