Complexes of 2-acetyl-c-butyrolactone and 2-furancarbaldehyde thiosemicarbazones: Antibacterial and antifungal activity

Cobalt, nickel, copper and zinc coordination compounds of two thiosemicarbazones with general composition ML2 (L: monodeprotonated ligand corresponding to 2-acetyl-c-butyrolactone thiosemicarbazone, HL1, and 2-furancarbaldehyde thiosemicarbazone, HL2) and also complexes with general composition MCl2(HL2) were synthesized (except [NiCl2(HL2)] and [Co(L2)2]). The interaction of CuCl2 with HL2 gave [CuCl(HL2)], a copper(I) complex. The ligands and metal complexes were characterized by IR, 1H and 13C NMR spectroscopy, and magnetic susceptibility measurements. The crystal structure of [Ni(L2)2]⋅2dmso was determined and a trans-square planar coordination of the two κ2-N,S chelate rings forming polymeric strips through H-bonds with dmso was observed. Actually, in all the reported complexes both ligands behaved as κ2-N,S chelates, except in the case of [Co(L1)2] in which HL1 is tridentate κ3-N,S,O. The antimicrobial properties of all compounds were studied using a wide spectrum of bacterial and fungal strains. The copper complexes of HL2 were the most active against all strains, including dermatophytes and phytopathogenic fungi. Most of the studied compounds, especially [Cu(L1)2], presented good activity against Haemophilus influenzae, a very harmful bacterium to humans.