Understanding of the bond dissociation energy of C-NO2 in five- and six-membered N-heteroaromatic derivatives

A clear structure-sensitivity relationship in energetic molecules is beneficial for designing energetic materials. At the molecular level, sensitivity is closely related to the bond dissociation energy (BDE) of trigger linkages like C/N/O-NO₂ in the widely used nitro compounds. Herein, the BDE of C-NO₂ in a series of designed five- and six-membered N-heteroaromatic derivatives, including pyrrole, pyrazole, imidazole, triazole, tetrazole, pyridine, pyridazine, pyrimidine, pyrazine, triazine, tetrazine, and pentazine, are investigated to quantify the impact of substituent groups and N atoms on aromatic rings on it. We find that introducing pyridine-type N atoms decreases the BDE and increasing their number further reduces it. Additionally, increasing vicinal pyridine-type N atoms and C-NO₂ also lowers the BDE. Conspicuously, the intramolecular hydrogen bonding between vicinal C-NO₂ and C-NH₂ facilitates high BDE.