Electron powers a weak but significant bond for building complex
structures
Chemists use elementary particle to catalyze molecular recognition

Date:
March 18, 2022
Source:
Northwestern University
Summary:
How do you bring together two molecules that positively repel
each other? A research team has developed a simple and versatile
solution: Introduce an electron with a jolt of electricity, and
resistance between the two is reduced and a bond formed. This
fundamentally new type of catalysis will offer chemists and
biologists a tool for promoting and controlling molecular
recognition and self-assembly, enabling them to build complex
structures.



FULL STORY ==========================================================================
How do you bring together two molecules that positively repel each
other? A Northwestern University-led research team has developed a simple
and versatile solution: Introduce an electron with a jolt of electricity,
and resistance between the two is reduced and a bond formed.


==========================================================================
The bond between molecules is admittedly a weak one, of the noncovalent
form, but an important one. This kind of bond powers molecular
self-assembly, a process used by biology and now scientists to build
highly structured, stable and functional arrangements of molecules from
the bottom up.

This fundamentally new type of catalysis will offer chemists and
biologists a tool for promoting and controlling molecular recognition. New strategies can be designed to fine-tune noncovalent events, control
assembly at different length scales and ultimately create new forms
of complex matter for use in fields ranging from regenerative medicine
to electronics.

"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." Although widely
used in synthetic covalent chemistry,electron catalysis of molecular recognition and self-assembly processes is rare. Now Stoddart and
an international team of theoretical physicists and supramolecular,
physical and computational chemists have extended that concept to
noncovalent chemistry.

They are the first to use an electron as a catalyst beyond the molecule.

The study was published recently by the journal Nature.



========================================================================== Stoddart, a 2016 Nobel laureate in chemistry and creator of the mechanical bond, is a corresponding author of the paper. He is the Board of Trustees Professor of Chemistry in Northwestern's Weinberg College of Arts and
Sciences.

William A. Goddard III of the California Institute of Technology also
is a corresponding author.

Co-first authors are Yang Jiao, a postdoctoral fellow, and Yunyan Qiu,
a research assistant professor of chemistry, both in Stoddart's lab.

"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
bond that forms when two atoms share an electron pair between them. A noncovalent interaction does not involve the sharing of electrons but
instead depends on electromagnetic interactions between molecules or
within a molecule. In supramolecular chemistry, molecules are brought
together to create superstructures.

In the paper, the researchers describe how they have taken electron
catalysis beyond the molecule and into the realm of noncovalent and supramolecular chemistry. The formation of a complex between the two
positively charged molecules used in the study (one a large ring-shaped molecule, the other a dumbbell shaped molecule) is kinetically
forbidden. How to overcome the fact that like charges repel?


==========================================================================
The researchers' solution is to inject one electron. The electron lowers
the resistance between the two molecules, and the two get together to
form a new complex. Having done its job, the electron is released and,
in typical catalyst behavior, moves on to catalyze another process of
molecular recognition. It does this over and over again.

"Previously people cared about thermodynamics, and now we care more about kinetics," Qiusaid. "The best way to control kinetics is by catalysis,
and here we use the smallest particle, the electron." Electrons can be supplied by an electric current or reductant compounds.

In addition to its simplicity, there are advantages to the electron
catalysis approach, the researchers report. The method is not limited
to a specific reducing agent; it can be carried out with a variety of
different reagents.

Also, the electrochemical reduction eliminates the need for reagents
altogether and provides the ability to control the concentration
distribution of the components in the solution over time.

Stoddart is a member of the International Institute for Nanotechnology
and the Robert H. Lurie Comprehensive Cancer Center of Northwestern
University.


========================================================================== Story Source: Materials provided by Northwestern_University. Original
written by Megan Fellman. Note: Content may be edited for style and
length.


========================================================================== Journal Reference:
1. Yang Jiao, Yunyan Qiu, Long Zhang, Wei-Guang Liu, Haochuan Mao,
Hongliang
Chen, Yuanning Feng, Kang Cai, Dengke Shen, Bo Song, Xiao-Yang
Chen, Xuesong Li, Xingang Zhao, Ryan M. Young, Charlotte L. Stern,
Michael R.

Wasielewski, R. Dean Astumian, William A. Goddard, J. Fraser
Stoddart.

Electron-catalysed molecular recognition. Nature, 2022; 603 (7900):
265 DOI: 10.1038/s41586-021-04377-3 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/03/220318092136.htm

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