Solvent effects on the geometry, electronic structure, and bonding style of Zn(N5)2: A theoretical study

Nitrogen-rich compounds involving the cyclo-pentazole anion (cyclo-N-5(-)) have attracted extensive attention due to higher energy release and environmental friendliness than traditional high energy density materials (HEDMs). However, the synthesis of stable HEDMs with cyclo-N-5(-) is still a challenge. In this study, the effect of nine solvents on the geometrical and electronic structures and solvation energies of Zn(N-5)(2), one of the recently synthesized nitrogen-rich compounds, was studied using the density functional theory and the polarized continuum model. The results indicated an increase in the stability of Zn(N-5)(2) in the solution phase compared to the vacuum phase, and the stability of Zn(N-5)(2) increases with increasing dielectric constants. The energy gap of frontier molecular orbitals and the absolute value of total energy in water are the largest, revealing that Zn(N-5)(2) is more stable in water than in other solvents. To understand the stabilization mechanism of Zn(N-5)(2) by water, further studies were performed with the natural bond orbital (NBO) analysis and the quantum theory of atoms in molecules (QTAIM) analysis using the explicit solvent model. The charge transfer and the hydrogen bonds are observed between Zn(N-5)(2) and water, which are beneficial to improvement of the stability of Zn(N-5)(2). This may indicate the solvents that have strong interactions with the cyclo-N-5(-) candidate may improve the possibility of success of synthesis.