Ionic liquid-supported chiral saldach with tunable hydrogen bonding: synthesis, metalation with Fe(III) and in vitro antimicrobial susceptibility

New water-soluble methylimidazolium ionic liquids (MIILs) bearing N,N′-bis-(salicylidene)-R,R-1,2-diaminocyclohexane (saldach) scaffold, H2(R1)2saldach(2-MeIm+X−)2 (4a: R1=H, X=Cl-; 4b: R1=H, X=PF6-; 4c: R1=H, X=BF4-; 4d: R1=iPr, X=Cl-; 4e: R1=iPr, X=PF6-; 4f: R1=iPr, X=BF4-), and their Fe(III) complexes have been synthesized and structurally characterized as well as their profile of antimicrobial susceptibility was identified. The new saldach-supported MIILs demonstrated a distinctly enhanced biocidal effect toward methicillin resistant Staphylococcus aureus (MRSA) and multidrug-resistant Escherichia coli (MDREC). Compound 4d is the most potent antibacterial agent and could inhibit the growth of all micro-organisms, except A. flavus, more effectively than standard antibiotics.