Molecular capsule: helical ribbon with closed ends takes up guest molecules

February 28, 2005

Tiny molecular "containers" that can take up other molecules as "guests" are of particular interest for technology and science, as catalysts, micro-reaction-chambers, transport containers for pharmaceutical agents, or protective covers for unstable molecules. Various strategies have now been established for building such miniature capsules. Ivan Huc and Joachim Garric (European Institute of Chemistry and Biology, Pessac), as well as Jean-Michel Léger (Laboratoire de Pharmacochimie, Bordeaux) have now developed a novel approach.

The French chemists synthesized a strand-like molecule from aromatic amine building blocks -- nitrogen-containing carbon rings. The building blocks are chosen so that the ribbon curls into a helix. The crucial trick is that the helix is not even: it has a significantly larger diameter in the middle than at the ends. The researchers can precisely control the inner diameter by the selection of individual building blocks and the precise arrangement of the nitrogen atoms within the ring system. They thus select correspondingly different building blocks for the middle and end sections of the spiral ribbon. This results in a helix with a real bubble in the middle and ends without a cavity, which close off the bubble. The capsule is thus complete.

"Our capsules are constructed so that they take up a single water molecule," says Huc. "They enclose it completely and shield it from surrounding organic solvents." And how does the water molecule get into the capsule? Nuclear magnetic resonance studies support the theory that the helices partially unravel at one end, let the water molecule slip in, and then close again."

The researchers now want to expand their highly promising concept. They are thus working on larger capsules that could take up larger or multiple molecules.

Explore further: Life's building blocks observed in spacelike environment

Related Stories

Life's building blocks observed in spacelike environment

December 12, 2017

Where do the molecules required for life originate? It may be that small organic molecules first appeared on earth and were later combined into larger molecules, such as proteins and carbohydrates. But a second possibility ...

DNA as a supramolecular building block

December 11, 2017

PhD student Willem Noteborn has investigated supramolecular structures. These can be useful for the loading of medicines and signalling molecules regarding, for example, cellular differentiation. In his thesis, he describes ...

Recommended for you

A not-quite-random walk demystifies the algorithm

December 15, 2017

The algorithm is having a cultural moment. Originally a math and computer science term, algorithms are now used to account for everything from military drone strikes and financial market forecasts to Google search results.

Single-photon detector can count to four

December 15, 2017

Engineers have shown that a widely used method of detecting single photons can also count the presence of at least four photons at a time. The researchers say this discovery will unlock new capabilities in physics labs working ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.