A novel compound [Mn(H₂O)₆](AMTZ)₂(PA) ₂ (AMTZ = 4-amino-3,5-dimethyl-1,2,4-triazole and PA = Picrate) with Extensive hydrogen bonds: Synthesis, structure and thermal characters

The title compound 1, [Mn(H₂O)₆](AMTZ) ₂(PA)₂, contains 4-animo-3,5-dimethyl-1,2,4-triazole (AMTZ) and picrate (PA) and was characterized by elemental analysis, FT-IR spectroscopy and Single-Crystal X-ray diffraction. The space group of compound 1 is triclinic P-1(2), with a = 6.797(2) Å, b = 9.800(3) Å, c = 13.197(4) Å, α=,β=,γ=. The central Mn²⁺ is octahedral and surrounded by two kinds of centrosymmetric molecules, AMTZ and PA. The compound has an extended 3-D supramolecular structure due to water molecules coordinated though hydrogen bonds to the nitrogen and oxygen atoms and the offset face-to-face π ··· π packing. The differential scanning calorimetry (DSC) analysis shows that two exothermic processes take place at 341.4°C and 473.9°C. The kinetic parameter of the first exothermic process was studied using Kissinger's method and Ozawa's method. This provided the enthalpy of formation (-3337.7 kJ·mol ^-1), critical temperature of thermal explosion (588.79 K). The entropy of activation (ΔS^≠), enthalpy of activation (ΔH^≠), and free energy of activation (ΔG ^≠) were, respectively, -209.78 J·K ^-1·mol^-1, 155.50 kJ·mol^-1 and 267.75 kJ·mol^-1. A flame sensitivity test showed that the 50% firing height (h₅₀) was 20 cm.