Infrared Spectroscopy of Matrix Isolated Polycyclic Aromatic Hydrocarbons. 3. Fluoranthene and the Benzofluoranthenes

Matrix isolation techniques have been used to measure the 4000−500 cm -1 infrared spectra of the polycyclic aromatic hydrocarbons (PAHs) fluoranthene, benzo[ a ]fluoranthene, benzo[ b ]fluoranthene, benzo[ j ]fluoranthene, benzo[ k ]fluoranthene, and benzo[ ghi ]fluoranthene. For the PAHs where previous matrix isolation and gas-phase laboratory studies are available, agreements between the data sets are generally very good. While the fluoranthenes as a class produce infrared spectra that share many of the same characteristics of the spectra of PAHs containing only benzenoid moieties, for comparably sized molecules, the fluoranthenes tend to produce more absorption bands overall and considerably more and stronger bands in the 1550−1350 cm -1 range. These differences are largely due to the presence of the five-membered cyclopentadienyl ring characteristic of the family.