Theoretical investigations on 4,4′,5,5′-tetranitro-2,2′-1H,1′H-2,2′-biimidazole derivatives as potential nitrogen-rich high energy materials

The -NH₂, -NO₂, -NHNO₂, -C(NO₂)₃ and -CF(NO₂)₂ substitution derivatives of 4,4′,5,5′-tetranitro-2,2′-1H,1′H-2. 2′-biimidazole were studied at B3LYP/aug-cc-pVDZ level of density functional theory. The crystal structures were obtained by molecular mechanics (MM) methods. Detonation properties were evaluated using Kamlet-Jacobs equations based on the calculated density and heat of formation. The thermal stability of the title compounds was investigated via the energy gaps (δ_ELUMO-HOMO) predicted. Results show that molecules T5 (D= 10.85 km·s^-1, P = 57.94GPa) and T6 (D=9.22km·s^-1, P = 39.21 GPa) with zero or positive oxygen balance are excellent candidates for high energy density oxidizers (HEDOs). All of them appear to be potential explosives compared with the famous ones, octahydro-1,3,5,7-tetranitro-1,3,5,7-tetraazocane (HMX, D=8.96km·s^-1, P= 35.96GPa) and hexanitrohexaazaisowurtzitane (CL-20, D=9.38km·s^-1, P= 42.00 GPa). In addition, bond dissociation energy calculation indicates that T5 and T6 are also the most thermally stable ones among the title compounds.