3-D aromaticity is not as usual as it may seem

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The aromaticity of 3-D closo boranes, zintl ions, and charged fullerenes is widely accepted. On the other hand, several fully p-conjugated macrocycles with puckered or cage-type structures were recently found to exhibit aromatic character according to both experiments and computations. We examine their electronic structures and put them in relation to 3D-aromatic molecules (e.g., closo-boranes) and to 2D-aromatic polycyclic aromatic hydrocarbons. Using qualitative theory combined with quantum chemical calculations, we find that the macrocycles explored hitherto should be described as 2D-aromatic with three-dimensional molecular structures (abbr. 2D-aromatic-in-3D) and not as truly 3D-aromatic. We establish the conditions that have to be fulfilled to classify a compound as 3D-aromatic. Indeed, we show that it is not easy to design new 3D-aromatic compounds. This work was carried out by Dr. Ouissam El Bakouri, Dr. Kjell Jorner, Dr. Rabia Ayub and Prof. Henrik Ottosson from the Ångström Laboratory of the Uppsala University, Prof. Patrick Bultinck from the Department of Chemistry of Chent University and Dr. Dariusz W. Szczepanik and Prof. Miquel Solà from the DiMoCat group of the Institute of Computational Chemistry and Catalysis of the University of Girona

El Bakouri, D. W. Szczepanik, K. Jorner, R. Ayub, P. Bultinck, M. Solà* and H Ottosson*. Three-Dimensional Fully p-Conjugated Macrocycles: When 3D-Aromatic and when 2D-Aromatic-in-3D? J. Am. Chem. Soc., 2022, DOI: 10.1021/jacs.1c13478.

The article has been highlighted and discussed in the following entry of Chemistry World:

Many molecules mislabelled as 3D aromatic

 

Photoinduced Reactions of C60 and C70 in Water

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Three types of water-soluble fullerene derivatives were prepared from their Prato adducts by conjugation with PEG. One Prato derivative of C60 ([6,6]-addition) and two Prato derivatives of C70 (ab-[6,6] and cc-[6,6]-addition) with carboxylic acids were synthesized, purified and subjected to the amide-forming conjugation with amine-PEG to form corresponding C60– or C70-PEG conjugates. All the conjugates showed photoinduced DNA cleavage by reactive oxygen species (ROS) formed by type II energy transfer pathway or type I electron transfer pathway.

The responsible ROS were measured by ESR spin-trapping methods using 4-oxo-TEMP (for singlet oxygen) and DEPMPO (for superoxide radical anion), and were shown to be significantly different in three materials.  To understand the mechanism of these differences, redox potentials of the precursor molecules were analyzed by cyclic voltammetry in order to determine the difference in electron transfer rates. The lifetimes of the triplet excited states were measured by laser-flash photolysis.  Finally, calculations were performed in the DiMoCat group by Dr. Anton Stasyuk, Prof. Alexander Voityuk and Prof. Miquel Solà to obtain rate constants for each step in the type I and II pathways.

The paper has been highlighted by the Spanish Biophysical Society (https://sbe.es/paperhighlights-oct2021-2/).

The paper can be read in JACS Au journal through the following link:

https://pubs.acs.org/doi/10.1021/jacsau.1c00239

Sergi Posada-Pérez, Juan de la Cierva-formación researcher at the Institute of Computational Chemistry and Catalysis

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Starting 1st July 2021, Sergi Posada-Pérez has become a Juan de la Cierva-formación postdoc researcher of the Institute of Computational Chemistry and Catalysis (IQCC) working in the DiMoCat group.

Sergio Posada-Pérez received his BSc in Chemistry and MSc in Theoretical Chemistry from the Rovira and Virgili University. The Master thesis was carried out under the supervision of Prof. Josep Maria Poblet and Dr. Anna Clotet and it was graded as excellent.

His PhD studies, supervised by Prof. Francesc Illas and Dr. Francesc Viñes, were focused on environmental chemistry, developing new cost-effective catalysts to convert harmful greenhouse effect gases to valuable compounds by means of ab initio computations. The most remarkable achievement of his thesis was to discover an excellent and promising catalyst for green chemistry reactions, especially for the CO2 hydrogenation reaction towards CO and methanol. During his thesis, he published 10 papers (9 of them as first author). In addition, the thesis was graded as Excellent “cum laude” and he received the extraordinary PhD mention award 2017-2018. During his Ph.D. he also did two internships (with a total duration of 6 months) in two research groups with international reputation in his research field. The first one, was in the group of Dr. José Rodriguez at Brookhaven National Laboratory, interacting first-hand with experimental partners. As a result of this internship, two peer-reviewed articles were published in JACS and Catalysis, Science & Technology (including one backcover). The second stay was in the group of Prof. Nora de Leeuw, at the Cardiff University, where he conducted a new research project about the CO2 reduction reaction on Iron/nickel sulfides, published in PCCP in 2018.

From June 2018 till June 2021, he conducted postdoctoral research in the group of Prof. Geoffroy Hautier at Université Catholique de Louvain. He carried out a research project that allowed him to underpin the mechanisms and factors that govern the water interaction with several well-known cathode materials for Li-ion rechargeable aqueous batteries by means of computational simulations.

During his postdoc in the IQCC, he will study the molecular structure and charge transfer processes of hybrid fullerene:perovskite solar cells. His large experience using the VASP program will be very helpful!

We wish him good luck and great success in his research work at DiMoCat!

Jesús Antonio Luque Urrutia wins the second prize for the best Spanish computational paper in 2020

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On 19th May 2021, the evaluation committee of the prizes to the best articles produced by Spanish PhD students in the area of Chemistry and Computation in 2020 were announced by the Computation and Chemistry specialized group of the Spanish Royal Society of Chemistry. To our delight, Dr. Jesús Antonio Luque Urrutia, former member of our research group, won the second prize with the paper:

Jesús Antonio Luque-Urrutia, Albert Poater, Miquel Solà
Do carbon nano-onions behave as nanoscopic Faraday cages? A comparison of the reactivity of C60, C240, C60@C240, Li+@C60, Li+@C240, and Li+@C60@C240
Chem. Eur. J., 2020, 26, 804-808
DOI: 10.1002/chem.201904650

Congratulations Xus!

This paper corresponds to the last chapter of the PhD thesis defended by Dr. Luque on 26th March 2021. If you are interested you can see his defense at:

https://www.twitch.tv/videos/1025916063?t=0h0m39s

Two recent DiMoCat works highlighted by ChemistryWorld

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ChemistryWorld has recently highlighted two works of our group:

The jellium model assumes a uniform distribution of positive charge corresponding to the cluster atomic nuclei and their innermost electrons in which the interacting valence electrons move. The energy levels of valence electrons for such a model are 1S21P61D102S21F142P61G182D103S2…, where S, P, D, F, and G letters denote the angular momentum and numbers 1, 2, 3 indicate the radial nodes. The abundance found in experimental mass spectra of alkali, alkaline earth metals, and gold clusters of 2, 8, 18, 20, 34, 40… atoms are justified taken into account that these numbers correspond to closed-shell electronic structures in the jellium model. We have proven that if the last energy level of valence electrons for the jellium model is half-filled with same-spin electrons, the system has also an aromatic character that provides extra stability. This situation is reached for the magic numbers of valence electrons of 1 (S =1/2), 5 (S = 3/2), 13 (S = 5/2), 19 (S = 1/2), 27 (S = 7/2), 37 (S = 3/2), 49 (S = 9/2)… This new set of magic numbers may become a powerful tool for researchers who work in the quest for stable single high-spin molecules for their use as single-molecule based magnets. The paper has been published in Chem. Commun. and can be found in the following link Chem. Commun., 55 (2019) 5559-5562.

In this recent Chem. Commun. paper, we have proved that C18 (a cycle of 18 carbon atoms connected with alternating single and triple bonds) it is an electron acceptor of similar characteristics as C60. C18  when coupled with a range of donor molecules can readily accept electrons. Electron acceptors are important components in molecular electronic devices and solar cells, and, therefore, C18 is added to the list of organic electron acceptors that can be potentially useful in photovoltaics.

Angew. Chem. Int. Ed. Inside Cover describing the first All-fullerene Electron Donor-Acceptor Conjugates

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Photoinduced electron transfer (PET) is a general nature occurring process which is related with the photosynthetic process. Scientists have always been interested in mimicking this process from artificial molecules in the search for controlling and tuning this process for practical purposes. The appropriate molecules and materials have been an important task in science. The aforementioned mimicking of the photosynthetic process requires the presence of appropriate electron donor molecules interacting (covalently or supramolecularly) with electron acceptor molecules. Light irradiation promotes the electron transfer from the donor to the acceptor units. Fullerenes are amazing ball-shape molecules formed exclusively by carbon atoms which are known to exhibit interesting electron accepting properties. Therefore, they have been extensively used in Donor-Acceptor systems.

A group of chemists from the Universidad Complutense de Madrid lead by Prof. Nazario Martín together with a group of researchers from the Friederich-Alexander Univesität Erlangen-Nürnberg lead by Dirk M. Guldi, and the DiMoCat members Antony J. Stasyuk, Olga A. Stasyuk, Alexander A. Voityuk, and Miquel Solà have shown the first example in which fullerenes, depending on their features, are able to act as acceptor but also as donor components in artificial photosynthetic systems. Furthermore, they have described the first example in which light irradiation promotes de electron transfer from the donor Lu3N@C80 to the acceptor C60 giving rise to a charge separated state involving two fullerene cages!

The paper has been published in Angew. Chem. Int. Ed. And can be found in the following link Angew. Chem. Int. Ed., 58 (2019) 6932-6937. The inside cover of the issue has been dedicated to this work: