Stabilization of cyclo-N6 by insertion into [18]-annulene: a DFT study

Abstract

The elusiveness of hexazine (a.k.a. hexaazabenzene) and its perhydrogenated derivative, hexazinane, prompted the author of this paper to investigate the possibility of stabilizing the six-membered nitrogen ring by inserting it into [18]-annulene. The resulting compound is made of a central N₆ ring surrounded by an outer ring of 18 carbon atoms that prevents its decomposition into dinitrogen. The N₆ ring is non-planar and with a chair-like conformation that does not undergo conformational isomerization. The designed molecule can be stabilized either by oxidation to a hexa-oxide derivative or by coordination of ZnCl⁺. Furthermore, a triangle-shaped macrocyclic isomer made of three pyridazine moieties connected to each other by ethylene bridges represents a possible precursor in the synthesis of the N₆-embedded hydrocarbon. By employing an alkali or alkaline-earth metal cation that coordinates the three pyridazine monomers it becomes possible to bring their nitrogen atoms in close proximity so that a subsequent aromatic fusion reaction could be attempted.