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The end of the Theory of a Chemistry Nobel Prize?

21 AUGUST 2018

The well-known theory of Marcus, the theory that explains the transfer of electrons in chemical reactions, was invalidated by a team of scientists of the Faculty of Sciences and Technology of the University of Coimbra (FCTUC), led by Professor Luís Arnaut.

The scientific paper recently published in the reputable Nature Communications (Nature group) proves beyond any doubt that the theory developed in 1956 by Rudolph Arthur Marcus, which earned him the Nobel Prize for Chemistry in 1992, is wrong.

The issue lies in the reorganization of molecules required for the transfer of electrons. For this type of chemical reactions to occur, Marcus's theory predicts that this reorganization has to be mainly done in solvents, but the study now published says that it is not so, showing that the key to electron transfer is in the reagents.

This discovery is the peak of two and a half decades of studies developed in the Department of Chemistry of the Faculty of Sciences and Technology, which generated much controversy within the scientific community along the way. The great enabler of all this research was the Chemist Formosinho Simões (FCTUC Professor, who died in December 2016), who has always questioned Marcus's theory.

“Doctor Formosinho Simões argued that the key to electron transfer was in the reagents, but there was no crucial experimental evidence to contradict Marcus's theory because Marcus was a highly credible researcher and his theory was awarded the Nobel Prize for Chemistry in 1992”, claims Luís Arnaut.

Faced with these two radically opposed views on this chemical reaction, Luís Arnaut "gathered in 1993 the most prominent chemists in the world at a NATO workshop in Portugal to discuss the problem. Besides Formosinho Simões, nobody dared to question the Nobel Prize. It was a very intensive discussion," said Arnaut. 

However, the Coimbra team did not give up and advanced alone in the conception of experiments that allowed to determine which of the two theories was correct. It took them 25 years: "It was an extremely difficult task. We had to conceive, design and implement a wide range of studies and experiences. There are many reasons that justify so many years of study, including the need for highly sophisticated equipment that we did not have, the need to synthesize molecules that did not exist and the hiring of highly qualified staff to develop the work ", stresses Luís Arnaut.

In addition to all these difficulties, the FCTUC scientists had to face criticism from the scientific community, who insisted on not accepting that a Chemistry Nobel could be wrong. Finally, in 2014, after a long and winding road, the team of Formosinho Simões and Luís Arnaut met the appropriate conditions to conduct "the decisive experience. The results were complete at the end of last year (2017). We submitted the scientific paper to the Nature group and, once again, the controversy was inevitable, "says the study's coordinator.

However, the arguments of the FCTUC researchers eventually convinced the reviewers of the magazine and the article was published this Wednesday (July 25). Asked about what the reaction of the scientific community may be, Luís Arnaut believes that "perhaps they will be bewildered because what is written in the article goes against the flow. It clearly states that Marcus's theory does not work. "

As for the practical implications of this new theory – called the "Intersecting-State Model " – the Professor comments: "I do not think that suddenly the theory developed in Coimbra will allows us to produce a product that reaches the market with advantages over existing ones. It took us 25 years to conduct this experiment, so it is expected that it will take many years to develop systems in a different way. However, our model can inspire better solutions in areas where electron transfer is important. "

Electron transfer reactions are the basis of oxidation-reduction reactions, occurring in biological systems such as photosynthesis and respiration, as well as in solar panels, conductive polymers used in televisions and computers, optoelectronics ", among others.