Containment of Polynitroaromatic Compounds in a Hydrogen Bonded Triarylbenzene Host

Co-crystallization of energetic materials
has emerged as an important
technique to modify their critical properties such as stability, sensitivity,
etc. Using 1,3,5-tris­(4′-aminophenyl)­benzene (TAPB)
as a novel co-crystal former, we have prepared co-crystals of 2,4,6-trinitrotoluene
(TNT), 2,4,6-trinitrophenol (TNP), and m-dinitrobenzene
(mDNB). Molecular structures of the co-crystals have
been determined from single crystal X-ray diffraction data. The diffraction
data analysis reveals that strong intermolecular π–π
interaction directs the intercalation of polynitroaromatic explosives
(PNACs) between the layers of TAPB molecules, which leads to the formation
of vertically overlapped -A-B-A-B- types of π-stacks. Both TNT
and TNP form π-interactions with the center of TAPB with 1:1
molar ratios, while mDNB forms a complex in a 1:3
stoichiometry through stacking between peripheral rings. The crystal
lattices are further stabilized through interstack hydrogen bonds
(N–H···N and N–H···O)
between amino groups of TAPB and nitro groups of PNACs. NMR and Fourier
transform infrared spectra further provide the information about the
presence of various interactions in the crystal systems. Owing to
the π electron-rich nature and ease of synthesis, triphenylbenzene
systems are promising host candidates for co-crystallization of PNAC
analytes.