“This is the first example of a molecular copper wire being formed in a stepwise, atom-by-atom process,” said Professor Julia Khusnutdinova, head of the OIST Coordination Chemistry and Catalysis Unit. “Our method can be compared to Lego construction in which you add one brick at a time.”
Also known as extended metal atom chains (EMACs), molecular wires have a range of potential uses, from LED lights to catalysts. Currently, the longest EMAC is based on nickel and contains 11 metal atoms in a single linear chain.
According to the team, creating molecular wires of different lengths is difficult because it requires a specific ligand to be synthesised each time. The ligand helps the wires to form by bringing the metal atoms together and aligning them into a linear string. However, creating ligands of different lengths can be an elaborate and complicated process.
The OIST researchers say they have overcome this problem. “We have created a single dynamic ligand that can be used to synthesise multiple chain lengths,” said Dr Orestes Rivada-Wheelaghan, first author of the paper. “This is more efficient than making a new ligand each time.”
“The ligand opens up from one end to let a metal atom enter and, when the chain extends, the ligand undergoes a sliding movement along the chain to accommodate more metal atoms,” said Prof Khusnutdinova. By adding or removing copper atoms one at a time in this way, the researchers can construct molecular wires of up to four copper atoms.
The team is now looking to develop dynamic ligands that could be used to create molecular wires made from other metals, or a combination of different metals. “For example, by selectively inserting copper atoms at the termini of the chain, and using a different type of metal at the centre of the chain, we could create new compounds with interesting electronic properties,” Prof Khusnutdinova concluded.
