A neutral octahedral mononuclear iron(II) tetrabromide complex, [Fe(Hampy) 2 Br 4 ], that consists of equatorial bromide and protonated aminopyrazinium axial ligands is successfully synthesised through redox chemistry and analysed using X-ray crystallography. The iron(II) oxidation state is balanced by the protonated pyrazinium nitrogen just outside the coordination sphere. The biological properties of this and two other related complexes are investigated using both Gram-negative and Gram-positive bacteria as well as methicillin resistant strains. They all exhibit some antimicrobial properties albeit at moderate to poor concentrations. However, the tetrahalide complexes analysed exhibit excellent anti biofilm properties well below cytotoxic levels. File list (2) download file view on ChemRxiv Expanding the Family of Tetrahalide Iron Complexes.pdf (0.92 MiB) download file view on ChemRxiv Expanding the Family of Tetrahalide Iron Complexes SI....

Antimicrobial resistance (AMR) has become one of the more serious threats to the global health. The emergence of bacteria resistant to antimicrobial substances decreases the potencies of current antibiotics. Consequently, there is an urgent and growing need for the developing of new classes of antibiotics. Three prepared novel iron complexes have a broad-spectrum antimicrobial activity with minimum bactericidal concentration (MBC) values ranging from 3.5 to 10 mM and 3.5 to 40 mM against Gram-positive and Gram-negative bacteria with antimicrobial resistance phenotype, respectively. Time-kill studies and quantification of the extracellular DNA confirmed the bacteriolytic mode of action of the iron-halide compounds. Additionally, the novel complexes showed significant antibiofilm activity against the tested pathogenic bacterial strains at concentrations lower than the MBC. The cytotoxic effect of the complexes on different mammalian cell lines show sub-cytotoxic values at concentrations lower than the minimum bactericidal concentrations.

Antimicrobial resistance (AMR) has become one of the more serious threats to the global health. The emergence of bacteria resistant to antimicrobial substances decreases the potencies of current antibiotics. Consequently, there is an urgent and growing need for the developing of new classes of antibiotics. Three prepared novel iron complexes have a broad-spectrum antimicrobial activity with minimum bactericidal concentration (MBC) values ranging from 3.5 to 10 mM and 3.5 to 40 mM against Gram-positive and Gram-negative bacteria with antimicrobial resistance phenotype, respectively. Time-kill studies and quantification of the extracellular DNA confirmed the bacteriolytic mode of action of the iron-halide compounds. Additionally, the novel complexes showed significant antibiofilm activity against the tested pathogenic bacterial strains at concentrations lower than the MBC. The cytotoxic effect of the complexes on different mammalian cell lines show sub-cytotoxic values at concentrations lower than the minimum bactericidal concentrations.

A neutral octahedral mononuclear iron(II) tetrabromide complex, [Fe(Hampy)₂Br₄], that consists of equatorial bromide and protonated aminopyrazinium axial ligands is successfully synthesised through redox chemistry and analysed using X-ray crystallography. The iron(II) oxidation state is balanced by the protonated pyrazinium nitrogen just outside the coordination sphere. The biological properties of this and two other related complexes are investigated using both Gram-negative and Gram-positive bacteria as well as methicillin resistant strains. They all exhibit some antimicrobial properties albeit at moderate to poor concentrations. However, the tetrahalide complexes analysed exhibit excellent anti biofilm properties well below cytotoxic levels.