The solvation of Mg2+ with gas-phase clusters composed of alcohol molecules

The dication Mg2+ has been clustered with a range of different alcohols to form [Mg(ROH)N]2+ complexes, where N lies in the range 2-10. Observations on the chemistry of the complexes reveal two separate patterns of behavior: (i) unimolecular metastable decay, where at small values of N the complexes undergo rapid charge separation via Coulomb explosion; and (ii) electron capture-induced decay, where collisional activation promotes bond-breaking processes via charge reduction. For the latter it has been possible to identify a generic set of reactions that are common to all of the different [Mg(ROH)N]2+ complexes; however, there are examples of reactions that are specific to individual alcohols and values of N. For metastable decay, it is shown that there is a clear correlation between the value of N at which a complex ceases to be metastable and the ionization energy of R, the radical that forms the complementary ion in the Coulomb explosion step. Metastable decay in two of the [Mg(ROH)N]2+ complexes follows a very different pathway that eventually results in proton abstraction. It is suggested that this difference is due to the precursor complexes adopting geometries that have at least one ROH molecule in a secondary solvation shell.