Anion A^- • HX clusters with reduced electron binding energies: Proton vs hydrogen atom relocation upon electron detachment

Clustering an anion with one or more neutral molecules is a stabilizing process that enhances the oxidation potential of the complex relative to the free ion. Several hydrogen bond clusters (i.e., A^- • HX, where A^- = H₂PO₄^- and CF₃CO₂^- and HX = MeOH, PhOH, and Me₂NOH or Et₂NOH) are examined by photoelectron spectroscopy and M06-2X and CCSD(T) computations. Remarkably, these species are experimentally found to have adiabatic detachment energies that are smaller than those for the free ion and reductions of 0.47 to 1.87 eV are predicted computationally. Hydrogen atom and proton transfers upon vertical photodetachment are two limiting extremes on the neutral surface in a continuum of mechanistic pathways that account for these results, and the whole gamut of possibilities are predicted to occur.