Research uncovers groundbreaking method of electron catalysis in noncovalent chemistry
Research has uncovered a groundbreaking method for hastening molecular recognition in supramolecular chemistry.
Catalysts are materials that increase the rate of, but are not consumed in chemical reactions. Often, catalysts are complex molecules with shapes finely tuned to match an intermediate structure known as a transition state between the reactant and product of the targeted reaction. However, this requires precise design and synthesis of the catalyst, a difficult and time consuming process. Another approach is the use of simple particles, protons and electrons, as catalysts, relying on the electrostatic interactions to allow reactants to surmount energy barriers more rapidly than otherwise possible. The use of electrons as catalysts of chemical reactions for the formation of covalent bonds is well established, but catalysis of molecular recognition and assembly – interactions that involve noncovalent bonds – is rare. The few existing examples of catalysts for these assembly reactions have relied on sophisticated catalyst design.
In a study published March 10, 2022 in the journal Nature, a team of scientists from six institutions around the world, including the University of Maine, described a simple and versatile strategy to facilitate molecular recognition using electrons as catalysts. The researchers found that the formation of a host–guest complex is accelerated 640-fold by introducing a chemical reducing agent as a source of electrons. The electrons lower the activation barrier for this process by decreasing the Coulombic repulsion between a ring compound and a dumbbell-shaped molecule, both of which are positively charged and hence repel each other.
“These results show the possibility of a very flexible approach to speed up assembly of a wide variety of molecular components,” says R. Dean Astumian, professor of physics and astronomy and co-author of the study.
Astumian explains that the addition of electrons can also be accomplished electrochemically, where the ability to turn the electricity on and off allows the reaction to be halted where the ratio between assembled and non-assembled molecules can be precisely set anywhere between all reactants and an equilibrium amount of reactants and products.
The research is a major breakthrough in both supramolecular chemistry and catalytic science. This approach is not limited to a specific reducing agent, and can instead be carried out with a variety of different reducing agents. Moreover, electrochemical reduction can eliminate the need for reducing agents altogether.
This new type of catalysis will inspire chemists and biologists to explore strategies that can be used to fine-tune noncovalent events, control assembly at different length scales and even create new forms of complex matter.
“The ability to fine tune the steady state levels of assembled and disassembled components allows a system to be set at its maximum sensitivity to an external change – temperature, pressure, proton concentration and more – opening up the possibility of designing optimally responsive sensors,” says Astumian.
Contact: Sam Schipani, firstname.lastname@example.org