Chemphyschem最新文献

Activating molecular nitrogen (N₂) under ambient conditions remains a major challenge. Dual Lewis acid–base molecular cages are investigated to cooperatively activate N₂ using computational chemistry. Cages composed of Lewis acids (LA) and Lewis bases (LB) connected by a linker chain ([LA,LB]_C) are analyzed via binding free energies, interaction and deformation energies, bond lengths, angles, and Wiberg bond indices and charge distributions. Two interaction arrangements emerge: 1) rigid systems with strong LA-LB dative bonds that deform substantially upon N₂ binding and do not act as frustrated Lewis pairs (FLPs), and 2) flexible cages with extended LA-LB separations displaying typical FLP behavior. Borylene donors enable strong, stable N₂ interactions, particularly in systems 6a and 7c, whereas Verkade's base is less effective. Structural flexibility and electronic tuning of LA/LB centers are fundamental for efficient activation. Natural bond orbital and quantum theory of atoms in molecules analyses reveal partially covalent electrostatic interactions at the acidic site and covalent interactions at the basic site. These results provide design principles for molecular cages for N₂ activation.

Cobalt selenides (CoSe_x) are promising oxygen evolution reaction (OER) catalysts due to their tunable electronic structure and reconstruction behavior. However, the role of selenium (Se) in this process remains incompletely understood. In this study, the electrochemical transformation of CoSe is investigated during alkaline OER, and explore how residual Se influences catalytic activity. The results show that while surface selenium is largely leached away, selenium retention is observed in the subsurface and bulk regions, with a uniform distribution even after prolonged electrolysis. This residual selenium appears to aid in the formation and stabilization of highly oxidized cobalt species, such as Co³⁺ and Co⁴⁺, by influencing the local electronic structure during potential-driven reconstruction. In particular, it modulates the oxidation pathway toward CoO₂ via β-CoOOH. These structural and compositional changes correlate with enhanced OER activity compared to Se-free Co samples. The findings suggest that residual Se acts as a modulator, which provides valuable insights for designing high-performance transition metal chalcogenide electrocatalysts.

Single-molecule Förster resonance energy transfer (smFRET) studies of highly structured RNA molecules are often frustrated by issues with efficient dye conjugation. Here, a DNA scaffold-based labeling strategy is developed, and applied to the frameshift-stimulating RNA pseudoknot from the SARS-CoV-2 genome. FRET-active reporters were prepared containing both Cy3 (donor) and Cy5 (acceptor) molecules and measurements conducted on freely-diffusing single molecules, enabling the evaluation of conformational heterogeneity via smFRET population distributions. Freely diffusing pseudoknots, modified at the base of stem 1, display a broad range of NaCl-dependent FRET states in solution, consistent with conformational freedom that extends beyond the static X-ray and cryo-EM structures. This work is a proof-of-principle demonstration of the feasibility of our DNA scaffold approach in enabling smFRET studies on this important class of biomolecule. Together, this work outlines new biochemical and biophysical approaches toward the study of RNA conformational dynamics in pseudoknots, riboswitches, and other structured RNA elements.

Ambipolar molecules are of significant importance in the field of organic electronics and semiconductor devices primarily due to their dual charge carrier transport nature, which results in simplification of device design, enhanced device performance, tuning of electrical properties, and versatility in application. In this study, density functional theory (DFT)-based calculations are performed to examine the effects of sequential cyanation (–CN) on the adiabatic ionization potential (IP), adiabatic electron affinity (EA), reorganization energies (λ_h and λ_e), and charge transfer rate (K^≠) along with charge (hole and electron) injection possibility for a series of derivatives based on already synthesized 5,7,12,14-tetraazapentacene (N4PENT) as the core moiety. The results illustrate that introducing two or more cyanide (–CN) groups onto the N4PENT core is sufficient to induce stable ambipolar charge transport properties, trending toward n-type semiconducting character. Besides, analysis of the density of states (DOS) offers a clear understanding of how sequential cyanation affects the distribution of electron density. Overall, this study underscores a rational foundation for designing stable ambipolar organic semiconductors (OSCs), which can significantly advance organic electronics, leading to more efficient and adaptable electronic devices applicable in flexible electronics, wearable technology, and low-cost displays.

A computational study has been performed to investigate the mechanisms of both the iridium-catalyzed amidocarbonylation of olefins and the CH bond activation using sulfoxonium ylide as a carbene precursor. For the iridium-catalyzed amidocarbonylation of olefins, the optimal mechanism involves deprotonation, migratory insertion of the olefin, carbenation, carbene insertion, and protonation, with protonation identified as the rate-determining step. Conversely, Ir-catalyzed CH activation proceeds through CH bond activation, carbenation, carbene insertion, and protonation, where CH bond activation constitutes the rate-determining step. Computational result further reveals that Rh-catalyzed amidocarbonylation of olefins exhibits a higher activation barrier (25.7 kcal mol⁻¹), with carbenation as the rate-limiting step, sharply contrasting with the iridium-catalyzed system. The second-order perturbation theory analysis (SOPT) reveals significant charge delocalization between lone-pair electrons, bonding (BD), and antibonding (BD*) orbitals. This electronic delocalization rationalizes the observed energy disparities during Ir- versus Rh-carbene formation. Supporting this, natural bond orbital charge analysis of carbenation transition states confirms a lower activation barrier for Ir-carbene formation compared to Rh-carbene formation.

This article focuses on the development of bioinspired hybrid polymeric microspheres for the efficient removal of tetracycline hydrochloride (TC) from aqueous solutions, leveraging the renewable and abundant nature of lignin as a sustainable component. The microspheres are synthesized via suspension polymerization, incorporating ethylene glycol dimethacrylate (EGDMA), vinyl acetate (VA), 1-vinyl-2-pyrrolidone (VP), various acrylate monomers, silane compounds, and fractionated lignin to enhance functionality and ecofriendliness. The objective is to create thermally stable, morphologically defined sorbents with high adsorption capacity. Thermogravimetric analysis revealed excellent thermal resistance up to 305–335 °C, while scanning electron microscopy confirmed uniform spherical morphology. Sorption studies demonstrated that microspheres with low-molecular-weight lignin (KS-6) exhibited a twofold increase in adsorption capacity (q_m up to 7.84 mg g⁻¹) compared to nonlignin counterparts, attributed to enhanced hydrogen bonding, π–π stacking, and electrostatic interactions. Kinetic data best fit the pseudo-second-order model (R² > 0.9999), indicating chemisorption as the dominant mechanism, with Freundlich isotherms suggesting multilayer adsorption on heterogeneous surfaces. These findings highlight the potential of lignin-based microspheres as cost-effective, sustainable sorbents for pharmaceutical pollutant removal, contributing to the valorization of lignin and advancing green water treatment technologies.

Determining the luminescent colors of phosphors used in display and lighting applications is a crucial step in discovering new functional luminescent materials. This study collects the experimental conditions for Ca₁₁(SiO₄)₄(BO₃)₂ (CSB) phosphor to produce different colors. Through 12 commonly used machine learning models and stacking ensemble model, the luminescence colors of CSB with different ion doping are accurately predicted, and the reliability of the results through experiments is verified. The findings demonstrate that the stacking ensemble model can effectively improve forecasting performance compared to a single optimal model, with overall accuracy, precision, recall score, and f1 score of 98.19%, 98.27%, 98.10%, and 98.18%, respectively. It is the best stacking ensemble model currently known. Compared with the single best classification model, the stacking ensemble model achieves relative improvements of ≈3.55%, 2.99%, 3.46%, and 3.89%, respectively. In addition, the Commission Internationale de L'Eclairage (CIE)-chromaticity diagram of the luminescence color of phosphors is successfully predicted by using a clustering method applied to the output of the stacking model; and experiments further verify the generalization performance of the model. The research results reveal that the stacking ensemble model has high precision and speed in predicting phosphor luminescence colors, and has great potential in optimizing luminescence properties.

Pt/TiO₂ catalysts show superior catalytic performance for HCHO removal. Unraveling the detailed mechanism of HCHO oxidation on Pt/TiO₂ is of great importance in guiding robust catalyst design. Herein, HCHO oxidation on Pt/TiO₂ (110) surface is studied by using density functional theory calculations. The results show that HCHO adsorbed at the Pt/TiO₂ interface and subsequent successive dehydrogenation formed CO* species. The Pt site acts as the active center for O₂ activation, and there is a positive linear relationship between the electrons accumulated on Pt site with O₂ adsorption energy. To elucidate how the active O* species is produced, the direct OO bond cleavage and hydrogen-assisted OOH bond cleavage are examined. With hydrogen assistance, the activation barrier of OOH bond cleavage is lowered to 0.33 eV, and the reaction is strongly exothermic (–1.48 eV), indicating that the hydrogen-assisted OOH cleavage path is both kinetically and thermodynamically more favorable. The present work provides mechanistic insight into HCHO oxidation on the Pt/TiO₂ (110) surface and useful guidance in catalyst design with high efficiency.

Complex IV of the mitochondrial respiratory chain, or cytochrome c oxidase (CcO), contributes to the proton motive force necessary for ATP synthesis. CcO can slow the formation of reactive oxygen species and is key to physiology and drug development. The exact molecular mechanisms underlying its proton-pumping function remain elusive. The redox state of CcO's metallic cofactors is intimately connected to structural changes and proton pumping via proton-coupled electron transfer. Time-resolved UV/Vis and IR spectroscopy are used to investigate the effects of the electronic backreaction triggered by photolyzing the CO-inhibited 2-electron reduced state, R₂CO, in the aa₃ oxidase from Cereibacter sphaeroides. An intermediate is identified, in which the binuclear center matches the redox state of the catalytic intermediate E (one-electron reduced state), with a rise time of ≈2 μs. The electron transfer induces structural changes that lead to E286 deprotonation, with a time constant of 13 μs. Thus, it is inferred that transient reduction of heme a alone drives E286 deprotonation. E286 is reprotonated with a time constant of 72 ms when CO rebinds. The results support the view that transient heme a reduction in the physiological E state modulates the electrostatic environment, triggering proton transfer toward the proton-loading site.

Electron transport in organic molecules and biomolecules is governed by electronic structure and molecular conformations. Despite recent progress, key challenges remain in understanding the role of intramolecular interactions and three-dimensional (3D) conformations on the electron transport behavior of organic molecules. In this work, the electronic properties of aromatic amide foldamers are characterized that organize into distinct 3D structures, including an extended secondary amide that adopts a trans-conformation and a folded N-methylated tertiary amide that adopts a cis-conformation. Results from single-molecule electronic experiments show that the extended secondary amide exhibits a fourfold enhancement in molecular conductance compared to the folded N-methylated tertiary amide, despite a longer contour length. The results show that extended amide molecules are governed by a through-bond electron transport mechanism, whereas folded amide molecules are dominated by through-space transport. Bulk spectroscopic characterization and density functional theory calculations further reveal that extended amides have a smaller HOMO–LUMO gap and larger transmission values compared to folded amides, consistent with single-molecule electronic experiments. Overall, this work shows that 3D molecular conformations significantly influence the electronic properties of single-molecule junctions.