A theoretical study of molecular structure, optical properties and bond activation of energetic compound FOX-7 under intense electric fields

- Stabilization effect of applied electric field on activated structures was addressed.
- Bond activation energy of FOX-7 decreases under electric fields in regardless of field direction.
- Bond rupture path, homolytic or heterolytic, is affected by field direction and strength.
- Field-induced peak splitting in stretching vibrations and redshift in electronic absorption were revealed.

Molecular structure, vibrational and electronic absorption spectra, chemical reactivity of energetic compound FOX-7, one of the most widely used explosives, were studied computationally in presence of an electrostatic field of 0.01-0.05 a.u. The CN bond, which usually triggers the decomposition of FOX-7, is shortened/elongated under a parallel/antiparallel field. The CN bond activation energy varies with the external electric field, decreasing remarkably with the field strength in regardless of the field direction. This is attributed to two aspects: the bond weakening by the field parallel to the CN bond and the stabilization effect on the transition-state structure by the field antiparallel to the bond. The variations in the structure and property of FOX-7 under the electric fields were further analyzed with its distributional polarizability, which is dependent on the charge transfer characteristics through the CN bond.

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