Versatile coordination chemistry of thiosemicarbazide and its non-Schiff base derivatives.

• Coordination chemistry of thiosemicarbazide and its non-Schiff base derivatives. • Summary of development in TSC ligands over the 90 years since the first complexes. • Different possibilities of thiosemicarbazide modification. • Structural properties and synthesis of complexes with non-Schiff base ligands. • Structural variety, biological and physicochemical properties of TSC complexes. Very rich coordination chemistry of thiosemicarbazide based ligands is mainly associated with the diversity of their Schiff base derivatives, known as thiosemicarbazones. The significant interest in thiosemicarbazones and their metal complexes arises from a wide range of valuable biological, chemical and physico-chemical features, as documented by numerous review papers in medicinal, structural, analytical chemistry, catalysis and other. The thiosemicarbazide based ligands other than Schiff bases did not draw the same attention. A literature survey, however, shows considerable number of non-Schiff base derivatives with interesting coordination chemistry, giving rise to metal complexes with pronounced structural diversity and useful properties. Considering the polydentate thiosemicarbazide scaffold [N–N–C(=S)–N] it is not surprising that its other derivatives can offer versatile coordination modes and stable complexes with variety of metal ions. This article attempts to bring together the thiosemicarbazide derived ligands other than Schiff bases, and to explore their coordination tendencies as well as the structural aspects of their metal complexes. The first papers in coordination chemistry of thiosemicarbazide were reported exactly 90 years ago. Therefore, it is also our aim to gain better overview of various types of thiosemicarbazide ligands that have emerged since, and to understand different possibilities of thiosemicarbazide modification. In order to present and compare the molecular and supramolecular properties the review primary relies on structurally characterized coordination compounds. It also includes some experimental charge density findings in an effort to explain behaviour of thiosemicarbazide ligands at subatomic level. [Display omitted] [ABSTRACT FROM AUTHOR]