Chemists create smaller carbon rings

Two new carbon allotropes have been developed using atomic force microscopy (AFM). Led by researchers from Dongji University Wei Chu Surface synthesis was used to form rings of 10 and 14 carbon atoms called cyclos.[10]Carbon (c10) and Cyclo[14]Carbon (c14). Although C10 and c14 Studied in the gas phase, this is the first time chemists have created and characterized them on a surface, giving a deeper insight into their bonding.

To do c10 and c14Xu’s group started with fully chlorinated naphthalene (c10 Cl8) and anthracene (C14 Cl10) and used an AFM tip to gradually flush out the chlorines. Removal of chlorines induced the precursor molecules to undergo ring-opening reactions, which ultimately produced 10- and 14-carbon rings (Nature 2023, DOI: 10.1038/s41586-023-06741-x)

Package differs from Cyclo[16]Carbon (c16) and Cyclo[18]Carbon (c18), which used more complex precursors. Oxford University’s Harry L. Andersen, who led the synthesis of those large rings, said in an email that starting with readily available polycyclic aromatic chlorocarbons „opens up the field by facilitating the synthesis of cyclocarbons.”

AFM imaging reveals that C10s and c14The bond characters of are different from their larger all-carbon siblings, C16 and c18. The bonds in the larger rings are polycyclic, meaning they alternate between single and triple bonds. C10The bonds of are cumulenic—basically continuous double bonds. C14 And there are only double bonds, but not all of those bonds are identical, indicating that the molecule is somewhere between cumulenic and polyenic.

Leo Gross of IBM Research-Zurich collaborated with Andersen on the compilations of C.16 and c18He says it is wonderful to see C10 has the cumulenic structure predicted by theory and c14 A transition structure between cumulenic and polyene. „For us experimenters, it’s exciting to see cyclocarbons in different forms,” ​​he says in an email.

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