An increasing number of studies report toxicity of ionic liquids, but without giving any insight. What are the molecular origins of toxicity? What biomolecules in the cells ionic liquids interact with? Clarifying references are very much appreciated.
A common motif of quaternary ammonium salts (ILs) and Phosphonium ILs, are long (C8-16) alkyl chains, that are structurally similar to phospholipid bilayers. While there exists a broad pattern in IL head group activity, certainly the lipid region of any IL is potentially toxic.
The potential cytotoxicity of some ionic liquids is associated, as Mr. Macneil mentioned by the longer side chain in the substituents, which during metabolism is released and acts as a neurotoxin, just as e.g. hexane does.
Hi, there are reviews on the subject, for example this one: doi:10.1016/j.watres.2009.09.030
To complete the answers, the hydrophobic ionic liquids can easily penetrate from the cell membrane.
Thanks!
I am compiling the review on environmental impact of ionic liquids and chemistry specific optimizations. I will post when it is ready.
Funnily enough, some of the most hydrophobic BTA ILs that we have are not acute orally toxic. This might have to do with the polarity, the fact that they do not have a polar "head", or just with their very low water solubility. As far as I know, you do need a certain Kow range in order for a substance to show acute toxicity.
Conventional ionic liquids are not truly ‘green’ as their constituents mainly comprise with nitrogen based cations like imidazolium, alkylammonium, dialkylimidazolium, or pyridinium with halogen as anions. Due to this reason they may release HCl or HF by hydrolysis under certain conditions, which cause hazards when they are release in the environment through waste water.
a) C. Deborah, G. Nicholas, Chem. Soc. Rev. 2010, 39, 600;
b) D. Zhao, Y. Liao, Z. Zhang, Clean: Soil, Air, Water 2007, 35, 42.
Our review that might be useful:
"Toxicity of Ionic Liquids: Eco(cyto)activity as Complicated, but Unavoidable Parameter for Task-Specific Optimization",
ChemSusChem, 2014, 7, 336-360
http://dx.doi.org/10.1002/cssc.201300459
I agree with Moises, among other contributors. As seen above, there are several reasons for ILs toxicity. The difficulty with most synthetic chemicals is in fact to avoid some toxicity...
Imidazolium ionic liquids are believed to not only disturb cell membrane, but also to cause oxidative stress. There are many interesting reports, for example this one:
Li X. Y., Jing C. Q., Lei W. L., Li J., Wang J. J., 2012, Apoptosis caused by imidazolium-based ionic liquids in PC12 cells, Ecotoxicol. Environ. Saf., 83, 102-107.
Major reason of IL toxicty being the surface tension of these liquids. Because of lower surface tension, it is easier for ILs to penetrate into skin and through membrane wall (cell membrane).
Our experience shows, that the correlations are not that simple. We have for example a hydrophobic IL which shows very low toxicity as well as hydrophillic ones, which show high toxicity.
It depends on two factors the cation group and it was published in number of articles that the lowest toxicity among cations is imidazolium based ILs also the length of the alkyl chain.
Ionic liquids are toxic in nature may be solubility due to ionic i.e. electro-valent characters
Madhukar Baburao Deshmukh this it totally and absolutely not true. There are indeed some ionic liquids that are toxic, but also quite a few that are not. Having in mind that there are more possible ionic liquids than there are people on this planet, to say that ILs are toxic in nature is the same as to say people have blond hair in nature, or wear glasses. Bottom line is: some of them do, some of them don't.
If I remember right from my experience in ILs 8 years ago toxicity occurs from C4 on at the imidazolium core. But in general I need to mention that apart from toxicity the classification depends on the studies needed for registratiion
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