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Controlling the Self‐Metalation Rate of Tetraphenylporphyrins on Cu(111) via Cyano Functionalization
Author(s) -
Lepper Michael,
Köbl Julia,
Zhang Liang,
Meusel Manuel,
Hölzel Helen,
Lungerich Dominik,
Jux Norbert,
de Siervo Abner,
Meyer Bernd,
Steinrück HansPeter,
Marbach Hubertus
Publication year - 2018
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.201803601
Subject(s) - metalation , chemistry , scanning tunneling microscope , density functional theory , molecule , free base , surface modification , adsorption , activation energy , crystallography , computational chemistry , stereochemistry , nanotechnology , organic chemistry , materials science , salt (chemistry)
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.