Polycyclic aromatic chains on metals and insulating layers by repetitive [3+2] cycloadditions

Nature Communications 11,1490, (2020)

Polycyclic aromatic chains on metals and insulating layers by repetitive [3+2] cycloadditions

Alexander Riss, Marcus Richter, Alejandro Pérez Paz, Xiao-Ye Wang, Rajesh Raju, Yuanqin He, Jacob Ducke, Eduardo Corral, Michael Wuttke, Knud Seufert, Manuela Garnica, Angel Rubio, Johannes V. Barth, Akimitsu Narita, Klaus Müllen, Reinhard Berger, Xinliang Feng, Carlos-Andres Palma & Willi Auwärter

The vast potential of organic materials for electronic, optoelectronic and spintronic devices entails substantial interest in the fabrication of π-conjugated systems with tailored functionality directly at insulating interfaces. On-surface fabrication of such materials on nonmetal surfaces remains to be demonstrated with high yield and selectivity. Here we present the synthesis of polyaromatic chains on metallic substrates, insulating layers, and in the solid state. Scanning probe microscopy shows the formation of azaullazine repeating units on Au(111), Ag(111), and h-BN/Cu(111), stemming from intermolecular homo-coupling via cycloaddition reactions of CN-substituted polycyclic aromatic azomethine ylide (PAMY) intermediates followed by subsequent dehydrogenation. Matrix-assisted laser desorption/ ionization (MALDI) mass spectrometry demonstrates that the reaction also takes place in the solid state in the absence of any catalyst. Such intermolecular cycloaddition reactions are promising methods for direct synthesis of regioregular polyaromatic polymers on arbitrary insulating surfaces.

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This work was financially supported by the European Research Council Consolidator Grant NanoSurfs (no. 615233), the Horizon 2020 research and innovation program 2D ink (no. 664878) and the National Science Foundation of China (no. 11974403 and SinoGerman Project no. 51761135130). W.A. acknowledges funding by the DFG via a Heisenberg professorship. M.R., R.B., and X.F. thank the German Research Foundation (DFG) within the Cluster of Excellence “Center for Advancing Electronics Dresden (cfaed)” and EnhanceNano (No. 391979941). M.G. acknowledges funding by the H2020- MSCA-IF−2014 program under GA no. 658070 (2DNano).

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