Fe+- and Mg+-polycyclic aromatic hydrocarbon complexes

The interactions of Fe+ and Mg+ with coronene (C24H12) and Fe+ with circumcoronene (C54H18) are studied. The binding energies are more than an eV. The IR spectra of the complexes are compared with those of the parent polycyclic aromatic hydrocarbon (PAH), both neutral and cationic. The 3.3 μm C–H stretching band and the 11.2 μm out-of-plane C–H bending band are more similar to the parent PAH cation than to the neutral molecule, while the 6.2 μm C–C stretching band and the 7.7 μm in-plane C–H bending bands are more similar to the neutral PAH parent than to the cation. The allowed electronic transitions in the Mg–coronene+ complex are at lower energies than for neutral coronene, but not as low as those found for coronene+. The total UV cross section for all excitations below 4.8 eV is similar for coronene, coronene+, and the Mg–coronene+ complexes.