Heterocyclic substituted thiosemicarbazones and their Cu(II) complexes: Synthesis, characterization and studies of substituent effects on coordination and DNA binding

By reacting thiosemicarbazides substituted on the aminic nitrogen with 5-formyluracil, several new 5-formyluracil thiosemicarbazones (H3ut) derivatives were synthesised and characterized. These ligands, treated with copper chloride and nitrate, afforded two different kinds of compounds. In the complexes derived from copper chloride the metal atom is pentacoordinated, being surrounded by the neutral ligand binding through SNO donor atoms and by two chlorines, while the nitrate derivatives consist of monocations and nitrate anions. The copper coordination (4 + 2) involves the SNO ligand atoms, two water oxygens and an oxygen atom of a monodentate nitrate group. On varying the substituents on the thiosemicarbazidic moiety, remarkable modifications of the coordination geometry are not observed for the complexes with the same counterion. For all the compounds, interactions with DNA (calf thymus) were studied using UV–Vis spectroscopy; the nuclease activity was verified on plasmid DNA pBR 322 by electrophoresis.

Graphical abstractNew 5-formyluracilthiosemicarbazones (H3ut) derivatives have been synthesised and characterized. In their complexes derived from copper chloride the metal atom is pentacoordinated, while in the nitrate derivatives the copper coordination is 4 + 2. The substituents on the thiosemicarbazidic moiety were varied. Interactions with DNA were studied and the nuclease activity was verified on plasmid DNA.Figure optionsDownload full-size imageDownload as PowerPoint slide