Gas-Phase Observation of the Heterolytic Dissociation of Negative Ions into Counter Ions: Dissociation of [Cu phthalocyanine (SO3)4Na]3−

Ion pair formation proceeding in solution at room-temperature, where it is driven by energies of solvation, has been observed in the gas-phase in the collision-induced dissociation of [Cu phthalocyanine (SO3)4Na]3− and [Cu phthalocyanine (SO3)4Na2]2− at low energies. The gas-phase observation of these charge separations into positive and negative ions, seemingly counter-intuitive, is favored sufficiently by thermodynamics to proceed at low collision energies. The combination of a high stability of the negative product anion against electron detachment and a low recombination energy of the departing positive counter ion appears to be the key requirement for such dissociations to proceed at low energies in the gas-phase.