Antimicrobial properties of ethoxyether-functionalized imidazolium salts

Abstract

Amphiphilic ionic liquids and ionic liquid crystals, comprising a cationic imidazolium head group (represents as Im), a hydrophobic N-alkyl chain (C_nH_2n+1, denoted as C_n, n = 10, 12, 14, 16 and 18), and an amphiphilic N-2-(2-(2-ethoxy)ethoxy)ethanol (3OEG) functional group were synthesized (denoted as [C_n-Im-3OEG][Cl]). While the lipophilicity of [C_n-Im-3OEG][Cl] increases along with the alkyl carbon chain length, the water solubility of these compounds is enhanced with the 3OEG functionality. Compounds with lengths of n = 10, 12 and 14 are room temperature ionic liquids, whereas n = 16 and 18 show thermotropic SmA liquid crystal properties. Meanwhile, compounds of n = 14, 16 and 18 also exhibit lyotropic liquid crystal properties. The ionic and lyotropic liquid crystalline natures of these compounds lead to their superior antimicrobial activity against infectious pathogens. This is especially true for compounds with longer alkyl chains. Rupture of the bioenvelop appears to be operative in the process of antimicrobial activity.