On-Surface Synthesis of Ethynylene-Bridged Anthracene Polymers

Engineering low-band-gap -conjugated polymers is a growing area in basic and applied research. The main synthetic challenge lies in the solubility of the starting materials, which precludes advancements in the field. Here, we report an on-surface synthesis protocol to overcome such difficulties and produce poly(p-anthracene ethynylene) molecular wires on Au(111). To this aim, a quinoid anthracene precursor with =CBr2 moieties is deposited and annealed to 400K, resulting in anthracene-based polymers. High-resolution nc-AFM measurements confirm the nature of the ethynylene-bridge bond between the anthracene moieties. Theoretical simulations illustrate the mechanism of the chemical reaction, highlighting three major steps: dehalogenation, diffusion of surface-stabilized carbenes, and homocoupling, which enables the formation of an ethynylene bridge. Our results introduce a novel chemical protocol to design -conjugated polymers based on oligoacene precursors and pave new avenues for advancing the emerging field of on-surface synthesis.
Funding Agencies|Comunidad de Madrid [Y2018/NMT-4783, S2013/MIT-3007, S2018/NMT]; European Research Council [ERC-320441-Chirallcarbon, ERC-766555-ELECNANO]; Spanish Ramon y Cajal programme [RYC-2012-11133]; MINECO of Spain [FIS 2015-67287-P, CTQ2017-83531-R, CTQ2016-81911-REDT]; Severo Ochoa Programme for Centers of Excellence in RD (MINECO) [SEV-2016-0686]; Praemium Academie of the Academy of Science of the Czech Republic [MEYS LM2015087, GACR 18-09914S]; Operational Programme Research, Development, and Education - European Structural and Investment Funds; Czech Ministry of Education, Youth, and Sports [CZ.02.1.01/0.0/0.0/16019/0000754]; Czech Science Foundation [19-27454X]; Swedish Research Council [642-2013-2080]; Swedish Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009 00971]