Regensburg 2025 – scientific programme
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O: Fachverband Oberflächenphysik
O 62: Focus Session Molecular Nanostructures on Surfaces: On-Surface Synthesis and Single-Molecule Manipulation III
O 62.2: Talk
Wednesday, March 19, 2025, 10:45–11:00, H24
On-surface synthesis and characterization of long azaacenes — •Zilin Ruan1, Liping Ye2, Jakob Schramm3, Tim Naumann1, Faming Kang1, Ralf Tonner-Zech3, Michael Mastalerz2, and J. Michael Gottfried1 — 1Department of Chemistry, Philipps-Universität Marburg, 35037 Marburg, Germany — 22Organisch-Chemisches Institut, Ruprecht-Karls-Universität Heidelberg, 69120 Heidelberg, Germany — 3Wilhelm Ostwald Institute of Physical and Theoretical Chemistry, Universität Leipzig, 04103 Leipzig, Germany
Introducing electronegative nitrogen into the backbone of acenes yields azaacenes, enabling fine-tuning of the energy alignment of frontier orbitals while enhancing resistance to oxidation, photodegradation, and dimerization. Here, we demonstrate the on-surface synthesis of tetraazanonacene and hexaazatridecacene, the latter being the longest azaacene known to date and here reported for the first time via atom-manipulation-induced dissociation of a trietheno-bridged precursor on a Au(111) surface in UHV. The geometric and electronic structures of the generated azaacenes were investigated by combined scanning tunneling microscopy/spectroscopy and non-contact atomic force microscopy. For tetraazanonacene, we observed an increase of the frontier orbital gap compared to pristine nonacene, attributed to a more pronounced downshift of occupied states. Meanwhile, hexaazanonacene exhibited an open-shell singlet ground state with a singlet-triplet gap of 110 meV, slightly smaller than that observed for long acenes.
Keywords: single-molecule manipulation; azaacene; on-surface synthesis