A structure-activity relationship study of the toxicity of ionic liquids using an adapted Ferreira-Kiralj hydrophobicity parameter

The Ferreira-Kiralj hydrophobicity parameter W-c is a number fraction of hydrophobic carbon atoms and can be regarded as a constitutional descriptor since its calculation depends only on the number of polar and nonpolar carbons in a compound. Hydrophobicity is important to the toxicity of ionic liquids (ILs), which are salts by nature. Herein, a descriptor for this property was calculated using a simple adaptation of the type of polar carbon atoms included (W(c)Adap) to explore the possibility of its use in quantitative structure-activity relationship (QSAR) studies of ILs. The resulting model was tested using a database of ILs with toxicity against the Leukemia rat cell line IPC-81. Two other models were constructed using CrippenlogP and Mannhold log P descriptors, which are both available in the free program PaDEL. The use of W(c)Adap led to a better and more indicative model. Thus, W(c)Adap may be a suitable molecular descriptor for the hydrophobicity of ILs in QSAR studies.