Crystallography of 2,2',4,4',6,6'-hexanitro-1,1"-biphenyl and its relation to initiation reactivity

X-ray crystallographic study of 2,2',4,4',6,6'-hexanitro-1,1'-biphenyl (HNBP, C12H4N6O12, M-r= 424.21) has been carried out with the following results: triclinic, a = 8.1860(7), b = 12.1370(8), c = 16.2040(12) angstrom, alpha = 98.728(6)degrees, alpha = 93.101(6)degrees, gamma = 104.688(6)degrees, V = 1532.05 angstrom(3), Z = 4, D-x = 1.839 g.cm(-3), lambda(Mo K alpha) = 0.71073 angstrom, u = 0.169 cm-1, F(000) = 856, temperature of 150 K, final R = 0.0765 for 4415 independent observed reflections. The interplanar angles between benzene rings are 85.38 and 86.82 degrees for two independent molecules. A possibility of intermolecular hydrogen bonds was indicated, and atypically short distances between oxygen atoms of nitro groups in the 2,6-positions of one molecule and nitro groups in the 4-position of adjacent molecules were found. These interactions might be a reason for the primary reaction of nitro group in the position 4(4'), compared to nitro groups in positions 2,6(2',6'), in the HNBP molecule during its initiation. In this respect, HNBP differs from the other members of polynitro polyphenylene series containing trinitrophenyl building blocks in their molecules.