Biofilm inhibition by a new Mn(II) complex with sulfamethoxazole: Synthesis, spectroscopic characterization and crystal structure

•The metal complex [Mn(H2O)6]0.5[Mn(SMX)3] was synthesized and characterized.•The crystal structure was determined by single crystal X-ray diffraction methods.•The complex crystallizes in the cubic crystal system, space group Pa-3.•IR, Raman and UV–Vis spectra show the coordination of the ligand.•The activity against S. aureus was evaluated.

The reaction in alkaline aqueous solution between sulfamethoxazole (SMX) and manganese (II) chloride produces colorless crystals with formula [Mn(H2O)6]0.5[Mn(SMX)3], which was characterized by UV–Vis, IR and Raman spectroscopy and thermal analysis. The crystal structure of [Mn(H2O)6]0.5[Mn(SMX)3] complex has been solved by X-ray diffraction methods. It crystallizes in the cubic Pa-3 space group with a = 19.5476(1) Å, and Z = 8 molecules per unit cell. [Mn(SMX)3]− complex is at a crystallographic special position of C3 symmetry with the Mn(II) ion cis-coordinated to three equivalent sulfamethoxazole molecules acting as bidentate ligands in a propeller-like conformation. [Mn(H2O)6]2+ hydrate ion is at crystal special position of S6 symmetry with the metal in an almost perfect octahedral coordination with six water molecules. At 100 μg/mL Mn(H2O)6]0.5[Mn(SMX)3] and SMX, inhibited the Staphylococcus aureus biofilm formation by 92% and 54%, respectively. However, at the same concentration Mn(H2O)6]0.5[Mn(SMX)3] and SMX inhibited the planktonic bacterial growth by 52% and 81%, respectively. The Mn(II) complex inhibited the biofilm formation in values higher than 35% at the concentration 0.5 μg/mL. These results suggest that the metal complex [Mn(H2O)6]0.5[Mn(SMX)3] is a good candidate for the development of new antimicrobial agent acting in part as bactericidal but mainly as antipathogenic agent.

Graphical abstractThe crystal structure of [Mn(H2O)6]0.5[Mn(SMX)3] complex has been solved by X-ray diffraction methods. It crystallizes in the cubic Pa-3 space group with a = 19.5476(1) Å, and Z = 8 molecules per unit cell. [Mn(SMX)3]− complex is at a crystallographic special position of C3 symmetry with the Mn(II) ion cis-coordinated to three equivalent sulfamethoxazole molecules acting as bidentate ligands in a propeller-like conformation. [Mn(H2O)6]2+ hydrate ion is at crystal special position of S6 symmetry with the metal in an almost perfect octahedral coordination with six water molecules.Figure optionsDownload full-size imageDownload as PowerPoint slide