Understanding covalency in molecular f-block compounds from the synergy of spectroscopy and quantum chemistry.

One of the most intensely studied areas of f-block chemistry is the nature of the bonds between the f-element and another species, and in particular the role played by covalency. Computational quantum chemical methods have been at the forefront of this research for decades and have a particularly valuable role, given the radioactivity of the actinide series. The very strong agreement that has recently emerged between theory and the results of a range of spectroscopic techniques not only facilitates deeper insight into the experimental data, but it also provides confidence in the conclusions from the computational studies.

Quantifying Covalency and Environmental Effects in RASSCF-Simulated O K-Edge XANES of Uranyl.

A RASSCF approach to simulate the O K-edge XANES spectra of uranyl is employed, utilizing three models that progressively improve the representation of the local crystal environment. Simulations successfully reproduce the observed three-peak profile of the experimental spectrum and confirm peak assignments made by Denning. The [UOCl] model offers the best agreement with experiment, with peak positions (to within 1 eV) and relative peak separations accurately reproduced.

Cytosponge procedures produce fewer respiratory aerosols and droplets than esophagogastroduodenoscopies.

Esophagogastroduodenoscopies (EGD) are aerosol-generating procedures that may spread respiratory pathogens. We aim to investigate the production of airborne aerosols and droplets during Cytosponge procedures, which are being evaluated in large-scale research studies and National Health Service (NHS)implementation pilots to reduce endoscopy backlogs. We measured 18 Cytosponge and 37 EGD procedures using a particle counter (diameters = 0.

Tailoring the pore size of expanded porphyrinoids for lanthanide selectivity.

Despite increase in demand, capacity for the recycling of rare earth elements remains limited, partly due to the inefficiencies with processes currently utilised in the separation of lanthanides. This study highlights the potential use of expanded porphyrinoids in lanthanide separation through selective binding, dependent on the tailored pore size of the macrocycle. Each emerging trend is subjected to multi-factored analysis to decompose the underlying source.

Bounding [AnO] (An = U, Np) covalency by simulated O K-edge and An M-edge X-ray absorption near-edge spectroscopy.

Restricted active space simulations are shown to accurately reproduce and characterise both O K-edge and U M-edge spectra of uranyl in excellent agreement with experimental peak positions and are extended to the Np analogue. Analysis of bonding orbital composition in the ground and O K-edge core-excited states demonstrates that metal contribution is underestimated in the latter. In contrast, An M-edge core-excited states produce bonding orbital compositions significantly more representative of those in the ground state.

The role of covalency in enhancing stability of Eu and Am complexes: a DFT comparison of BTP and BTPhen.

We compare the stabilities and bonding nature of [Eu/Am(BTPhen)(NO)] complexes to those previously reported for [Eu/Am(BTP)], and investigate whether more accurately reflecting the reaction conditions of the separation process by considering [Eu/Am(NO)(HO)] ( = 3, 4) complexes instead of aquo complexes increases the selectivity of the separation ligands BTP and BTPhen for Am over Eu. The geometric and electronic structures of [Eu/Am(BTPhen)(NO)] and [Eu/Am(NO)(HO)] ( = 3, 4) have been evaluated using density functional theory (DFT) and used as the basis for analysis of the electron density through the application of the quantum theory of atoms in molecules (QTAIM). Increased covalent bond character for the Am complexes of BTPhen over Eu analogues was found, with this increase more pronounced than that found in BTP complexes.

Detailed statistical analysis plan for a randomised controlled trial of the effects of a modified muscle sparing posterior technique (SPAIRE) in hip hemiarthroplasty for displaced intracapsular fractures on post-operative function compared to a standard lateral approach: HemiSPAIRE.

Background: The HemiSPAIRE trial is being conducted to determine whether a modified muscle sparing technique (SPAIRE-"Save Piriformis and Internus, Repairing Externus") in hip hemiarthroplasty brings clinical benefits compared to the standard lateral technique in adults aged 60 years or older, with a displaced intracapsular hip fracture. This article describes the detailed statistical analysis plan for the trial.  METHODS AND DESIGN: HemiSPAIRE is a definitive, pragmatic, superiority, multicentre, randomised controlled trial (with internal pilot) with two parallel groups.

A theoretical investigation of uranyl covalency symmetry-preserving excited state structures.

Time dependent density functional theory (TDDFT) calculations have been performed on a series of symmetry-preserving excited states of the uranyl dication, UO. The simulated excited state electronic structures are compared to that of the ground state at both ground and excited state-optimised geometries. For the first time, the Quantum Theory of Atoms in Molecules (QTAIM) has been applied to the excited states electronic structures of uranyl in order to quantify the variation in bond covalency upon electronic excitation.

Exploring the Electrochemistry of Iron Dithiolene and Its Potential for Electrochemical Homogeneous Carbon Dioxide Reduction.

In this work, the dithiolene complex iron(III) bis-maleonitriledithiolene [Fe(mnt)] is characterised and evaluated as a homogeneous CO reduction catalyst. Electrochemically the Fe(mnt) is reduced twice to the trianionic Fe(mnt) state, which is correspondingly found to be active towards CO. Interestingly, the first reduction event appears to comprise overlapping reversible couples, attributed to the presence of both a dimeric and monomeric form of the dithiolene complex.

Does Reduction-Induced Isomerization of a Uranium(III) Aryl Complex Proceed via C-H Oxidative Addition and Reductive Elimination across the Uranium(II/IV) Redox Couple?

Reaction of the uranium(III) bis(amidinate) aryl complex {TerphC(NPr)}U(Terph) (, where Terph = 4,4″-di--butyl--terphenyl-2'-yl) with a strong reductant enabled isolation of isomeric uranium(III) bis(amidinate) aryl product {TerphC(NPr)}U(Terph*) (, where Terph* = 4,4″-di--butyl--terphenyl-4'-yl). In terms of connectivity, differs from only in the positions of the U-C and C-H bonds on the central aryl ring of the -terphenyl-based ligand. A deuterium labeling study ruled out mechanisms for this isomerization involving intermolecular abstraction or deprotonation of the ligand C-H bonds activated during the reaction.

Use of a Cytosponge biomarker panel to prioritise endoscopic Barrett's oesophagus surveillance: a cross-sectional study followed by a real-world prospective pilot.

Background: Endoscopic surveillance is recommended for patients with Barrett's oesophagus because, although the progression risk is low, endoscopic intervention is highly effective for high-grade dysplasia and cancer. However, repeated endoscopy has associated harms and access has been limited during the COVID-19 pandemic. We aimed to evaluate the role of a non-endoscopic device (Cytosponge) coupled with laboratory biomarkers and clinical factors to prioritise endoscopy for Barrett's oesophagus.

Photoluminescence of Pentavalent Uranyl Amide Complexes.

Pentavalent uranyl species are crucial intermediates in transformations that play a key role for the nuclear industry and have recently been demonstrated to persist in reducing biotic and abiotic aqueous environments. However, due to the inherent instability of pentavalent uranyl, little is known about its electronic structure. Herein, we report the synthesis and characterization of a series of monomeric and dimeric, pentavalent uranyl amide complexes.

Systematic Investigation of the Molecular and Electronic Structure of Thorium and Uranium Phosphorus and Arsenic Complexes.

In continuing to examine the interaction of actinide-ligand bonds with soft donor ligands, a comparative investigation with phosphorus and arsenic was conducted. A reaction of (CMe)AnMe, An = Th, U, with 2 equiv of HAsMes, Mes = 2,4,6-MeCH, forms the primary bis(arsenido) complexes, (CMe)An[As(H)Mes]. Both exhibit thermal instability at room temperature, leading to the elimination of H, and the formation of the diarsenido species, (CMe)An(η-AsMes).

Ab initio molecular dynamics studies of hydroxide coordination of alkaline earth metals and uranyl.

Ab initio molecular dynamics (AIMD) simulations of the Mg2+, Ca2+, Sr2+ and UO22+ ions in either a pure aqueous environment or an environment containing two hydroxide ions have been carried out at the density functional level of theory, employing the generalised gradient approximation via the PBE exchange-correlation functional. Calculated mean M-O bond lengths in the first solvation shell of the aquo systems compared very well to existing experimental and computational literature, with bond lengths well within values measured previously and coordination numbers in line with previously calculated values. When applied to systems containing additional hydroxide ions, the methodology revealed increased bond lengths in all systems.

Energy-Degeneracy-Driven Covalency in Actinide Bonding.

Evaluating the nature of chemical bonding for actinide elements represents one of the most important and long-standing problems in actinide science. We directly address this challenge and contribute a Cl K-edge X-ray absorption spectroscopy and relativistic density functional theory study that quantitatively evaluates An-Cl covalency in AnCl (An = Th, U, Np, Pu). The results showed significant mixing between Cl 3p- and An 5f- and 6d-orbitals (t*/t* and t*/e *), with the 6d-orbitals showing more pronounced covalent bonding than the 5f-orbitals.

Coordination Chemistry and QTAIM Analysis of Homoleptic Dithiocarbamate Complexes, M(SCNPr) (M = Ti, Zr, Hf, Th, U, Np).

In a systematic approach to comparing the molecular structure and bonding in homoleptic transition-metal and actinide complexes, a series of dithiocarbamates, M(SCNPr) (M = Ti, Zr, Hf, Th, U, Np), have been synthesized. These complexes have been characterized through spectroscopic and X-ray crystallographic analysis, and their bonding has been examined using density functional theory calculations. Computational results indicate that the covalent character associated with the M-S bonds shows the trend of Hf < Zr < Th < Ti < U ≈ Np.

Elucidation of the inverse trans influence in uranyl and its imido and carbene analogues via quantum chemical simulation.

The inverse trans influence (ITI) is investigated in uranyl, UO22+, and its isoelectronic imido (U(NH)22+) and carbene (U(CH2)22+) analogues at the density functional and complete active space self consistent field levels of theory. The quantum theory of atoms in molecules is employed to quantify, for the first time, the effect of the ITI on covalent bond character and its relationship to bond lengths and complex stability.

Solubility prediction from first principles: a density of states approach.

Solubility is a fundamental property of widespread significance. Despite its importance, its efficient and accurate prediction from first principles remains a major challenge. Here we propose a novel method to predict the solubility of molecules using a density of states (DOS) approach from classical molecular simulation.

How to Bend the Uranyl Cation via Crystal Engineering.

Bending the linear uranyl (UO) cation represents both a significant challenge and opportunity within the field of actinide hybrid materials. As part of related efforts to engage the nominally terminal oxo atoms of uranyl cation in noncovalent interactions, we synthesized a new uranyl complex, [UO(CHN)(CHClO)]·2HO (complex 2), that featured both deviations from equatorial planarity and uranyl linearity from simple hydrothermal conditions. Based on this complex, we developed an approach to probe the nature and origin of uranyl bending within a family of hybrid materials, which was done via the synthesis of complexes 1-3 that display significant deviations from equatorial planarity and uranyl linearity (O-U-O bond angles between 162° and 164°) featuring 2,4,6-trihalobenzoic acid ligands (where Hal = F, Cl, and Br) and 1,10-phenanthroline, along with nine additional "nonbent" hybrid materials that either coformed with the "bent" complexes (4-6) or were prepared as part of complementary efforts to understand the mechanism(s) of uranyl bending (7-12).

Author Correction: The inverse-trans-influence in tetravalent lanthanide and actinide bis(carbene) complexes.

This corrects the article DOI: 10.1038/ncomms14137.

Unravelling the electronic structure and dynamics of an isolated molecular rotary motor in the gas-phase.

Light-driven molecular motors derived from chiral overcrowded alkenes are an important class of compounds in which sequential photochemical and thermal rearrangements result in unidirectional rotation of one part of the molecule with respect to another. Here, we employ anion photoelectron spectroscopy to probe the electronic structure and dynamics of a unidirectional molecular rotary motor anion in the gas-phase and quantum chemistry calculations to guide the interpretation of our results. We find that following photoexcitation of the first electronically excited state, the molecule rotates around its axle and some population remains on the excited potential energy surface and some population undergoes internal conversion back to the electronic ground state.

Quantification of f-element covalency through analysis of the electron density: insights from simulation.

The electronic structure of f-element compounds is complex due to a combination of relativistic effects, strong electron correlation and weak crystal field environments. However, a quantitative understanding of bonding in these compounds is becoming increasingly technologically relevant. Recently, bonding interpretations based on analyses of the physically observable electronic density have gained popularity and, in this Feature Article, the utility of such density-based approaches is demonstrated.

Actinide covalency measured by pulsed electron paramagnetic resonance spectroscopy.

Our knowledge of actinide chemical bonds lags far behind our understanding of the bonding regimes of any other series of elements. This is a major issue given the technological as well as fundamental importance of f-block elements. Some key chemical differences between actinides and lanthanides-and between different actinides-can be ascribed to minor differences in covalency, that is, the degree to which electrons are shared between the f-block element and coordinated ligands.

Ligand size dependence of U-N and U-O bond character in a series of uranyl hexaphyrin complexes: quantum chemical simulation and density based analysis.

A series of uranyl complexes with hexaphyrin ligands are investigated at the density functional level of theory and analysed using a variety of density-based techniques. A relationship is identified between the size of the ligand and the stability of the complex, controlled by the presence of meso-carbon centres in the porphyrin ring. The complex with the smallest ligand, cyclo[6]pyrrole, is found to have enhanced covalent character in equatorial U-N bonds as defined by the quantum theory of atoms in molecules (QTAIM), as well as enhanced stability, compared to the larger complexes.