Imidazolium room-temperature ionic liquids with alkoxymethyl substituent: A quest for improved microbiological selectivity

Developing of novel, sustainable, and cost-effective antimicrobial substances is a global challenge. Our study on new bis(trifluoromethylsulfonyl)imide salts has led to environmentally benign pathways to process roomtemperature ionic liquids (RTILs) with alkoxymethyl substituent. The process (containing a small number of steps), carried out under mild conditions with easily available substrates, produced a high yield (>97%) and excellent purity of the final product (>0.99969). The prepared salts are insoluble in water but soluble in most organic solvents (except DMF, diethyl ether and hexane). Their solubilities do not depend on the number of carbon atoms in the hydrophobic chain or on the temperature (in the range of 25-50 degrees C). The antimicrobial properties of synthesised RTILs are strongly correlated with the length of the alkyl chain, and interestingly, their strength is dependent on the microbial strain. The salt with the longest alkyl chain of the alkoxymethyl group-1dodecyloxymethyl-3-ethylimidazolium bis(trifluoromethylsulfonyl)imide-shows strong and selective antibacterial properties particularly against Staphylococcus spp., comparable or higher to that of benzalkonium chloride. Moreover, compound with a dodecyloxymethyl moiety does not cause haemolysis and destabilises the artificial Gram-positive bacteria membrane. Due to its antiadhesive effect, the investigated imidazolium ionic liquid with dodecyloxymethyl functional group due to its antiadhesive effect has potential as a disinfectant and a short-term eradicator of adherent cells or biofilm against highly increasing antibiotic resistance toward Staphylococcus spp. Moreover, the salt with a dodecyloxymethyl moiety has the best applicative potential from an economic point of view among all the investigated RTILs.