A Crystalline Nitrogen Chain Radical Anion

Long chain nitrogen ions and radicals ([N _n ] ^x+ / [N _n ] ^x– , n > 3) are naturally occurring under the intense radiative conditions of the Earth’s ionosphere, and those of other planetary bodies. However, the strong thermodynamic driving force to lose N ₂ renders these types of molecules extremely reactive under ambient conditions such that they can typically be studied only under extreme conditions, for example at ultrahigh pressures (10 to >200 GPa). We now report the isolation of a molecule featuring a metal-unsupported {N ₄ } ^•– unit under ambient conditions which demonstrates remarkable multi-week long persistence in the solid-state. Spectroscopic, crystallographic and computational studies provide insight into the bonding across the {N ₄ } ^•– chain. Reactivity studies reveal that the chain can cleave into N1 and N3 fragments, and can act as a source of nitrene radical anion, an observation that such molecules could act as storable nitrogen group transfer reagents.