1. We developed a new approach to introduce π-magnetism into graphene-based nanomaterials, i.e. the reduction of ketone-substituted molecules/structures followed by mild annealing or tip manipulation. The conventional approach is largely relied on the synthesis of specially designed precursor molecules, which is usually challenging. In addition, the yield of target magnetic structure is quite limited. In contrast, ketone-substituted molecules are chemically stable and facile to synthesize, which can easily react to form the target product only with ketone-substitution on surfaces. These ketone functional groups can be removed by atomic hydrogen in the next step. Finally, a mild annealing or tip manipulation will give rise to the final product of magnetic graphene-based nanomaterials. This approach significantly lower the difficulty of precursor synthesis and improve the quality of target magnetic materials.
Related publications: (1) Wang, T. et al. Magnetic Interactions Between Radical Pairs in Chiral Graphene Nanoribbons. Nano Lett. 2022, 22, 164-171. (2) Wang, T. et al. Aza-Triangulene: On-Surface Synthesis and Electronic and Magnetic Properties. J. Am. Chem. Soc. 2022, 44, 4522-4529.
2. Circumventing the stability problems of graphene nanoribbon zigzag edges. Carbon nanostructures with zigzag edges exhibit unique properties—such as localized electronic states and spins—with exciting potential applications. Such nanostructures however are generally synthesized under vacuum because their zigzag edges are unstable under ambient conditions: a barrier that must be surmounted to achieve their scalable integration into devices for practical purposes. We developed two chemical protection/deprotection strategies, demonstrated on labile, air-sensitive chiral graphene nanoribbons. Upon hydrogenation, the chiral graphene nanoribbons survive exposure to air, after which they are easily converted back to their original structure by annealing. We also approach the problem from another angle by synthesizing a form of the chiral graphene nanoribbons that is functionalized with ketone side groups. This oxidized form is chemically stable and can be converted to the pristine hydrocarbon form by hydrogenation and annealing. In both cases, the deprotected chiral graphene nanoribbons regain electronic properties similar to those of the pristine nanoribbons. We believe both approaches may be extended to other graphene nanoribbons and carbon-based nanostructures and can be utilized to the fabrication of nanodevices in the near future.
Related publication: Lawrence, J. et al. Circumventing the Stability Problems of Graphene Nanoribbon Zigzag Edges. Nat. Chem. 2022, 14, 1451-1458.
3. The mechanism of antiaromaticity promoted diradical electronic character of pentacene derivatives has been revealed. The destabilizing antiaromatic effects of a four-membered ring confine the bond alternation, in turn bringing in open-shell character into the pentacene dimer linked by four-membered ring to lower the overall energy. Understanding these structure−property relations is desirable not only for fundamental reasons but also for designing new complex and functional molecular structures.
Related publication: Wang, T. et al. Tuning the Diradical Character of Pentacene Derivatives via NonBenzenoid Coupling Motifs. J. Am. Chem. Soc. 2023, 145, 10333−10341.
