Nanographene “Butterfly” with Tetraradical Character

Nanographene “Butterfly” with Tetraradical Character

Author: ChemistryViews

Unpaired π-electrons, e.g., in graphene-based nanostructures, can give rise to π-magnetism. Such nanographenes could be useful, e.g., in spintronics  (electronics that depend not only on charge, but also on electron spin) and quantum computing. Synthesizing such π-magnetic nanographenes in a precise manner in solution can be challenging, especially for unsubstituted nanographenes due to their high reactivities and low solubilities. On-surface synthesis, using either thermally activated reactions or atomic manipulation with the probe of a scanning tunneling microscope (STM), can be helpful in this context.

Libor Veis, Czech Academy of Sciences, Prague, Czech Republic, Jishan Wu, National University of Singapore, Pavel Jelinek, Czech Academy of Sciences and Palacký University Olomouc, Czech Republic, Jiong Lu, National University of Singapore and National University of Singapore (Suzhou) Research Institute, Suzhou, China, and colleagues have synthesized a butterfly-shaped nanographene with a tetraradical character (pictured) on an Au(111) surface. The nanographene combines electron–electron interactions between the π-electrons and the topology of the structure to induce the presence of four unpaired electrons, which show both ferromagnetic and anti-ferromagnetic coupling.

The team used a precursor with a rhombene center (a rhomboid shape made from benzene-type rings) and four dimethylphenyl-functionalized anthracene-based substituents. This precursor was sublimated onto an Au(111) surface and thermally annealed at ca. 327 °C. This induces cyclodehydrogenation reactions and gives the desired nanographene. STM images confirmed the formation of the butterfly-shaped product, as well as byproducts with defects.

The butterfly-shaped tetraradical nanographene was further characterized using voltage-dependent differential conductance spectroscopy, a nickelocene-functionalized probe to study the magnetic properties, and quantum chemical calculations to understand the molecule’s spin states. The team found that the nanographene features four highly entangled spins. According to the researchers, molecules with such strongly correlated spins could be useful, e.g., as building blocks for scalable, complex quantum networks.



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