On-surface synthesis of higher acenes beyond undecacene: Evolution of conductance and electronic states
Final Report Abstract
The main goal of the project was to investigate the electronic structure and the radical character of the ground state of higher acenes adsorbed on the Au(111) surface by increasing the number of linearly fused benzene rings. The goal was to determine the electronic properties and the conductance of long oligoacenes synthetized on surface, studying the evolution of the electronic resonances and the decay of the tunneling current. After successfully investigating dodecacene on Au(111) before the official start of the project, the topic partially shifted focusing on the on-surface synthesis of acenes longer than 12 rings and to obtain further information about the energy and localization of electronic states, also after heteroatom substitution or in the presence of non-benzenoid rings. We first investigated a tetramethyl-substituted diepoxy precursor on Au(111), performing the onsurface synthesis of an isomer of undecacene bearing two four-membered rings and two paraquinodimethanes. The transformation implied a thermal double deoxygenation followed by a stepwise double dehydrogenation reaction locally induced by inelastic tunneling electrons. We investigated the structures and electronic properties of intermediates and final product at the single molecule level with high spatial resolution, confirming the results by density functional theory calculations. In the last part of the project, we investigated a 14-cene precursor including 6 epoxy groups in the carbon rings on the Au(111) surface. After depositing the molecule by flash heating to avoid interactions between molecules and/or decomposition, we studied the topography and electronic resonances at different stages of the on-surface reactions induced by voltage pulses. Furthermore, we performed on-surface synthesis experiments including the study of a large dissymmetric starphene molecule, the formation of cyano-vinylene chains by Knoevenagel condensation, and the ring closure of vinylheptafulvene molecular dipole switches. Further studies on the mechanical properties of single molecules on Au(111) included the reversible conformational change of a thiophene based molecule and the study of zwitterionic DMBI derivatives as unidirectional single molecule rotors and nanocars.
Publications
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On‐Surface Formation of Cyano‐Vinylene Linked Chains by Knoevenagel Condensation. Chemistry – A European Journal, 27(69), 17336-17340.
Au‐Yeung, Kwan Ho; Kühne, Tim; Becker, Daniel; Richter, Marcus; Ryndyk, Dmitry A.; Cuniberti, Gianaurelio; Heine, Thomas; Feng, Xinliang & Moresco, Francesca
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Preparation of Tetrabenzo[4.4.2]undecastarphene by On‐Surface Synthesis. ChemPlusChem, 86(7), 991-996.
Jancarik, Andrej; Khanh, Hung Nguyen; Skidin, Dmitry; Moresco, Francesca & Gourdon, Andre
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STM-induced ring closure of vinylheptafulvene molecular dipole switches on Au(111). Nanoscale Advances, 4(20), 4351-4357.
Au-Yeung, Kwan Ho; Kühne, Tim; Aiboudi, Oumaima; Sarkar, Suchetana; Guskova, Olga; Ryndyk, Dmitry A.; Heine, Thomas; Lissel, Franziska & Moresco, Francesca
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A Nanocar and Rotor in One Molecule. ACS Nano, 17(3), 3128-3134.
Au-Yeung, Kwan Ho; Sarkar, Suchetana; Kühne, Tim; Aiboudi, Oumaima; Ryndyk, Dmitry A.; Robles, Roberto; Lorente, Nicolas; Lissel, Franziska; Joachim, Christian & Moresco, Francesca
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Adsorption and reversible conformational change of a thiophene based molecule on Au(111). Scientific Reports, 13(1).
Sarkar, Suchetana; Au-Yeung, Kwan Ho; Kühne, Tim; Waentig, Albrecht; Ryndyk, Dmitry A.; Heine, Thomas; Cuniberti, Gianaurelio; Feng, Xinliang & Moresco, Francesca
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Thermal with Electronic Excitation for the Unidirectional Rotation of a Molecule on a Surface. The Journal of Physical Chemistry C, 127(34), 16989-16994.
Au-Yeung, Kwan Ho; Sarkar, Suchetana; Kühne, Tim; Aiboudi, Oumaima; Ryndyk, Dmitry A.; Robles, Roberto; Lissel, Franziska; Lorente, Nicolas; Joachim, Christian & Moresco, Francesca
