Selecting the Reaction Path in On-Surface Synthesis through the Electron Chemical Potential in Graphene.
Selecting the Reaction Path in On-Surface Synthesis through the Electron Chemical Potential in Graphene.
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DOI：
10.1021/jacs.2c04359
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发表时间：
2022-06
影响因子：
15
通讯作者：
S. Kraus;A. Herman;Felix Huttmann;Christian Krämer;K. Amsharov;S. Tsukamoto;H. Wende;N. Atodiresei;T. Michely
中科院分区：
文献类型：
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作者：
S. Kraus;A. Herman;Felix Huttmann;Christian Krämer;K. Amsharov;S. Tsukamoto;H. Wende;N. Atodiresei;T. Michely
在接近电荷中性点的石墨烯(Gr)上，八元碳基环八碳四烯(C8H8，Cot)与相邻的稀土元素Yb和Tu的有机金属表面合成得到了两种不同的产物。由Yb原子和竖立的CoT分子交替排列而成的长度超过500？的三明治分子YbCot丝是由Yb表面合成得到的。相反，由一个CoT分子和一个Tm原子组成的排斥相互作用的TmCot点是由Tm表面合成的结果。虽然YbCot导线通过van der Waals相互作用与衬底结合，但与Yb原子相比，Tm原子更具正电性，从而将点化学吸附到Gr上。当Gr中的电子化学势通过插层背面掺杂而显著提高(n掺杂)时，与Tm合成的反应产物可以被调谐为TmCot三明治分子线而不是TmCot点。用密度泛函理论研究发现，n掺杂后Gr的电负性降低，削弱了反应中间体TmCot点与Gr之间的结合和电荷转移。因此，将TmCot点组装成长的TmCot三明治分子线在能量上是有利的。由此证明，Gr中的电子化学势可以作为有机金属表面合成的控制参数来调节反应的结果。
The organometallic on-surface synthesis of the eight-membered sp2 carbon-based ring cyclooctatetraene (C8H8, Cot) with the neighboring rare-earth elements ytterbium and thulium yields fundamentally different products for the two lanthanides, when conducted on graphene (Gr) close to the charge neutrality point. Sandwich-molecular YbCot wires of more than 500 Å length being composed of an alternating sequence of Yb atoms and upright-standing Cot molecules result from the on-surface synthesis with Yb. In contrast, repulsively interacting TmCot dots consisting of a single Cot molecule and a single Tm atom result from the on-surface synthesis with Tm. While the YbCot wires are bound through van der Waals interactions to the substrate, the dots are chemisorbed to Gr via the Tm atoms being more electropositive compared to Yb atoms. When the electron chemical potential in Gr is substantially raised (n-doping) through backside doping from an intercalation layer, the reaction product in the synthesis with Tm can be tuned to TmCot sandwich-molecular wires rather than TmCot dots. By use of density functional theory, it is found that the reduced electronegativity of Gr upon n-doping weakens the binding as well as the charge transfer between the reaction intermediate TmCot dot and Gr. Thus, the assembly of the TmCot dots to long TmCot sandwich-molecular wires becomes energetically favorable. It is thereby demonstrated that the electron chemical potential in Gr can be used as a control parameter in an organometallic on-surface synthesis to tune the outcome of a reaction.