- Infrared spectra of protonated polycyclic aromatic hydrocarbon molecules: Azulene
- Journal of Chemical Physics
- Volume | Issue number
- 131 | 18
- Number of pages
- Document type
- Faculty of Science (FNWI)
- Van 't Hoff Institute for Molecular Sciences (HIMS)
The infrared (IR) spectrum of protonated azulene (AzuH(+), C10H9+) has been measured in the fingerprint range (600-1800 cm(-1)) by means of IR multiple photon dissociation (IRMPD) spectroscopy in a Fourier transform ion cyclotron resonance mass spectrometer equipped with an electrospray ionization source using a free electron laser. The potential energy surface of AzuH(+) has been characterized at the B3LYP/6-311G** level in order to determine the global and local minima and the corresponding transition states for interconversion. The energies of the local and global minima, the dissociation energies for the lowest-energy fragmentation pathways, and the proton affinity have been evaluated at the CBS-QB3 level. Comparison with calculated linear IR absorption spectra supports the assignment of the IRMPD spectrum to C4-protonated AzuH(+), the most stable of the six distinguishable C-protonated AzuH(+) isomers. Comparison between Azu and C4-AzuH(+) reveals the effects of protonation on the geometry, vibrational properties, and the charge distribution of these fundamental aromatic molecules. Calculations at the MP2 level indicate that this technique is not suitable to predict reliable IR spectra for this type of carbocations even for relatively large basis sets. The IRMPD spectrum of protonated azulene is compared to that of isomeric protonated naphthalene and to an astronomical spectrum of the unidentified IR emission bands.
- go to publisher's site
If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library, or send a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible.