Hydrophobic ionic liquids containing 1-butyl-2,3-dimethylpyridinium [B2M3MPYR], 1-butyl-3,5-dimethylpyridinium [B3M5MPYR], 1-butyl-2-methyl-5-ethylpyridinium [B2M5EPYR], 1-butyl-2,3,5-trimethylpyridinium [B2M3M5MPYR], 1-octyl-2,3-dimethylpyridinium [O2M3MPYR], 1-octyl-3,5-dimethylpyridinium [O3M5MPYR], 1-octyl-2-methyl-5-ethylpyridinium [O2M5EPYR], or 1-octyl-2,3,5-trimethylpyridinium [O2M3M5MPYR] as the cation and bis(trifluoromethanesulfonyl)imide [NTf2], trifluoromethanesulfonate [TfO], dicyanamide [N(CN)2], thiocyanate [SCN] or iodide as the anion have been synthesized, and their physicochemial properties have been studied. Thermal properties, solubilities in water and water contents, UV−vis spectra, densities, refractive indices, electrochemical windows, and toxicities on Vibrio fischeri have been measured. These ionic liquids, most of which are liquid at room temperature, exhibit high refractive indices and increased hydrophobicity. Despite high toxicity values toward V. fischeri, ionic liquids containing a dialkylpyridinium or trialkylpyridinium cation with an octyl chain represent good alternatives to extracting solvents.