Wrapping up molecules
ChemSci Pick of the Week
In today’s pick of the week, Dr Stefanie Susanne Dehnen and her colleagues at Philipps-Universität Marburg in Germany describe a new synthetic method for a difficult-to-access class of molecules.
The molecules in question are chalcogenideometalate clusters – compounds containing metal cations and group 16 anions – and Dr Dehnen has discovered an easy way to add a methyl group to one end of the cluster.
They synthesis is special in three different ways. Firstly, it avoids using toxic reagents such as methyl iodide. Instead, the methylation agent is an ionic liquid – a liquid salt – that doubles as the reaction medium. Ionic liquids are much more environmentally friendly than conventional solvents. Secondly, the method works on very weakly nucleophilic cluster molecules, which are normally very difficult to methylate. And finally, this is the first time methylation has been achieved selectively in the terminal positions of the chalcogenide.
Dr Dehnen explains the reasons for developing this synthesis:
"The 'wrapping' of inorganic molecules in organic molecules is an important method of how to change their chemical and also their physical properties – like pulling over a neoprene suit to make oneself insensitive to cold water, or like wrapping a chocolate Easter bunny to make is look more colourful and be touchable without getting sticky fingers.
"However, the addition of such 'wrapping' is difficult for certain types of molecules that we are interested in for their specific physical properties. Hence, these molecules could not be modified in the desired way to date with common reagents, which are moreover very problematic due to high toxicities.
"We overcame this drawback by using a relatively harmless substance in an efficient way, by serving simultaneously as the reaction medium and as source for the wrapping organic groups."
Whilst the synthesised compounds don’t have any direct applications as yet, the new method offers a route to a variety of compounds and materials, which could lead to exciting developments in the fields of technology, medicine, green energy and more.
This article is free to read in our open access, flagship journal Chemical Science: Stefanie Dehnen et al., Chem. Sci., 2019, Advance Article. DOI: 10.1039/C9SC01358J. You can access our 2019 ChemSci Picks in this article collection.
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