Periodic Reporting for period 1 - CFMOS (Controlling Chemical Reactions For Carbon-Based Functional Materials Production on Surfaces)
Période du rapport: 2021-08-08 au 2023-08-07
Magnetic carbon-based nanomaterials have attracted increasing interests due to their potential applications in quantum computation and spin devices. However, the precise synthesis and characterization of such carbon-based nanostructures holding π-magnetism have been challenging, because of their high reactivity. The emerging on-surface synthesis approach under ultra-high vacuum opens a new path for the synthesis and characterization of highly reactive carbon magnetic structures. The overall objectives of this project is the precise and high-quality synthesis of various magnetic graphene-based nanomaterials on solid surfaces and characterization of their chemical structures and electronic/magnetic properties at a single-molecule level with the aid of scanning tunneling microscopy and spectroscopy.
1. Synthesis of magnetic chiral graphene nanoribbons (chGNRs) and characterization of their magnetic states. These magnetic chGNRs have been produced by the partial reduction of ketone-chGNRs or the oxidization of pristine chGNRs.
2. Protection and deprotection of chiral graphene nanoribbons with zigzag edges, which holds low-energy states thus being reactive. The developed protection and deprotection procedure proceed the utilization of chGNRs into real applications in nanodevices.
3. Synthesis and characterization of aza-triangulene on different metal surfaces. We elucidate the relationship between molecular symmetry, magnetism, and charge transfer between molecule and substrate.
4. Synthesis and characterization of pentacene dimers connected by non-benzenoid rings was studied. The diradical character of the products was tuned according to the coupling section.
Overall, the above results all together provide insight to both theoretically model and devise GNR-based nanostructures with tunable magnetic properties. These results have been disseminated via academic conferences in the specific field (e.g WE-Heraeus-Seminars “Exploring the Limits of Nanoscience with Scanning Probe Methods” and “Molecular Functionality at Surfaces: Self‐Assembly, Manipulation, Reactivity and the Role of Decoupling” in Bad Honnef, Germany, 27-31 Oct., 2019 and 30 Sept.-4 Oct., 2022) and also in conferences with more general topics (e.g. C’Nano 2020 The nanoscience meeting, Toulouse, France, 23-25 Nov., 2021). In addition, they have been disseminated by Google scholar and ResearchGate accounts of the beneficiary as well as the Twitter account of the organization. Partial results have also been shown in the outreach activities of the research center and the city.
2. Protection and deprotection of chiral graphene nanoribbons with zigzag edges, which holds low-energy states thus being reactive. The developed protection and deprotection procedure proceed the utilization of chGNRs into real applications in nanodevices.
3. Synthesis and characterization of aza-triangulene on different metal surfaces. We elucidate the relationship between molecular symmetry, magnetism, and charge transfer between molecule and substrate.
4. Synthesis and characterization of pentacene dimers connected by non-benzenoid rings was studied. The diradical character of the products was tuned according to the coupling section.
Overall, the above results all together provide insight to both theoretically model and devise GNR-based nanostructures with tunable magnetic properties. These results have been disseminated via academic conferences in the specific field (e.g WE-Heraeus-Seminars “Exploring the Limits of Nanoscience with Scanning Probe Methods” and “Molecular Functionality at Surfaces: Self‐Assembly, Manipulation, Reactivity and the Role of Decoupling” in Bad Honnef, Germany, 27-31 Oct., 2019 and 30 Sept.-4 Oct., 2022) and also in conferences with more general topics (e.g. C’Nano 2020 The nanoscience meeting, Toulouse, France, 23-25 Nov., 2021). In addition, they have been disseminated by Google scholar and ResearchGate accounts of the beneficiary as well as the Twitter account of the organization. Partial results have also been shown in the outreach activities of the research center and the city.
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.
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.