Strategy for chemically riveting catenated nitrogen chains.

Catenated nitrogen chains (CNCs) attract considerable attention because of their structural novelty, their high energy, and their potential as precursors for all-nitrogen materials. However, pure CNCs are unstable under ambient conditions, limiting their on-site or practical applications. Chemical riveting of a CNC involves the maintenance of the structure of a CNC and placing the CNC in a special chemical structure as a moiety of an entire molecule to stabilize it. Other structures, except from the CNC, are named rivets. In this study, the molecular geometry, bond order, natural bond orbital charge, and frontier orbital among the pure CNCs (Nx), Nx-, Nx+, and NxHy (x = 2-11) and CNCs riveted and implemented experimentally in several former studies are systematically analyzed and compared. The lone-pair repulsion between two neighboring N atoms is one of the primary factors for the low molecular stability of the pure CNCs and their derivatives. The riveted CNCs with rings are usually more stable than those with open chains. Moreover, the standard deviation of the bond orders or the bond lengths can be employed as an indicator for molecular stability, i.e., a lower standard deviation suggests higher molecular stability. Hence, electron-donating groups, groups with electronegativity within those of H and N atoms, as well as atoms or groups with empty orbitals are proposed to trap the lone pairs of CNCs as rivets to stabilize the CNCs. This strategy is expected to facilitate the creation of stable CNC-contained compounds with high structural novelty or high energy contents. Graphical abstractA strategy is proposed for chemically riveting instable CNCs to transform them into more stable ones.