Coordination chemistry with 1-methyl-5H-tetrazole: cocrystallization, laser-ignition, lead-free primary explosives – one ligand, three goals

Abstract

The synthesis and characterization of 1-methyl-5H-tetrazole (1, MTZ) from 1,5H-tetrazole and methyl iodide is achieved. This neutral ligand was evaluated for its use in energetic transition metal complexes. The formation of complexes is a valuable concept because of their easy synthesis and the large number of possible combinations: (i) metal, (ii) ligand, and (iii) anion. A series of 31 new complexes based on MTZ as the ligand was prepared in order to tune their optical properties and sensitivity values by using seven different metals (Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, and Ag⁺) and six different anions (chloride, nitrate, perchlorate, cyanodinitromethanide, picrate, and styphnate). This variation allows tailoring of the energetic properties of the desired molecule toward e.g. suitable primary explosives or laser-ignitable materials. Obtained compounds were characterized by low temperature single crystal X-ray diffraction, IR spectroscopy, elemental analysis and thermal analysis (DTA, DSC and TGA). The sensitivities toward external stimuli (impact, friction and electrostatic discharge) were determined according to the Bundesamt für Materialforschung und -prüfung (BAM) standard methods. These complexes have been characterized in laser ignition experiments and as new primary explosives. UV-vis measurements of selected complexes were carried out to get a possible insight into the laser initiation mechanism. For the first time a large number of compounds with sensitivities ranging from insensitive to very sensitive were synthesized to give a wide range of new materials for different possible applications.