Coordinative versatility of a Schiff base containing thiophene: Synthesis, characterization and biological activity of zinc(II) and silver(I) complexes

The synthesis, spectroscopic characterization and crystal description based on powder diffraction data, and antimycobacterial assays of silver(I) and zinc(II) complexes with Schiff base N,N′-bis(thiophen-2-ylmethylene) ethane-1,2-diamine ThioEn, are here reported. The [Ag(ThioEn)]NO3, AgThioEn, [Ag(ThioEn)2]NO3, Ag(ThioEn)2 and [ZnCl2(ThioEn)], ZnThioEn complexes were obtained by reaction of the ThioEn with silver(I) nitrate or zinc(II) chloride in methanolic solution. ThioEn was previously obtained by reacting ethylenediamine (En) with 2-thiophenecarboxaldehyde (Thio). The complexes were characterized by elemental (C, H and N) and thermal (TG-DTA) analyses and 13C and 1H NMR and FT-IR spectroscopic measurements. The three crystal structures were determined and refined from laboratory powder diffraction data only. The AgThioEn complex has a polymeric structure where the ligand acts as bridge between Ag(I) ions, while Ag(ThioEn)2 and ZnThioEn are monomers complexes with ThioEn acting as chelating ligand. Both silver(I) complexes showed to be effective against Mycobacterium tuberculosis.