NCAFM2023 Programme Booklet

Wednesday 0920 - 0940

TIP INDUCED CHEMISTRY: SELECTIVE REACTIONS, CYCLOCARBONS AND INDENOFLUORENE

Leo Gross*, Shantanu Mishra, Florian Albrecht

1 IBM Research Europe – Zurich, Rüschlikon (Switzerland) Email: LGR@zurich.ibm.com

Atomic resolution by NC-AFM on molecules [1] facilitated progress in on-surface synthesis, including tip-induced chemistry, that is, chemical reactions performed using the tip of the microscope for atom manipulation. Recently, we demonstrated selective tip-induced reactions on a surface [2]. By the value of a voltage pulse from the tip, we can select which bond is formed within a molecule. Elusive molecules can be created and studied by tip-induced chemistry. I will present our progress on cyclocarbons, i.e., sp1-hybridized molecular carbon allotropes with two orthogonal pi-systems [3,4]. And on indenofluorenes that can be switched between open-shell and closed-shell states by changing the adsorption site on a surface [5], see Figure.

Figure. Characterization of indeno[1,2-a]fluorene on bilayer NaCl/Au(111). The molecule was generated by dehydrogenation of a custom synthesized precursor molecule [5]. In open-shell form (calculations shown in triplet state) and in closed-shell para form (the ortho closed-shell form was never observed). Closed-shell and open-shell form can be assigned independently by orbital density maps with STM or by using AFM for bond-order discrimination [6]. By changing the adsorption site, the molecule can be switched between open-shell and closed-shell para form (see right-hand side panels). All images with CO functionalized tips. Scale bars: 10 Å in STM images and 5 Å in AFM images. Reproduced from https://doi.org/10.48550/arXiv.2303.04483 [5].

References [1] L. Gross et al. Science , 325 , 1110-1114 (2009) [2] F. Albrecht et al. Science , 377 , 298-301 (2022) [3] K. Kaiser et al. Science , 365 , 1299-1301 (2019)

[4] Y. Gao et al., ChemRxiv , DOI: 10.26434/chemrxiv-2023-w124b-v2. (2023) [5] S. Mishra et al. arXiv , https://doi.org/10.48550/arXiv.2303.04483 (2023) [6] L. Gross et al. Science 337 , 1326-1329 (2012)

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