Modelling and Simulation of Ecotoxicity of Ionic Liquids Using QSAR

Development of safer and environm~ntally friendly processes and products is required to achieve
sustainable production and consumption patterns. Ionic liquids are compounds of high interest
for industry because of their attractive properties as solvents, but the water solubility of these
compounds may lead to aquatic pollution and related risks. Experimental toxicity evaluation
(Daphnia magna EC50) is a measurement of aquatic toxicity but there are theoretically over l
trillion ionic liquids, which makes it necessary to estimate their properties by means of
quantitative structure-activity relationships (QSARs). In this work, a novel QSAR based on
multilinear regression analysis method is applied to estimate the ecotoxicity of ionic liquids. A
data set of Daphnia magna EC50 was assembled to develop a novel group contribution method
for estimating the EC50 of ionic liquids. The ionic liquids are the combination of different anion
and cation which are bromide (B(), chloride (Cr), tetrafluoroborate (BF 4), hexafluorophosphate
(PF6-) and bis((trifluoromethyl)sulfonyl)imide (TF2N-) as anions with imidazolium (im),
pyridinium (py), dirnethylamino pyridinium (DMApy), piperidino pyridinium (pipy), ammonium
(N) and pyrrolidinium (pyr) as cations. However, due to complexicity of equations and time
consuming to apply multilinear regression analysis by hand calculation, SPSS software 11.5 was
used to apply the method. 44 data of ionic liquids were assembled and the results illustrated that
the data range covered for log EC50 values in between 2.07 and -4.33. From the results, the
contributions of anion, cation and alkyl substitutions has been established and found a good
fitting value for predicting the EC50 with fl = 0.934, fladi = 0.910 and variance= 0.022. From the
results, it can be concluded that the toxicity contribution in increasing order for anions ts
hexafluorophosphate (PF6") < chloride (Cr) < tetrafluoroborate (BF4") <
bis((trifluoromethyl)sulfonyl)irnide (TF2N), for cations is ammonium (N) < pyrrolidinium (pyr)
< irnidazolium (im) < pyridinium (py) < dimethylamino pyridinium (DMApy) < piperidino
pyridinium (pipy), and while for alkyl is R < R1 with R is long n-alkane chain and R1 is an
additional short chain (methyl). However, further investigations are necessary to increase the
number of data in the training set in order to reduce the confidence range of some group
contributions (e.g., pyrrolidinium based ionic liquids). In addition, other cations and anions need
to be studied to increase the application of the novel group contribution method.