Zeng Zhiwen, Guo Dezhou, Wang Tao, Chen Qifan, Matěj Adam, Huang Jianmin, Han Dong, Xu Qian, Zhao Aidi, Jelínek Pavel, de Oteyza Dimas G, McEwen Jean-Sabin, Zhu Junfa
National Synchrotron Radiation Laboratory, Department of Chemical Physics and Key Laboratory of Surface and Interface Chemistry and Energy Catalysis of Anhui Higher Education Institutes, University of Science and Technology of China, Hefei 230029, P. R. China.
The Gene & Linda Voiland School of Chemical Engineering and Bioengineering, Washington State University, Pullman, Washington 99164, United States.
J Am Chem Soc. 2022 Jan 19;144(2):723-732. doi: 10.1021/jacs.1c08284. Epub 2021 Dec 29.
We report an example that demonstrates the clear interdependence between surface-supported reactions and molecular-adsorption configurations. Two biphenyl-based molecules with two and four bromine substituents, i.e., 2,2'-dibromobiphenyl (DBBP) and 2,2',6,6'-tetrabromo-1,1'-biphenyl (TBBP), show completely different reaction pathways on a Ag(111) surface, leading to the selective formation of dibenzo[,]pyrene and biphenylene dimer, respectively. By combining low-temperature scanning tunneling microscopy, synchrotron radiation photoemission spectroscopy, and density functional theory calculations, we unravel the underlying reaction mechanism. After debromination, a biradical biphenyl can be stabilized by surface Ag adatoms, while a four-radical biphenyl undergoes spontaneous intramolecular annulation due to its extreme instability on Ag(111). Such different chemisorption-induced precursor states between DBBP and TBBP consequently lead to different reaction pathways after further annealing. In addition, using bond-resolving scanning tunneling microscopy and scanning tunneling spectroscopy, we determine with atomic precision the bond-length alternation of the biphenylene dimer product, which contains 4-, 6-, and 8-membered rings. The 4-membered ring units turn out to be radialene structures.
我们报道了一个例子，该例子展示了表面支撑反应与分子吸附构型之间明显的相互依存关系。两个分别带有两个和四个溴取代基的联苯类分子，即2,2'-二溴联苯（DBBP）和2,2',6,6'-四溴-1,1'-联苯（TBBP），在Ag(111)表面呈现出完全不同的反应路径，分别导致二苯并[，]芘和联亚苯基二聚体的选择性形成。通过结合低温扫描隧道显微镜、同步辐射光电子能谱和密度泛函理论计算，我们揭示了潜在的反应机理。脱溴后，双自由基联苯可通过表面Ag原子稳定，而四自由基联苯由于其在Ag(111)上的极端不稳定性而发生自发的分子内环化。DBBP和TBBP之间这种不同的化学吸附诱导前驱体状态因此导致进一步退火后不同的反应路径。此外，使用键分辨扫描隧道显微镜和扫描隧道光谱，我们以原子精度确定了包含4元、6元和8元环的联亚苯基二聚体产物的键长交替。结果表明，4元环单元是环丙烯结构。
