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The influence of different (LRu)nII (L=Cp– (n=1, 2); C6H6) moieties η6‐coordinated to corannulene ((CpRu)+, (Benzene)Ru2+ and (CpRu)22+) has been explored by using the Activation Strain Model (ASM) of reactivity together with the Energy Decomposition Analysis (EDA) scheme. The results obtained have been compared with those obtained for the non‐coordinated corannulene counterpart. It has been observed that the presence of the ruthenium moiety favors both kinetically and thermodynamically the [4+2]‐cycloaddition reaction with cyclopentadiene. The factors governing these differences depend on the nature of the [Ru] complex. Whereas the interaction energy is solely responsible for the lower activation energy for the monocationic system (CpRu)+, not only the higher interaction but also the lower strain energy explain the much higher reactivity observed for the dicationic systems ((C6H6)Ru2+ and (CpRu)22+). In this latter case, the Pauli repulsion energy term is the factor controlling the differences in the interaction energies, following the so‐called Pauli repulsion‐lowering concept. Finally, when η6‐coordinating mono‐ or dicationic ruthenium complexes, although the [4+2]‐cycloaddition reaction in the external rim bonds remains the thermodynamically and kinetically more favourable, the cycloaddition becomes also thermodynamically feasible in some internal bonds. [ABSTRACT FROM AUTHOR]

We present a straightforward and low-cost computational protocol to estimate the variation of the charge transfer rate constant, kCT, in a molecular donor–acceptor caused by an external electric field. The proposed protocol also allows for determining the strength and direction of the field that maximize the kCT. The application of this external electric field results in up to a >4000-fold increase in the kCT for one of the systems studied. Our method allows the identification of field-induced charge-transfer processes that would not occur without the perturbation caused by an external electric field. In addition, the proposed protocol can be used to predict the effect on the kCT due to the presence of charged functional groups, which may allow for the rational design of more efficient donor–acceptor dyads. [ABSTRACT FROM AUTHOR]

In this study we present a method for functionalizing C60 through a Rh‐catalyzed cyclization reaction with 1,6‐enynes, resulting in the formation of a fused bicyclic structure. Additionally, fullerene derivatives are further functionalized through regioselective photooxygenation reactions. Our DFT calculations reveal two distinct reaction pathways: one involving rhodium‐catalyzed cycloisomerization of the enyne followed by Diels‐Alder with C60, and the other featuring a rhodium‐catalyzed [2+2+2] cycloaddition of enyne and C60 followed by isomerization. Surprisingly, both pathways exhibit nearly identical energy barriers. However, experimental tests indicate that the predominant pathway varies depending on the substitution motifs of the substrates. [ABSTRACT FROM AUTHOR]

We have quantum chemically investigated the boron‐boron bonds in B2, diborynes B2L2, and diborenes B2H2L2 (L=none, OH2, NH3) using dispersion‐corrected relativistic density functional theory at ZORA‐BLYP‐D3(BJ)/TZ2P. B2 has effectively a single B−B bond provided by two half π bonds, whereas B2H2 has effectively a double B=B bond provided by two half π bonds and one σ 2p–2p bond. This different electronic structure causes B2 and B2H2 to react differently to the addition of ligands. Thus, in B2L2, electron‐donating ligands shorten and strengthen the boron‐boron bond whereas, in B2H2L2, they lengthen and weaken the boron‐boron bond. The aforementioned variations in boron‐boron bond length and strength become more pronounced as the Lewis basicity of the ligands L increases. [ABSTRACT FROM AUTHOR]

Aqueous lithium‐ion batteries (ALIBs) are attracting significant attention as promising candidates for safe and sustainable energy storage systems. This paper delves into the crucial aspects of ALIB technology focusing on the interaction between LiCoO2 (lithium cobalt oxide) cathode material and water electrolytes, with a specific emphasis on the Oxygen Evolution Reaction (OER) process. Fundamental understanding of the electrochemical behavior of LiCoO2 in aqueous electrolytes is crucial for enhancing the performance, safety, and longevity of ALIBs using LiCoO2 as the cathode material. Through a comprehensive periodic density functional analysis of the LiCoO2‐water at the cathode interface, the potential catalytic contributions to the OER mechanism of LiCoO2 are explored. The catalytic properties of LiCoO2 towards OER are investigated considering different steady states of the lowest energy surfaces of LiCoO2 and three different Li concentrations. Our results do not predict the formation of oxygen gas due to the expected large overpotentials, although the exergonic water decomposition to hydroxyl by means the first proton‐electron transfer is predicted at equilibrium potential. This work contributes to the fundamental understanding of LiCoO2 as cathode for aqueous lithium‐ion batteries, reporting the pros and cons of one of the most common cathode materials for traditional non‐aqueous batteries. [ABSTRACT FROM AUTHOR]

Nowadays, an active research topic is the connection between Clar's rule, aromaticity, and magnetic properties of polycyclic benzenoid hydrocarbons. In the present work, we employ a meticulous magnetically induced current density analysis to define the net current flowing through any cyclic circuit, connecting it to aromaticity based on the ring current concept. Our investigation reveals that the analyzed polycyclic systems display a prominent global ring current, contrasting with subdued semi‐local and local ring currents. These patterns align with Clar's aromatic π‐sextets only in cases where migrating π‐sextet structures are invoked. The results of this study will enrich our comprehension of aromaticity and magnetic behavior in such systems, offering significant insights into coexisting ring current circuits in these systems. [ABSTRACT FROM AUTHOR]

The homolytic elimination of two H atoms from two adjacent carbons in benzene results in the aromatic product o‐benzyne. In a similar way, the homolytic elimination of two H atoms from the two adjacent carbons in 1,2‐C2B10H12 results in the aromatic product o‐carboryne. In this work, we provide experimental and computational evidences that despite the similarity of o‐carboryne and o‐benzyne, the nature of the C−C bond generated between two adjacent carbons that lose H atoms is different. While in o‐benzyne the C−C bond behaves as a triple bond, in o‐carboryne the C−C bond is a double bond. Therefore, we must stop naming 1,2‐dehydro‐o‐carboryne as o‐carboryne but instead call it o‐carborene. [ABSTRACT FROM AUTHOR]

The aim of this work is to investigate the influence of the ethanol content of adducts on the catalytic behavior of related Ziegler–Natta (ZN) catalysts in propylene homo- and copolymerizations (with 1-hexene comonomer) in terms of activity, isotacticity, H2 response, and comonomer incorporation. For this purpose, three MgCl2.nEtOH adducts with n values of 0.7, 1.2, and 2.8 were synthesized and used in the synthesis of related ZN catalysts. The catalysts were thoroughly characterized using XRD, BET, SEM, EDX, N2 adsorption–desorption, and DFT techniques. Additionally, the microstructure of the synthesized (co)polymers was distinguished via DSC, SSA, and TREF techniques. Their activity was found to enhance with the adduct's ethanol content in both homo- and copolymerization experiments, and the increase was more pronounced in homopolymerization reactions in the absence of H2. Furthermore, the catalyst with the highest ethanol content provided a copolymer with a lower isotacticity index, a shorter meso sequence length, and a more uniform distribution of comonomer within the chains. These results were attributed to the higher total surface area and Ti content of the corresponding catalyst, as well as its lower average pore diameter, a larger proportion of large pores compared to the other two catalysts, and its spherical open bud morphology. It affirms the importance of catalyst/support ethanol-content control during the preparation process. Then, molecular simulation was employed to shed light on the iso-specificity of the polypropylene produced via synthesized catalysts. [ABSTRACT FROM AUTHOR]

Synthetic strategies to access high‐valent iridium complexes usually require use of π donating ligands bearing electronegative atoms (e. g. amide or oxide) or σ donating electropositive atoms (e. g. boryl or hydride). Besides the η5‐(methyl)cyclopentadienyl derivatives, high‐valent η1 carbon‐ligated iridium complexes are challenging to synthesize. To meet this challenge, this work reports the oxidation behavior of an all‐carbon‐ligated anionic bis(CCC‐pincer) IrIII complex. Being both σ and π donating, the diaryl dipyrido‐annulated N‐heterocyclic carbene (dpa‐NHC) IrIII complex allowed a stepwise 4e− oxidation sequence. The first 2e− oxidation led to an oxidative coupling of two adjacent aryl groups, resulting in formation of a cationic chiral IrIII complex bearing a CCCC‐tetradentate ligand. A further 2e− oxidation allowed isolation of a high‐valent tricationic complex with a triplet ground state. These results close a synthetic gap for carbon‐ligated iridium complexes and demonstrate the electronic tuning potential of organic π ligands for unusual electronic properties. [ABSTRACT FROM AUTHOR]

Beryllium is a metallomimetic main-group element, i.e., it behaves similarly to transition metals (TMs) in some bond activation processes. To investigate the ability of Be compounds to activate C–X bonds (X = F–I), we have computationally investigated, using DFT methods, the reaction of (CAAC)2Be (CAAC = 1-(2,6-diisopropylphenyl)-3,3,5,5-tetramethylpyrrolidin-2-ylidene) and a series of five-membered heterocyclic beryllium bidentate ligands with phenyl halides. We have analysed all plausible reaction mechanisms and our results show that, after the initial C–X oxidative addition, migration of the phenyl group occurs towards the less electronegative heteroatom. Our theoretical study highlights the important role of bidentate non-innocent ligands in providing the required electrons for the initial Ph–X oxidative addition. In contrast, the monodentate ligand, CAAC, does not favour this oxidative addition. [ABSTRACT FROM AUTHOR]

An approach to modulating the properties of carbon nanorings by incorporating pyrrolo[3,2‐b]pyrrole units is of particular interest due to the combined effect of heteroatom and antiaromatic character on electronic properties. The inclusion of units other than phenylene leads to the formation of stereoisomers. In this work, we computationally study how the spatial orientation of monomeric units in the ring affects the properties of cyclic dibenzopyrrolo[3,2‐b]pyrroles and their complexes with C60 fullerene. For [4]PP and [4]DHPP, the most symmetrical AAAA isomer is the most stable and forms stronger interactions with fullerene than the isomers where one or two monomeric units are flipped, mostly due to less Pauli repulsion. π‐Electron delocalization in the monomeric unit is crucial for directing the electron transfer (from or to nanoring). The energy of excited states with charge transfer depends on the HOMO–LUMO gap, which varies from one stereoisomer to another only for [4]DHPP⊃C60 with aromatic 1,4‐dihydropyrrolo[3,2‐b]pyrrole units. The rates of electron transfer and charge recombination reactions are relatively weakly dependent of the spatial isomerism of nanorings. [ABSTRACT FROM AUTHOR]

CO2 is the gas that contributes the most to the greenhouse effect and, therefore, to global warming. One of the greatest challenges facing humanity is the reduction of the concentration of CO2 in the air. Here, we analyze the possible use of Au1@g-C3N4 electrocatalyst to transform CO2 into added-value products. We use density functional theory (DFT) to determine the reaction Gibbs energies for eight electron–proton transfer reaction paths of the electrochemical carbon dioxide reduction reaction (CO2RR) using a single Au atom supported on 2D carbon nitride support. Our simulations classify the Au1@g-C3N4 electrocatalysts as "beyond CO" since their formation is energetically favored, although their strong binding with a Au single atom does not allow the desorption process. DFT calculations revealed that the lowest energy pathway is CO2 (g) → COOH* → CO* → HCO* → HCOH* → CH2OH* → CH2* → CH3* → CH4 (g), where the first hydrogenation of CO to HCO is predicted as the rate-limiting step of the reaction with slightly lower potential than predicted for Cu electrodes, the most effective catalysts for CO2RR. Methane is predicted to be the main reaction product after eight proton–electron transfers (CO2 + 8 H+ + 8e− → CH4 + 2H2O). The generation of formaldehyde is discarded due to the large formation energy of the adsorbed moiety and the production of methanol is slightly less favorable than methane formation. Our computational study helps to identify suitable electrocatalysts for CO2RR by reducing the amount of metal and using stable and low-cost supports. [ABSTRACT FROM AUTHOR]

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For decades there were many attempts to dispense with stoichiometric amounts of metal reagents for the synthesis of secondary alcohols. In 2021, the synthetic results of Newman and collaborators pioneered a synthesis still with metals, but not as reactants. Instead, they serverd as catalytic engines. Here we present a description by means of Density Functional Theory calculations of how this process can occur, and an attempt is made to shed light on the mechanism that facilitates the attainment of secondary alcohols, emphasizing the eternal cross‐coupling debate of whether the catalytically active species is Ni(0) or they are really taking shortcuts following the course of Ni(II). Effective Orbital analyses give a clear picture. Furthermore, this paper provides insight not only into the nature of the ligands of the metal catalyst but also the role of the base. [ABSTRACT FROM AUTHOR]

The electrochemical conversion of CO2 into value-added chemicals is an important approach to recycling CO2. In this work, we have combined the most efficient metal catalysts for this reaction, namely Cu, Ag, and Au, as single-atom particles dispersed on a two-dimensional carbon nitride support, with the aim of exploring their performance in the CO2 reduction reaction. Here, we report density functional theory computations showing the effect of single metal-atom particles on the support. We found that bare carbon nitride needed a high overpotential to overcome the energy barrier for the first proton–electron transfer, while the second transfer was exergonic. The deposition of single metal atoms enhances the catalytic activity of the system as the first proton–electron transfer is favored in terms of energy, although strong binding energies were found for CO adsorption on Cu and Au single atoms. Our theoretical interpretations are consistent with the experimental evidence that the competitive H2 generation is favored due to the strong CO binding energies. Our computational study paves the road to finding suitable metals that catalyze the first proton–electron transfer in the carbon dioxide reduction reaction and produce reaction intermediates with moderate binding energies, promoting a spillover to the carbon nitride support and thereby serving as bifunctional electrocatalysts. [ABSTRACT FROM AUTHOR]

Given the importance of serine proteases for biochemical processes, we have studied the peptide bond rupture mechanism using three sequential scale models as representations of the KLK5 enzyme (a protein overexpressed in ovarian cancer). The first model contains the basic functional groups of the residues that conform to the catalytic triad present in serine proteases; the second model contains some additional residues and, finally, the last representation includes all atoms of the KLK5 protein together with 10.000 explicit water molecules. This separation into three scale models allows us to separate the intrinsic reactivity of the catalytic triad from the process taking place in the enzyme. The methodologies employed in this work include full DFT calculations with a dielectric continuum in the first two models and a multi-level setup with a Quantum Mechanics/Molecular Mechanics (QM/MM) partition in the whole protein system. Our results show that the peptide-bond rupture mechanism is a stepwise process involving two proton transfer reactions. The rate-determining step is the second proton transfer from the imidazole group to the amidic nitrogen of the substrate. In addition, we find that the simplest model does not provide accurate results compared to the full protein system. This can be attributed to the electronic stabilization conferred by the residues around the reaction site. Interestingly, the energy profile obtained with the second scale model with additional residues shows the same trends as the full system and could therefore be considered an appropriate model system. It could be used for studying the peptide bond rupture mechanism in case full QM/MM calculations cannot be performed, or as a rapid tool for screening purposes. [ABSTRACT FROM AUTHOR]

Boron‐boron multiple bonds, such as those found in diborenes and diborynes, are typically stabilized by σ‐donor ligands that furnish electron density to these otherwise electron‐deficient species. These compounds are not only of fundamental importance in the study of chemical bonding, but can also activate small molecules in a chemistry reminiscent of that carried out by transition metals. In the pursuit of designing new and improved σ‐donor ligands to stabilize diborenes and diborynes suitable to activate small molecules, we performed density functional calculations to evaluate the Lewis basicity of a series of σ‐donor ligands. For this evaluation, we analysed the interaction between the boranes and the σ‐donor ligands in model systems L→BX3 (X=F and Me) using energy decomposition analyses. We found that electronic bond energies of the L→BX3 adducts correlate well with the ionization energies of the ligands and that ligands with high or medium basicity stabilize diborynes better than ligands with low basicity. We also learnt that beryllium‐based ligands are promising since they are able to stabilize L→B≡B←L diborynes without significantly reducing the triple bond character of the B≡B bond. [ABSTRACT FROM AUTHOR]

The increasing concentration of anthropogenic CO2 in the air is one of the main causes of global warming. The Paris Agreement at COP 21 aims to reach the global peak of greenhouse gas emissions in the second half of this century, with CO2 conversion towards valuable added compounds being one of the main strategies, especially in the field of heterogeneous catalysis. In the current search for new catalysts, the deposition of metallic nanoparticles (NPs) supported on metal oxides and metal carbide surfaces paves the way to new catalytic solutions. This review provides a comprehensive description and analysis of the relevant literature on the utilization of metal-supported NPs as catalysts for CO2 conversion to useful chemicals and propose that the next catalysts generation can be led by single-metal-atom deposition, since in general, small metal particles enhance the catalytic activity. Among the range of potential indicators of catalytic activity and selectivity, the relevance of NPs' size, the strong metal–support interactions, and the formation of vacancies on the support are exhaustively discussed from experimental and computational perspective. [ABSTRACT FROM AUTHOR]