Synthesis, crystal structure and bioactivity of a novel 18-metallacrown-6 [Mn6(H2O)6 (anshz)6] · 10DMF

A novel macrocyclic hexanuclear manganese(III) 18-metallacrown-6 compound, [Mn6(H2O)6 (anshz)6] · 10DMF, has been prepared using a trianionic pentadentate ligand N-acetyl-5-nitrosalicylhydrazide (anshz3−) and characterized by X-ray diffraction (DMF = N,N-dimethylformamide). The crystal structure contains a neutral 18-membered metallacrown ring consisting of six Mn(III) and six anshz3− ligands. The 18-membered metallacrown ring is formed by the succession of six structural moieties of the type [Mn(III)single bondNsingle bondN]. Due to the meridional coordination of the ligand to the Mn3+ ion, the ligand enforces the stereochemistry of the Mn3+ ions as a propeller configuration with alternating Δ/Λ forms. The disc-shaped hexanuclear ring shows at its largest diameter about 7.14 Å at entrance, about 9.76 Å at the center of the cavity, respectively. Antibacterial screening data showed that the manganese metallacrown has strong antimicrobial activity against Bacillus subtilis.