Journal of Chemical Sciences最新文献

We investigated the shape resonances of DNA and RNA nucleobases using time-dependent density functional theory (TD-DFT). Benchmark calculations are conducted on gas-phase thymine using a range of DFT functionals to identify the most suitable one for subsequent studies. Resonance transition energies are obtained through the TD-DFT/RVP stabilization method and compared with EA-EOM-DLPNO-CCSD reference values to evaluate the performance of various functionals. The comparison reveals that CAM-B3LYP yields the smallest deviations relative to the EA-EOM-DLPNO-CCSD/RVP results. Consequently, resonance positions and widths for all DNA and RNA nucleobases are computed using stabilization plots generated with the TD-DFT with CAM-B3LYP functional. The calculated resonance positions for low-lying resonance states of all nucleobases are within ±0.4 eV of those from the EA-EOM-DLPNO-CCSD method, except for the high-lying 3π* and 4π* resonance of adenine. Resonance widths are largely underestimated, except for cytosine.

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The gas phase acidities of phenol C₆H₅OH, benzoic acid C₆H₅COOH and o-, m-, and p-hydroxybenzoic acids HOC₆H₄COOH were calculated at the MP2/6-31+G(d) and CAM-B3LYP/6-31+G(d,p) levels of theory and the values were closed with the experimental (Delta_{acid} G^{0}) values reported in the literature. The resonance effect operating in the acidity properties of the molecules were studied by analyzing the electronic density in terms of the Fukui function of their anionic compounds C₆H₅O(−), C₆H₅COO(−), o-, m-, and p-(−)OC₆H₄COOH and o-, m-, and p-OC₆H₄COO(−). The Fukui function f ⁻(r) for electrophilic attack explained the effect and suggested how the resonance contribution describe the anions stability.

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Analysis of charge delocalization in the phenoxide and carboxylate anions of p-hydroxybenzoic acid using the Fukui function for electrophilic attack

A comparative analysis between the procedure originally followed to establish the local hardness concept and a recent one based on a local chemical potential, defined within the grand canonical ensemble formalism, is done to get a better understanding of the main aspects involved in both procedures and to show that the local and non-local counterparts of global reactivity descriptors recently developed, constitute an excellent complement to analyze chemical reactivity within the framework of conceptual density functional theory.

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A comparative analysis between the procedure originally followed to establish the local hardness and the hardness kernel concepts and a recent one based on a local chemical potential, defined within the grand canonical ensemble formalism, is done. The original local softness and softness kernel remain unchanged.

This work emphasizes the potential of (benzo)chalcogenadiazole in recognizing anions via chalcogen bonding as a key interaction. We employed various theoretical tools to analyse the binding affinity and selectivity of substituted (benzo)thiadiazole for fluoride. The molecular electrostatic potential surface provided qualitative insights into the influence of substituents on electronic properties and the (sigma ) hole of the sulfur atom in directing the interaction strength with the anionic counterpart. Quantitative evaluations using symmetry-adapted perturbation theory, natural bond orbital analysis and topological descriptors at bond critical points confirmed the interaction mechanisms. Notably, the study revealed that the S···F^- bond strength was moderately enhanced for bis(trifluoromethyl)thiadiazole compared to tetrafluorobenzothiadiazole. Finally, the significant S···F^- bond was found to exhibit a partial covalent character, which has important implications for the design of novel chalcogenadiazole-derived anion receptors and sensors, contributing to the advancement of anion recognition.

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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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