Journal Article

FZJ-2026-01633

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Multi-Orbital Charge Transfer into Nonplanar Cycloarenes Revealed with CO-Functionalized STM Tips

Haags, A. (First author)FZJ* ; Reichmann, A. ; Ruan, Z. ; Fan, Q. ; Egger, L. ; Kirschner, H. ; Naumann, T. ; Werner, S. ; Kleykamp, O. ; Martinez Castro, J. ; Lüpke, F.FZJ* ; Bocquet, F. C.FZJ* ; Kumpf, C.FZJ* ; Soubatch, S.FZJ* ; Gottwald, A. ; Koller, G. ; Ramsey, M. G. ; Richter, M. ; Sundermeyer, J. ; Puschnig, P. ; Gottfried, J. M. ; Tautz, F. S.FZJ* ; Wenzel, S. (Corresponding author)

2026
ACS Washington, DC

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Please use a persistent id in citations: doi:10.1021/acs.jpclett.5c03268

Abstract: On-surface synthesis enables the tunable preparation of diverse molecular systems with tailored properties. Recently, the highly selective synthesis of kekulene (>99%) on Cu(111) and isokekulene (92%) on Cu(110) from the same molecular precursor was demonstrated. Scanning tunneling microscopy (STM) with CO-functionalized tips can identify individual molecules based on their geometric structure at low coverage on Cu(110) but also reveals complex features arising from electronic contributions near the Fermi energy. Here, we investigate the origin of these features by simulating STM images based on a weighted sum of multiple molecular orbitals, for which we employ weights based on the calculated molecular-orbital projected density of states. This analysis provides direct experimental evidence for charge transfer from the surface into multiple formerly unoccupied molecular orbitals for single molecules of kekulene as well as isokekulene in its two nonplanar adsorption configurations. In comparison, the area-integrating photoemission orbital tomography technique confirms the charge transfer as well as the high selectivity for the formation of a full monolayer of predominantly isokekulene on Cu(110). Our STM-based approach is applicable to a wide range of adsorbed molecular systems and specifically also suited for strongly interacting surfaces, nonplanar molecules, and compounds accessible only in extremely low yields.

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Contributing Institute(s):

1. Quantum Nanoscience (PGI-3)

Research Program(s):

1. 5213 - Quantum Nanoscience (POF4-521) (POF4-521)
2. SFB 1083 A12 - Struktur und Anregungen von hetero-epitaktischen Schichtsystemen aus schwach wechselwirkenden 2D-Materialien und molekularen Schichten (A12) (385975694) (385975694)
3. ML4Q - Machine Learning for Quantum (101120240) (101120240)
4. Orbital Cinema - Photoemission Orbital Cinematography: An ultrafast wave function lab (101071259) (101071259)

Appears in the scientific report 2026

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Database coverage:
; Clarivate Analytics Master Journal List ; Current Contents - Physical, Chemical and Earth Sciences ; Essential Science Indicators ; IF >= 5 ; JCR ; SCOPUS ; Science Citation Index Expanded ; Web of Science Core Collection

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