Chiral‐Selective Formation of 1D Polymers Based on Ullmann‐Type Coupling: The Role of the Metallic Substrate

• Published in: Small (Weinheim an der Bergstrasse, Germany) Germany), 2017-04, Vol.13 (13), p.np-n/a
• Main Authors: Pham, Tuan Anh, Tran, Bay V., Nguyen, Manh‐Thuong, Stöhr, Meike
• Format: Article
• Language: English
• Subjects: 1D polymers; Annealing; chiral selective formation; Coupling (molecular); Covalence; Deposition; Formations; Graphene; graphene nanoribbons; Nanotechnology; on‐surface polymerization; Polymers; Substrates; Ullmann coupling
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.201603675

The chiral‐selective formation of 1D polymers from a prochiral molecule, namely, 6,12‐dibromochrysene in dependence of the type of metal surface is demonstrated by a combined scanning tunneling microscopy and density functional theory study. Deposition of the chosen molecule on Au(111) held at room temperature leads to the formation of a 2D porous molecular network. Upon annealing at 200 °C, an achiral covalently linked polymer is formed on Au(111). On the other hand, a chiral Cu‐coordinated polymer is spontaneously formed upon deposition of the molecules on Cu(111) held at room temperature. Importantly, it is found that the chiral‐selectivity determines the possibility of obtaining graphene nanoribbons (GNRs). On Au(111), upon annealing at 350 °C or higher cyclo‐dehydrogenation occurs transforming the achiral polymer into a GNR. In contrast, the chiral coordination polymer on Cu(111) cannot be converted into a GNR. The role of metallic substrates on the chiral‐selective formation of 1D polymers based on Ullmann‐type coupling is demonstrated for the first time. Upon annealing at 200 °C, an achiral covalently linked polymer of 6,12‐dibromochrysene is formed on Au(111), while a chiral Cu‐coordinated polymer is spontaneously formed after deposition of the molecules on Cu(111) held at room temperature.