Rationalizing Spin-Crossover Properties of Substituted Fe (II) Complexes.

We investigate spin-state transitions in a series of 24 [Fe(bpp)] spin-crossover (SCO) complexes using density functional theory (DFT). The TPSSh/def2-TZVP approach demonstrates reasonable accuracy in predicting spin-state energetics compared to other functionals, though significant deviations persist in transition temperature () estimates. Temperature-dependent and quasi-harmonic corrections for low-frequency vibrational contributions to enthalpic and entropic terms yielded only marginal improvements.

Effective Oxidation State Analysis for Solids.

We present the generalization of the effective oxidation state (EOS) method to assign oxidation states from wave function analysis to solid-state calculations. The scheme is realized in the framework of the Quantum Theory of Atoms in Molecules (QTAIM), and makes use of the atomic overlap matrices (AOM) of the atoms of the unit cell, expressed (whenever possible) in terms of maximally localized Wannier functions (MLWFs). The method is generally applicable to ionic solids or molecular crystals.

Capturing electronic substituent effect with effective atomic orbitals.

The occupations of the effective atomic orbitals (eff-AOs) of the carbon atoms in the aromatic ring serve as the basis for deriving accurate descriptors of the inductive () and resonance () effects exerted by substituents in substituted benzene derivatives. The eff-AOs enable a clear separation of the σ-type electron density into contributions originating from the C-H/X bonds (where X represents a substituent) and those from the C-C bonding framework. Our analysis reveals that the inductive effect of a substituent is effectively captured by the shift in the occupation of the eff-AOs associated with the C-C bonding framework at the position.

Hexaphenyl-1,2-Diphosphonium Dication [PhP-PPh]: Superacid, Superoxidant, or Super Reagent?

The oxidation of triphenylphosphine by perfluorinated phenazinium aluminate in difluorobenzene affords hexaaryl-1,2-diphosphonium dialuminate . Dication is valence isoelectronic with elusive hexaphenylethane, where instead the formation of a mixture of the trityl radical and Gomberg's dimer is favored. Quantum-chemical calculations in combination with Raman/IR spectroscopies rationalize the stability of the P-P bonded dimer in and suggest, akin to the halogens, facile homolytic as well as heterolytic scission.

CCC-NHC Au(iii) pincer complexes as a reliable platform for isolating elusive species.

The reactivity of unprecedented CCC-NHC Au(iii) pincer complexes has been investigated, employing a novel methodology for their preparation. Notably, this marks the inaugural case of CCC-NHC Au(iii) pincer complexes with a central aryl moiety where the two arms of the pincer ligand consist of N-heterocyclic carbenes (NHC). The stability conferred by the CCC-NHC ligand facilitated the isolation of elusive Au(iii) species, encompassing Au(iii)-formate, Au(iii)-F, Au(iii)-Me, and Au(iii)-alkynyl.

Unraveling the Mechanism of Hydrogen Atom Transfer by a Nickel-Hypochlorite Species and the Influence of Electronic Effects.

The oxidation of hydrocarbons is an important chemical transformation with relevance to biology and industry. Ni-catalyzed transformations are more scarce compared to Mn or Fe but have gained attention in recent years, affording efficient oxidations. Understanding the mechanism of action of these catalysts, including the detection and characterization of the active nickel-oxygen species, is of interest to design better catalysts.

Quantification of the Donor-Acceptor Character of Ligands by the Effective Fragment Orbitals.

Metal-ligand interactions are at the heart of transition metal complexes. The Dewar-Chat-Duncanson model is often invoked, whereby the metal-ligand bonding is decomposed into the simultaneous ligand→metal electron donation and the metal→ligand back-donation. The separate quantification of both effects is not a trivial task, neither from experimental nor computational exercises.

Can Aromaticity Be Evaluated Using Atomic Partitions Based on the Hilbert-Space?

Aromaticity is a fundamental concept in chemistry that explains the stability and reactivity of many compounds by identifying atoms within a molecule that form an aromatic ring. Reliable aromaticity indices focus on electron delocalization and depend on atomic partitions, which give rise to the concept of an atom-in-the-molecule (AIM). Real-space atomic partitions present two important drawbacks: a high computational cost and numerical errors, limiting some aromaticity measures to medium-sized molecules with rings up to 12 atoms.

Estimating the probability of occurrence of African dust outbreaks over regions of the western Mediterranean basin from thermodynamic atmospheric parameters.

Desert dust is currently recognized as a health risk factor. Therefore, the World Health Organization (WHO) is actively promoting the establishment of early warning systems for sand and dust storms. This study introduces a methodology to estimate the probability of African dust outbreaks occurring in eight different regions of the Iberian Peninsula and the Balearic Islands.

Air quality and characterization of synoptic circulation weather patterns in a South American city from Argentina.

The potential cause-effect relationship between synoptic meteorological conditions and levels of criteria air pollutants, including CO, NO, O, PM, PM and SO, in Bahia Blanca, Argentina, was assessed for the period of 2018-2019. Daily back-trajectories and global meteorological data fields were employed to characterize the primary transport paths of air masses reaching the study site, and to identify the synoptic meteorological patterns responsible for these atmospheric circulations. Time series of surface-level meteorological parameters and midday mixing layer height were collected to examine the impact of the synoptic meteorological patterns on local meteorology.

Influence of synoptic meteorology on airborne allergenic pollen and spores in an urban environment in Northeastern Iberian Peninsula.

The influence of the most frequent patterns of synoptic circulation on the dynamics of airborne pollen/spores recorded at the Barcelona Aerobiological Station (BCN) was analysed. Six pollen types (Platanus, Cupressaceae, Olea, Poaceae, Urticaceae and Amaranthaceae), and one fungal spore (Alternaria) were selected for their high allergenic effect in sensitive people. Six synoptic meteorological patterns were identified through cluster analysis of sea level pressure fields as the main responsible of the weather conditions in the Iberian Peninsula.

Exact decompositions of the total KS-DFT exchange-correlation energy into one- and two-center terms.

In the so-called Interacting Quantum Atoms (IQA) approach, the molecular energy is numerically decomposed as a sum of atomic and diatomic contributions. While proper formulations have been put forward for both Hartree-Fock and post-Hartree-Fock wavefunctions, this is not the case for the Kohn-Sham density functional theory (KS-DFT). In this work, we critically analyze the performance of two fully additive approaches for the IQA decomposition of the KS-DFT energy, namely, the one from Francisco et al.

Merging the Energy Decomposition Analysis with the Interacting Quantum Atoms Approach.

Energy decomposition analysis (EDA) is a well-established approach to dissect the interaction energy into chemically sound components. Despite the inherent requirement of reference states has been a long-standing object of debate, the direct relation with the molecular orbital analysis helps in building up predictive models. The alternative molecular energy decomposition schemes that decompose the total energy into atomic and diatomic contributions, such as the interacting quantum atoms (IQA), has no external reference requirements and also the intra- and intermolecular interactions are treated on equal footing.

Does Serial Femtosecond Crystallography Depict State-Specific Catalytic Intermediates of the Oxygen-Evolving Complex?

Recent advances in serial femtosecond crystallography (SFX) of photosystem II (PSII), enabled by X-ray free electron lasers (XFEL), provided the first geometric models of distinct intermediates in the catalytic S-state cycle of the oxygen-evolving complex (OEC). These models are obtained by flash-advancing the OEC from the dark-stable state (S) to more oxidized intermediates (S and S), eventually cycling back to the most reduced S. However, the interpretation of these models is controversial because geometric parameters within the MnCaO cluster of the OEC do not exactly match those expected from coordination chemistry for the spectroscopically verified manganese oxidation states of the distinct S-state intermediates.

Force Decomposition Analysis: A Method to Decompose Intermolecular Forces into Physically Relevant Component Contributions.

Computational quantum chemistry can be more than just numerical experiments when methods are specifically adapted to investigate chemical concepts. One important example is the development of energy decomposition analysis (EDA) to reveal the physical driving forces behind intermolecular interactions. In EDA, typically the interaction energy from a good-quality density functional theory (DFT) calculation is decomposed into multiple additive components that unveil permanent and induced electrostatics, Pauli repulsion, dispersion, and charge-transfer contributions to noncovalent interactions.

Reply to the 'Comment on "The oxidation state in low-valent beryllium and magnesium compounds"' by S. Pan and G. Frenking, , 2022, , DOI: 10.1039/D2SC04231B.

A recent article by Pan and Frenking challenges our assignment of the oxidation state of low valent group 2 compounds. With this reply, we show that our assignment of Be(+2) and Mg(+2) oxidation states in Be(cAAC) and Mg(cAAC) is fully consistent with our data. Some of the arguments exposed by Pan and Frenking were based on visual inspection of our figures, rather than a thorough numerical analysis.

Mechanistic Insights into the Oxidative and Reductive Quenching Cycles of Transition Metal Photoredox Catalysts through Effective Oxidation State Analysis.

The electronic structures of the ground and excited electronic states involved in the oxidative and reductive quenching cycles of 12 relevant ruthenium, iridium, and copper photoredox catalysts (, , , and ) are characterized using the recently developed effective oxidation state (EOS) analysis, allowing the monitoring of metal and ligand oxidation states (OSs) along the catalytic cycles. The formal oxidation state assignments derived from the EOS analysis are in agreement with those commonly assumed for these complexes in both ground and excited states. Rather clean and separate ligand- and metal-centered redox events along the different quenching cycles are observed in most of the studied molecular systems.

C-H Amination Reactions Mediated by Metastable Pseudo- Masked Aryl-Co-nitrene Species.

Cobalt-catalyzed C-H amination via M-nitrenoid species is spiking the interest of the research community. Understanding this process at a molecular level is a challenging task, and here we report a well-defined macrocyclic system featuring a pseudo- aryl-Co species that reacts with aliphatic azides to effect intramolecular C-N bond formation. Strikingly, a putative aryl-Co═NR nitrenoid intermediate species is formed and is rapidly trapped by a carboxylate ligand to form a carboxylate masked-nitrene, which functions as a shortcut to stabilize and guide the reaction to productive intramolecular C-N bond formation.

The oxidation state in low-valent beryllium and magnesium compounds.

Low-valent group 2 (E = Be and Mg) stabilized compounds have been long synthetically pursued. Here we discuss the electronic structure of a series of Lewis base-stabilized Be and Mg compounds. Despite the accepted zero(0) oxidation state nature of the group 2 elements of some recent experimentally accomplished species, the analysis of multireference wavefunctions provides compelling evidence for a strong diradical character with an oxidation state of +2.

Cage-size effects on the encapsulation of P by fullerenes.

The classic pnictogen dichotomy stands for the great contrast between triply bonding very stable N molecules and its heavier congeners, which appear as dimers or oligomers. A banner example involves phosphorus as it occurs in nature as P instead of P , given its weak π-bonds or strong σ-bonds. The P synthetic value has brought Lewis bases and metal coordination stabilization strategies.

Diagnosis of Lofgren's Syndrome and the Role of Ultrasound.

We report the case of a 32-year-old woman presenting to the emergency department with ankle edema and arthralgia. Only later in the follow-up period, she developed erythema nodosum. The study revealed bilateral hilar and mediastinal lymphadenopathy and biopsy demonstrated non-caseating granulomas consistent with a diagnosis of Lofgren's syndrome.

Oxidation State Localized Orbitals: A Method for Assigning Oxidation States Using Optimally Fragment-Localized Orbitals and a Fragment Orbital Localization Index.

Oxidation states represent the ionic distribution of charge in a molecule and are significant in tracking redox reactions and understanding chemical bonding. While effective algorithms already exist based on formal Lewis structures as well as using localized orbitals, they exhibit differences in challenging cases where effects such as redox noninnocence are at play. Given a density functional theory (DFT) calculation with chosen total charge and spin multiplicity, this work reports a new approach to obtaining fragment-localized orbitals that is termed oxidation state localized orbitals (OSLO), together with an algorithm for assigning the oxidation state using the OSLOs and an associated fragment orbital localization index (FOLI).

Accurate Fe Mössbauer Parameters from General Gaussian Basis Sets.

The prediction of isomer shifts in Fe Mossbauer spectra is typically achieved by building calibration lines using the values of the density at the nuclear position. Using Slater-type orbital basis or large and specific Gaussian-type orbital basis has been thus far mandatory to achieve accurate predictions with density functional theory methods. In this work, we show that replacing the value of the density at the nucleus by the density integrated in a sphere of radius 0.