Wang Kai

Sequential N-alkylations of tetrabenzotetraaza[8]circulene provided mono-, di-, tri, and tetra-N-alkylated products in a controlled manner. Curiously, only opp isomer was obtained as a di-N-alkylated product. Upon increase of the N-alkyl groups, the absorption and emission spectra exhibit continuous red-shifts, and the excited-state lifetimes become shortened, probably because of increased steric congestion at the nitrogen atoms that causes the central core to deviate from planarity. Mixed N-substituted [8]circulenes have been also prepared.

Decorating the circle: Controlled N-butylation of tetrabenzotetraaza[8]circulene afforded mono-, di-, tri-, and tetra-N-butylated derivatives. N-Benzylation of dibutylated and tributylated products provided mixed tetra-N-alkylated [8]circulenes (see figure). These novel aza[8]circulenes exhibit slightly but distinctly perturbed UV/Vis absorption, emission, and excited-state dynamics owing to the structural deformation induced by the N-substituents.

To create intermolecular N−H⋅⋅⋅O and N−H⋅⋅⋅N hydrogen-bond (HB) interactions, a series of energetic N-heterocyclic anions including polynitro- and multi-nitrogen anions were introduced into the 3,6,7-triamino-7 H-s-triazolo[5,1-c]-s-triazole (TATT) cation to get numerous novel energetic salts. Single-crystal X-ray diffraction was employed to confirm the crystal structure and crystal packing properties of compounds 2⋅H₂O, 6, and 9. Additionally, Hirshfeld surface analysis and atoms-in-molecules topology analysis provided insights into the intermolecular hydrogen-bond interaction of these new salts. With the assistance of the EXPLO5 program, the detonation velocities, detonation pressures, and specific impulses of the salts were found to fall in the ranges 8113–9477 m s⁻¹, 24.1–31.4 GPa, and 203.2–224.2 s, respectively. The predicted detonation performance indicate that all the energetic salts based on TATT are similar to those of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX) or even overtake octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), which reveal that they can be candidates for the future insensitive high-performance energetic materials (IHPEMs).

Big bang theory: To create intermolecular N−H⋅⋅⋅O and N−H⋅⋅⋅N hydrogen-bond interactions, energetic N-heterocyclic anions were introduced to 3,6,7-triamino-7 H-s-triazolo[5,1-c]-s-triazole cations with polyamino groups to afford novel energetic salts. Single-crystal X-ray diffraction, Hirshfeld surface analysis, and topology analysis provided insight into the intermolecular interactions before and after the formation of energetic crystals. Their physicochemical properties were also evaluated.