Mesoporous High-Entropy Alloy Films.

High-entropy alloys (HEAs) are promising materials for electrochemical energy applications due to their excellent catalytic performance and durability. However, the controlled synthesis of HEAs with a well-defined structure and a uniform composition distribution remains a challenge. Herein, a soft template-assisted electrodeposition technique is used to fabricate a mesoporous HEA (m-HEA) film with a uniform composition distribution of Pt, Pd, Rh, Ru, and Cu, providing a suitable platform for investigating structure-performance relationships.

If the Crown Fits: Sterically Demanding -Heterocyclic Carbene Promotes the Formation of AuPt Nanoclusters.

While -heterocyclic carbenes (NHCs) have recently been shown to be effective ligands for gold nanoclusters, very few examples of heterometallic clusters incorporating nongroup 11 metals are known. We present herein an Au-Pt NHC cluster featuring a crown-shaped [AuPt(NHC)] core, produced in high yield without the need for chromatographic purification. The method was largely independent of the substitution pattern of the NHC backbone; however, bulky wingtip groups were needed for clean conversion to the AuPt cluster.

Tailored Design of Mesoporous Nanospheres with High Entropic Alloy Sites for Efficient Redox Electrocatalysis.

High Entropy Alloys (HEAs) are a versatile material with unique properties, tailored for various applications. They enable pH-sensitive electrocatalytic transformations like hydrogen evolution reaction (HER) and hydrogen oxidation reactions (HOR) in alkaline media. Mesoporous nanostructures with high surface area are preferred for these electrochemical reactions, but designing mesoporous HEA sis challenging.

Effect of porphyrin ligands on the catalytic CH oxidation activity of monocationic μ-nitrido-bridged iron porphyrinoid dimers by using HO as an oxidant.

The μ-nitrido-bridged iron phthalocyanine homodimer is a potent molecule-based CH oxidation catalyst that can effectively oxidize chemically stable CH under mild reaction conditions in an acidic aqueous solution including an oxidant such as HO. The reactive intermediate is a high-valent iron-oxo species generated upon reaction with HO. However, a detailed comparison of the CH oxidation activity of the μ-nitrido-bridged iron phthalocyanine dimer with those of μ-nitrido-bridged iron porphyrinoid dimers containing one or two porphyrin ring(s) has not been yet reported, although porphyrins are the most important class of porphyrinoids.

First-principles studies of enhanced oxygen reduction reactions on graphene- and nitrogen-doped graphene-coated platinum surfaces.

Developing innovative platinum-based electrocatalysts and enhancing their efficiency are crucial for advancing high-performance fuel cell technology. In this study, we employed DFT calculations to provide a theoretical basis for interpreting the impact of graphene coatings on various Pt surfaces on oxygen reduction reaction (ORR) catalytic activity, which are currently applied as protective layers in experiments. We comprehensively assess the geometric and electronic properties of Pt(100), Pt(110), and Pt(111) surfaces in comparison to their graphene-coated counterparts, revealing different adsorption behaviors of O across these surfaces.

Close Stacking of Antiaromatic Ni(II) Norcorrole Originating from a Four-Electron Multicentered Bonding Interaction.

A π-conjugated molecule with one electronic spin often forms a π-stacked dimer through molecular orbital interactions between two unpaired electrons. The bonding is recognized as a multicentered two-electron interaction between the two π-conjugated molecules. Here, we disclose a multicentered bonding interaction between two antiaromatic molecules involving four electrons.

Stereochemistry-Dependent Labeling of Organelles with a Near-Infrared-Emissive Phosphorus-Bridged Rhodamine Dye in Live-Cell Imaging.

The development of near-infrared (NIR) fluorophores that have both excellent chemical stability and photostability, as well as efficient cell permeability, is highly demanded. In this study, we present phospha-rhodamine (POR) dyes which display significantly improved performance for protein labeling. This is achieved by incorporating a 2-carboxy-3-benzothiophenyl group at the 9-position of the xanthene scaffold.

Local Oxidation States in {FeNO} Porphyrins: Insights from DMRG/CASSCF-CASPT2 Calculations.

A first DMRG/CASSCF-CASPT2 study of a series of paradigmatic {FeNO}, {FeNO}, and {FeNO} heme-nitrosyl complexes has led to substantial new insight as well as uncovered key shortcomings of the DFT approach. By virtue of its balanced treatment of static and dynamic correlation, the calculations have provided some of the most authoritative information available to date on the energetics of low- versus high-spin states of different classes of heme-nitrosyl complexes. Thus, the calculations indicate low doublet-quartet gaps of 1-4 kcal/mol for {FeNO} complexes and high singlet-triplet gaps of ≳20 kcal/mol for both {FeNO} and {FeNO} complexes.

Insight into Scattering Mechanisms and Transport Properties of AgCuS for Flexible Thermoelectric Applications.

The development of flexible thermoelectric devices requires materials possessing ductility and high thermoelectric performance at room temperature. However, only a few existing materials meet both criteria. In this study, the ductile properties, electronic structure, and transport properties of the low-temperature phase α-AgCuS were elucidated using first-principles calculations combined with Boltzmann transport theory.

Unraveling the Spin-State Energetics of FeN Complexes with Ab Initio Methods.

A systematic analysis was conducted to explore the spin-state energetics of a series of 19 FeN complexes. The performance of a large number of multireference methods was assessed, highlighting the significant challenges associated with accurately describing the spin-state energetics of FeN complexes. Most multireference methods were found to be susceptible to errors originating from the reference CASSCF wavefunction, leading to an overstabilization of high-spin states.

The OpenMolcas : A Community-Driven Approach to Advancing Computational Chemistry.

The developments of the open-source OpenMolcas chemistry software environment since spring 2020 are described, with a focus on novel functionalities accessible in the stable branch of the package or via interfaces with other packages. These developments span a wide range of topics in computational chemistry and are presented in thematic sections: electronic structure theory, electronic spectroscopy simulations, analytic gradients and molecular structure optimizations, ab initio molecular dynamics, and other new features. This report offers an overview of the chemical phenomena and processes OpenMolcas can address, while showing that OpenMolcas is an attractive platform for state-of-the-art atomistic computer simulations.

A DMRG/CASPT2 Investigation of Metallocorroles: Quantifying Ligand Noninnocence in Archetypal 3d and 4d Element Derivatives.

Hybrid density functional theory (B3LYP) and density matrix renormalization group (DMRG) theory have been used to quantitatively compare the degree of ligand noninnocence (corrole radical character) in seven archetypal metallocorroles. The seven complexes, in decreasing order of corrole noninnocent character, are Mn[Cor]Cl > Fe[Cor]Cl > Fe[Cor](NO) > Mo[Cor]Cl > Ru[Cor](NO) ≈ Mn[Cor]Ph ≈ Fe[Cor]Ph ≈ 0, where [Cor] refers to the unsubstituted corrolato ligand. DMRG-based second-order perturbation theory calculations have also yielded detailed excited-state energetics data on the compounds, shedding light on periodic trends involving middle transition elements.

Lifetimes of Be and Mg Cluster Dianions.

The alkaline earth metal trimer cluster dianions Be and Mg lie energetically above their respective monoanions and can therefore decay by electron autodetachment. Consequently, these dianions possess only short-lived resonance states, and here we study these states using regularized analytic continuation as well as complex absorbing potentials combined with a wide a variety of quantum chemistry methods including CCSD(T), SACCI, EOM-CCSD, CASPT2, and NEVPT2. For both Be and Mg, four low-energy resonance states corresponding to different occupation patterns of the two excess electrons in the two lowest p-σ and p-π orbitals are identified: Two states are dominated by doubly occupied configurations and can be characterized as showing σ and π aromatic character.

Polarization consistent basis sets using the projector augmented wave method: a renovation brought by PAW into Gaussian basis sets.

A recently introduced framework incorporating the Projector Augmented Wave method and Gauss-type function (GTF-PAW) [X.-G. Xiong and T.

Electronic Structure of Neutral and Anionic Iron-Nitrosyl Corrole. A Multiconfigurational and Density Matrix Renormalization Group Investigation.

An elaborate study with multireference second-order perturbation theory has been performed to elucidate the electronic structure and relative energy of three relevant states of FeNO corroles, namely the = 0 ground state, the lowest = 1 state, and the anion = / state. On the basis of CASSCF and DMRG calculations with an active space including up to 37 orbitals, the electronic structure of the ground state was analyzed, with special emphasis on the diradical nature of the Fe-corrole and Fe-NO bonds. The results essentially confirm an earlier suggestion from B3LYP of a non-innocent corrole bound to an {FeNO} unit, although the contribution of diradical character to the iron-corrole bond is found to be limited to 35%.

Combination of a Voronoi-Type Complex Absorbing Potential with the XMS-CASPT2 Method and Pilot Applications.

Electronic resonances are metastable ( + 1) electron states, in other words, discrete states embedded in an electronic continuum. While great progress has been made for certain types of resonances-for example, temporary anions created by attaching one excess electron to a closed shell neutral-resonances in general remain a great challenge of quantum chemistry because a successful description of the decay requires a balanced description of the bound and continuum aspect of the resonance. Here, a smoothed Voronoi complex absorbing potential (CAP) is combined with the XMS-CASPT2 method, which enables us to address the balance challenge by appropriate choice of the CAS space.

OpenMolcas: From Source Code to Insight.

In this Article we describe the OpenMolcas environment and invite the computational chemistry community to collaborate. The open-source project already includes a large number of new developments realized during the transition from the commercial MOLCAS product to the open-source platform. The paper initially describes the technical details of the new software development platform.

Electronic Structure of N-Bridged High-Valent Diiron-Oxo.

Density functional theory (DFT) and an advanced ab initio technique based on density matrix renormalization group (DMRG-CASPT2) were employed to investigate a reactive N-bridged high-valent diiron-oxo species involved in H-abstraction reactions. We studied in detail two important doublet states, the ground state with two iron(IV) centers and a mixed valence Fe -Fe excited state. We found that the latter state is low-lying.

Ab Initio Calculations for Spin-Gaps of Non-Heme Iron Complexes.

We employed our recently proposed multireference approach CASPT2/CC to calculate the quintet-triplet gaps Δ of a series of non-heme Fe═O species and subsequently used these results to benchmark density functional theory (DFT) as well as two variants of local coupled-cluster approaches (DLPNO-CCSD(T) and LUCCSD(T0)). We showed that current implementations of the local coupled-cluster method are not sufficiently accurate. DLPNO-CCSD(T) systematically overstabilizes the quintet state, whereas LUCCSD(T0) overestimates the triplet one.

Understanding the Reactivity of Mn-Oxo Porphyrins for Substrate Hydroxylation: Theoretical Predictions and Experimental Evidence Reconciled.

The Mn-oxo porphyrin (MnOP) mechanism for substrate hydroxylation is computationally studied with the aim to better understand reactivity in these systems. Theoretical studies suggest Mn(V)OP species to be very reactive intermediates with thermally accessible reaction barriers represented by low-spin/high-spin-crossover occurring in the Mn(V)OP oxidant, and kinetics for selected Mn(V)OP species indeed find high reactivity. On the other hand, MnOP complexes lead to modest yields in hydroxylation reactions of several different substrates, implying low rate constants and high reaction barriers.

Low-Lying Electromeric States in Chloro-Ligated Iron(IV)-Oxo Porphyrin as a Model for Compound I, Studied with Second-Order Perturbation Theory Based on Density Matrix Renormalization Group.

Employing second-order perturbation theory based on the density matrix renormalization group (DMRG-CASPT2), this work aims at providing a quantitative description of the spin state energetics of a chloro-ligated iron(IV)-oxo porphyrin as a model for the cytochromes P450 active species, also known as compound I (Cpd I). We explored DMRG-CASPT2 to its full extent with an extensive active space (up to 31 active orbitals) as well as a large number of renormalized states m (up to 10000). Different flavors of DMRG-CASPT2, using either the costly exact 4-particle reduced density matrix (4-RDM) or the cheaper cumulant approximated 4-RDM (cu(4)), were analyzed.

Limits of Coupled-Cluster Calculations for Non-Heme Iron Complexes.

In a large variety of studies, the coupled-cluster method with singles, doubles, and perturbative triples (CCSD(T)) is used as a reference for benchmarking the performance of density functional theory (DFT) functionals. In the case of open-shell species, this theory can be applied in different forms depending on the restricted or unrestricted treatment of spin. In this study, we show that these different approaches can produce results which deviate by ∼5 kcal/mol for different species on the potential energy surfaces.

Reaction Mechanism of [NiFe] Hydrogenase Studied by Computational Methods.

[NiFe] hydrogenases catalyze the reversible conversion of molecular hydrogen to protons and electrons. This seemingly simple reaction has attracted much attention because of the prospective use of H as a clean fuel. In this paper, we have studied the full reaction mechanism of this enzyme with various computational methods.

Switching the Spin-Crossover Phenomenon by Ligand Design on Imidazole-Diazineiron(II) Complexes.

The iron(II) complexes of two structural isomers of 2-(1 H-imidazol-2-yl)diazine reveal how ligand design can be a successful strategy to control the electronic and magnetic properties of complexes by fine-tuning their ligand field. The two isomers only differ in the position of a single diazinic nitrogen atom, having either a pyrazine (Z) or a pyrimidine (M) moiety. However, [Fe(M)](ClO) is a spin-crossover complex with a spin transition at 241 K, whereas [Fe(Z)](ClO) has a stable magnetic behavior between 2 and 300 K.

The dioxygen adducts of iron and manganese porphyrins: electronic structure and binding energy.

In this paper, we present a thorough study of the electronic structures and binding energies of O2 to iron and manganese porphyrins (FeP and MnP), employing a state-of-the-art computational technique known as second-order perturbation theory based on density matrix renormalization group (DMRG-CASPT2). By investigating an extensive list of different binding modes and spin states, we provide a clear and conclusive description of the ground state of MnP-O2, confirming available experimental evidences. Our results show that MnP-O2 favours a side-on quartet structure, with strong charge transfer between MnP and O2.