Distinguishing the Packing Modes of Planar Energetic Molecules with Two “H<sub>2</sub>N–C–C–NO<sub>2</sub>” Groups Based on π-Holes
Yilin Cao, Zhixiang Zhang, Weipeng Lai, Tao Yu, Yiding Ma, Yingzhe Liu, Bozhou Wang
Abstract
Energetic materials (EMs) with layered packing structures exhibit good balances between high energy and low sensitivity, while it is a challenge to create them due to unclear correlations between planar molecules and packing modes. In this work, a systematic investigation on 10 geometrically similar planar EMs was performed with the help of computational methods, aiming to dig out the dominant factors responsible for layered and non-layered packing modes. After a comprehensive analysis, including packing structures, Hirshfeld surfaces, energy frameworks, the “Atoms in Molecules” theory, molecular electrostatic potential, and so on, we found that π-holes around C–NO2 bonds can act as indicators to distinguish layered and non-layered packing modes. The π-holes with a positive electrostatic potential and a large region can form directional interactions with electron-rich nitro groups, resulting in non-layered packing structures. Thus, it is reasonable that no obvious π-holes are observed in the layered energetic crystals. The present contribution is hopefully to accelerate the development of advanced layered EMs.