An iron(III) 18-metallacrown-6 complex: synthesis, crystal structure, and bioactivity

Abstract

A macrocyclic hexanuclear iron(III) 18-metallacrown-6 complex, [Fe₆(C₉H₆BrN₂O₃)₆(CH₃OH)₄(H₂O)₂] · 7CH₃OH · 4H₂O, has been prepared using a trianionic pentadentate ligand N-acetyl-5-bromosalicylhydrazidate, abshz^3–, and characterized by X-ray diffraction. The crystal structure contains a neutral 18-membered metallacrown ring consisting of six Fe(III) and six abshz^3– ligands. The 18-membered metallacrown ring is formed by combination of six structural moieties, [Fe(III)–N–N]. Due to meridional coordination of ligand to Fe³⁺, the ligand enforces the stereochemistry of the Fe³⁺ ions as a propeller configuration with alternating Δ/Λ forms. Methanol and water are linked with Fe1, Fe1A, Fe,3 and Fe3A. The ratios of methanol to water are 0.76 : 0.24 for Fe1 and Fe1A, and 0.30 : 0.70 for Fe3 and Fe3A, which results in four component crystals of metallacrown rings with ratio of 0.168 : 0.072 : 0.532 : 0.228. Antibacterial screening data showed that the iron metallacrown has moderate antimicrobial activity against Bacillus subtilis.

Keywords:

• Metallacrown
• Iron complex
• Crystal structure
• Antimicrobial activity

Acknowledgements

This work was supported by the Key Project of Natural Science Foundation of Hubei Province, China (2008CDA067).