Synthesis, characterization, thermal properties and theoretical investigation on Bis(guanidinium) 4,4′- Azo-1H-1,2,4-triazol-5-one

• Published in: Journal of molecular structure Vol. 1147; pp. 754 - 762
• Main Authors: Cao, Wen-li, Guo, Jia-jia, Chen, Xiang, Ding, Zi-mei, Xu, Kang-zhen, Song, Ji-rong, Fan, An, Huang, Jie
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.11.2017
• Subjects: Crystal structure; Nitrogen-rich triazolone-based heterocycles; Non-isothermal decomposition kinetics; Quantum-chemical calculations; Thermal behavior; Nitrogen-rich triazolone-based heterocycles; Non-isothermal decomposition kinetics; Thermal behavior; Crystal structure; Quantum-chemical calculations
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2017.06.115

Bis(guanidinium) 4,4′-Azo-1H-1,2,4-triazol-5-one [G2(ZTO)] was synthesized and characterized by X-ray single crystal diffraction, elemental analyzer and Fourier Transform Infrared (FT-IR) spectrometer. The result from X-ray single crystal diffraction indicates that G2(ZTO) crystallizes in the monoclinic space group P2(1)/c with parameters of a = 4.779(2) Å, b = 9.081(4) Å, c = 14.676(6) Å, α = 90.00°, β = 92.43(7)°, γ = 90.00°, V = 636.4(5) Å3, Z = 2, μ(Mo Kα) = 0.131, F(000) = 328, S = 1.071, Dc = 1.640 g·cm−3, R1 = 0.0510 and wR2 = 0.1389. Interestingly enough, its structure does not contain crystallization water, which is a unique characteristic in this material. Besides, the molecular geometry of the compound was optimized by using Density Functional Theory (DFT) method at B3LYP/6-31G (d, p) level in the ground state, revealing that the obtained geometric parameters are in accordance with the X-ray result of the structure. The experimental vibrational spectrum was compared with the calculated spectrum. Besides, molecular electrostatic potential (MEP) of G2(ZTO) was computed with the same method in gas phase, theoretically. The thermal properties of this compound were investigated by DSC, TG/DTG and micro-DSC methods. The results manifest that its thermal behavior can be divided into two main decomposition stages, the first intense decomposition peak temperature is 248.11 °C at the heating rate of 10 °C·min−1, which is higher than that of RDX (219 °C) but slightly lower than that of G(ZTO)·H2O (252.08 °C). The constant-volume combustion heat (ΔcU) of G2(ZTO), G(ZTO)·H2O and ZTO were determined and then the enthalpy of formation were calculated. The results show that G2(ZTO) possesses the highest standard molar enthalpy of formation, which may be explained by the fact that G2(ZTO) contains no water and possesses the highest nitrogen content in all guanidine salts. Moreover, the apparent activation energy (E), thermal stability and safety parameters (TSADT, TTIT, Tb) were also calculated. Besides, the calculated thermodynamic functions (ΔS≠, ΔH≠ and ΔG≠) for the main exothermic decomposition process of the title compound are 47.25 J·mol−1·K−1, 169.20 kJ·mol−1 and 144.24 kJ·mol−1, respectively. [Display omitted] •Water-free energetic compound G2(ZTO) was firstly prepared and characterized.•The experimental and theoretical data were correlated using quantum-chemical calculations.•It is firstly reported the difference between the bis(guanidinium) salt, guanidine salts and their precursor ZTO.•Non-isothermal decomposition kinetics was analyzed by thermal decomposition data from DSC curves.•Thermal stability and safety parameters, thermodynamic functions for exothermic decomposition process were calculated.