Snegir S, Dappe YJ, Sysoiev D, Pluchery O, Huhn T, Scheer E. Where do the counterions go? Tip-induced dissociation of self-assembled triazatriangulenium-based molecules on Au(111).
Phys Chem Chem Phys 2021;
23:9930-9937. [PMID:
33861285 DOI:
10.1039/d1cp00221j]
[Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Chemical coupling of functional molecules on top of the so-called platform molecules allows the formation of functional self-assembled monolayers (SAMs). An often-used example of such a platform is triazatriangulenium (TATA), which features an extended aromatic core providing good electronic contact to the underlying metal surface. Here, we present a study of the SAM formation of a TATA platform on Au(111) employing scanning tunneling microscopy (STM) under ambient atmospheric conditions. In solution, the TATA platform is stabilized by BF4 counterions, while after deposition on a gold substrate, the localization of the BF4 counterions remains unknown. We used 1,2,4-trichlorobenzene as a solvent of TATA-BF4 to induce SAM formation on a heated (∼50 °C) Au substrate. We show by STM how to detect and distinguish TATA-BF4 from TATA platforms, which lost their BF4 counterions. Finally, we observe a change of the counterion position on the SAM during the STM scanning, which we explain by an electric-field-induced decrease of the electrostatic interaction in TATA-BF4 on the surface. We applied DFT calculations to reveal the influence of the gold lattice and the electric field of the STM tip on the stability of TATA-BF4 physisorbed on the surface.
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