Cobalt and nickel complexes of versatile imidazole- and pyrrole-2-carbaldehyde thiosemicarbazones. Synthesis, characterisation and antimicrobial activity

Abstract

Ni(II), Co(II) and Co(III) complexes of imidazole- and pyrrole-2-carbaldehyde thiosemicarbazone ligands (H 2L 1 and H 2L 2, respectively) have been prepared. The X-ray crystal structures of [Co(L 1)(HL 1)], [Ni(H 2L 1) 2]Cl 2 · 3.5H 2O and [Ni(HL 2) 2] have been solved. The Co(III) ion assumes a slightly distorted octahedral coordination geometry, involving both N 2S binding domain of di- and monoanionic ligand molecules. Whereas in [Ni(HL 2) 2] the metal ion is tetracoordinated in a square planar geometry by two pyrrole-2-carbaldehyde thiosemicarbazone molecules acting as NS-donor, the spatial array of non deprotonated H 2L 1 ligand molecules in [Ni(H 2L 1) 2]Cl 2 · 3.5H 2O is equivalent to that found for [Co(L 1)(HL 1)]. The in vitro antimicrobial properties of the ligands and their complexes were tested against representative bacterial and fungal strains in broth culture. The compounds H 2L 2 and [Co(L 2)(HL 2)(H 2L 2)] · 1.5H 2O exhibit a moderate inhibitory effect on the microbial proliferation and only against some Gram positive bacteria.