π-ring-hole bond around difluoroethyne: stabilization of hydrogen bonding cyclohexamer and dicyclohexamer of ammonia molecules.

The present paper displays new supramolecular structural forms of ammonia molecules. The computation reveals that two novel threading structures of CF·(NH) and CF·(NH) can be assembled between difluoroethyne and ammonia molecules, in which cyclohexamer (NH) and dicyclohexamer (NH) are constructed by robust N-H···N hydrogen bonds and stabilized all by π-ring-hole···N bonds as supporting spokes of annular structures. More interestingly, annular structures of NH still maintain stability as CF is removed. Additionally, the electronic properties and nature of the related noncovalent bonds are explored, which illuminate the important role of π-ring-hole bond for the stabilization of annular structures of NH. This study could provide valuable insights into chemistry of ammonia, new energy and astronomy aspects by single or multiple noncovalent interactions.Graphical abstract Ammonia molecules can exist stably in dodecahedral cage CF·(NH) and (NH) via N-H···N hydrogen bonds and π-ring-hole···N bonds.