The vibrational structure of dibenzo-p-dioxin: IR linear dichroism, Raman spectroscopy, and quantum chemical calculations

The title compound (DD) was investigated by IR and Raman spectroscopy, including FTIR linear dichroism (LD) measurements on samples aligned in stretched polyethylene. The observed IR and Raman wavenumbers, IR polarization directions, and relative intensities were generally well reproduced by the results of a harmonic analysis based on B3LYP/cc-pVTZ density functional theory (DFT). The combined experimental and theoretical results led to proposal of a nearly complete assignment of the fundamental vibrational transitions of DD, involving reassignment of several transitions. The results are consistent with the assumption of molecular D_2h symmetry, thereby supporting the conclusion reached earlier by Gastilovich and coworkers.