Theoretical calculations about nitro-substituted pyridine as high-energy-density compounds (HEDCs).

A series of derivatives of pyridine were designed through substituting hydrogen atoms by nitro groups systematically. By using the density functional theory at B3PW91/6-311++G(d,p)//MP2/311++G(d,p) level, heats of formation, bond orders, and bond dissociation energies were calculated to explore the thermodynamic stabilities of title molecules. Furthermore, the regularity of stability was explained based on the electronic population. Our results indicated that title molecules had enough stability to exist. To evaluate the potential usage as a high-energy-density molecule, the detonation pressure and detonation velocity were explored by using the semi-empirical Kamlet-Jacobs equation and excellent detonation character was confirmed. Overall consideration of the thermal stability and energetic character, four molecules (2,3,4,5-tetranitropyridine, 2,3,5,6-tetranitropyridine, 2,4,5,6-tetranitrop-pyridine, 2,3,4,5,6-pentanitropyridine) were confirmed to be better than RDX and filtered as potential energetic molecules.