How do you bring two molecules that are attracted to each other yet repel each other? A research team lead by Northwestern University has devised a simple and adaptable solution: The resistance between the two is lowered and a bond is created when an electron is introduced with a jolt of electricity.
The noncovalent bond between molecules is somewhat weak, but it is a crucial one. This type of interaction is responsible for molecular self-assembly, a process utilized by biology and scientists to form highly organized, stable, and useful molecule groupings from the bottom up.
Chemists and biologists will be able to use this brand-new sort of catalysis to promote and govern molecular recognition. New tactics for fine-tuning noncovalent processes, controlling assembly at different length scales, and ultimately creating new forms of complex matter for use in disciplines ranging from regenerative medicine to electronics can be devised.
“This work represents a major breakthrough in both supramolecular chemistry and catalytic science,” said Northwestern’s Sir Fraser Stoddart, an expert in molecular recognition and self-assembly processes. “It facilitates the coming together of molecules in a highly organized way, which is critical in building complex structures.”
Electron catalysis of molecular recognition and self-assembly processes is uncommon, despite its widespread application in synthetic covalent chemistry. Stoddart and an international team of theoretical physicists, supramolecular, physical, and computational chemists have now taken that concept and applied it to noncovalent chemistry. They are the first to use an electron outside of a molecule as a catalyst.
The journal Nature published recently the study.
This work is about using the electron, an elemental particle, to catalyze the molecular recognition process. Molecular recognition and self-assembly are the foundation of many valuable functions and materials. We have figured out a way to promote and control these processes at the most fundamental of levels. Areas such as nanotechnology, chemical biology, and materials science stand to benefit from our catalysis.
Yang Jiao
The paper’s corresponding author is Stoddart, a 2016 Nobel Laureate in Chemistry and the inventor of the mechanical bond. In Northwestern’s Weinberg College of Arts and Sciences, he is the Board of Trustees Professor of Chemistry. A corresponding author is William A. Goddard III of the California Institute of Technology.
Yang Jiao, a postdoctoral researcher, and Yunyan Qiu, a research assistant professor of chemistry at Stoddart’s group, are co-first authors.
“This work is about using the electron, an elemental particle, to catalyze the molecular recognition process,” Jiao said. “Molecular recognition and self-assembly are the foundation of many valuable functions and materials. We have figured out a way to promote and control these processes at the most fundamental of levels. Areas such as nanotechnology, chemical biology and materials science stand to benefit from our catalysis.”
A covalent bond is a type of chemical link formed when two atoms share the same electron pair. Noncovalent interactions rely on electromagnetic interactions between molecules or within a molecule rather than the exchange of electrons.
Molecules are brought together to form superstructures in supramolecular chemistry. The researchers detail how they have extended electron catalysis beyond the molecule into noncovalent and supramolecular chemistry in their publication.
Kinetically, the development of a complex between the two positively charged molecules used in the study (one a big ring-shaped molecule, the other a dumbbell-shaped molecule) is prohibited. How can you get around the fact that like charges repel each other?
The approach proposed by the researchers is to inject one electron. The electron lowers the resistance between the two molecules, causing them to combine and form a new complex.
After completing its task, the electron is liberated and moves on to catalyze another molecular recognition process, as is characteristic of a catalyst. This happens again and over again.
“Previously people cared about thermodynamics, and now we care more about kinetics,” Qiu said. “The best way to control kinetics is by catalysis, and here we use the smallest particle, the electron.”
An electric current or reductant compounds can supply electrons.
The electron catalysis strategy has advantages in addition to its simplicity, according to the researchers. The approach is not restricted to a single reducing agent; it can be used with a wide range of reagents.
Furthermore, the electrochemical reduction eliminates the requirement for reagents and allows for the control of the concentration distribution of the solution’s components throughout time.
