金属化
化学
扫描隧道显微镜
密度泛函理论
分子
自由基
表面改性
吸附
活化能
结晶学
物理化学
计算化学
立体化学
纳米技术
有机化学
材料科学
盐(化学)
作者
Michael Lepper,Julia Köbl,Liang Zhang,Manuel Meusel,Helen Hölzel,Dominik Lungerich,Norbert Jux,Abner de Siervo,Bernd Meyer,Hans‐Peter Steinrück,Hubertus Marbach
标识
DOI:10.1002/anie.201803601
摘要
The reaction rate of the self-metalation of free-base tetraphenylporphyrins (TPPs) on Cu(111) increases with the number of cyano groups (n=0, 1, 2, 4) attached at the para positions of the phenyl rings. The findings are based on isothermal scanning tunneling microscopy (STM) measurements. At room temperature, all investigated free-base TPP derivatives adsorb as individual molecules and are aligned with respect to densely packed Cu substrate rows. Annealing at 400 K leads to the formation of linear dimers and/or multimers via CN-Cu-CN bonds, accompanied by self-metalation of the free-base porphyrins following a first-order rate equation. When comparing the non-cyano-functionalized and the tetracyano-functionalized molecules, we find a decrease of the reaction rate by a factor of more than 20, corresponding to an increase of the activation energy from 1.48 to 1.59 eV. Density functional theory (DFT) calculations give insights into the influence of the peripheral electron-withdrawing cyano groups and explain the experimentally observed effects.
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