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

Abstract

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.