Gas-phase redox dynamics in high-energy collisions

Mass analysed ion kinetic energy (MIKE) spectra following collisions have been recorded using a double focusing mass spectrometer with 5 kV acceleration voltage. Metal complexes studied were formed by pick-up of metal atoms in mixed argon/solvent clusters made by supersonic expansion. DFT calculations were used to rationalise experimental data. Complexes of the form MLn+ where M = Mg, Ca, Mn, Cu, and Zn while L = NH3, CO2, benzene, pyridine, acetonitrile, and acetone have been collided with O2 and MgLn+ also with CO2, N2O, acetonitrile, and benzene. Complexes with few ligands are the most prone to oxidation due to their high speed which facilitates electron transfer. Calculated electron affinities, Mulliken populations, and natural bond orbitals of collision gases were used to rationalise electron transfer trends. Collision gases trap electrons more efficiently if they have π-bonds or adjacent electronegative atoms. Metal complex and molecular dications were collided with H2 and O2 to determine the stability of their reduced products. No systematic differences were found between collisions with the two gases at the collision energies examined. The fate of monocations formed in collision depends on their relaxation energy and the dissociation energy of relaxed monocations. LZ theory was unable to explain MIKE spectra. Metal complexes MLn+ and MLn2+ were collided with O2 to determine the propensity to form MXLn-m+ where M = Mg, Ca, Mn, Cu, and Zn while L = CH3X with X = F and Cl. Reactivity is determined by the IE of MLn+ which decrease with increasing n. Dications due to their high dissociation energy are much more likely to react as they can have enough internal energy to overcome potential barriers