Formyl- and 2-Acetylthiophene Thiosemicarbazones

Both 2-formylthiophene thiosemicarbazone, 26, and 2-acetylthiophene thiosemicarbazone, 27, form six coordinate [FeL2A2] complexes (A = Cl, Br) [156], The complexes formed with 26 are low spin, but complexes of 27 are high spin. For both ligands the bidentate coordination is via the azomethine nitrogen 

The copper(II) complexes of 3-ethoxy-2-oxobutyraldehyde bis(thiosemicarbazone) and related compounds are active in vivo agents [151, 158, 159]. The metal complexes of 2-heterocyclic thiosemicarbazones were evaluated for their cytotoxicities [160, 161]. Further studies have revealed that these ligand s iron and copper complexes are effective inhibitors of DNA synthesis at much lower concentrations than the free thiosemicarbazones without apparent cytotoxicity [127]. Although the iron(III) complex of 2-isoformylquinoline thiosemicarbaz-one, 21, is considerably more active than free 21, the copper(II) complex is only moderately more active [127]. 

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