Studying the Role of CO···CO, CO···N–O, and N–O···N–O Dipole–Dipole Interactions in the Crystal Packing of 4‑Nitrobenzoic Acid and 3,3′-Dinitrobenzophenone Polymorphs: An Experimental Charge Density Study

An experimental charge density study
of 4-nitrobenzoic acid and
3,3′-dinitrobenzophenone polymorphs has been performed to study
the role played by various intermolecular interactions in the crystal
packing. The study highlights the importance of dipole–dipole
interactions analyzed with the help of Bader’s quantum theory
of atoms in molecules (QTAIM), low-reduced density gradient (RDG)
based topological descriptors of electron density and computations.
The molecular pairs held by antiparallel CO···CO,
CO···N–O, and N–O···N–O
type dipole–dipole interactions were found to contribute significantly
toward stability especially in the case of 3,3′-dinitrobenzophenone,
Form II. The low-RDG based descriptors were used for
understanding the nature of these dipole–dipole interactions,
which indicates the involvement of multiple atoms in stabilizing many
of these interactions. The significant contributions from the O···C,
O···O, and O···N contacts arising from
these dipole–dipole interactions in crystal packing are also
revealed from the Hirshfeld surface analysis of these crystals.

本研究针对对硝基苯甲酸与3,3′-二硝基二苯甲酮的多晶型物开展实验电荷密度研究，以探究各类分子间相互作用在晶体堆积中所发挥的作用。本研究借助巴德的分子中原子量子理论（QTAIM）、基于低约化密度梯度（RDG）的电子密度拓扑描述子与计算手段，分析了偶极-偶极相互作用的重要性。研究发现，由反平行CO···CO、CO···N–O以及N–O···N–O型偶极-偶极相互作用维系的分子对，对晶体稳定性具有显著贡献，在3,3′-二硝基二苯甲酮的晶型II（Form II）中尤为突出。基于低约化密度梯度的描述符被用于解析此类偶极-偶极相互作用的本质，结果表明多个原子共同参与了多数这类相互作用的稳定过程。通过对上述晶体的赫希菲尔德表面分析（Hirshfeld surface analysis），还揭示出此类偶极-偶极相互作用所产生的O···C、O···O以及O···N接触，在晶体堆积中具有重要贡献。