High-pressure method can differentiate proton-coupled electron transfer mechanisms

Redox reactions form the basis of many fundamental processes of life. Without them, neither cellular respiration nor photosynthesis can occur. REDOX reactions also play an important role in applications in the use of light for chemistry, biochemistry domains and energy production. Therefore, understanding the basic principles of these reactions is important to pursue new techniques.

Using an innovative method based on high pressures, LMU chemist Professor Ivan Evanovic-Burmazovic and Fau Erlangen-Nurnberg, led by Professor Durk Guldy, have managed to separate two related response mechanisms for the first time. Research is Published In the journal Nature chemistry,

Balance between electrons and protons

In redox reactions, electrons are transferred between molecules. Because electrons have a negative charge, it can lead to changing the charge of the agents, which is demanding energetically. Nature has found an elegant solution to prevent this: often, the transfer of electrons is paired positively with the transfer of charged protons. This proton-eagled electron transfer (PCET), as it is known, does not produce any changes-the most efficient way to a redox response.

There are two potential mechanisms here: either electrons and protons are transferred together (“concerted”), or transfer in steepwaise fashion – it is to say that electrons and protons have been moved separately. “To be able to customize these processes, we need to know the exact mechanism,” called Ivanovic-Buramzovic. “Before now, however, there is no direct way to separate the two options with certainty. Our job determines it to remedy.”

Pressure answers

For their studies, the researchers examined the effect of pressure on light-inspired response very rapidly (within nanoconds) of a photosensitive molecule in the solution. It was already known that this molecule moves both protons and electrons to the same accepting molecules, but the exact course of these processes – mechanism – was unknown. “Our results suggest that measuring the effect of pressure at the response rate allows direct conclusions to be attracted to the mechanism,” Ivanovic-Bermazovic.

If high pressure – in use, up to 1,200 atmosphere – applies and the reaction rate remains unchanged, then it is a solid reaction. “When electrons and protons are moved together, the charge of the reaction species does not change nor the associated solution field–that is, the cluster of solvent molecules around the molecules. Therefore, there is no effect on the response rate of pressure-there is a clear indication of a solid system,” Ivanoviology-Bermagovi-poetry.

If the rate changes, however, it indicates the change in charge and the change in the volume of the solution area – reflects a phased process.

For their surprise, researchers were not only able to determine the type of mechanism, but also affect the process. “By increasing the pressure, we managed to advance the reaction from a solid mechanism to a solid mechanism,” called Ivanovic-Bermazovic.

New conclusions are highly important for many research fields that deal with electrons and protons speed, emphasizing writers. They provide new insight not only in fundamental chemical processes, but can also help in furthering new techniques related to conversion and storage of chemical energy – such as redox catalisis for a generation of solar fuel or for hydrogen production.