Dichotomy in dissociative electron capture: electron paramagnetic resonance detection of iodine atoms in methanol glasses

Abstract

Exposure of dilute solutions of N-iodosuccinimide and other iodo-derivatives (RI) in methanol to ⁶⁰Co γ-rays at 77 K gives features assigned to σ* radical anions, in which the excess electron is accommodated in the R–I σ* orbital. On annealing, these features gave way to a new set of features exhibiting large hyperfine coupling to iodine and large g-shifts which were the same for all substrates. It is postulated that this centre is an iodine atom forming a weak three-electron bond to methanol. This was strongly supported by the observation that UV photolysis of solutions of potassium iodide in methanol gave the same electron paramagnetic resonance (EPR) features.

The results are discussed in terms of the polarity of the R–I bonds, and the effects of solvation. Attempts to prepare a similar bromine atom centre using bromo-analogues have not yet been successful.