Biocompatible tetrabutylphosphonium-based ionic liquids with medium-chain fatty acids as anions: Thermo-physical and antimicrobial profile

Abstract

The importance of developing effective antimicrobial agents has become more evident recently, and quaternary phosphonium-based ionic liquids with fatty acid anions have shown great potential in this regard. Tetrabutylphosphonium-hexanoate, -octanoate, -decanoate, and -dodecanoate were synthesized as potential antimicrobial ionic liquids. Confirmation of the structure of the synthesized ionic liquids was determined by IR and NMR spectroscopy. Also, the thermal stability was examined by thermogravimetric (TG) and differential scanning calorimetry (DSC) analysis. Physicochemical characterization was carried out, which included the measurement of density, viscosity, and electrical conductivity in a wide temperature range to understand the interactions that occur in synthesized ionic liquids. The antimicrobial activity against various microorganisms was determined, including three Gram-negative and Gram-positive bacteria, two yeast, and four filamentous fungal strains. Based on the results, ILs were more efficient against Gram-positive than Gram-negative bacteria, whereby the longest-chained anion contributes to the best antibacterial activity. Yeast Candida guillermondii and all tested filamentous fungi were most sensitive to tetrabutylphosphonium-decanoate.