Halogen-Free On-Surface Synthesis of Rylene-Type Graphene Nanoribbons
Halogen-Free On-Surface Synthesis of Rylene-Type Graphene Nanoribbons
复制标题
无卤表面合成萘嵌苯型石墨烯纳米带
DOI：
10.1002/macp.201700155
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发表时间：
2017
影响因子：
2.5
通讯作者：
Zhong Dingyong
中科院分区：
文献类型：
--
作者：
Cai Zeying;She Limin;He Yangyong;Wu Liqin;Cai Lang;Zhong Dingyong
石墨烯纳米带是纳米电子和自旋电子器件的重要组成部分。作为一种自下而上的方法，从预定义的前体分子进行表面合成被广泛应用于制造具有精确控制的边缘结构和宽度的GNR。为了以所需的方式引导表面反应，大多数所选的前体分子被卤素原子官能化，而用于GNR合成的无卤素策略至今仍具有挑战性。本文报道了在Au（111）表面上通过直接双碳偶联合成五个碳原子的超窄扶手椅型GNRs（5-aGNRs）。作为前体分子，quaterrylene分子在亚单层覆盖下经历各种环化脱氢途径：代替直的GNR，大部分反应产物以150°的角度扭结。当覆盖率增加到接近一个单层时，对直GNRs的选择性显著增强。覆盖度依赖性反应偏好归因于分子间空间效应，其中反应途径受相邻分子的取向约束。这种分子间空间效应被认为是一种新的方法，以引导表面合成所需的纳米结构。
Graphene nanoribbons (GNRs) are promising building blocks for nanoelectronic and spintronic devices. As a bottom‐up approach, on‐surface synthesis from predefined precursor molecules is widely applied for the fabrication of GNRs with precisely controlled edge structure and width. In order to guide the on‐surface reaction in a desired style, most of the chosen precursor molecules are functionalized with halogen atoms, while halogen‐free strategy for GNR synthesis is still challenging so far. Here, the on‐surface synthesis of ultranarrow armchair GNRs with five carbons across the ribbon (5‐aGNRs) on Au(111) surfaces via direct dehydrogenative CC coupling is reported. As the precursor molecule, quaterrylene molecules undergo various pathways of cyclodehydrogenation at submonolayer coverage: Instead of straight GNRs, a large proportion of the reaction products are kinked with an angle of 150°. When increasing the coverage to nearly one monolayer, the selectivity toward the straight GNRs is significantly enhanced. The coverage‐dependent reaction preference is ascribed to the intermolecular steric effect, in which the reaction pathway is constrained by the orientation of the neighboring molecules. Such an intermolecular steric effect is considered a novel approach to guide the on‐surface synthesis toward desired nanostructures.