By replacing the pyrazolyl fragment in 3,6-bis(3,5-dimethyl-1Hpyrazol-1-yl)-1,2,4,5-tetrazine with 3-nitro-1,2,4-triazol-5-one (NTO), both mono-and disubstitution products have been synthesized. Further interaction of the obtained compounds with O-and N-nucleophiles led to the preparation of a number of polynitrogen tetrazine derivatives, including 2-[6-amino-1,2,4,5-tetrazin-3-yl]-5-nitro-2,4-dihydro-3H-1,2,4-triazol-3-one and 5-nitro-2-[6-(1H-tetrazol-5-ylamino)-1,2,4,5-tetrazine-3-yl]-2,4-dihydro-3H-1,2,4-triazol-3-one. The reactions of nucleophilic substitution of symmetrically substituted tetrazine were shown to proceed more selectively. The resulting compounds were identified using 1 H, 13 CNMR spectroscopy, FTIR, LC-MS, and elemental analysis, as well as using X-ray diffraction analysis. The thermal stability of the new compounds was evaluated under isothermal and non-isothermal conditions and their energy characteristics were calculated. An unusual drop in stability was found on going from symmetrically substituted tetrazines to asymmetric ones.