Toxicity of various anions associated with methoxyethyl methyl imidazolium-based ionic liquids on Clostridium sp.

We investigated the effects on the growth of the anaerobic bacterium. Clostridium sp., of the ionic liquid, 1-methoxyethyl-3-methyl imidazolium [MOEMIM](+), derived from imidazolium cation and paired with one of a variety of counter-ions, viz., tetrafluoroborate [BE4](-), hexafluorophosphate [PF6](-). trifluoroacetate [CF3COO](-), bis(trifluoromethane)sulfonamide [Tf2N](-), methane sulfonate [OMS], and 1-butyl-3-methyl imidazolium tetrafluoroborate [BMIM][BF4]. These anions, in association with [MOEMIM](+). lowered the growth rate of the bacterium, showing the following trend: [Tf2N](-) >= [PF6](-) > [BF4](-) > [CF3COO](-) > [OMS](-). Anions incorporating fluorine were more toxic than those without it, and their toxicity rose with an increase in the number of fluorine atoms. Also, [MOEMIM](+) [BE4](-) was less toxic than [BMIM](+) [BF4](-), probably due to the presence of a methoxyethyl functional group integrated in the cation side chain. (C) 2010 Elsevier Ltd. All rights reserved.