The thermal expansion coefficient (αexp.), the molecular volume (Vm), the entropy of surface formation (Sa), and the Gibbs energy of surface formation (Ea) of four pentaalkylguanidinium-based MILs [CnTMG][FeCl3Br] (n = 2, 4, 6, 8) were calculated based on the density and surface tension data determined from 278.15 to 323.15 K. In terms of classical semiempirical methods, the standard molar entropy ( S 0 ), the lattice energy (UPOT), the molar enthalpy of evaporation (Δg lH0 m(Tb), Δg lH0 m(298 K)), and the thermal expansion coefficient (αest.) of the MILs were further estimated. The estimation results indicate that the classical semiempirical methods are suitable for estimating the thermophysical properties of the MILs, except the unusual αexp., which were extremely larger than those of representative non-magnetic ionic liquids (ILs). We further optimized the estimation methods and discussed the potential reasons for the unusual thermal expansion coefficient of the MILs.

Chameleon sequences are amino acid sequences found in several distinct configurations in experiment. They challenge our understanding of the link between sequence and structure, and provide insight into structural competition in proteins. Here, we study the energy landscapes for three such sequences, and interrogate how pulling and twisting forces impact the available structural ensembles. Chameleon sequences do not necessarily exhibit multiple structural ensembles on a multifunnel energy landscape when we consider them in isolation. The application of even small forces leads to drastic changes in the energy landscapes. For pulling forces, we observe transitions from helical to extended structures in a very small span of forces. For twisting forces, the picture is much more complex, and highly dependent on the magnitude and handedness of the applied force as well as the reference angle for the twist. Depending on these parameters, more complex and more simplistic energy landscapes are observed alongside more and less diverse structural ensembles. The impact of even small forces is significant, confirming their likely role in folding events. In addition, small forces exerted by the remaining scaffold of a protein may be sufficient to lead to the adoption of a specific structural ensemble by a chameleon sequence.

One-dimensional titanium dioxide photocatalysts with a Pt co-catalyst exhibit a remarkable selectivity of nearly 100 % in converting ethanol into valuable 1,1-diethoxyethane, which is different from typical acetaldehyde production on titanium dioxide nanoparticles. The introduced oxygen vacancies in the catalyst help double the ethanol transformation rate with respect to that of its pristine counterpart.

Abstract

Developing an environmentally benign and highly effective strategy for the value-added conversion of biomass platform molecules such as ethanol has emerged as a significant challenge and opportunity. This challenge stems from the need to harness renewable solar energy and conduct thermodynamically unfavorable reactions at room temperature. To tackle this challenge, one-dimensional titanium dioxide photocatalysts have been designed and fabricated to achieve a remarkable photocatalytic selectivity of almost 100 % for transforming ethanol into value-added 1,1-diethoxyethane, contrasting the primary production of acetaldehyde in titanium dioxide nanoparticles. By incorporating a Pt co-catalyst and infusing oxygen vacancies into the one-dimensional catalyst, the ethanol transformation rate was doubled to 128.8 mmol g⁻¹ h⁻¹ with respect to that of its unmodified counterpart (about 66.7 mmol g⁻¹ h⁻¹). The underlying mechanism for this high conversion and selectivity resides in the narrowed bandgap of the catalyst and the prolonged lifetime of the photo-generated carriers. This is a promising strategy for the photocatalytic transformation of essential biomass platform molecules that intertwines morphological control and defect engineering.

The performance of heteronuclear cluster [AlFeO3]+ in activating methane has been explored by a combination of high-level quantum chemical calculations with gas-phase experiments. At room temperature, [AlFeO3]+ is a mixture of 7[AlFeO3]+ and 5[AlFeO3]+, in which two states lead to different reactivity and chemoselectivity for methane activation. While hydrogen abstraction from methane is the only product channel for the 7[AlFeO3]+/CH4 couple, 5[AlFeO3]+ is able to convert this substrate to formaldehyde. In addition, the introduction of an external electric field may regulate the reactivity and product selectivity. The interesting doping effect of Fe and the associated electronic origins are discussed, which may guide one on the design of Fe-involved catalyst for methane conversion.

Using density functional calculations, transition metal (TM₁)-graphdiyne (GDY), where TM=Mn, Co and Cu, are shown to exhibit good catalytic activity for CO₂ reduction. For Cu₁−GDY, CO₂ converts to HCOOH with a limiting potential of −0.16 V. Additionally, Mn₁−GDY and Co₁−GDY show excellent catalytic selectivity for CO₂ reduction to CH₄.

Abstract

Anchoring transition metal (TM) atoms on suitable substrates to form single-atom catalysts (SACs) is a novel approach to constructing electrocatalysts. Graphdiyne with sp−sp² hybridized carbon atoms and uniformly distributed pores have been considered as a potential carbon material for supporting metal atoms in a variety of catalytic processes. Herein, density functional theory (DFT) calculations were performed to study the single TM atom anchoring on graphdiyne (TM₁−GDY, TM=Sc, Ti, V, Cr, Mn, Co and Cu) as the catalysts for CO₂ reduction. After anchoring metal atoms on GDY, the catalytic activity of TM₁−GDY (TM=Mn, Co and Cu) for CO₂ reduction reaction (CO₂RR) are significantly improved comparing with the pristine GDY. Among the studied TM₁−GDY, Cu₁−GDY shows excellent electrocatalytic activity for CO₂ reduction for which the product is HCOOH and the limiting potential (U_L) is −0.16 V. Mn₁−GDY and Co₁−GDY exhibit superior catalytic selectivity for CO₂ reduction to CH₄ with U_L of −0.62 and −0.34 V, respectively. The hydrogen evolution reaction (HER) by TM₁−GDY (TM=Mn, Co and Cu) occurs on carbon atoms, while the active sites of CO₂RR are the transition metal atoms . The present work is expected to provide a solid theoretical basis for CO₂ conversion into valuable hydrocarbons.

A high-level ab initio benchmark study of copper clusters Cu₅ is presented. It reveals the key role of non-adiabatic effects and Jahn-Teller distortions in making them fluxional. This property ultimately facilitates their interaction with environmental molecules, thus enhancing their functioning as catalysts.

Abstract

Novel highly selective synthesis techniques have enable the production of atomically precise monodisperse metal clusters (AMCs) of subnanometer size. These AMCs exhibit ‘molecule-like’ structures that have distinct physical and chemical properties, significantly different from those of nanoparticles and bulk material. In this work, we study copper pentamer Cu₅ clusters as model AMCs by applying both density functional theory (DFT) and high-level (wave-function-based) ab initio methods, including those which are capable of accounting for the multi-state multi-reference character of the wavefunction at the conical intersection (CI) between different electronic states and augmenting the electronic basis set till achieving well-converged energy values and structures. After assessing the accuracy of a high-level multi-multireference ab initio protocol for the well-known Cu₃ case, we apply it to demonstrate that bypiramidal Cu₅ clusters are distorted Jahn-Teller (JT) molecules. The method is further used to evaluate the accuracy of single-reference approaches, finding that the coupled cluster singles and doubles and perturbative triples CCSD(T) method delivers the results closer to our ab initio predictions and that dispersion-corrected DFT can outperform the CCSD method. Finally, we discuss how JT effects and, more generally, conical intersections, are intimately connected to the fluxionality of AMCs, giving them a ‘floppy’ character that ultimately facilitates their interaction with environmental molecules and thus enhances their functioning as catalysts.

“In order to explain the enhancement of catalytic activities in atomic metal clusters, the concept of ‘structural fluxionality’ has been frequently invoked…” This and more about the story behind the front cover can be found in the Research Article at 10.1002/cphc.202300317.

Abstract

The front cover artwork is provided by María Pilar de Lara-Castells, Head of the AbinitFot Group at IFF-CSIC (Madrid), Coordinator of the National Project “COSYES”, and Chair of the COST Action CA21101 “COSY“, and Alexander O. Mitrushchenkov from the Université Paris-Est. The image shows the connection between the Jahn-Teller effect featured by bypiramidal Cu₅ clusters and the property of fluxionality. Cover design by Katarzyna Krupka. Read the full text of the Research Article at 10.1002/cphc.202300317.

The Cover Feature illustrates the decay of a resonance state of the water molecule into a vibrationally excited water cation (autoionization) or to neutral fragments (dissociative recombination). The branching ratio between the two channels depends on the resonance properties. More information can be found in the Research Article by Ismanuel Rabadán and co-workers .

The Cover Feature illustrates the transfer of polarization from ¹²⁹Xe nuclear spins, polarized via spin exchange optical pumping, to thermally polarized ¹H spins in solution. The enhancement of the ¹H spin polarization is obtained by simply bubbling hyperpolarized ¹²⁹Xe gas in solution, under standard temperature and pressure, and can be directly observed at ultralow magnetic field strengths, without the need to suppress the signal originating from thermally polarized ¹H. More information can be found in the Research Article by Rosa Tamara Branca and co-workers.

The functional amyloid fibril forming parathyroid hormone exhibits a prenucleation monomer-oligomer equilibrium with concentration dependent cluster sizes. Here, the critical concentration for fibril formation is the minimum concentration of a trimer/tetramer which is furthermore involved in primary fibril nucleation. In equilibrium with fibrils, the soluble fraction adopts to the monomer-dimer equilibrium below the critical concentration.

Abstract

Nucleation and growth of amyloid fibrils were found to only occur in supersaturated solutions above a critical concentration (c _crit). The biophysical meaning of c _crit remained mostly obscure, since typical low values of c _crit in the sub-μM range hamper investigations of potential oligomeric states and their structure. Here, we investigate the parathyroid hormone PTH₈₄ as an example of a functional amyloid fibril forming peptide with a comparably high c _crit of 67±21 μM. We describe a complex concentration dependent prenucleation ensemble of oligomers of different sizes and secondary structure compositions and highlight the occurrence of a trimer and tetramer at c _crit as possible precursors for primary fibril nucleation. Furthermore, the soluble state found in equilibrium with fibrils adopts to the prenucleation state present at c _crit. Our study sheds light onto early events of amyloid formation directly related to the critical concentration and underlines oligomer formation as a key feature of fibril nucleation. Our results contribute to a deeper understanding of the determinants of supersaturated peptide solutions. In the current study we present a biophysical approach to investigate c _crit of amyloid fibril formation of PTH₈₄ in terms of secondary structure, cluster size and residue resolved intermolecular interactions during oligomer formation. Throughout the investigated range of concentrations (1 μM to 500 μM) we found different states of oligomerization with varying ability to contribute to primary fibril nucleation and with a concentration dependent equilibrium. In this context, we identified the previously described c _crit of PTH₈₄ to mark a minimum concentration for the formation of homo-trimers/tetramers. These investigations allowed us to characterize molecular interactions of various oligomeric states that are further converted into elongation competent fibril nuclei during the lag phase of a functional amyloid forming peptide.