Positive charge distribution in (benzene)1(toleune)2+ and (benzene)2(toluene)1+ studied by photodissociation spectroscopy

The positive charge distribution in benzene–toluene heterotrimer ions is investigated by photodissociation spectroscopy in the near-infrared (6000–14 000 cm−1) and infrared (2800–3150 cm−1) regions. The electronic spectra of (benzene)1(toluene)2+ and (benzene)2(toluene)1+ in the near-infrared region display a strong band at 9430 and 8330 cm−1, respectively. These bands are ascribed to the charge resonance band; the positive charge is not localized on a single molecule. The vibrational spectrum of (benzene)1(toluene-d8)2+ shows three distinct bands at 3054, 3084, and 3108 cm−1; these bands are assigned to the CH stretching vibrations of the benzene moiety. The similarity of the spectral features to those of the neutral benzene monomer suggests that the benzene molecule in the (benzene)1(toluene)2+ ion has a neutral character. The positive charge is localized on the toluene dimer unit with a structure written as (toluene)2+⋯(benzene)1. The vibrational spectrum of (benzene)2(toluene)1+ bears a resemblance to...