The title Zn II complex, [Zn(C 18 H 18 N 3 S) 2 ], (I), features two independent but chemically equivalent molecules in the asymmetric unit. In each, the thiosemicarbazonate monoanion coordinates the Zn II atom via the thiolate-S and imine-N atoms, with the resulting N 2 S 2 donor set defining a distorted tetrahedral geometry. The five-membered ZnSCN 2 chelate rings adopt distinct conformations in each independent molecule, i.e. one ring is almost planar while the other is twisted about the Zn-S bond. In the crystal, the two molecules comprising the asymmetric unit are linked by amine-N-HÁ Á ÁN(imine) and amine-N-HÁ Á ÁS(thiolate) hydrogen bonds via an eight-membered heterosynthon, {Á Á ÁHNCNÁ Á ÁHNCS}. The dimeric aggregates are further consolidated by benzene-C-HÁ Á ÁS(thiolate) interactions and are linked into a zigzag supramolecular chain along the c axis via amine-N-HÁ Á ÁS(thiolate) hydrogen bonds. The chains are connected into a three-dimensional architecture via phenyl-C-HÁ Á Á (phenyl) and -interactions, the latter occurring between chelate and phenyl rings [inter-centroid separation = 3.6873 (11) Å ]. The analysis of the Hirshfeld surfaces calculated for (I) emphasizes the different interactions formed by the independent molecules in the crystal and the impact of theinteractions between chelate and phenyl rings.
Chemical contextThiosemicarbazone molecules, derived from thiosemicarbazide, H 2 N-NH-C( S)-NH 2 , constitute an important class of mixed hard-soft, nitrogen-sulfur donor ligands which have been extensively investigated in their coordination chemistry towards both transition metals (Lobana et al., 2009) and main group elements (Casas et al., 2000). Complexes of thiosemicarbazones, including Zn II complexes (Da Silva et al., 2013), have been evaluated variously as potential anti-cancer (Afrasiabi et al., 2003), anti-viral (Garoufis et al., 2009) and anti-bacterial (Quiroga & Ranninger, 2004) therapeutics for over 50 years (Dilworth & Hueting, 2012). The interesting properties of their metal complexes, such as structural diversity, accessible redox activities, the ability to fine-tune ligand substitution, access to radical species, catalytic properties, distinct spectroscopic properties, etc. afford them many potential advantages over organic-based drugs (van Rijt & ISSN 2056-9890 Sadler, 2009Meggers, 2009). Recent studies have focused upon their suitability as single-source precursors for ZnS nanomaterials (Pawar et al., 2017). Thiosemicarbazones can exist as thione-thiol tautomers and can bind to a metal centre in neutral or anionic forms as monodentate, bidentate or bridging ligands (Viñ uelas-Zahínos et al., 2011). The presence of additional, suitably positioned donor atoms can increase their coordination ability/denticity, giving rise to different coordination geometries, such as tetrahedral, octahedral and pentagonal-bipyramidal. (Umamatheswari et al., 2011). As part of a programme investigating thiosemicarbazones and their metal complexes (Tan et al., 2015), the crystal and molecular s...