Theoretical IR spectra of coronene and pyrene and the defected forms in the region of 6−10 μm. Cations, neutrals, and anions are shown from left to right. The calculations were performed using the B3LYP density functional. The changes in intensity and shifts in position of the bands are clearly visible. UIR bands at 6.2 μm, 6.9 μm, 7.7 μm and 8.6 μm are indicated by dashed lines.