Highly Stereospecific On-Surface Dimerization into Bishelicenes: Topochemical Ullmann Coupling of Bromohelicene on Au(111).

Chemistry

Molecular Surface Science and Coating Technology Laboratory, Empa, Swiss Federal Laboratories for Materials Science and Technology, Überlandstrasse 129, 8600, Dübendorf, Switzerland.

Published: May 2023


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Article Abstract

The on-surface dimerization into bis(hexahelicene) on a gold(111) surface has been studied by means of scanning tunneling microscopy and time-of-flight secondary mass spectrometry. C-C Ullmann coupling of (rac)-2-bromo-hexahelicene leads to formation of the (M,M)- and (P,P)-diastereomers of 2,2'-bis(hexahelicene), whilst formation of the (M,P)-diastereomer is not observed. Upon cooling, the bis(hexahelicene) aggregates into an ordered two-dimensional lattice with partly randomly distributed enantiomers. The highly specific diastereomeric coupling is explained by the surface alignment of educt in combination with the strong steric overcrowding in a possible surface-confined (M,P)-product.

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http://dx.doi.org/10.1002/chem.202300134DOI Listing

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