Nanoscale wrench is just 1.7 nanometers wide

A blue wrench (of molecules) to adjust a green bolt (a pillarene ring) that binds a yellow chemical "guest."(Credit: Severin Schneebeli)

Envision a nanoscale wrench, capable of controlling shapes at the nanoscale level to create customized molecules. That's what Severin Schneebeli, a University of Vermont chemist and his team have developed. The opening on this mini wrench is only 1.7 nanometers, roughly a hundred-thousand-times smaller than the width of human hair.

To create the wrench, the scientists used a new approach called chirality-assisted synthesis, that allows them to specify the shapes of large molecules. A molecule that's chiral, has two identical forms that are mirror opposites of each other. Being able to minutely control the shapes of large molecules could help scientists create more complex medicines, polymers and other synthetic materials.

Schneebeli and his team created C-shaped strips of molecules by utilizing a coal-derived substance called anthracene. Resembling Legos, these strips fit with each other in a certain geometric orientation, giving it a specific shape. The resulting wrench retains its shape under a variety of conditions.

"It completely keeps its shape," Schneebeli explains, even in various solvents and at many different temperatures, "which makes it pre-organized to bind to other molecules in one specific way."

For instance, the wrench binds well with large molecules called pillarene macrocycles that are used to modify other chemicals, with potential applications that range from light-emitting substances to controlled drug delivery. The wrench allows chemists to remotely alter the chemical environments within the pillarene, in much the same manner that a mechanic might tweak an exterior bolt to adjust an engine's performance. Additionally the wrench makes the binding to the inside of the pillarene rings around a hundred times stronger.

The team conducted detailed simulations to evaluate exactly how the wrench would work. The fine control of the wrench's shape allowed them to know what might happen before they began synthesizing substances within the laboratory.

Going forward, the team plans to modify the C-shaped pieces to create other types of shapes. Currently the team is working on creating a spiral that's as flexible as a real spring but can retain its shape even when under stress.

"This helical shape could be super-strong and flexible," Schneebeli says. "It could create new materials, perhaps for safer helmets or materials for space. In the big picture, this work points us toward synthetic materials with properties that, today, no material has."

The team’s results were presented online recently, in the Journal Angewandte Chemie.

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