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Issue 10, 2019

The fate of bromine after temperature-induced dehydrogenation of on-surface synthesized bisheptahelicene

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Abstract

The on-surface synthesis of bisheptahelicene by Ullmann coupling of 9-bromoheptahelicene on Au(111) and its temperature-induced dehydrogenation is studied using temperature-programmed reaction spectroscopy and time-of-flight secondary ion mass spectrometry. Specific dehydrogenation products of bisheptahelicene after loss of 6, 8 and 10 hydrogen atoms are identified, corresponding to molecules having undergone Diels–Alder transformations and intramolecular C–C coupling reactions. By combining with atomic hydrogen produced by dehydrogenation, the Ullmann coupling side-product bromine desorbs as HBr. H2 desorption emerges only after all Br has desorbed. Such characteristic behavior is explained by a kinetic model which explicitly considers the coverage of transient atomic H on the surface. Heating experiments performed with saturated layers of different Br-containing molecules reveal that the onset of HBr desorption depends strictly on the dehydrogenation step and therefore on the structure of the molecules.

Graphical abstract: The fate of bromine after temperature-induced dehydrogenation of on-surface synthesized bisheptahelicene

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Article information


Submitted
23 Oct 2018
Accepted
15 Jan 2019
First published
15 Jan 2019

This article is Open Access
All publication charges for this article have been paid for by the Royal Society of Chemistry

Chem. Sci., 2019,10, 2998-3004
Article type
Edge Article

The fate of bromine after temperature-induced dehydrogenation of on-surface synthesized bisheptahelicene

A. Mairena, M. Baljozovic, M. Kawecki, K. Grenader, M. Wienke, K. Martin, L. Bernard, N. Avarvari, A. Terfort, K. Ernst and C. Wäckerlin, Chem. Sci., 2019, 10, 2998 DOI: 10.1039/C8SC04720K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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