Intermolecular interactions in aniline–benzene hetero-trimer and aniline homo-trimer ions

The charge distribution and binding features of aniline–benzene hetero-trimer and aniline homo-trimer ions are investigated by vibrational spectroscopy and by near-infrared photodissociation and spontaneous unimolecular dissociation of mass-selected cluster ions. The absence of the charge resonance absorption indicates the charge localization in the trimer ions. Substantial red-shifts and enhanced intensities of the vibrational transitions suggest strong perturbations to the NH oscillators. The trimer ions are stabilized by the hydrogen-bonding interaction through the NH2 group of the charged aniline with the neutral molecules rather than the charge-delocalization interaction among the component molecules.