Solvent-Mediated Electron Hopping: Long-Range Charge Transfer in IBr ⁻ (CO ₂ ) Photodissociation

CO 2 Lends a Hand Solvent plays a complex and multifaceted role in facilitating charge transfer events. One obstacle to understanding its influence is that solvent molecules are in constant motion; just teasing out their arrangement in space at the point in time when an electron hops from one substrate to another is often a great challenge. Sheps et al. (p. 220 ; published online 4 March) have studied a highly simplified prototype system, in which a single CO 2 molecule coordinates, as a solvent might, to an IBr − ion in the gas phase. A combination of ultrafast photoelectron spectroscopy and theoretical simulations was applied that suggests that even this solitary interaction is sufficient to induce electron transfer from iodide to bromine during a dissociation reaction. Energy channeled through CO 2 -bending vibrations promoted formation of I(CO 2 ) and Br − .