UV photodissociation spectroscopy of cryogenic cooled gas phase host-guest complex ions of crown ethers

• Published in: Physical chemistry chemical physics : PCCP Vol. 17; no. 29; pp. 25925 - 25934
• Main Authors: Inokuchi, Yoshiya, Haino, Takeharu, Sekiya, Ryo, Morishima, Fumiya, Dedonder, Claude, Féraud, Géraldine, Jouvet, Christophe, Ebata, Takayuki
• Format: Journal Article
• Language: English
• Published: Royal Society of Chemistry 21.10.2015
• Subjects: Atomic and Molecular Clusters; Physics
• DOI: 10.1039/C5CP01960E
• ISSN: 1463-9076

The best determination of the most stable protonation site in aromatic molecules relies nowadays on the IR spectroscopy and ab initio calculations. It appears that these methods are not necessarily unambiguous and cannot always be safely employed. We present in this paper an example showing that electronic spectroscopy of cold ions complemented with ab initio calculations gives clear results on the protonation site. In the example given on the aminophenol isomers (in ortho, meta and para positions), the protonation site is assigned from the electronic spectroscopy and in particular we show that for the meta isomer the proton is not on the amino group as observed for the other isomers. It shows also that the protonation site is not conserved in the electrospray evaporation–ionization process.