Département de génie physique et Regroupement québécois sur les matériaux de pointe (RQMP), Polytechnique Montréal, Montréal, Québec H3C 3A7, Canada.
Phys Chem Chem Phys. 2018 Jun 6;20(22):15350-15357. doi: 10.1039/c8cp01184b.
The formation of highly organized structures based on two ligands with pyridyl functionalities, 4,4'-bipyridine (BPY) and 1,4-di(4,4''-pyridyl) benzene (BPYB), and Cu adatoms on the Cu(111) surface has been studied with low temperature and variable temperature scanning tunneling microscopy (STM) and first-principles calculations. We show that the formation of a highly organized adlayer built from adatom-molecule and molecule-molecule units strongly depends on the number of mobile Cu atoms on the surface. While a high concentration of Cu adatoms (high adatom/BPY ratio, ≥1) leads systematically to the formation of organometallic nanolines, their absence (low adatom/BPY ratio, ≈0) gives a compact self-assembled molecular network, and more specifically hydrogen-bond networks (HBN) with BPY molecules organized in a T-shaped fashion. Alternatively, an intermediate concentration of Cu adatoms (0 < adatom/BPY < 1) allows the formation of a well-organized and compact structure where both organometallic and HBN components coexist. Although STM images cannot clearly reveal the presence of Cu adatoms within the organometallic moiety, the bonding of BPY to a single or two Cu adatoms can be clearly identified by scanning tunneling spectroscopy (STS), and is supported by Density Functional Theory (DFT) results. Additional STM simulations suggest that the relative position of the Cu adatom with respect to the organic ligands just above has a significant impact on its detection by STM. This study exemplifies the prominent role of metallic adatoms on the formation of a complex organometallic network and should open more rational practices to optimize the formation of these supramolecular networks.
基于吡啶官能团的两种配体 4,4'-联吡啶（BPY）和 1,4-二（4,4''-吡啶基）苯（BPYB）以及 Cu 原子在 Cu(111)表面上形成高度有序结构的研究已经通过低温和变温扫描隧道显微镜（STM）和第一性原理计算来进行。我们表明，由原子-分子和分子-分子单元组成的高度有序的吸附层的形成强烈依赖于表面上可移动的 Cu 原子的数量。虽然高浓度的 Cu 原子（高原子/BPY 比，≥1）会导致有机金属纳米线的系统形成，但它们的缺乏（低原子/BPY 比，≈0）会形成一个紧密的自组装分子网络，更具体地说，是具有 BPY 分子以 T 形方式排列的氢键网络（HBN）。或者，中间浓度的 Cu 原子（0 <原子/BPY <1）允许形成一个高度有序和紧凑的结构，其中既有有机金属部分，也有 HBN 部分共存。尽管 STM 图像无法清楚地显示出有机金属部分中 Cu 原子的存在，但通过扫描隧道光谱（STS）可以清楚地识别 BPY 与单个或两个 Cu 原子的键合，并且得到密度泛函理论（DFT）结果的支持。额外的 STM 模拟表明，Cu 原子相对于有机配体上方的相对位置对其通过 STM 的检测有重大影响。这项研究说明了金属原子在形成复杂有机金属网络中的突出作用，并应该为优化这些超分子网络的形成提供更多合理的实践方法。
