Safe Stockpiling of the MTX‑1 Primary Explosive in Alkali or Alkaline Earth Metal Complexes and Coordination Polymers

The safe stockpiling of high-energy combustible and explosive
materials
is important for environmental and human population protection, particularly
in mining and military areas. MTX-1 (2-(tetrazol-5-yl-diazenyl)guanidine)
is used in percussion primer compositions that react rapidly with
the hydroxides of alkali or alkaline earth metals to form complexes
of diverse composition. These are insensitive to mechanical stimuli
and to intense heat under high confinement. The most stable complexes
were found to be those with ions having the smallest effective ion
radii (Mg2+ and Ca2+),
followed by Li+. These complexes form discrete mononuclear
(Mg2+ and Ca2+) or dimeric
(Li+) structures in the solid state. One-dimensional (1D)
(Na+, Sr2+, and Ba2+), 2D (K+ and Rb+), and 3D (Cs+) coordination polymeric structures were found for the remaining
complexes with larger ions. Detailed topological analysis of the electron
density and quantitative estimation of π–π stacking
interactions were performed. Complexes could be used for intense flame
coloring in pyrotechnics. Upon thermal treatment of complexes over
∼200 °C, water is lost from the coordination sphere of
the metal ion, which leads to materials that are slightly sensitive
and rehydrate in moist air. Recovery of insoluble MTX-1 is possible when these complexes are treated with an aqueous acid.

高能可燃与易爆材料的安全储存，对于环境保护与民众生命安全保障至关重要，在采矿与军事领域尤为如此。MTX-1（2-(四唑-5-基偶氮基)胍，2-(tetrazol-5-yl-diazenyl)guanidine）可用于制备撞击式底火组合物，该组合物可与碱金属或碱土金属氢氧化物快速反应，生成组成多样的配合物。此类配合物对机械刺激及高压下的强热均不敏感。研究发现，有效离子半径最小的金属离子（Mg²+与Ca²+）所形成的配合物稳定性最高，其次为Li+形成的配合物。此类配合物在固态下可形成离散的单核（Mg²+、Ca²+）或二聚体（Li+）结构。其余由更大半径离子形成的配合物，则分别呈现一维（1D，Na+、Sr²+与Ba²+）、二维（2D，K+与Rb+）及三维（3D，Cs+）配位聚合物结构。研究人员对电子密度开展了详细的拓扑分析，并对π-π堆积（π–π stacking）相互作用进行了定量评估。此类配合物可用于烟火药剂中以产生鲜艳的火焰色彩。当配合物在约200℃以上的温度下受热时，金属离子配位球中的配位水会脱离，所得材料会表现出轻度敏感性，且可在潮湿空气中重新吸水。若将此类配合物用酸性水溶液处理，则可回收得到不溶性的MTX-1。