Is the protactinium(V) mono-oxo bond weaker than what we thought?

The bond distance is the simplest and most obvious indicator of the nature of a given chemical bond. However, for rare chemistry, it may happen that it is not yet firmly established. In this communication, we will show that the formally-triple protactinium(V) mono-oxo bond is predicted to be longer than what was previously reported in the solid state and in solution, based on robust quantum mechanical calculations, supported by an extensive methodological study.

Toward a realistic theoretical electronic spectra of metal aqua ions in solution: The case of Ce(H2O)n3+ using statistical methods and quantum chemistry calculations.

Accurately predicting spectra for heavy elements, often open-shell systems, is a significant challenge typically addressed using a single cluster approach with a fixed coordination number. Developing a realistic model that accounts for temperature effects, variable coordination numbers, and interprets experimental data is even more demanding due to the strong solute-solvent interactions present in solutions of heavy metal cations. This study addresses these challenges by combining multiple methodologies to accurately predict realistic spectra for highly charged metal cations in aqueous media, with a focus on the electronic absorption spectrum of Ce3+ in water.

Experimental and Theoretical Study of the Reaction of F with Thiirane.

The kinetics of the F reaction with thiirane (CHS) was studied for the first time in a flow reactor combined with mass spectrometry at a total helium pressure of 2 Torr and in the temperature range of 220 to 800 K. The rate constant of the title reaction was determined under pseudo-first-order conditions, either monitoring the kinetics of F or CHS consumption in excess of thiirane or of F, respectively: = (5.79 ± 0.

Interoperable workflows by exchanging grid-based data between quantum-chemical program packages.

Quantum-chemical subsystem and embedding methods require complex workflows that may involve multiple quantum-chemical program packages. Moreover, such workflows require the exchange of voluminous data that go beyond simple quantities, such as molecular structures and energies. Here, we describe our approach for addressing this interoperability challenge by exchanging electron densities and embedding potentials as grid-based data.

Stability of the Protactinium(V) Mono-Oxo Cation Probed by First-Principle Calculations.

This study explores the distinctive behavior of protactinium (Z=91) within the actinide series. In contrast to neighboring elements like uranium or plutonium, protactinium in the pentavalent state diverges by not forming the typical dioxo protactinyl moiety PaO in aqueous phase. Instead, it manifests as a monooxo PaO cation or a Pa .

Early Steps in the O Scavenger Process in the Aqueous Phase: Hydrazine vs DEHA.

We investigate the first direct proton abstraction reactions from reducing agents () hydrazine and diethyl hydroxylamine (DEHA), toward dioxygen (O) in the aqueous phase, spanning ambient to high-temperature conditions. Quantum chemistry methods and molecular dynamics simulations are employed in this study. Quantum chemistry methods are used to analyze the quasi-equilibrium between a reactive conformation and a transition state in the [,O] cluster.

Excited states of polonium(IV): electron correlation and spin-orbit coupling in the Po free ion and in the bare and solvated [PoCl] and [PoCl] complexes.

Polonium (Po, = 84) is a main-block element with poorly known physico-chemical properties. Not much information has been firmly acquired since its discovery by Marie and Pierre Curie in 1898, especially regarding its speciation in aqueous solution and spectroscopy. In this work, we revisit the absorption properties of two complexes, [PoCl] and [PoCl], using quantum mechanical calculations.

The hydration of an oxy-polycyclic aromatic compound: the case of naphthaldehyde.

The study of the intermolecular interactions of polycyclic aromatic compounds, considered as important pollutants of the Earth's atmosphere since they are emitted by the partial combustion of fuels, is essential to understand the formation and aging of their aerosols. In this study, the hydration of α-naphthaldehyde and β-naphthaldehyde isomers was investigated through a combination of Fourier transform microwave spectroscopy and quantum chemical calculations. Monohydrate structures were observed experimentally for both isomers, with two hydrate structures observed for β-naphthaldehyde and only one for α-naphthaldehyde, consistent with computational predictions.

Protein-ligand interactions from a quantum fragmentation perspective: The case of the SARS-CoV-2 main protease interacting with α-ketoamide inhibitors.

We present a hybrid, multi-method, computational scheme for protein/ligand systems well suited to be used on modern and forthcoming massively parallel computing systems. The scheme relies on a multi-scale polarizable molecular modeling, approach to perform molecular dynamics simulations, and on an efficient Density Functional Theory (DFT) linear scaling method to post-process simulation snapshots. We use this scheme to investigate recent α-ketoamide inhibitors targeting the main protease of the SARS-CoV-2 virus.

Coordination and thermodynamic properties of aqueous protactinium(V) by first-principle calculations.

Protactinium ( = 91) is a very rare actinide with peculiar physico-chemical properties. Indeed, although one may naively think that it behaves similarly to either thorium or uranium by its position in the periodic table, it may in fact follow its own rules. Because of the quite small energy gap between its valence shells (in particular the 5f and 6d ones) and also the strong influence of relativistic effects on its properties, it is actually a challenging element for theoretical chemists.

Uranium(iv) alkyl cations: synthesis, structures, comparison with thorium(iv) analogues, and the influence of arene-coordination on thermal stability and ethylene polymerization activity.

Reaction of [(XA)U(CHSiMe)] (1; XA = 4,5-bis(2,6-diisopropylanilido)-2,7-di--butyl-9,9-dimethylxanthene) with 1 equivalent of [PhC][B(CF)] in arene solvents afforded the arene-coordinated uranium alkyl cations, [(XA)U(CHSiMe)(η -arene)][B(CF)] {arene = benzene (2), toluene (3), bromobenzene (4) and fluorobenzene (5)}. Compounds 2, 3, and 5 were crystallographically characterized, and in all cases the arene is π-coordinated. Solution NMR studies of 2-5 suggest that the binding preferences of the [(XA)U(CHSiMe)] cation follow the order: toluene ≈ benzene > bromobenzene > fluorobenzene.

Geometries, interaction energies and bonding in [Po(HO)] and [PoCl] complexes.

Polonium ( = 84) is one of the rarest elements on Earth. More than a century after its discovery, its chemistry remains poorly known and even basic questions have not yet been satisfactorily addressed. In this work, we perform a systematic study of the geometries, interactions energies and bonding in basic polonium(IV) species, namely the hydrated [Po(HO)] and chlorinated [PoCl] complexes by means of gas-phase electronic structure calculations.

Frozen-Density Embedding for Including Environmental Effects in the Dirac-Kohn-Sham Theory: An Implementation Based on Density Fitting and Prototyping Techniques.

Frozen density embedding (FDE) represents an embedding scheme in which environmental effects are included from first-principles calculations by considering the surrounding system explicitly by means of its electron density. In the present paper, we extend the full four-component relativistic Dirac-Kohn-Sham (DKS) method, as implemented in the BERTHA code, to include environmental and confinement effects with the FDE scheme (DKS-in-DFT FDE). The implementation, based on the auxiliary density fitting techniques, has been enormously facilitated by BERTHA's python API (PyBERTHA), which facilitates the interoperability with other FDE implementations available through the PyADF framework.

Environment Effects on X-Ray Absorption Spectra With Quantum Embedded Real-Time Time-Dependent Density Functional Theory Approaches.

In this work we implement the real-time time-dependent block-orthogonalized Manby-Miller embedding (rt-BOMME) approach alongside our previously developed real-time frozen density embedding time-dependent density functional theory (rt-TDDFT-in-DFT FDE) code, and investigate these methods' performance in reproducing X-ray absorption spectra (XAS) obtained with standard rt-TDDFT simulations, for model systems comprised of solvated fluoride and chloride ions ([X@ , X = F, Cl). We observe that for ground-state quantities such as core orbital energies, the BOMME approach shows significantly better agreement with supermolecular results than FDE for the strongly interacting fluoride system, while for chloride the two embedding approaches show more similar results. For the excited states, we see that while FDE (constrained not to have the environment densities relaxed in the ground state) is in good agreement with the reference calculations for the region around the K and L edges, and is capable of reproducing the splitting of the 1s (n + 1)p final states ( + 1 being the lowest virtual p orbital of the halides), it by and large fails to properly reproduce the 1s (n + 2)p states and misses the electronic states arising from excitation to orbitals with important contributions from the solvent.

Influence of the First Coordination of Uranyl on Its Luminescence Properties: A Study of Uranyl Binitrate with ,-Dialkyl Amide DEHiBA and Water.

Uranyl binitrate complexes have a particular interest in the nuclear industry, especially in the reprocessing of spent nuclear fuel. The modified PUREX extraction process is designed to extract U(VI) in the form of UO(NO)(L) as has been confirmed by extended X-ray absorption fine structure (EXAFS), X-ray diffraction (XRD), and time-resolved laser-induced fluorescence spectroscopy (TRLFS) measurements. In this study, the L ligands are two molecules of ,-di-(ethyl-2-hexyl)isobutyramide (DEHiBA) monoamide used to bind uranyl in its first coordination sphere.

Revisiting the Complexation of Cm(III) with Aqueous Phosphates: What Can We Learn from the Complex Structures Using Luminescence Spectroscopy and Simulations?

The coordination chemistry of Cm(III) with aqueous phosphates was investigated by means of laser-induced luminescence spectroscopy and simulations. For the first time, in addition to the presence of Cm(HPO), the formation of Cm(HPO) was unambiguously established from the luminescence spectroscopic data collected at various H concentrations (-log [H] = 2.52, 3.

Structure-Property Relationships in Photoluminescent Bismuth Halide Organic Hybrid Materials.

Seven novel bismuth(III)-halide phases, BiCl(terpy)·0.5(HO) (), BiCl(terpy)(-TC)() (TC = 2-thiophene monocarboxylate), BiCl(terpy)(-TC) (), BiBr(terpy)(-TC) (), BiCl(terpy)(-TC) (), [BiCl(terpy)(-TC)][Bi(terpy)(-TC)]·0.55(TCA) (), [BiBr(terpy)(MeOH)] (), and [BiBr(terpy)(-TC)][BiBr(terpy)(-TC)] (), were prepared under mild synthetic conditions from methanolic/aqueous solutions containing BiX (X = Cl, Br) and 2,2':6',2″-terpyridine (terpy) and/or 2-thiophene monocarboxylic acid (TCA).

Insights from quantum chemical calculations into inner and outer-sphere complexation of plutonium(IV) by monoamide and carbamide extractants.

The strong influence of the structure of amide derivatives on their extraction properties has been demonstrated in several studies in the literature. To investigate and rationalize the influence of the nature and length of the monoamide alkyl chains on Pu(iv) extraction/complexation, a theoretical study was performed using the Density Functional Theory (DFT) method in the scalar relativistic framework. For that, the geometries for the inner/outer-sphere complexes and interaction energies of [Pu(NO3)4] and [Pu(NO3)6]2- with different ligands have been calculated.

Influence of Alkaline Earth Metal Ions on Structures and Luminescent Properties of NaMUO(CO) (M = Mg, Ca; , = 0-2): Time-Resolved Fluorescence Spectroscopy and Studies.

The luminescence spectra of triscarbonatouranyl complexes were determined by experimental and theoretical methods. Time-resolved laser-induced fluorescence spectroscopy was used to monitor spectra of uranyl and bicarbonate solutions at 0.1 mol kg ionic strength and pH 8.

Synthesis and photoluminescence of three bismuth(III)-organic compounds bearing heterocyclic N-donor ligands.

Three bismuth(iii)-organic compounds, [Bi4Cl8(PDC)2(phen)4]·2MeCN (1), [BiCl3(phen)2] (2), and [Bi2Cl6(terpy)2] (3), were prepared from solvothermal reactions of bismuth chloride, 2,6-pyridinedicarboxylic acid (H2PDC), and 1,10-phenanthroline (phen) or 2,2';6',2''-terpyridine (terpy). The structures were determined through single crystal X-ray diffraction and the compounds were further characterized via powder X-ray diffraction, Raman and infrared spectroscopy, and thermogravimetric analysis. The photoluminescence properties of the solid-state materials were assessed using steady state and time-dependent techniques to obtain excitation and emission profiles as well as lifetimes.

Conformational Landscape of Oxygen-Containing Naphthalene Derivatives.

Polycyclic aromatic compounds (PACs) constitute an important class of molecules found in various environments and are considered important pollutants of the Earth's atmosphere. In particular, functionalization of PACs modify the ring aromaticity, which greatly influences the chemical reactivity of these species. In this work we studied several oxygen-containing PACs, relevant to atmospheric chemistry.

Carbon-sulfur bond strength in methanesulfinate and benzenesulfinate ligands directs decomposition of Np(v) and Pu(v) coordination complexes.

Gas-phase coordination complexes of actinyl(v) cations, AnO, provide a basis to assess fundamental aspects of actinide chemistry. Electrospray ionization of solutions containing an actinyl cation and sulfonate anion CHSO or CHSO generated complexes [(AnO)(CHSO)] or [(AnO)(CHSO)] where An = Np or Pu. Collision induced dissociation resulted in C-S bond cleavage for methanesulfinate to yield [(AnO)(CHSO)(SO)], whereas hydrolytic ligand elimination occurred for benzenesulfinate to yield [(AnO)(CHSO)(OH)].