The Infrared Spectra of Polycyclic Aromatic Hydrocarbons With Some or All Hydrogen Atoms Removed

The loss of one hydrogen from C 96 H 24 does not significantly affect the infrared spectra of the neutral, cation, or anion. Excluding a very weak C–C stretching band at 5.1 μm, the loss of two adjacent duo hydrogens does not significantly affect the spectra compared with the parent. Removing all of the hydrogen atoms significantly increases the intensity of the new C–C stretching band, and, for the cation, shifts it to a longer (5.2 μm) wavelength. Observations show a feature near 5.25 μm, which has been attributed to overtone and combination bands from polycyclic aromatic hydrocarbons (PAHs). This current work suggests that dehydrogenated PAHs might also contribute to this band, but its weakness implies that fully dehydrogenated cationic or dicationic species are very rare.