Preparation and molecular structure of (SCZ)(TNPG)·2H₂O

The (SCZ)(TNPG)·2H₂O prepared by mixing semicarbazide (SCZ) and trinitrophloroglucinol (TNPG) was characterized by elemental analysis and IR measurement, and its crystal structure was determined by X-ray single-crystal diffraction analysis. The crystal belongs to triclinic, space group P1, (NH₂CONHNH₃)⁺(C₆H ₂N₃O₉)^-·2H₂O, M_r = 372.23, a = 0.68853(14), b = 0.93966(19), c = 1.1925(2) nm, α = 67.48(3), β= 77.56(3), γ = 78.93(3)°, V = 0.6908(2) nm³, Z = 2, D_c = 1.789 g/cm³, M_r = 373.23, F(000) = 384, S = 0.999 and μ(Mokα) = 0.172 mm^-1. The final R and wR are 0.0394 and 0.1057 for 1724 observed reflections with I > 2σ(I). It is concluded that (SCZ)(TNPG) 2H₂O is an ionic compound composed of a cation SCZ⁺, an anion TNPG^- and two water molecules. The TNPG^- anion and SCZ⁺ cation are bonded together by electrostatic attraction and hydrogen bonds, and the compound structure is stable. The thermal decomposition of (SCZ)(TNPG) 2H₂O was studied by using TG-DTG and DSC techniques with a heating rate of 10 °C/min, showing the compound contains one endothermic process of dehydrating stage and two intensive exothermic decomposition stages. The enthalpy of exothermic decomposition reaction is 452.31 kJ/mol.