Structures and infrared photodissociation of [(aniline)-(methanol)-(water)2

Abstract

The structures of [(aniline)-(methanol)-(water)2]+ were investigated by infrared spectroscopy coupled with linear tandem mass spectrometry. We suggest the most stable structure of [(aniline)-(methanol)-(water)2]+ through infrared photodissociation spectra supported by the density functional theory calculations at the level of ωB97X-D/cc-pVQZ. Methanol and one water molecule formed hydrogen bonding with the amino group of aniline, while the other water formed hydrogen bonding with methanol. Upon infrared excitation of [(aniline)-(methanol)-(water)2]+, the water molecule connected to methanol turned out to be preferentially ejected, although the total internal energy in the cluster ion was large enough to dissociate other solvent molecules. This unique dissociation feature was attributed to the significant difference in the dissociation rates as obtained by the Rice-Ramsperger-Kassel-Marcus theory calculations as well as structural restriction.