Radical Formation by Direct Single Electron Transfer between Nitrobenzene and Anionic Organo Bases

The presence of unpaired electrons in organic molecules, i.e., radicals, offers transformative magnetic and reactivity properties. However, due to the very nature of these radicals, strict electronic and structural limitations are imposed on the molecules that bear them, limiting the scope of what can be achieved. Thus, counting with mechanisms that lead to a facile radical formation in simple reaction conditions, employing available and inexpensive reactants, and applicable to general types of molecules, holds the key to capitalise on the extraordinary properties that radicals have to offer. Here, combining electron paramagnetic resonance spectroscopy and ab initio calculations, we reveal a direct single electron transfer from multiple anionic organic bases (B-X+) to nitrobenzene [1] that operates the formation of stable nitrobenzenide radical ion-pair [1•-][X+] (X = Li, Na, K) and transient oxidized, radical bases B•. Our results open the door to incorporating radical properties on the wide family of nitroarenes and offer a simple way to access heteroatom-centred radicals, which are highly valuable species in the activation of multiple inert substrates. Finally, we propose the [1] – [B-X+] couple as a versatile, yet unexplored, platform with the potential to expand the field of frustrated radical pairs.