Synthesis, Crystal Structure, and Bioactivity of a Novel Iron(III) 18-Metallacrown-6 Complex

Abstract

A macrocyclic hexanuclear iron(III) 18-metallacrown-6 compound, [Fe6(H2O)6 (abshz)6]·38H2O, has been prepared using a trianionic pentadentate ligand N-acetyl-5-bromosalicylhydrazidate (abshz3−) and characterized by X-ray diffraction. The crystal structure contains a neutral 18-member metallacrown ring consisting of six Fe(III) and six abshz3− ligands. The 18-member metallacrown ring is formed by the succession of six structural moieties of the type [Fe(III)-N-N]. Due to the meridional coordination of the ligand to the Fe3+ ion, the ligand enforces the stereochemistry of the Fe3+ ions as a propeller configuration with alternating Λ/Δ forms. The disc-shaped hexanuclear ring shows at its largest diameter about 7.27 Å at entrance and about 9.80 Å at the center of the cavity. Antibacterial screening data showed that the iron metallacrown has strong antimicrobial activity against Bacillus subtilis and Staphylococcus aureus.