Maciej Barycki

Towards designing environmentally safe ionic liquids: the influence of the cation structure

Ionic liquids (ILs) are considered to be excellent alternatives to organic solvents, and are commonly used nowadays. However, introducing new classes of compounds always comes with the possibility of environmental threat and health issues they may induce. This work was aimed at examining which structural features of ILs are responsible for their toxicity. There are examples of structure–activity relationship models for ILs in the literature. However, in our approach, we have analysed this issue globally for a wide range of ionic liquids and their toxicity was measured by multiple toxicological tests (multiple endpoints). We have collected the experimentally measured available literature data on the toxicity of ILs for various organisms. Then, by employing Principle Component Analysis (PCA), we examined the structural similarity of 375 different ionic liquids having six different types of cations (namely imidazolium, ammonium, phosphinium, pyridinium, pyrolidinium and sulfonium). For expressing the structural features of studied ILs we used Weighted Holistic Invariant Molecular (WHIM) descriptors, calculated for cations and anions separately. The geometry of each structure was optimized at the level of the semi-empirical PM7 method. The toxicological response was thereafter analyzed in the space of the first and second principle components. We pointed out that for most of the tested cases there is a strong relationship between the variance in the observed toxicity and the cations’ descriptors. We also proved the anions’ influence on the IL toxicity to be less meaningful. After repeating PCA using only the cations’ descriptors, we proved that the toxicity of ILs against selected targets depends mostly on the size and branching of the cation. On this basis, we have proposed a Toxicity Ranking Index based on the structural similarity of Cations (TRIC) for the initial toxicity screening studies of ILs. It should be mentioned however that the use of TRIC is limited to the prediction of toxicity endpoints used in its development. The use of TRIC as a preliminary toxicity indicator would provide a general view on ILs’ toxicological potential and its predictions may provide valuable conclusions, which, taken under consideration, may help in simplifying the procedure of designing new greener and safer ionic liquids in future.

Filling environmental data gaps with QSPR for ionic liquids: Modeling n-octanol/water coefficient

Ionic liquids (ILs) form a wide group of compounds characterized by specific properties that allow using ILs in different fields of science and industry. Regarding that the growing production and use of ionic liquids increase probability of their emission to the environment, it is important to estimate the ability of these compounds to spread in the environment. One of the most important parameters that allow evaluating environmental mobility of compound is n-octanol/water partition coefficient (KOW). Experimental measuring of the KOW values for a large number of compounds could be time consuming and costly. Instead, computational predictions are nowadays being used more often. The paper presents new Quantitative Structure-Property Relationship (QSPR) model that allows predicting the logarithmic values of KOW for 335 ILs, for which the experimentally measured values had been unavailable. We also estimated bioaccumulation potential and point out which group of ILs could have negative impact on environment.

Towards the Application of Structure-Property Relationship Modeling in Materials Science: Predicting the Seebeck Coefficient for Ionic Liquid/Redox Couple Systems.

This work focuses on determining the influence of both ionic-liquid (IL) type and redox couple concentration on Seebeck coefficient values of such a system. The quantitative structure-property relationship (QSPR) and read-across techniques are proposed as methods to identify structural features of ILs (mixed with LiI/I2 redox couple), which have the most influence on the Seebeck coefficient (Se ) values of the system. ILs consisting of small, symmetric cations and anions with high values of vertical electron binding energy are recognized as those with the highest values of Se . In addition, the QSPR model enables the values of Se to be predicted for each IL that belongs to the applicability domain of the model. The influence of the redox-couple concentration on values of Se is also quantitatively described. Thus, it is possible to calculate how the value of Se will change with changing redox-couple concentration. The presence of the LiI/I2 redox couple in lower concentrations increases the values of Se , as expected.

ILPC: simple chemometric tool supporting the design of ionic liquids

BackgroundIonic liquids (ILs) found a variety of applications in today’s chemistry. Since their properties depend on the ions constituting particular ionic liquid, it is possible to synthetize IL with desired specification, dependently on its further function. However, this task is not trivial, since knowledge regarding the influence of particular ion on the property of concern is crucial. Therefore, there is a strong need for new, fast and inexpensive methods supporting the process of ionic liquids’ design, making it possible to predefine IL’s properties even before the synthesis.ResultsWe have developed a simple tool (called Ionic Liquid PhysicoChemical predictor: ILPC) that allows for the simultaneous qualitative prediction of four physicochemical properties of ionic liquids: viscosity, n-octanol–water partition coefficient, solubility and enthalpy of fusion. By the means of Principal Component Analysis, we studied 172 ILs and defined distribution trends of those four properties, dependently on the ILs structures. We proved that the qualitative prediction of mentioned properties could be performed on the basis of most simple information we can deliver about ILs, which are their molecular formulas.ConclusionsCreated tool presented in this paper allows fast, pre-synthesis screening of ILs, with the omission of any experimental steps. It can be helpful in the process of designing ILs with preferred properties. We proved that the information encrypted in molecular formula of ionic liquid could be a valuable source of knowledge regarding the IL’s viscosity, n-octanol–water partition coefficient, solubility and enthalpy of fusion. Moreover, we proved that the influence of both ions, constituting the IL, on each of those four properties indicates same, additive trend.Graphical AbstractSchematic representation of ILPC performance - the exact position of the ionic liquid on the linear map is determined by its chemical structure

AquaBoxIL – a computational tool for determining the environmental distribution profile of ionic liquids

We present the AquaBoxIL tool for comparing ionic liquids (ILs) in terms of their theoretical Environmental Distribution Profile (EDP). We define the EDP as the most probable scenario of an ILs distribution among various environmental compartments, in the case of its deposition in the environment. In the AquaBoxIL tool, these compartments are water, sediment and organic matter (representing biota). The calculations are performed with the consideration of an ILs solubility and biodegradability and its ability to create micelles. This tool provides the information about the amount and concentration of an IL in each of the three compartments, making it possible to compare ILs in terms of their EDP and therefore recognizing which one presents the biggest threat to the environment once deposited in it. AquaBoxIL is a tool that is inspired by the popular Multimedia Mass-balance (MM) models and it can be classified as a level I MM model itself. The EDP calculations are being performed on the basis of the physicochemical properties of ILs, with the use of the properties of the modelled environment as well. The IL properties required for calculations can be obtained from Quantitative Structure–Property Relationship (QSPR) models included in the tool. Such a solution makes it possible to calculate and compare EDPs for different ILs based only on their molecular structures.