Evidence for a Water-Stabilised Ion Radical Complex: Photoelectron Spectroscopy and Ab Initio Calculations

A photoelectron spectrum corresponding to an unknown 174 m/z anion complex has been recorded. Initially believed to be I^-...CH₃CH₂OH (173 m/z), the spectrum has been assigned as belonging to that of an I^-...H₂O...CH₃CH₂ radical anion complex. The major peaks in the photoelectron spectrum occur at 3.54 eV and 4.48 eV as the ²P_3/2 and ²P_1/2 spin-orbit states of iodine respectively. Ab initio calculations were performed in order to rationalise the existence of the complex, with all structures converging to a 'ring-like' geometry, with the iodide anion bound to both the water molecule as well as a hydrogen of the ethyl radical, with the other hydrogen of water bound to the unpaired electron site of the ethyl. Simulated vertical detachment energies of 3.59 eV and 4.53 eV were found to be in agreement with the experimental results.