Controling the molecular spin by means of chemical reactions promoted by functionalized metal-supported graphene

J.J. Navarro^a,d, M. Pisarra^b, B. Nieto-Ortega^d, J. Villalva^d, C.G. Ayani^d, C. Diaz^b,c, F. Calleja^d, R. Miranda^a,c,d, F. Martin^b,c,d, E.M. Perez^d, A.L. Vazquez de Parga^a,d

^aDep. Física de la Materia Condensada, Universidad Autónoma de Madrid, Cantoblanco 28049, Madrid, Spain

^bDep. Química C-13, Universidad Autónoma de Madrid, Cantoblanco, 28049, Madrid Spain

^cCondensed Matter Physics Center IFIMAC, Cantoblanco 28049, Madrid, Spain

^dIMDEA-Nanociencia, Calle Faraday 9, Cantoblanco 28049, Madrid, Spain

fabian.calleja@imdea.org

Graphitic carbon structures are usually a major obstacle for catalytic processes on transition metals: Due to their chemical inertness, carbon deposits physically block the surface active sites poisoning the catalytic reaction. In principle the effect is more pronounced as the amount of carbon increases, where an extreme scenario would be the case of a complete graphene layer. However, as we demonstrated in a recent work, nanostructured graphene on Ru(0001) can be covalently functionalized employing CH2CN• radicals [1], obtaining an extremely high yield and site-selectivity down to the atomic scale [2]. The resulting functionalized system is an ideal platform to explore chemical reactions with other molecular radicals diffusing on the graphene surface. In this work we show that TCNQ radicals [3] can react with the previously attached -CH2CN groups on gr/Ru(0001) forming a new C-C bond, in a chemical reaction promoted by graphene [4]. We study this reaction by means of Scanning Tunnelling Microscopy (STM) and Density Functional Theory (DFT). The resulting new molecule presents a different electronic configuration and spin state than the original TCNQ, as demonstrated by probing a Kondo resonance. We also show that the chemical reaction can be reversed using STM manipulation techniques, so the whole process can be viewed as a controlled switch for the molecular spin.

[1] J.J. Navarro et al. Nano Lett.16, 355-361 (2016)

[2] J.J. Navarro et al. Chem. Commun.53, 1041-10452 (2017)

[3] M. Garnica et al. Nat. Phys.9, 368 (2013)

[4] J.J. Navarro et al. Sci. Adv. 4, (2018)