Roads to pentazolate anion: a theoretical insight.

Area of Science:

• Computational Chemistry
• Inorganic Chemistry
• Reaction Mechanism Studies

Background:

• The formation mechanism of the pentazolate anion (PZA) remains unclear.
• Understanding PZA formation is crucial for its potential applications.

Purpose of the Study:

• To elucidate the possible formation pathways of the pentazolate anion (PZA).
• To investigate the thermodynamic feasibility and kinetic barriers of different PZA formation routes.
• To study the stability and reactivity of PZA under various conditions.

Main Methods:

• Computational electronic structure calculations including hybrid density functional, double hybrid density functional, and coupled-cluster theories.
• Potential energy surface calculations for key intermediates like phenylpentazole (PPZ) and its derivatives.
• Analysis of reaction barriers and thermodynamic stability for proposed PZA formation mechanisms.

Main Results:

• C-N bond cleavage in PPZ and its radical are energetically unfavorable at ambient conditions.
• Oxidation of p-pentazolylphenolate anion (p-PZPolA) and p-pentazolylphenol (p-PZPol) with m-chloroperbenzoic acid (m-CPBA) can form PZA with competitive barriers.
• The pentazolate anion exhibits improved kinetic stability when confined in coordinate compounds with crystal waters.

Conclusions:

• Oxidation mechanisms involving p-PZPolA and p-PZPol with m-CPBA are promising pathways for PZA synthesis.
• PZA formation barriers compete with dinitrogen evolution, suggesting potential for energetic material applications.
• The stability of PZA is influenced by its environment, with proton transfer and coordination complexation affecting its dissociation and kinetic stability.