4,4′-Bis(nitramino)azofurazan and its salts. Study of molecular and crystal structure based on X-ray and quantum chemical data

4,4′-Bis(nitramino)azofurazan 2 was obtained by nitration of 4,4-diaminoazofurazan 1. Molecular and crystal structure of nitramine 2 and its ammonium salt 3 were studied by X-ray method and quantum chemical calculations at M052X/aug-cc-pvdz level of theory. Both compounds adopt ap-ap-ap conformation. It was shown that the structure of furazan cycle significantly depends on the nature of the substituents at carbon atoms. Crystal structures of 2 and 3 are characterized by sufficiently high density (1.996 and 1.832 g cm⁻³ at 110K and 1.919 and 1.766 g cm⁻³ at 295 K, respectively), which is provided, in particular, by strong intermolecular hydrogen bonding and π-π stacking interactions. Among substituted azofurazans and primary nitramines examined by X-ray diffraction analysis, 4,4′-bis(nitramino)azofurazan 2 is characterized by the highest density.