Structure and bonding trends of bisthiosemicarbazones: An overview

This review gives a comprehensive account in terms of the synthesis, characterization and biological application of bisthiosemicarbazone ligands and their metal complexes that have been reported until 2022. Their coordination chemistry with p and d block elements, where the structure is solved by single crystal X‐ray crystallography is explored. Complexes are placed group‐wise and their structure as well as bonding aspects are discussed separately. Various spectroscopic techniques for the characterization of ligands and their complexes like infrared (IR), ultraviolet‐visible (UV–Vis), electron spin resonance (ESR), and nuclear magnetic resonance (NMR) (1H, 13C, 31P, 59Co, 119Hg) are discussed. Complexes formed by bisthiosemicarbazones are generally mononuclear; however, in some cases, binuclear or polynuclear complexes have also been found. Square planar, square pyramidal, octahedral, and pentagonal pyramidal are some of the common geometries exhibited by these complexes. Structure–activity relationship was established for substituted and unsubstituted diimine bisthiosemicarbazone complexes of different metal ions. The effect of co‐ligands on biological activity is also discussed.