Preparation, crystal structure and thermal behavior of diaminoglyoxime

Diaminoglyoxime (DAG) was prepared by adding glyoxal and hydroxylamine hydrochloride into a cooled solution of sodium hydroxide in water, and the single crystal of DAG was cultured by dehydration at high pressure. The crystal was characterized by using X-ray single crystal diffraction, elemental analysis and FT-IR measurement. The crystal is monoclinic, space group P2₁ with cell parameters: a = 0.6763(8) nm, b = 0.3578(4) nm, c = 0.9658(12) nm, β = 90.78(2)°, V = 0.2338(5) nm³, Z = 2, D_c = 1.678 g · cm^-3, F(000) = 124, μ(Mo Kα) = 0.146 mm^-1, final R indices [I > 2σ(I)] R₁, = 0.0403, wR₂ = 0.1098; R indices (all data) R₁ = 0.0422, wR₂ = 0.1122. The obtained results indicate that DAG is a kind of planar symmetric molecules, and its crystal is acicular crystal. The thermal decomposition process of DAG was predicted by TG-DTG and DSC techniques with a heating rate of 10°C · min^-1. The measure results show that DAG melting at 203.5°C, has two steps of intense thermolysis between 209-212°C and 212-240°C, and decompose completely up to 240°C.