On‐Surface Stepwise Double Dehydrogenation for the Formation of a para‐Quinodimethane‐Containing Undecacene Isomer

• Published in: Chemistry : a European journal Vol. 30; no. 55; pp. e202402297 - n/a
• Main Authors: Sarkar, Suchetana, Álvarez, Berta, Ho Au‐Yeung, Kwan, Cobas, Agustín, Robles, Roberto, Lorente, Nicolás, Peña, Diego, Pérez, Dolores, Moresco, Francesca
• Format: Journal Article
• Language: English
• Published: Germany Wiley Subscription Services, Inc 01.10.2024
• Subjects: Acenes; Aromaticity; Arynes; Atomic force microscopy; Dehydrogenation; Density functional theory; Deoxygenation; High-resolution AFM/STM; Isomers; On-surface synthesis; Scanning tunneling microscopy; Spatial discrimination; Spatial resolution; Spectroscopy; Thermal transformations; High-resolution AFM/STM; Acenes; Aromaticity; On-surface synthesis; Arynes
• ISSN: 0947-6539; 1521-3765; 1521-3765
• DOI: 10.1002/chem.202402297

The on‐surface synthesis of an isomer of undecacene, bearing two four‐membered rings and two para‐quinodimethane moieties, starting from a tetramethyl‐substituted diepoxy precursor, is presented. The transformation implies a thermal double deoxygenation followed by a stepwise double dehydrogenation reaction on the Au(111) surface, locally induced by inelastic tunneling electrons. This results in the transformation of para‐dimethylbenzene moieties into non‐aromatic para‐quinodimethanes. The structures and electronic properties of the intermediate and final products are investigated at the single molecule level with high spatial resolution, using both scanning tunneling microscopy/spectroscopy and non‐contact atomic force microscopy. The experimental results are supported by density functional theory calculations. The synthesis of an undecacene isomer with unique structural features, including two cyclobutadiene and two para‐quinodimethane (p‐QDM) moieties within the 1D polycyclic system, was achieved via a novel on‐surface dehydrogenation reaction induced by voltage pulses. This work broadens the arsenal of on‐surface synthesis methods and provides new insights into modifying the electronic properties of acene analogs through the incorporation of nonbenzenoid rings.