A Lego-Brick Approach To Creating Molecular Wires

Using a dynamic ligand to string together copper atoms one at a time, researchers in Japan have managed to build molecular copper wires of varying lengths.

AsianScientist (Jan. 26, 2018) – A team of researchers in Japan has created molecular wires that can be used to develop minuscule electronic devices. Their findings are published in the journal Angewandte Chemie International Edition.

Electronic devices are getting smaller and smaller. Early computers filled entire rooms. Today, you can hold one in the palm of your hand. Researchers are now creating electronic components so tiny that they cannot be seen with the naked eye.

Molecular electronics is a branch of nanotechnology that uses single molecules, or nanoscale collections of molecules, as electronic components. The purpose is to create miniature computing devices, replacing bulk materials with molecular blocks.

For instance, metal atoms can be made into nanoscale ‘molecular wires.’ Also known as extended metal atom chains (EMACs), molecular wires are one-dimensional chains of single metal atoms connected to an organic molecule, called a ligand, that acts as a support. Molecular wire-type compounds have a diverse array of potential uses, from LED lights to catalysts.

In this study, researchers at the Okinawa Institute of Science and Technology Graduate University (OIST) in Japan have found a simple way to create copper molecular wires of different lengths by adding or removing copper atoms one by one.

“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.”

Molecular wires can vary in length, with different lengths having different molecular properties and practical applications. At present, the longest EMAC reported in the literature is based on nickel and it contains 11 metal atoms in a single linear chain.

Creating molecular wires of different lengths is difficult because it requires a specific ligand to be synthesized each time. The ligand, which is analogous to an ‘insulator’ in the macro world, 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 found a way to simplify the process by introducing a ligand with dynamic properties, enabling the continuous synthesis of multiple chain lengths.

“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,” Khusnutdinova added. This can be likened to a molecular accordion that can be extended and shortened.

By adding or removing copper atoms one at a time in this way, the researchers can construct molecular wires of different lengths, varying from one to four copper atoms. Their ligand and method offers a new way for chemists to synthesize molecules with specific shapes and properties, paving the way for many practical applications in microelectronics and beyond.

“The next step is to develop dynamic ligands that could be used to create molecular wires made from other metals, or a combination of different metals,” said Rivada-Wheelaghan.

“For example, by selectively inserting copper atoms at the termini of the chain, and using a different type of metal at the center of the chain, we could create new compounds with interesting electronic properties,” Khusnutdinova explained.

The article can be found at: Rivada-Wheelaghan et al. (2017) Controlled and Reversible Stepwise Growth of Linear Copper(I) Chains Enabled by Dynamic Ligand Scaffolds.


Source: Okinawa Institute of Science and Technology Graduate University.
Disclaimer: This article does not necessarily reflect the views of AsianScientist or its staff.

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