Reactions of a distonic peroxyl radical anion influenced by SOMO-HOMO conversion: an example of anion-directed channel switching.

In free radicals the singly occupied molecular orbital (SOMO) typically has the highest energy. Recent examples of distonic radical anions were found, however, to disobey the usual orbital configuration, with the singly occupied molecular orbital buried energetically underneath doubly occupied orbitals. This unusual ordering of electrons, which contradicts the aufbau principle, has been characterized as SOMO-HOMO orbital conversion and is expected to perturb radical anion reactivity by branching toward anion-driven over radical-driven processes. Here, we use ion trap mass spectrometry and ab initio calculations to demonstrate that SOMO-HOMO orbital conversion influences the reactivity of a distonic peroxyl radical anion. Experimentally, we generated a distonic radical anion of β-hydroxy glutaric acid, ˙CH