Synthesis, characterization and bioactivity of a novel 18-metallacrown-6: [Mn(pcshz)(CH3OH)]6 · 4CH3OH · 4H2O

The reaction of N-propionyl-5-chlorosalicylhydrazide (H3pcshz) with Mn(OAc)2 · 4H2O in methanol solution gives a novel 18-metallacrown-6 [Mn(pcshz)(CH3OH)]6 · 4CH3OH · 4H2O (1). The structure of 1 has been determined by X-ray diffraction and it crystallizes in the monoclinic system and space group P2(1)/n. The ring of the metallacrown is consisted of six interlink [Mn–N–N] repeated units through hydrazide N–N group bridging the ring manganese ions. And the ligand enforces the metal ions to form the stereochemistry as a propeller configuration with alternation Λ/Δ form. The largest diameters of the disc-shaped hexanuclear ring are about 8.82 Å at entrance, 9.83 Å at the central of the cavity, respectively. The solution integrity and stability of the metallacrown was studied by electrospray ionization (ESI)-MS and UV–Vis spectroscopy. The results show it is soluble and stable in methanol. Antibacterial screening data indicate the forming of the complex weakens dramatically the antibacterial activity of the ligand H3pcshz except for Eschericha coli.

Graphical abstractA novel macrocyclic hexanuclear Mn(III) 18-metallacrown-6 compound, [Mn(pcshz)(CH3OH)]6 · 4CH3OH · 4H2O, has been prepared using a trianionic pentadentate ligand N-propionyl-5-chlorosalicylhydrazidate (pcshz3−) and characterized by X-ray diffraction. The ring of the metallacrown remains integrity and stable in methanol. Antibacterial screening data showed the metallacrown has strong antimicrobial activity against Eschericha coli.Figure optionsDownload full-size imageDownload as PowerPoint slide