Nitro Derivatives of 1,3,5-Triazepine as Potential High-Energy Materials

Abstract

Structure optimization and frequency calculation of six nitro derivatives of 1,3,5-triazepine were performed using a MP2(FULL)/6-311G(d,p) method. In order to obtain reliable energy data, single-point energy and subsequently thermodynamic properties of the species considered were calculated at a fairly high level of theory, CCSD(T)/6-311G(d,p). Solid-phase heats of formation and crystal density were determined using an electrostatic potential (ESP) method utilizing wave function analysis-surface analysis suite (WFA-SAS) code. The result shows that all nitro derivatives possess high positive heats of formation that increase with an increase in the number of nitro groups attached to the ring moiety. The crystal density was found to be in the range of 1.67–1.90 g/cm³. Detonation properties of the compounds were estimated using the Kamlet-Jacobs equation. The results showed that detonation velocity (D) and detonation pressure (P) increased with an increase in the number of nitro groups attached at the ring moiety. It was found that all six nitro derivatives of the title compound had better or comparable performance characteristics than the most widely used commercial explosives, such as TNT, research and development explosives (RDX), and 1,3,5,7-tetranitro-1,3,5,7-tetrazocane (HMX). The trinitro derivative (1,3,5-trinitro-1,3,5-triazepine, F) yielded detonation pressure (P) and detonation velocity (D) of 45.5 GPa and 9.23 km/s, respectively, at a loading density of 1.90 g/cm³, which are superior to the most powerful available explosive HMX (P = 39.00 GPa and D = 9.11 km/s). The results obtained during the present study show that the title compounds can be used as promising futuristic high-energy-density materials (HEDMs).

Keywords:

• CCSD (T) methods
• crystal density
• ESP method
• heat of formation
• heat of sublimation
• HEDM
• Kamlet-Jacobs method
• MP2
• 1,3,5-triazepine
• WFA-SAS code

Acknowledgments

One of the authors (M.K.U.) is thankful to UGC, New Delhi, for providing financial support under its DSA (BSR) program. Thanks are also due to the UP State Government for providing financial assistance under its Centre of Excellence Program to the Department of Chemistry to work in the thrust area of computer modeling.

Notes

ΔΔH ⁰ = change in enthalpy of the respective species on going from 0 to 298 K.

^a Values taken from Keshavarz [30].

^b Values taken from Keshavarz [31].

^c Values taken from Keshavarz and Pouretedal [32].

^d Values taken from Wei et al. [33].