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Organometallic Bonding in an Ullmann‐Type On‐Surface Chemical Reaction Studied by High‐Resolution Atomic Force Microscopy

The on‐surface Ullmann‐type chemical reaction synthesizes polymers by linking carbons of adjacent molecules on solid surfaces. Although an organometallic compound is recently identified as the reaction intermediate, little is known about the detailed structure of the bonded organometallic species and its influence on the molecule and the reaction. Herein atomic force microscopy at low temperature is used to study the reaction with 3,9‐diiododinaphtho[2,3‐b:2′,3′‐d]thiophene (I‐DNT‐VW), which is polymerized on Ag(111) in vacuum. Thermally sublimated I‐DNT‐VW picks up a Ag surface atom, forming a CAg bond at one end after removing an iodine. The CAg bond is usually short‐lived, and a CAgC organometallic bond immediately forms with an adjacent molecule. The existence of the bonded Ag atoms strongly affects the bending angle and adsorption height of the molecular unit. Density functional theory calculations reveal the bending mechanism, which reveals that charge from the terminus of the molecule is transferred via the Ag atom into the organometallic bond and strengths the local adsorption to the substrate. Such deformations vanish when the Ag atoms are removed by annealing and CC bonds are established.

High‐resolution atomic force microscopy with a functionalized CO tip allows us to observe inner structures of molecules. Here, a structural information of the organometallic bond formed on a Ag(111) surface is obtained at low temperature. The detailed behavior of the Ag atom to the molecular unit was in‐depth investigated.

Authors:   Shigeki Kawai, Ali Sadeghi, Toshihiro Okamoto, Chikahiko Mitsui, Rémy Pawlak, Tobias Meier, Jun Takeya, Stefan Goedecker, Ernst Meyer
Journal:   Small
Year:   2016
Pages:   n/a
DOI:   10.1002/smll.201601216
Publication date:   17-Aug-2016
Facts, background information, dossiers
  • molecules
  • atoms
  • adsorption
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