Unimolecular Decomposition Mechanism of the Pyrazolo‐Triazine Fused‐Ring Skeletons: Quantum Chemistry Modeling

ABSTRACT To obtain the thermal decomposition mechanism and key intermediates of pyrazolo‐triazine fused‐ring skeletons (PT1∼PT10), the decay pathways were studied by using the M062X method for optimization and DLPNO‐CCSD(T)/cc‐pVTZ methods for energies. Results showed that the most stable structure of the pyrazolo‐triazine fused‐ring is characterized by a structure with two C  H bonds connected on the triazine ring (PT9). Notably, the H transfer has become the main reaction to promote the ring‐opening reaction. The introduction of the O atom changes the dominant reaction pathway. Except for PT9 and PT10, the position arrangement of N atoms in the molecule significantly affects its decomposition path and stability. On the one hand, structures containing three or more N atoms directly connected are the most likely to undergo a ring‐opening reaction, while other structures tend to undergo H transfer reactions. On the other hand, an increase in the number of N atoms directly connected further reduces the stability. These conclusions were expected to contribute significantly to the design and application of novel high energy density materials.