title: Theoretical study of structure, vibrational frequencies, and electronic spectra of dibenzofuran and its polychlorinated derivatives.
abstract: Minimum structures and harmonic vibrational frequencies of dibenzofuran (DF), 2,3,7,8-tetrachlorodibenzofuran (TCDF), and octachlorodibenzofuran (OCDF) were calculated using the multiconfigurational complete active space self-consistent field (CASSCF) and density functional theory (DFT) methods. The electronic transitions in these compounds were studied via the single-state multireference second-order perturbation theory (CASPT2) based on the CASSCF(14,13) references, as well as the time-dependent DFT (TD-B3P86) employing the cc-pVDZ (CASSCF/CASPT2) and 6-31G(d,p) (TD-B3P86) basis sets. The B3P86 geometry and harmonic vibrational frequencies of ground state DF agree very well with the experimental data, and the CASSCF/CASPT2 excitation energies and oscillator strengths are accurate enough to provide a reliable assignment of the absorption bands in the 200-300 nm region. The close agreements with experiment for the parent DF give the present theoretical approaches a valuable credit in predicting the properties of the environmentally toxic polychlorinated congeners, which is all the more important considering the difficulties and hazards in obtaining the experimental data.
authors.affiliation: Department of Physical Chemistry, Rud-er Bosković Institute, P. O. Box 180, HR-10002, Zagreb, Republic of Croatia. iljubic@irb.hr
authors.forename: Ivan
authors.initials: I
authors.lastname: Ljubić
authors.forename: Aleksandar
authors.initials: A
authors.lastname: Sabljić
mesh_terms: D001572:Benzofurans / Q000737:chemistry*; D000072338:Dibenzofurans, Polychlorinated; D004583:Electrons; D008433:Mathematics; D008958:Models, Molecular; D008968:Molecular Conformation; D014732:Vibration
chemical_list: D001572:Benzofurans; D000072338:Dibenzofurans, Polychlorinated; C023614:dibenzofuran