Chemphyschem最新文献

The Cover Feature shows vacuum ultraviolet absorption spectra of fenchone (O) and its derivates thiofenchone (S) and selenofenchone (Se) in the centre, showcasing the bathochromic shifts of valence (π !π*) and Rydberg (3s, 4s, 5s) states. These shifts also lead to the colour changes in our samples, which are shown on the right. Calculated molecular structures are displayed on the left. In the background is shown an image of the vacuum chamber that was used to detect photo electrons, for example, to measure the photoelectron circular dichroism of these chiral molecules. More information can be found in the Research Article by A. Senftleben and co-workers (DOI: 10.1002/cphc.202500319).

Understanding the mechanism of CO₂ cycloaddition with epoxides under mild conditions is vital for advancing green carbon capture and utilization strategies. This work investigates the catalytic role of a defective ZIF-8 model with Zn–OH–Zn moieties and bromide (Br⁻) assistance in promoting the conversion of CO₂ and propylene oxide into propylene carbonate. Density-functional theory calculations reveal that, in the absence of a catalyst, the reaction proceeds through high activation barriers (52.02 kcal mol⁻¹ and 59.31 kcal mol⁻¹ for the α and β pathways, respectively). Upon introducing the Zn–OH–Zn site and Br⁻, the energy barrier for the rate-limiting ring-opening step is drastically lowered to 14.45 kcal mol⁻¹, confirming the synergistic effect between Lewis acid/base sites and halide assistance. The calculated reaction energy of −13.89 kcal mol⁻¹ aligns well with the experimental enthalpy change (−12.64 kcal mol⁻¹). This study provides molecular-level insights into the cooperative catalytic mechanism and supports defect-engineering strategies for metal–organic frameworks in CO₂ fixation applications.

Germanium (Ge) is a crucial semiconductor material. Germanium powder is typically manufactured through hydrogen reduction of germanium dioxide (GeO₂). However, the traditional reduction method frequently results in suboptimal hydrogen utilization, larger-than-desired granular sizes, and nonuniform granular distribution. In this article, a novel vertical gas-flow field reduction process is proposed for addressing the above challenges, and the effects of reduction temperature and hydrogen flow rate are investigated. The results show that the novel process promotes the contact between GeO₂ and hydrogen, reducing H₂O partial pressure at the reduction interface. Accordingly, conversion efficiency (the ratio of weight loss ratio W_t to the theoretical maximum weight loss ratio W_max) is much higher than the traditional method by 20%-30%, and the obtained Ge powder conforms to the desired dimensions and uniformity. This article provides a novel process for manufacturing high-quality germanium powder with a short production cycle, less hydrogen consumption, and low energy consumption.

Electrocatalytic nitrogen reduction reaction (NRR) provides a promising strategy for effective nitrogen fixation under mild conditions. Herein, structural stability and NRR catalytic activity of 29 transition metal (TM, Sc-Hg) atoms adsorbed Janus 2H-WSSe monolayers are studied using the first-principles calculations. Six screened TM@S/Se-WSSe (TM = Os, Re) and TM@Se-WSSe (TM = Ir, Mo) systems are considered promising single-atom catalysts (SACs) due to low limiting potential (−0.36 to −0.73 V) and high Faradaic efficiency (FE > 90.61%). High catalytic activity arises from the donation and back-donation mechanisms between the empty/unoccupied TM-d orbitals and the bonding/antibonding N₂-p orbitals, which significantly promote the activation of N₂ and the charge transfer in the subsequent hydrogenation reactions. In addition, the catalytic activity trend of the screened TM@WSSe systems is further analyzed by four descriptors (ΔG_*NNH, ΔG_*NH2, ΔG_*N, and φ). The high activity can be achieved by individually tuning ΔG_*NH2 or ΔG_*NNH. Meanwhile, the TM@WSSe with ΔG_*N = −1.38 eV and φ = 6 exhibits the best catalytic activity. The results provide insights into designing efficient nitrogen fixation electrocatalysts.

Stronger molecule-electrode coupling is associated with higher conductance in single-molecule junctions. This has been taken to imply that more coordination-what will be referred to here as higher denticity-between the molecule and the electrode is expected to impart higher conductance to the overall junction. Herein, this assumption using a single molecule construct, a rigid N-heterohexacene molecule with tetradentate ethyl sulfide (-SEt) anchors, is examined. Thus, rather than comparing a series of molecules with different anchoring groups, it is investigated how variations in effective denticity arise naturally within one molecule. Using the nonequilibrium Green's function technique in conjunction with density functional theory and mechanically controlled break-junction (MCBJ) experiments, it is found that increasing the denticity between the molecule and the electrode does not yield the expected higher conductance. Instead, simulated break-junction traces reveal a strong correlation between conductance and the dihedral angle between the electrode and the molecular core, with changes to dihedral angles providing far more variation in conductance values than denticity alone. In fact, it is shown that counter to naïve expectations, different denticities cannot be distinguished by conductance, merging instead into a single conductance feature. This is supported by MCBJ experiments on this molecule, where only a single conductance state is identified, suggesting that the expected denticity-dependent multistate conductance behavior is dominated by the effect of dihedral angles. By restricting dihedral angles to more favorable values by molecular design, the calculations show that significantly higher conductance values can still be achieved despite the limitations imposed by dihedral-denticity coupling. The work demonstrates that mere denticity may not be sufficient to design highly conductive molecular junctions, and that the association of conductance features with different denticities should be treated with caution.

In this work, a computational protocol has been developed to predict the ligand-based low-lying excited-state energies of Eu³⁺ coordination compounds with antenna ligands. A computational strategy, based on density functional theory (DFT) and time-dependent density functional theory (TD-DFT), has been developed using compounds with reliable structural and spectroscopic experimental data as a reference set. This approach aims to predict both the geometry and energy of the lowest-excited triplet state, critical factors influencing the efficiency of the antenna effect and energy transfer to the Eu³⁺ ion. The model not only shows the ability to replicate available experimental data at a relatively low computational cost, but also accurately predicts triplet-state energies for compounds that have not been included in the training set. This work is a first step toward the development of an affordable method for accurate predictions of the quantum yield of lanthanide-based complexes to assess their potential application as down-shifting spectral converters in solar cells.

Both the carbonyl and hydroxyl O atoms of the carboxyl group are capable of acting as electron donor in the context of noncovalent bonds. These two O atoms of acetic acid are each allowed to form an H-bond with HCl and a halogen bond with IF, and the interactions are monitored by quantum chemical calculations. The electrostatic potential on the carbonyl O is more negative than that on OH, and the HOMO is weighted toward the carbonyl. The interaction energies are consequently considerably stronger for the CO. A series of ligands are added to the carboxyl group that extract electron density from the carbonyl O and add density to OH. These arrangements enhance the interaction energies involving OH, some by nearly 50%. These same ligands have a lesser effect on bonds involving CO, many of which are actually strengthened, despite the reduced magnitude of its negative potential. Consequently, the CO remains the favored site for an electrophile, regardless of the ligands that might be present.

Upregulation of serine arginine protein kinase 1 (SRPK1), a protein responsible for phosphorylation of Ser–Arg rich residues aimed at SR proteins, is associated with apoptosis, poor survival, etc. Catalytic sites of the kinase proteins are incompetently preserved, causing difficulty in developing competitive inhibitors for ATP binding sites with broad selectivity; hence, search for inhibitor for the ATP binding pocket of SRPK1 is a necessity for medication against carcinogenesis. Natural product database is explored, and six small molecules are identified; having tolerable pharmacokinetics (low blood brain barrier, moderate clearance rate etc.) and quantum chemical properties are checked. Molecular docking study followed by molecular dynamics give insights into the effective interactions at the ATP pocket. Ligands are screened by MM-GBSA/NMA protocol, followed by estimation of unbinding potential of mean force (PMF) using well-tempered metadynamics. Well-tempered metadynamics confirmed unbinding PMF of −23.71 kcal mol⁻¹ for CNP0199214 and −14.81 kcal mol⁻¹ for MSC1186 (Lig_ref) to a relative difference in PMF of the screened ligand to be ≈7 kcal mol⁻¹. A probable gating mechanism is observed for the reference ligand (Lig_ref) at the protein interface resulting multiple minima in PMF, whereas Lig_4 (CNP0199214) exhibits greater affinity toward the active pocket and therefore choice for a potent compound.

Halide perovskite (HP) versatility for optoelectronic and electrochemical applications is mainly due to their ability to engineer cation mixtures at the A-site within the ABX₃ stoichiometry. Acetamidinium (AC⁺) is a common cation used in these mixed compositions, but its effects on the material's properties have not been addressed in detail. In this work, prototypical methylammonium lead iodide (MAPbI₃) compositions partially substituted with AC⁺ are synthesized and analyzed for structural, electrical, optoelectronic, and stability properties. Results reveal a solubility limit of around 10% AC⁺, lower than encountered in the literature, with slight effects on the phase transition temperatures. As expected, substitution with AC⁺ significantly reduces electronic conductivity and I–V hysteresis but only marginally increases the bandgap energy. Contrary to literature results, light-accelerated degradation tests show that AC⁺ incorporation does not significantly enhance the materials’ stability. Among several reasons, this might be related to weak interactions between AC⁺ cations and the inorganic framework. This study establishes the effects of AC⁺ substitution in halide perovskites and provides insights into optimizing A-site compositions for optoelectronic and electrochemical applications.

The Front Cover illustrates the solvent-controlled branching of a post-transition-state bifurcation (PTSB) in the reaction between 2-aminoacrolein and buta-1,3-diene. While a single ambimodal transition state connects to both 4+2 and 4+3 cycloadducts, explicit water molecules modulate the energy landscape and govern product selectivity. More information can be found in the Research Article by T. Murakami and co-workers (DOI: 10.1002/cphc.202500494). Artwork created by Art Action Inc.