Abstract
We demonstrate the bottom-up in-situ formation of organometallic oligomer chains at the single-molecule level. The chains are formed using the mechanically controllable break junction technique operated in a liquid environment, and consist of alternating isocyano-terminated benzene monomers coordinated to gold atoms. We show that the chaining process is critically determined by the surface density of molecules. In particular, we demonstrate that by reducing the local supply of molecules within the junction, either by lowering the molecular concentration or by adding side groups, the oligomerization process can be suppressed. Our experimental results are supported by ab-initio simulations, confirming that the isocyano terminating groups display a high tendency to form molecular chains, as a result of their high affinity for gold. Our findings open the road for the controlled formation of one-dimensional, single coordination-polymer chains as promising model systems of organometallic frameworks.
Highlights
Highly-ordered systems combining metal and organic components have recently generated a considerable interest for applications in catalysis, storage and sensing applications
The large influence of the local environment on the chain conformations largely dominates the microscopic dynamics of the growth process, resulting in chain-to-chain variations of the length, tacticity and comononer incorporation
We demonstrate the controlled formation, unit-by-unit, of single conductive coordination-oligomer chains, up to three units. Key to this achievement is the strong interaction of the isocyano groups with the gold electrodes which leads to a junction formation probability close to unity
Summary
Highly-ordered systems combining metal and organic components have recently generated a considerable interest for applications in catalysis, storage and sensing applications. Oligomerization has been achieved in molecular devices by the incorporation of metal ions between receptor molecules connected to metal[12] and graphene[13] electrodes or by means of click chemistry[14,15] In these cases the growth process was not monitored in real-time, and a stepwise addition of precursors was required. Key to this achievement is the strong interaction of the isocyano groups with the gold electrodes which leads to a junction formation probability close to unity This high affinity combined with the strongly dipolar nature of the isocyano anchor allow the molecules in a break junction system to form organometallic chains mediated by the incorporation of gold atoms. The chains are formed using mechanically controllable break junctions (MCBJ), and the chain formation is monitored in real-time by means of electrical characterization
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