Transition metal (Mn/Co/Ni/Cu) complexes based on 1-ethylimidazole and dicyandiamide: syntheses, characterizations, and catalytic effects on the thermal decomposition of ammonium perchlorate

Four new coordination compounds were synthesized by the reactions of transition-metal inorganic salts with 1-ethylimidazole (EIMI) and sodium dicyanamide (NaDCA), and were characterized by elemental analysis, infrared spectroscopy (FT-IR), and X-ray crystal diffraction (XRD). Their molecular structures were confirmed as [Mn(EIMI)₄](DCA)₂ (1), [Co(EIMI)₄](DCA)₂ (2), [Ni(EIMI)₄](DCA)₂ (3), [Cu(EIMI)₄](DCA)₂ (4). The thermal decomposition processes of 1–4 were studied by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). Catalytic effects on the thermal decomposition of ammonium perchlorate (AP) of these complexes were investigated in detail by employing the DSC technique. Complex 1 shows an outstanding catalytic activity. The low-temperature decomposition process of AP with 30 wt.% complex 1 disappeared, and its peak temperature was advanced by 75°C with an improved heat release (4306 J g⁻¹). The E_a of the high-temperature decomposition process of AP with 30 wt.% complex 1 calculated by Kissinger’s method is 60 kJ mol ⁻¹ lower than pure AP. The manganic complex 1 was suggested for a potential combustion additive for solid propellant.