Fabrication of Novel Carbon-based Polymers by On-surface Cycloaromatization of Isopropyl Substituents

Surface-catalyzed reactions have been employed for the synthesis of carbon nanomaterials featuring precisely defined atomic structures. A recent breakthrough involves the gold surface-catalyzed 3 + 3 cycloaromatization of isopropyl-substituted arenes, allowing for on-surface synthesis of novel carbon-based polymers1-3. In this process, the surface plays a crucial role in activating the isopropyl substituents, facilitating the formation of phenylene rings through intermolecular coupling. For instance, such investigations might open new avenues in the field of carbon magnetism, which has gained an increased attention in view of the recent progress made in the synthesis and characterization of open-shell polycyclic aromatic hydrocarbons2. Under this scenario, the comprehensive fabrication of magnetic polymers emerges as a highly appealing field of research. Here, we introduce exemplary approaches toward the bottom-up fabrication of different carbon-based polymers homocoupled via surface-catalyzed 3 + 3 cycloaromatization of isopropyl substituents studied on Au(111) under ultra-high vacuum (UHV) conditions. The chemical structures of the polymers have been clearly elucidated by non-contact atomic force microscopy (nc-AFM). Scanning tunneling spectroscopy (STS), complemented by computational investigations reveals their ground state. Our approach can be a highly relevant step towards the on-surface synthesis of covalently linked 1D organic polymers with prospects in sensing, catalysis and nanoscale spintronic devices. References: 1 - Kinikar, A. et al. (2022). On-surface polyarylene synthesis by cycloaromatization of isopropyl substituents. Nature Synthesis, 1(4), 289-296. 2 - Biswas, K., et al. (2022). Interplay between π-Conjugation and Exchange Magnetism in One-Dimensional Porphyrinoid Polymers. Journal of the American Chemical Society, 144(28), 12725-12731. 3 - Kinikar, A. et al. (2023). Sterically Selective 3 + 3 Cycloaromatization in the On-Surface Synthesis of Nanographenes. ACS Nanoscience Au. Figure 1