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2-D Materials

Huge 2-D metallo-supramolecule

Self-assembled supramolecular grid measures 20 nm across

by Laura Howes
April 19, 2020 | A version of this story appeared in Volume 98, Issue 15


The structure forms a hexagonal net held together by metal ions.
Credit: Xiaopeng Li
A new supramolecular structure measuring 20 nm across is shown here in a scanning tunneling microscope image with a molecular model laid over it.
A general structure of the hexagons that make up the structure.
Each hexagon in the supramolecular structure is made up of one of these units.

In its quest to make a really big 2-D nanostructure, Xiaopeng Li’s University of South Florida team pulled out all the stops. It used both intra- and intermolecular self-assembly to build a grid of hexagons held together with ruthenium and iron ions. This monster of a metallo-supramolecule, made with help from collaborators at Argonne National Laboratory, Ohio University, and many other institutes, measures about 20 nm across (Nat. Chem. 2020, DOI: 10.1038/s41557-020-0454-z). Li says it ranks among the largest discrete metallo-supramolecules produced to date. Each hexagon of the grid is made from organic linkers that stick out in three directions. At all three ends of the spiky molecule are the nitrogen-containing terpydine ligands that complex ruthenium ions. These combine until you get a hexagonal building block with some unbound ligands. Add iron(II), and the hexagons start snapping together to make a linked-up lattice. The iron ions’ positions can produce different isomers. This giant molecule is more than a novelty. The team hopes to replace the iron with other metal ions, such as cobalt, to produce variations that can act as single-molecule information storage devices by using different spin states.


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