Anionic N(18) Macrocycles and a Polynitrogen Double Helix in Novel Yttrium Polynitrides YN(6) and Y(2)N(11) at 100 GPa

Two novel yttrium nitrides, YN(6) and Y(2)N(11), were synthesized by direct reaction between yttrium and nitrogen at 100 GPa and 3000 K in a laser‐heated diamond anvil cell. High‐pressure synchrotron single‐crystal X‐ray diffraction revealed that the crystal structures of YN(6) and Y(2)N(11) feature a unique organization of nitrogen atoms—a previously unknown anionic N(18) macrocycle and a polynitrogen double helix, respectively. Density functional theory calculations, confirming the dynamical stability of the YN(6) and Y(2)N(11) compounds, show an anion‐driven metallicity, explaining the unusual bond orders in the polynitrogen units. As the charge state of the polynitrogen double helix in Y(2)N(11) is different from that previously found in Hf(2)N(11) and because N(18) macrocycles have never been predicted or observed, their discovery significantly extends the chemistry of polynitrides.