The mechanism by which oxygen binds to metallo-porphyrins is an essential process in organisms that breathe oxygen as well as in catalysis processes
The mechanism by which oxygen binds to metallo-porphyrins is an essential process in organisms that breathe oxygen. Understanding the mechanism by which small gas molecules chemically bind to a metallic conjugate is also important for catalysis processes and in the field of chemical sensors. When studying these binding mechanisms, scientists use porphyrin rings with a core of an iron or cobalt atom.
An important characteristic of porphyrin rings (the term in Wikipedia) is their spatial flexibility. Recent research has shown that each specific geometrical configuration of metallo-porphyrins (porphyrins containing metal) has a different effect on their function. Based on the available scientific information, the researchers expected that only one molecule of carbon monoxide would bind to the central metal atom. However, detailed experiments using a scanning tunneling microscope (STM) made by the researcher Knud Seifert revealed that, in fact, two gas molecules are positioned between the central metal atom and between the two nitrogen atoms that are opposite. In this situation, the coupling structure is a kind of saddle, where the gas molecules Taking the position of the rider.
The importance of the saddle configuration became apparent following theoretical calculations performed by a researcher from the University of Lyon. The researcher's theoretical analysis helped the researchers to understand in detail the new binding mechanism. In addition, the model showed that the configuration of the molecular saddle remains stable, even after the binding of two molecules the gas to porphyrin.
The porphyrins reacted completely differently when the researchers replaced the carbon monoxide with the stronger binding molecule, nitric oxide. As expected, this molecule bound directly to the central metal atom with only one molecule occupying each porphyrin ring. This arrangement leads to a significant effect on the electronic structure of the carrier molecule, and the saddle configuration becomes flatter. That is - porphyrins react in a completely different way with different types of gas - a finding that can be important for the development of possible applications, such as sensors.
Explains one of the researchers: "The novelty of our findings is that we were able to show, for the first time ever, the binding mechanism at the molecular level. We are even able to selectively transfer individual gas molecules from one porphyrin to another."
The research group intends to use these findings to explain the chemical processes that occur on surfaces in nanostructures. When the solutions to these basic questions are found, the researchers will turn to new challenges: What is the effect of the central atom? How does the way of linking change in a planar configuration? In order to develop efficient catalysts and sensors using controlled charge transitions.
