Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 42: Poster Tuesday: Organic Molecules on Inorganic Surfaces

O 42.9: Poster

Dienstag, 2. April 2019, 18:00–20:00, Poster D

Surface Chemical Bond of Alternant vs. Non-Alternant Aromatic Isomers — •Ruppenthal Lukas, Bendedikt P. Klein, Jan Herritsch, Stefan R. Kachel, and J. Michael Gottfried — Fachbereich Chemie, Philipps-Universität Marburg, Germany

Metal/organic interfaces have a large impact on the performance of organic-electronic devices. The detailed understanding of their chemical, electronic and geometric structure is therefore important for the further technological development. Many common organic semiconductors contain aromatic structures with alternant topologies, whereas non-alternant alternatives have found far less interest. Here, we compare naphthalene as an alternant aromatic molecule to azulene as its non-alternant isomer, both on Cu(111), using PES, NEXAFS, TPD, STM, and LEED. With the same approach, we compare the larger aromatic compounds pyrene and its isomer dicyclopenta[ef,kl]heptalene (azupyrene), which is also important as a model for the Stone-Wales defects in graphene. Related studies on organometallic sandwich complexes include bis(benzene)chromium and the corresponding non-alternant cyclopentadienyl-cycloheptatrienyl-chromium. In all cases, we find that the non-alternant structure forms a stronger bond to the metal surface than its alternant counterpart. The main reason for this is that the non-alternant species have a smaller HOMO-LUMO gap, which makes them both better donors and better acceptors compared to the alternant species. The resulting effects on the electronic and geometric structure will be discussed on the basis of DFT calculations.