On-Surface Synthesis of Multiple Cu Atom-Bridged Organometallic Oligomers

A metal–metal
bond between coordination complexes has the
nature of a covalent bond in hydrocarbons. While bimetallic and trimetallic
compounds usually have three-dimensional structures in solution, the
high directionality and robustness of the bond can be applied for
on-surface syntheses. Here, we present a systematic formation of complex
organometallic oligomers on Cu(111) through sequential ring opening
of 11,11,12,12-tetraphenyl-1,4,5,8-tetraazaanthraquino­dimethane
and bonding of phenanthroline derivatives by multiple Cu atoms. A
detailed characterization with a combination of scanning tunneling
microscopy and density functional theory calculations revealed the
role of the Cu adatoms in both enantiomers of the chiral oligomers.
Furthermore, we found sufficient strength of the bonds against sliding
friction by manipulating the oligomers up to a hexamer. This finding
may help to increase the variety of organometallic nanostructures
on surfaces.