Nanopatterning by Length-Dependent Self-Assembly from Fluorene-Terpyridine Derivatives

• Published in: Journal of physical chemistry. C 2022-07, Vol.126 (26), p.10833-10841
• Main Authors: Seydou, M., Sall, S., Lafolet, F., Lemercier, G., Maurel, F., Lacroix, J. C., Sun, X.
• Format: Article
• Language: English
• Subjects: C: Physical Properties of Materials and Interfaces
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.2c01550

Nanopatterning of photoactive precursors by self-assembly is an efficient nanoscale approach to optimize materials with tailored photoluminescence properties. Ditopic ligands are designed that contain terpyridine terminals connected through one or two photoactive fluorene central units. The tpy-Fluo-tpy and tpy-bisFluo-tpy molecules are self-assembled on HOPG surfaces and are investigated by high-resolution scanning tunneling microscopy, where similar organizations are observed due to the intermolecular terpyridine-terpyridine interactions. By an increase in the number of central fluorenes (single to double), the molecular centers bridges appear as distinct “X” or “S” shapes under STM. Moreover, the adsorption spectra shift toward a longer wavelength and an obvious improvement of the quantum luminescence yield is observed. In the tpy-bisFluo-tpy molecules, the STM tip is functionalized to observe the different HOMO or LUMO electronic contrasts that are interpreted by density functional theory (DFT) calculations. Our work provides a novel nanopatterning approach to organize photoactive precursors with molecular-scale precision for designing efficient light-emitting materials.