Hydrogen-bonding stabilization in energetic perchlorate salts:: 5-amino-1H-tetrazolium perchlorate and its adduct with 5-amino-1H-tetrazole

Protonation of 5-amino-1H-tetrazole (5-At) with concentrated perchloric acid in water rendered 5-amino-1H-tetrazolium perchlorate (1), in good yield and purity, or an adduct of 1 with 5-At (2) depending on the experimental conditions used. 1 was more conveniently prepared by metathesis of 5-amino-1H-tetrazolium bromide (3) with anhydrous silver perchlorate in alcoholic solution. Both perchlorate salts were characterized by NMR, Raman and IR spectroscopy, differential scanning calorimetry, mass spectrometry and elemental analysis. Additionally, the crystal structures of I and 2 were determined by X-ray diffraction techniques. Both salts crystallize in monoclinic cells in the space group P2(1)/n (1: a = 5.3691(6), b = 7.8470(6), c = 15.2770(13) angstrom, beta = 91.381(8)degrees, V = 643.45(10) angstrom(3), Z = 4, rho = 1.915 g cm(-3), R-1 = 0.0403 (F > 4 sigma(F)), wR(2) (all data) 0.0977 and 2: a = 5.2615(1), b = 8.5311(2), c = 21.4870(4) angstrom, beta = 96.127(1)degrees, V = 958.96(3) angstrom(3), Z = 4, rho = 1.874 g cm(-3), R-1 = 0.0330 (F > 4 sigma(F)), wR(2) (all data) = 0.0890). Lastly, the energetic properties of 1 and 2 were assessed. With an impact (i) and friction (f) sensitivity of 1.5 J and 8 N, respectively, and a sensitivity of 0.1 J against electrical discharge (ESD) perchlorate I is a powerful primary explosive, whereas the presence of a second tetrazole ring in 2 makes it a very stable compound (i = 22 J, f 260 N, ESD = 0.4 J).