Journal of Chemical Sciences最新文献

Anionic redox chemistry has emerged as a promising strategy to enhance the capacity of sodium-ion battery (SIB) cathode materials by leveraging both cationic and anionic redox processes. While anionic redox offers the potential for higher capacities, its practical implementation is often limited by challenges such as irreversibility, molecular oxygen release, and structural degradation at elevated voltages. In this study, we examine a series of hypothetical prototype cathode materials such as NaAlO₂, Na₂TiO₃, Na₂NiO₃, and Na₂MnO₃, using a funnel-based screening approach. Machine learning interatomic potentials are employed to efficiently pre-screen a wide range of structures with different vacancy orderings, enabling the identification of low-energy configurations. These candidate structures are subsequently refined through first-principles calculations based on density functional theory (DFT). To probe the underlying anionic redox mechanisms, we apply both the PBE and SCAN meta-GGA functionals, capturing the behaviour in iono-covalent and strongly covalent Na-ion systems. We define and evaluate key descriptors to quantitatively characterize oxygen redox activity, including changes in the occupancy of metal-d and oxygen-p orbitals, the number of holes generated in these states, and shifts in average net atomic charges. Additionally, we calculate the electronic structure, integrated Crystal Orbital Hamilton Population (COHP) and average operating voltage, using the SCAN functional. This comprehensive investigation offers valuable insights into tuning metal-oxygen bonding to achieve reversible anionic redox, facilitating the rational design of next-generation, high-capacity sodium-ion cathodes.

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An efficient and environmentally benign cyclocondensation of anthranilamide, aldehyde, and Anderson-type hexamolybdochromate (III) is described for the synthesis of 2,3-dihydroquinazolin-4(1H)-ones analog (DHQs) through a one-pot two-component reaction at room temperature. This method offers mild reaction conditions, simple purification without column chromatography, and moderate to good yields for constructing 2-substituted-2,3-dihydroquinazolin-4(1H)-one derivative. Various spectroscopic investigations are used to establish the structures of the target molecules.

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The present work reports the environmentally benign synthesis of 2-substituted-2,3-dihydroquinazolin-4(1H)-one analogs (2,3-DHQs) via the cyclocondenzation of 2-aminobenzamide and aldehydes at room temperature in an aqueous medium, using sodium hexamolybdochromate (III) as a catalyst. This methodology is efficient and simple, providing better product yield and reduced reaction time.

Halide double perovskites have been considered as the most competitive alternative of lead-based perovskite for various optoelectronic applications. With the aim of understanding the intricacies of electronic diversity in halide double perovskites, this work reports a comparative theoretical investigation of Cs₂NaEuCl₆ and Cs₂NaBiCl₆ using Density Functional Theory with the PBE and HSE06 functionals. In electronic structure, the distribution of states on the energy scale is found to vary with the functional, and the extent of variance is greater for Cs₂NaEuCl₆. In the case of Cs₂NaEuCl₆, Eu-4f states emerge as isolated states within the mid gap region, and the extent of isolation was found to be greater for the HSE06 functional. In contrast, Bi-6p states in Cs₂NaBiCl₆ have been found to significantly mingle with anion states. The isolation and mingling of Eu's and Bi's valence electrons, respectively, in the two HDPs, have been confirmed by B3LYP calculation on the corresponding molecular analogue under the LCAO-MO approach. Since the facets of perovskite are important for its chemical reactivity, the electron localization function has been plotted along the [010], [110] and [111] directions and a greater extent of localization of electrons around the anion is observed for Cs₂NaEuCl₆ in contrast to Cs₂NaBiCl_6.

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The transport of water at the nanoscale is fundamental to advancements in nanofluidics, membrane technology, and biological systems. While numerous studies have investigated the one-dimensional diffusion of water in carbon nanotubes (CNTs), its viscosity remains underreported. Experimental measurements of viscosity at this scale are challenging, but molecular dynamics simulations offer a viable alternative for predicting the viscosity of cylindrically confined water. Various methods have been employed for this purpose; however, their limitations raise questions about the accuracy of the predicted values. Our group has developed a novel approach, the Jump-corrected confined Stokes–Einstein (JCSE) method, based on the confined Stokes–Einstein equation, to estimate the viscosity of water within cylindrical nanopores. This technique is particularly promising because it accounts for the breakdown of the Stokes–Einstein relation in both confined and supercooled water, enhancing the reliability of viscosity predictions. In this short perspective, we introduce the JC-CSE method and its application to supercooled water confined in hydrophobic and superhydrophobic CNTs. Additionally, we rationalize viscosity trends using hydrogen-bond analysis. Finally, we provide a brief outlook on the broader applicability of this method to other confined liquids.

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This figure illustrates approaches to determining the viscosity under confinement. Traditional Green–Kubo relations are often inadequate, while the confined Stokes–Einstein relation offers alternatives. The Jump-corrected Confined Stokes–Einstein (JCSE) equation introduces corrections for molecular jumps and confinement effects, relating viscosity to diffusion, temperature, and confinement length scale, improving accuracy in nanoscale systems.

In this work, an extensive theoretical investigation on the stability and reactivity of different sizes of molybdenum carbide clusters was performed. For this investigation, the linear combination of Gaussian-type orbitals auxiliary density functional theory (LCGTO-ADFT) approach has been employed. The reactivity study was carried out considering the first benzene hydrogenation reaction on these clusters. The catalytic behavior in the studied reactions was analyzed with respect to the cluster sizes. For this study, molybdenum carbide clusters with the same stoichiometry (Mo:C=2:1), varying from systems containing a few atoms, up to systems characterized by a nanometric size have been considered. The lowest energy structures of the considered nanometric sized clusters are presented for the first time. Results of the obtained minima and transition state structures, harmonic frequencies, HOMO-LUMO gap and activation energy are presented. The relationship between the calculated activation energy and the atomic arrangements on the surface of the clusters, as well as the trend of the cluster size with respect to their metallic behavior are analyzed. This work shows that the catalytic behavior of these systems is strongly related to their size and HOMO-LUMO gap.

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We use the elongated hydrogen chain as an illustration to affirmatively answer the question, “Can the FCI energies/properties be predicted with Hartree–Fock (HF) or density function theory (DFT) densities?” as proposed by the late Bob Parr. We employ some simple physics-inspired density-based quantities from the information-theoretic approach (ITA) to linearly correlate with the full configuration interaction (FCI) energies with the approximate DMRG (density matrix renormalization group) method as a solver. We have showcased that the deviations between the calculated and predicted ground-state energies are only about a few milliHartree. Moreover, with the “gold standard” CCSD(T) (coupled cluster with singles and doubles, and perturbative triples) polarizabilities as a reference, we have found a way to systematically reduce the severe overestimation of the molecular polarizabilities as calculated by the approximate DFT functionals. Accordingly, we have applied this strategy to simultaneously predict the energies and molecular properties of strongly correlated systems only with the ground-state electron densities as an input, which should be a good starting point for more complex systems.

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In a remarkable leap forward for synthetic chemistry, MacMillan and co-workers have unveiled a clever way to directly forge C(sp²)–H alkyl bonds in arenes using light and copper catalysis. At the heart of their discovery lies the inventive idea of dynamic orbital selection, a concept that allows the catalyst to distinguish between aryl and alkyl radicals generated in situ. This precise control enables the selective union of these two distinct radical species, something long considered a major challenge. What makes the method especially appealing is its practicality: simple alcohols and carboxylic acids serve as alkyl radical sources, making the reaction broadly applicable and ideal for the late-stage functionalization of complex molecules. By elegantly sidestepping the harsh conditions and poor selectivity of classical Friedel–Crafts alkylations, this strategy opens new horizons for sustainable C–H functionalization, paving the way for innovations in drug discovery and molecular design.

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