NCAFM2023 Programme Booklet

Wednesday 1400 - 1420

Kalyan Biswas,1 Maxence Urbani,1 Ana Sánchez-Grande, 1 Diego Soler, 2 Pingo Mutombo, 2 Koen Lauwaet, 1 José M. Gallego, 3 Rodolfo Miranda, 1,4 David Écija, 1,* Pavel Jelínek, 2,* Tomás Torres 5,* and José I. Urgel 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 Instituto de Ciencia de Materiales de Madrid, CSIC, Cantoblanco, 28049 Madrid, Spain 4 Departamento de Física de la Materia Condensada, Universidad Autónoma de Madrid, 28049 Madrid, Spain 5 Departamento de Química Orgánica, Universidad Autónoma de Madrid, 28049 Madrid, Spain INTERPLAY BETWEEN π CONJUGATION AND EXCHANGE MAGNETISM IN ONE DIMENSIONAL PORPHYRINOID POLYMERS The field of carbon magnetism has gained an increased attention in view of the recent progress made in the synthesis and characterization of open-shell polycyclic aromatic hydrocarbons following a bottom-up synthetic approach [1,2]. Under this scenario, the comprehensive fabrication of magnetic porphyrinoid-based polymers emerges as a highly appealing field of research. However, the vast majority of the porphyrinoid species and polymers studied to date exhibit a closed-shell ground state [3]. In this work, we introduce an exemplary approach toward the bottom-up fabrication of magnetic porphyrinoid-based polymers homocoupled via surface-catalyzed [3 + 3] cycloaromatization of isopropyl substituents studied on Au(111) under ultra-high vacuum (UHV) conditions. The chemical structure of the polymer have been clearly elucidated by non-contact atomic force microscopy (nc-AFM). Scanning tunneling spectroscopy (STS), complemented by computational investigations reveals the open-shell character, i.e. antiferromagnetic singlet ground state (S=0) of the formed polymers, which display singlet−triplet inelastic excitations observed between spins of adjacent porphyrinoid units only along a specific π-conjugation pathway, thus revealing the interplay between π-conjugation and magnetic exchange. We envision that our approach can be a highly relevant step towards the on-surface synthesis of covalently linked 1D magnetic organic polymers with prospects in nanoscale spintronic devices. Email: jose-ignacio.urgel@imdea.org

Figure caption: On-surface reaction scheme and nc-AFM images toward the synthesis of one-dimensional porphyrinoid polymers.

References [1] Auwärter, W.; Écija, D.; Klappenberger, F.; Barth, J. V. Porphyrins at Interfaces. Nat Chem. 2015, 7 ,105–120. [2] Gottfried, J. M. Surface Chemistry of Porphyrins and Phthalocyanines. Surf. Sci. Rep. 2015, 70 ,259–379. [3] Shimizu, D.; Osuka, A. Porphyrinoids as a Platform of Stable Radicals. Chem. Sci. 2018, 9 , 1408–1423.

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