Scientists have confirmed a decades-old theory about the uneven distribution of electron density within aromatic molecules, opening up possibilities for designing new nanomaterials. This study builds on their previous work and utilized advanced scanning electron microscopy for subatomic resolution.
Researchers have experimentally tested the long-standing theory that electron density is unevenly distributed within aromatic molecules.
Researchers from IOCB Prague, the Institute of Physics of the Czech Academy of Sciences and Olomouc Palacký University have once again made great progress in unraveling the mysteries of the molecular and atomic world. They experimentally tested a long-standing theory suggesting that electron density is not uniformly distributed within aromatic molecules.
This phenomenon has a significant impact on the physicochemical properties of molecules and their interactions. This work expands the possibilities for designing new nanomaterials and is the subject of a recently published paper. nature communications.
The same author team as the previous groundbreaking study published in science We have discussed the uneven distribution of electrons in the body. atom, the so-called σ hole. Now researchers have confirmed the existence of so-called π holes. In aromatic hydrocarbons, electrons exist in clouds above and below the plane of the carbon atom. When the surrounding hydrogen is replaced by a more electronegative atom or group of atoms that pulls the electrons away, the originally negatively charged cloud turns into positively charged electron-holes.
![Pavel Khobza](https://scitechdaily.com/images/Pavel-Hobza-777x519.jpg 777w,https://scitechdaily.com/images/Pavel-Hobza-400x267.jpg 400w,https://scitechdaily.com/images/Pavel-Hobza-768x513.jpg 768w,https://scitechdaily.com/images/Pavel-Hobza-1536x1025.jpg 1536w,https://scitechdaily.com/images/Pavel-Hobza-2048x1367.jpg 2048w)
Professor Pavel Hobza, Special Chair and Head of the Non-Covalent Interactions Group at IOCB Prague;Credit: Tomáš Belloň / IOCB Prague
Scientists have taken the advanced method of scanning electron microscopy and pushed its capabilities even further. The method works at subatomic resolution, so it can image not only the atoms within a molecule, but also the structure of an atom’s electron shell. One of the researchers involved, Bruno de la Torre from the Czech Institute for Advanced Technology Research (CATRIN) at Olomouc Palacký University, attributes the success of the experiment described here primarily to the excellent facilities at his alma mater. Participating students of outstanding Ph.D.
“Thanks to our previous experience with Kelvin probe force microscopy (KPFM) technology, we have developed a very complete model that helps us refine our measurements and understand not only how charge is distributed within molecules. “We were able to obtain a dataset,” but also what observations can be made with this technique,” Bruno de la Torre said.
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Experimental measurements confirmed the theoretical prediction of the existence of π holes. From left to right: chemical structure of the investigated molecule, calculated electrostatic potential map of the molecule, experimental Kelvin probe force microscopy (KPFM) image, and simulated KPFM image.Credit: IOCB Prague
Modern force microscopy has long been the domain of researchers in physics laboratories. In addition to molecular structure, we took full advantage of unprecedented spatial resolution. Some time ago they confirmed the existence of an uneven distribution of electron density around halogen atoms, so-called σ holes. This result was published in his 2021 year. science. Previous and current research was significantly contributed by one of the most cited Czech scientists today, Professor Pavel Hovza of the Institute of Organic Chemistry and Biochemistry of the Czech Academy of Sciences (IOCB Prague).
“The confirmation of the existence of the π-hole and the σ-hole before it is ample proof of the quality of the theoretical predictions of quantum chemistry that have explained both phenomena for decades. This is because the available experimental Even if they don’t exist, it shows that they can be trusted,” says Pavel Khobza.
The results of Czech scientists’ research at the subatomic and submolecular level can be likened to the discovery of a cosmic black hole. It was also theorized for decades before experiments confirmed its existence.
Knowing more about the distribution of electron charge helps the scientific community understand many chemical and biological processes in the first place. At a practical level, it translates into the ability to construct new supramolecules and subsequently into the development of advanced nanomaterials with improved properties.
Reference: “Visualization of π-holes in molecules by Kelvin probe force microscopy” B. Mallada, M. Ondráček, M. Lamanec, A. Gallardo, A. Jiménez-Martín, B. de la Torre, P. Hobza and P. Jelinek, August 16, 2023; nature communications.
DOI: 10.1038/s41467-023-40593-3