Four cytotoxic N4-substituted thiosemicarbazones derived from 2-hydroxynaphthalene-1-carboxaldehyde.

The X-ray crystal structures are reported of four novel and potentially O,N,S-tridentate donor ligands that demonstrate antitumour activity. These ligands are 1-[(4-methylthiosemicarbazono)methyl]-2-naphthol, C(13)H(13)N(3)OS, (III), 1-[(4-ethylthiosemicarbazono)methyl]-2-naphthol, C(14)H(15)N(3)OS, (IV), 1-[(4-phenylthiosemicarbazono)methyl]-2-naphthol, C(18)H(15)N(3)OS, (V), and 1-[(4,4-dimethylthiosemicarbazono)methyl]-2-naphthol dimethyl sulfoxide solvate, C(14)H(15)N(3)OS.C(2)H(6)OS, (VI). These chelators are N4-substituted thiosemicarbazones, each based on the same parent aldehyde, namely 2-zhydroxynaphthalene-1-carboxaldehyde isonicotinoylhydrazone. Conformational variations within this series are discussed in relation to the optimum conformation for metal-ion binding.