the center into a 7-membered ring and two adjacent rings are changed into 5-membered rings. Coronene with defect is denoted as $C_{24}H_{12}$d.

The geometry optimizations and harmonic frequency calculations were performed using the B3LYP density functional, which uses Becke’s three parameter hybrid exchange functional (Becke [@becke]) and a correlation functional of Lee, Yang and Parr comprising both local and non-local terms (Lee et al. [@lee]), in conjunction with the 4-31G basis set (Frisch et al. [@frisch]). It has been shown previously (Langhoff [@langhoff]; Bauschlicher & Langhoff [@bausch]; Boersma et al. [@boersma]) that this combination of functional, basis set and a single scale factor of 0.958 leads to harmonic frequencies that are in excellent agreement with experiments. IR spectra, calculated using this level of theory, of molecules for which no experimental data exists are at least consistent with the data of other PAH molecules of the same size and charge (Ricca et al. [@ricca]). In the cases of the (5,7)-ring defected molecules no experimental data exists for comparison. Furthermore, it has been shown in previous work that the inclusion of diffuse functions is not required even for the investigation of anions (Ricca et al. [@ricca]). However, considering intensities, it has been 