Coordination Chemistry of Zinc(II) Dithiocarbamate with Polypyridine Ligands: Synthesis and Detailed Spectroscopic Insights

Abstract

Zinc(II) dithiocarbamate complexes continue to attract considerable attention due to their versatile coordination behaviour, rich spectroscopic features, and relevance in coordination and materials chemistry. In the present study, a parent zinc(II) dithiocarbamate complex, bis{[4-(piperidin-1-yl)piperidine]carbodithioato-κ²S,S′}zinc(II), and its coordination adducts with the neutral nitrogen-donor ligands 1,10-phenanthroline and 2,2′-bipyridine were successfully synthesized. The complexes were obtained in good yields and characterized comprehensively using elemental analysis, ultraviolet–visible (UV–Vis) spectroscopy, Fourier-transform infrared (FT-IR) spectroscopy, and nuclear magnetic resonance (¹H and ¹³C NMR) spectroscopy. Elemental analysis confirmed the proposed stoichiometry and high purity of the synthesized compounds. FT-IR spectra revealed characteristic thioureide ν(C–N) and ν(C–S) bands, supporting bidentate coordination of the dithiocarbamate ligand through sulphur atoms, while additional ν(Zn–N) bands in the adducts confirmed coordination of the nitrogen-donor ligands. Electronic absorption spectra were dominated by ligand-centred and charge-transfer transitions, consistent with the d¹⁰ electronic configuration of Zn(II). The ¹H and ¹³C NMR spectra provided definitive evidence for dithiocarbamate formation, retention of the Zn(dtc)₂ core, and ligand-induced electronic modulation, particularly through systematic downfield shifts of the thioureide carbon resonance. Overall, the combined spectroscopic results clearly establish the coordination environment and electronic features of the parent and adduct complexes, highlighting the influence of polypyridine ligands on the structural and spectroscopic properties of zinc(II) dithiocarbamate systems.