Theoretical prediction of the trigger linkages, surface electrostatic potentials, and explosive sensitivities of 1,4-dinitroimidazole-N-oxide in the external electric fields

In order to introduce effectively the external electric fields into the explosive systems, the change trends of the strengths of trigger linkages, nitro group charges, and explosive sensitivities of 1,4-dinitroimidazole-N-oxide (1,4-DNIO) were investigated in the external electric fields at the B3LYP/6–311++G(2d,p) and M06–2X/aug–cc–pVTZ levels. The formulas for calculating the impact sensitivity by the surface electrostatic potentials were discussed. The results show that the N–NO2 bond is always the most likely trigger linkage, followed by N → O. This is the very valuable information for the researchers engaged in the molecular design or synthesis of the energetic explosives: The influences of the weak N → O coordination bond attached to the aromatic ring on the explosive sensitivity can be ignored when the N–NO2 bond exists. In the external electric fields along the positive directions of the N → O and C–NO2 bond axes as well as the negative direction of the N–NO2 bond axis, the dissociation energies (BDEs) of the N–NO2 bond and h50 values are increased, leading to the decreased impact sensitivities. The changes of the bond lengths, AIM electron density values, nitro group charges, BDEs of the trigger linkages, and impact sensitivities correlate well with the external electric field strengths, respectively. The effects of the fields on the electric spark sensitivities and shock initiation pressures are not obvious. The essence of the low BDEs of the N–NO2 bond was revealed by the resonance theory of the aromatic ring.