Chemistry World features an article about the amphiphilic behavior of carboranes
- News 07 January 2020 298 hits
The article published in Angewandte Chemie Int. Ed. about boron-based amphiphiles without a head‐and‐tail design displaying surfactant behavior, by co-authors David C. Malaspina, Clara Viñas, Francesc Teixidor and Jordi Faraudo is now featured in Chemistry World. The question is: how can a molecule without the classic hydrophilic head and hydrophobic tail of surfactants can behave like one? The atomistic simulations and experiments of this study can bring now an answer.
An abstract of the article, written by Katrina Krämer in Chemistry World is:
Chemists often draw surfactant molecules as a dot, representing the molecule’s water-loving or hydrophilic head, and wavy lines for its water-hating, hydrophobic tail. But there is a class of inorganic compounds that turns this image on its head. Some boron anions – such as dodecaborate [B12H12]2– – like to sit at oil–water interfaces and even form micelles. This typical amphiphilic behaviour is usually seen in organic surfactants.
However, these clusters look completely different to classic surfactants. They have neither head nor tail. In fact, they have no discernible hydrophilic or hydrophobic features at all, which is why they were dubbed stealth amphiphiles. The reason for their behaviour had remained somewhat of a mystery. Some scientists suspected a non-classical hydrophobic effect. Known as a chaotropic effect, it is driven by enthalpy changes, unlike the entropy-driven hydrophobic effect.
Now, chemists led by Francesc Teixidor and Jordi Faraudo at the Institute of Materials Science of Barcelona have found a solution to the stealth surfactant puzzle, at least when it comes to cobaltabisdicarbollide (Cosan, [Co(C2B9H11)2]–). Their simulations showed that the phenomenon is simply classic amphiphilic behaviour of one of the molecule’s isomers. In water, Cosan takes on a shape that gives it a distinct hydrophilic head – the boron atoms – and hydrophobic tail – the carbon atoms.
Atomistic Simulations of COSAN: Amphiphiles without a Head‐and‐Tail Design Display “Head and Tail” Surfactant Behavior. D. C. Malaspina et al, Angew. Chem., Int. Ed., 2019, DOI: 10.1002/anie.201913257
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