Cyano-Substituted Triptycene-Based Monolayers on Au(111): Tripodal Adsorption, Dipole Engineering, and Charge Transfer
Cyano-Substituted Triptycene-Based Monolayers on Au(111): Tripodal Adsorption, Dipole Engineering, and Charge Transfer
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DOI：
10.1021/acs.jpcc.1c05618
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发表时间：
2021-09
期刊：
影响因子：
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通讯作者：
Saunak Das;A. Asyuda;Yoshiaki Shoji;A. Kosaka;T. Fukushima;M. Zharnikov
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作者：
Saunak Das;A. Asyuda;Yoshiaki Shoji;A. Kosaka;T. Fukushima;M. Zharnikov
具有三足锚定基团的分子通常能够形成自组装单层（SAM），然而，其经常遭受不均匀的键合构型和有限的质量。避免这些问题的合适平台是三蝶烯，它可以用三个底物特异性锚定基团装饰，并用一个或三个功能性尾基取代。沿着这些思路，分别选择硫醇和氰基作为锚定和尾部官能团，我们合成了1,8,13-三氰基-4,5,16-三巯基三蝶烯，并在Au(111)上制备了各自的SAM。这些 SAM 表现出致密的分子堆积和近乎完美的三齿吸附构型，所有三个硫醇盐基团均与基材结合。由于这种堆积，这些 SAM 中功能性尾基的密度接近于类似的单齿单分子层中的密度，对极性氰基基团具有类似的静电效应，但三足锚定提供了更好的鲁棒性。尾部基团和基底之间的电子通信通过吸附分子的各个叶片发生，并且几乎不受连接这些叶片的脂肪族桥的存在的影响，这一点通过电子转移动力学的测量得到证实。三个并行的电荷传输通道可实现与基板的有效电子耦合，这代表了基于三蝶烯的 SAM 在应用中的另一个优势。
Molecules with tripodal anchoring groups are generally capable of forming self-assembled monolayers (SAMs), which, however, frequently suffer from inhomogeneous bonding configurations and limited quality. A suitable platform to avoid these problems are triptycenes, which can be decorated with three substrate-specific anchoring groups and substituted with one or three functional tail groups. Along these lines, selecting thiol and cyano groups as the anchoring and tail functionalities, respectively, we synthesized 1,8,13-tricyano-4,5,16-trimercaptotriptycene and fabricated the respective SAMs on Au(111). These SAMs exhibit dense molecular packing and nearly perfect tridentate adsorption configuration, with bonding of all three thiolate groups to the substrate. Due to such a packing, the density of functional tail groups in these SAMs is close to that in the analogous monodentate monolayers, with a similar electrostatic effect for polar cyano groups but better robustness provided by the tripodal anchoring. The electronic communication between the tail groups and the substrate occurs through individual blades of the adsorbed molecules and is hardly affected by the presence of the aliphatic bridge connecting these blades, as verified by the measurements of electron transfer dynamics. Three parallel charge transport channels enable efficient electronic coupling to the substrate, representing an additional advantage of the triptycene-based SAMs for applications.