NCAFM2023 Programme Booklet

Tuesday 1640 - 1700

GENERATING ANTIAROMATICITY: THERMALLY-SELECTIVE SKELETAL REARRANGEMENTS AT INTERFACES Ana Barragán 1 , Elena Pérez-Elvira 1 , Qifan Chen 2,3 , Diego Soler-Polo 2 , Ana Sánchez-Grande 1,2,4 , Diego J. Vincent 5 , Koen Lauwaet 1 , José Santos 5 , Pingo Mutombo 2 , Jesús I.Mendieta-Moreno 2 , Bruno de la Torre 6 , José M. Gallego 7 , Rodolfo Miranda 1,4 , Nazario Martín 1,5 , Pavel Jelinek 2,6 , José I. Urgel 1 , David Écija 1

1 IMDEA Nanoscience, C/Faraday 9, Campus de Cantoblanco, 28049 Madrid, Spain 2 Institute of Physics of the Czech Academy of Science, CZ-16253 Praha, Czech Republic 3 Regional Centre of Advanced Technologies and Materials, University Olomouc, Czech Republic 4 Dept. de Química Orgánica, Universidad Complutense de Madrid, 28040 Madrid, Spain 5 Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC), Cantoblanco, 28049 Madrid, Spain 6 Dept. de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain

Email: ana.barragan@imdea.org

On-surface synthesis is a promising strategy for the design of novel nanomaterials complementary to solution-based chemistry. The chemical structure of the final products depends on the reaction mechanism followed by the precursor upon sublimation onto the selected surface. For instance, ring-rearrangement reactions are recently gaining increasing attention as a possible alternative toward the generation of novel nanostructures 1-2 . However, controlling such reaction mechanisms remain challenging due to the enormous amount of possible skeletal rearrangements. Here, we show the sublimation of dibromomethylene-functionalized molecular precursors on a pristine Au (111) substrate held at high temperature, which results in a novel intra- and intermolecular reaction affording a skeletal ring-rearrangement (Scheme 1). Such reaction pathway differs from the covalent polymerization of the same species upon deposition on Au(111) at room temperature followed by subsequent annealing 3 . Combined scanning tunneling microscopy (STM) and non-contact atomic force microscopy (nc-AFM) investigations unveil the chemical structures of the obtained compounds showing the formation of antiaromatic subunits within the molecular backbones. We envision that the control of ring-rearrangement reactions of carbon-based compounds on surfaces may open new routes toward the design of electron-rich low dimensional materials with prospects in molecular optoelectronics.

Scheme 1. On-surface generation of antiaromatic subunits in PCHs and 1D polymers by a) Intramolecular thermal rearrangement and organometallic polymerization of dibromomethylene-functionalized p-quinoid-based precursors, and b) Intramolecular thermal rearrangement and subsequent homocoupling polymerization.

References [1] A. Shiotari, T Nakae, K. Iwata, et al. Nat. Commun. 2017, 8 , 16089 [2] N. Pavliček, P. Gawel, D.R. Kohn, et al. Nature Chem. 2018, 10 , 853-858 [3] B. Cirera, A. Sánchez-Grande, B. de la Torre, et al. Nat. Nanotechnol. 2020, 15 , 437-443

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