Polymorphism and weak noncovalent interactions with unique halogen bonding in the supramolecular assemblies of (Z)-3-[(4-bromophenyl)amino]-2-cyanoprop-2-enoate

A new polymorphic form of (Z)-3-[(4-bromophenyl)amino]-2-cyanoprop-2-enoate was obtained from an ethanolic solution. Single-crystal X-ray diffraction (SCXRD) analysis revealed that the compound crystallizes in the monoclinic system with space group P21/c, Z = 8, and an asymmetric unit comprising two crystallographically independent molecules (Z′ = 2). An intramolecular N–H···O hydrogen bond forms an S(6) ring motif. The intramolecular and intermolecular interactions, as well as the supramolecular architecture of this new polymorph (form II), are compared with the previously reported polymorph (form I). Topological analysis indicates that the intramolecular N–H···O hydrogen bond in both forms I and II exhibits closed-shell character. Intermolecular interaction energies for dimers in both forms were quantified using the Coulomb-London–Pauli-PIXEL (CLP-PIXEL) and density functional theory (DFT) methods. The nature and strength of various intermolecular interactions were further analyzed and quantified using Bader’s quantum theory of atoms in molecules (QTAIM) approach. The crystal structure of form II is stabilized by weak intermolecular C–H···N, C–H···O, and C–H···Br and molecular stacking interactions. Unique halogen bonds are observed in polymorphic forms I (Br···N) and II (Br···Br) and were examined using molecular electrostatic potential (MESP) surface maps and deformation electron density maps. These halogen bonds significantly influence the crystal packing of their respective polymorphs. Hirshfeld surface (HS) analysis indicated that H···H, H···N, H···Br, C···H, and O···H contacts make substantial contributions to the overall packing.