New polymorphs of 1-benzylidene thiosemicarbazides: crystal structure and hirshfeld surface analysis

Thiosemicarbazides are sulfur-based nitrogen-rich donor ligands, characterized by π-delocalized electronic charge and flexible molecular chain. The flexible molecular chain and polydentate nature is responsible for their wide biological and synthetic profile to synthesize several classes of heterocycles. In this context, the molecular and crystal structures coupled with Hirshfeld surface (HS) analysis of benzylidene thiosemicarbazides: (E)-2-(4-hydroxybenzylidene) hydrazine-1-carbothioamide, (3a) and (E)-2-(3-nitrobenzylidene) hydrazine-1-carbothioamide, (3b) are reported. Consequently, single crystal x-ray revealed interesting results, and the analyzed compounds were found to be polymorphs of the previously reported structures each having widely different unit cell. Briefly, compound (3a) crystallized with a single molecule in the asymmetric unit whereas its polymorph has six. In contrast, compound (3b) crystallized with Z = 2 having single molecule in asymmetric unit of the polymorph. Subsequently, HS analysis successfully visualized, explored, and quantified weak interactions present in the crystal lattices of the polymorphs. HS analysis revealed oxygen atoms of the nitro group significantly influence HS of molecule (3b). Graphical Abstract: [Figure not available: see fulltext.]