Trigger bond analysis of nitroaromatic energetic materials using wiberg bond indices

Area of Science:

• Computational chemistry
• Materials science
• Chemical physics

Background:

• Developing novel high energy density materials (HEDMs) requires understanding initiation mechanisms.
• Identifying trigger bonds, crucial for explosive decomposition, is key to designing safer energetic materials.

Purpose of the Study:

• To computationally identify trigger bonds in nitroaromatic energetic molecules.
• To establish a relative scale for bond activation (%ΔWBIs) using Wiberg bond indices (WBIs).
• To correlate bond activation with impact sensitivity and intramolecular interactions.

Main Methods:

• Calculated Wiberg bond indices (WBIs) for 63 nitroaromatic compounds.
• Assessed bond activation (%ΔWBIs) by comparing energetic materials to reference molecules.
• Analyzed the influence of intramolecular hydrogen bonding, steric effects, and electronic factors on trigger bond strength.

Main Results:

• Intramolecular hydrogen bonding can deactivate C-NO2 trigger bonds in nitroanilines but activate them in nitrophenols.
• Steric effects, electron-withdrawing groups, and dihedral angles activate trigger bonds.
• %ΔWBIs correlate well with impact sensitivity, particularly for HEDMs with intramolecular hydrogen bonding.

Conclusions:

• %ΔWBIs provide a valuable metric for trigger bond strength, outperforming bond dissociation energies (BDEs) in many cases.
• Understanding intramolecular interactions is crucial for predicting and tuning the sensitivity of HEDMs.
• This computational approach aids in the rational design of next-generation energetic materials.