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Chemistry In Pictures

Chemistry in Pictures: Watching molecules get comfortable

by Manny I. Fox Morone
January 27, 2022

Five atomic force microscopy micrographs showing the structures of molecules with about a dozen rings each, all in different configurations. Line structures below them show their structure specifically and show the single precursor molecule that reacted to form them all.
Credit: Bruno de la Torre (micrographs)

Some molecules have trouble sitting still. That’s what a team of researchers found out when they peeked at this cyclization reaction using atomic force microscopy, which allows them to zoom in on individual molecules. In the starting molecule, the small gap (bottom of the leftmost structure) between the hydrocarbon rings causes the molecule to twist into a helical shape instead of lying flat—which is why this sort of molecule is called a helicene. After depositing helicene molecules on a gold surface and heating to about 300 °C, the researchers took a look at what was left over. In order to lie flat, the helicenes had wiggled around and started to cyclize in unusual ways, creating irregular ring structures, including the five shown here.

The team, which is based at Palacky University Olomouc; Charles University; and the Institute of Physics, the J. Heyrovsky institute of Physical Chemistry, and the Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences, aims to design reactions like this to give chemists ways to access to cyclized molecules that are hard to make in solution.

Credit: Bruno de la Torre (micrographs). Follow the Nanosurf Lab at the Institute of Physics of the Czech Academy of Sciences on Twitter.

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