Direct Observation of <i>Cyclo</i> ‐Pentazolate Anion Decomposition in a Tailored Molecular Trap

Abstract The cyclo ‐pentazolate anion ( cyclo ‐N 5 − ) has garnered significant attention as an all‐nitrogen, five‐membered‐ring ion with a high energy state and unique aromaticity. Typically, the free cyclo ‐N 5 − anion is a highly unstable species, and its stabilization relies on strong interactions, such as a hydrogen bonding network or metal coordination. However, these interactions often compromise the independence of the anion, thus diminishing its aromaticity. Herein, we present a molecular trap designed to encapsulate and isolate cyclo ‐N 5 − through collective weak interactions. This approach utilizes a pre‐positioned ion to subsequently displace the cyclo ‐N 5 − anion into the cage cavity, addressing the challenge posed by the absence of strong‐interaction‐driven binding. This setup preserves the aromaticity of the anion to a significant extent, as predicted by computational studies. More importantly, the decomposition of free cyclo ‐N 5 − within the microenvironment was directly recorded for the first time using single‐crystal X‐ray diffraction analysis.