Synthesis, characterization and bioactivity of a novel iron(III) 18-metallacrown-6 complex with S-donor ligands

The reaction of 4-salicyloyl thiosemicarbazide (H(3)st) (1) with FeCl3 center dot 6H(2)O in methanol solution gives a novel 18-metallacrown-6 [Fe(st)(H2O)](6)center dot 21H(2)O (2). The structure containing S-Fe bonds was determined for 2 by using X-ray crystallography. The ring of the metallacrown was consisted of six interlink [Fe-N-N] repeated units. And the ligand enforces the metal ions to form the stereochemistry as a propeller configuration with alternation Lambda/Delta form. The largest diameters of the disc-shaped hexanuclear ring are about 7.44 angstrom at entrance, 9.91 angstrom at the central of the cavity, respectively. The structural integrity and stability of the metallacrown ring were studied by electronspray ionization ESI-MS and UV-Vis spectroscopy. The results show that it is stable and soluble in methanol. Antibacterial screening data show that the complex 2 weakened dramatically the antibacterial activity of the ligand H(3)st. (C) 2007 Elsevier B.V. All rights reserved.