Antibacterial Activity of Short-Chained 1-Alkyl-3-methylimidazolium Bis(trifluoromethylsulfonyl) Imide Ionic Liquids

Abstract

The antibacterial activity of a series of ionic liquids containing short-chained 1-alkyl-3-methylimidazolium cations ([C_nmim⁺]; n = 2, 4, 6 and 8) and bis (trifluoromethylsulfonyl) imide anion ([Tf₂N]) against <em>E. coli</em> and <em>B. subtilis</em> was measured, for the first time. All ILs used in this work were synthesized and analyzed by Fourier transform infrared (FT-IR) spectroscopy, NMR, and Karl-Fischer titration. Antimicrobial activity was determined by the tube dilution method. The ILs investigated showed antibacterial activity against <em>E. coli </em>and <em>B. subtilis</em>. The minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were in the ranges of 0.041-6.39 mM and 0.67-12.78 mM, respectively<em>.</em> The antibacterial activity for ionic liquids with longer alkyl chain (n ≥ 4) increased with increasing alkyl chain length. The highest inhibition against <em>E. coli </em>was found for [C₈mim][Tf₂N] (MIC = 0.041 mM and MBC = 0.67 mM). The mechanism of action of these ionic liquids was bacteriostatic.