Characterization of the triple ion [] in the gas-phase

The triple ion [ ( CH 3 ) 4 N + · PF 6 - · ( CH 3 ) 4 N + ], generated by electrospray ionization of tetramethylammonium hexafluorophosphate, is characterized by collision-induced dissociation and infrared spectroscopy of the mass-selected gaseous ion in the range from 1000 to 2000 cm−1. Quantum chemical calculations are used to elucidate the structures and energetics of the triple ion and its subunits and for the assignment of the infrared frequencies. The infrared bands observed in the gas-phase match quite closely with those of the bulk substance, suggesting that for this particular kind of ion associate the structural differences between the gas-phase and the condensed state are almost negligible.