Nitrogen-rich alkali metal salts (Na and K) of [bis(N,N-bis(1h-tetrazol-5-yl)amine)-zinc(ii)] anion: Syntheses, crystal structures, and energetic properties

Two nitrogen-rich alkali metal salts based on nitrogen-rich anion [Zn(bta)₂]^2-: {[Na₂Zn(bta)₂(H₂O)₈]·H₂O}_n (1) and {[K₂Zn(bta)₂(H₂O)₄]}_n (2) were synthesized by reactions of alkali hydroxide, N,N-bis(1H-tetrazol-5-yl)amine (H₂bta), and zinc chloride in aqueous solutions. The crystal structures of 1 and 2 were determined by low temperature single-crystal X-ray diffraction and fully characterized by elemental analysis and FT-IR spectroscopy. The structures demonstrate that an infinite 1-dimensional (1D) chain structure is constructed by Na⁺ ions and bridging water molecules in compound 1, which is connected by extensive hydrogen bonds forming a complex 3D network, whereas compound 2 features a more complicated 3D metal-organic framework (MOF). The thermal behaviors of 1 and 2 were investigated by differential scanning calorimetry (DSC) measurements. The DSC results illustrate that both compounds exhibit high thermal stabilities (decomposition temperature > 345 C). In addition, the heats of formation were calculated on the basis of the experimental constant-volume energies of combustion measured by using bomb calorimetry. Lastly, the sensitivities towards impact and friction were assessed according to Bundesamt für Materialforschung (BAM) standard methods.