Evaluation of the antimicrobial activity of some chloro complexes of imidazole-2-carbaldehyde semicarbazone: X-ray crystal structure of cis-NiCl2(H2L)(H2O)

Some first row transition metal(II) complexes of imidazole-2-carbaldehyde semicarbazone (H2L) have been synthesised and characterised. Single crystal X-ray diffraction studies have revealed the molecular structure of the neutral complex NiCl2(H2L)(H2O). This latter complex shows a pseudo-octahedral geometry, with both chloride ions displaying a cis disposition. The asymmetry of this complex allows the formation of two enantiomers in the racemic crystal structure. The non-deprotonated semicarbazone ligand behaves as an N,N,O-donor, through the imidazole and imine N atoms and the Oketo atom. The coordinative behaviour of H2L in CuCl2(H2L)(H2O), ZnCl2(H2L)20.5EtOH and CoCl2(H2L)20.5H2O is reported as only N,O-donor. The antimicrobial activity of the semicarbazone ligand and its metal complexes has been tested against some representative bacteria and fungi. A moderate inhibitory activity of the cobalt complex was detected towards the assayed phytopathogenic fungi Alternaria tenuis and Sclerotinia minor (MIC 50 microg/mL).