Polycyclic aromatic hydrocarbons (PAHs) are one of the most interesting components of the interstellar medium (ISM). But different from laboratory - the isolation of a single species is not possible. The spectra contain a superposition of many different molecules. Therefore a sophisticated understanding of all possible subtypes is required. We present an investigation of the IR spectra of PAHs containing (5, 7)-member ring defects. Using density functional theory, the influence of those defects on the IR spectra of coronene (C24H12) and pyrene (C16H10) and their cations and anions were examined in detail. Additionally, the potential energy surface of the neutral species is explored and an alternative formation pathway is taken into account.