Infrared multiphoton dissociation spectrum of isolated protonated 1-azapyrene

The infrared spectrum of protonated 1-azapyrene has been obtained by infrared multiphoton dissociation (IRMPD) spectroscopy using a Fourier-transform ion cyclotron resonance mass spectrometer coupled to an infrared tunable free electron laser. Found when electrospraying a pyrene/methanol/acetic acid solution, the carrier of the dominant m/z 204 peak was determined by comparison of the IRMPD spectrum with density functional theory calculations (B3LYP/6-31G(d,p)). The greater proton affinity and solubility of 1-azapyrene explains the competitive protonation of azapyrene over pyrene despite its apparent smaller abundance in the electrospray solution. The possible contribution of 1-azapyrene to the interstellar infrared emission bands is briefly discussed.