Journal of Chemical Sciences最新文献

Linoleic acid modified through autoxidation, hydroxylation, and bromination was utilized for the first time in controlled/living radical polymerization methods such as atom transfer radical polymerization (ATRP). A brominated polymeric linoleic acid macromonomer initiator (ATRP–MIM) was synthesized as a macromolecular initiator (MIM) based on polymeric linoleic acid for use in ATRP. Using this ATRP–MIM and styrene monomer, novel graft copolymers were successfully synthesized via ATRP. The effects of various reaction parameters, including monomer concentration, initiator concentration, and polymerization kinetics, were systematically investigated. Additionally, the impact of reaction conditions on molecular weight and polydispersity was studied. The percentage compositions of the structural contents of graft copolymers were determined using ¹H NMR. Detailed characterization, including structural analysis, thermal properties, and molecular weight determination, was performed using techniques such as Fourier-transform infrared spectroscopy (FT-IR), nuclear magnetic resonance (NMR), gel permeation chromatography (GPC), differential scanning calorimetry (DSC), and thermogravimetric analysis (TGA). The obtained graft copolymers exhibited enhanced thermal stability and well-defined molecular structures, contributing to the development of bio-based polymeric materials with specialized properties for applications in coatings, biocompatible systems, and advanced functional materials.

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This study introduces the use of modified linoleic acid, altered through autoxidation, hydroxylation, and bromination, in controlled radical polymerization methods such as atom transfer radical polymerization (ATRP) for the first time. The research focuses on the synthesis of graft copolymers by using a brominated polymeric linoleic acid initiator (ATRP-MIM) in copolymerization with styrene.

In a previous communication (Comp. Theor. Chem. 1091 (2016) 150), concerted isomerization reactions of 15 C₇H₇⁺ cations in the gas phase had been studied. The present study deals with the kinetics of these concerted isomerization reactions using the M06-2X functional. From the potential energy profiles of these reactions, the rate coefficients are estimated by using transition state theory along with the estimation of Wigner’s empirical transmission coefficient for quantum tunnelling. The rate coefficient values are calculated over a temperature range of 200–500 K, where the Arrhenius activation energies, along with the pre-exponential factors, are determined for each of these reactions.

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The graphical abstract highlight the two representative isomerisation reactions of bicyclo[3.2.0]heptadienyl cation 4 to tropyl cation 1 (global minimum) by C-C σ-bond collapse to π-bond via transition state TS1 and o-tolyl cation 5 to benzyl cation 2 by 1,3-hydride shift via TS4.

Due to the high computational scaling of correlated quantum chemical methods, their application to large molecular systems presents significant challenges, particularly for computation of infrared (IR) and Raman spectra, which is often prohibitively expensive. The fragment-based Molecular Tailoring Approach (MTA), an indigenously developed methodology, has significantly broadened the scope of such studies. The MTA-based software package, MTASpec https://doi.org/10.17632/m5b5zhxkfh.1, enables the computation of molecular properties such as the electronic energy, vibrational IR and Raman spectra of large molecules and molecular clusters. This short review provides a comprehensive overview of the capabilities of such MTA-based studies which strike an effective balance between computational efficiency and accuracy. Future directions for enhancing and expanding the applicability of MTASpec for other spectroscopic methods are also discussed, highlighting its potential as a user-friendly, black-box tool for routine quantum chemical spectral investigations.

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Molecular tailoring approach (MTA) and MTASpec codes provide an accurate yet inexpensive calculation of vibrational infrared and Raman spectra of spatially extended molecular systems using minimal hardware. Vibrational features of large molecular clusters and biomolecules such as carbohydrates, polypeptides and proteins can thereby be explored in gas- and solvent phases using HF, DFT and correlated methods with extended basis sets.

The ability to tailor the optical properties of graphene quantum dots (GQDs) is critical for their application in optoelectronics, bioimaging and sensing. However, a comprehensive understanding of how shape, size and doping influence their emission properties remains elusive. In this study, we conduct a systematic high-throughput time-dependent density functional theory (TDDFT) and machine learning analysis of 284 distinct GQDs, varying in shape (square, hexagonal, amorphous), size ((sim)1–2 nm) and doping configurations with elements B, N, O, S and P at varying concentrations (1.5–7%). Our findings reveal clear design principles for tuning emission wavelengths based on dopant type, concentration and GQD geometry. Notably, sulfur doping at specific concentrations consistently results in higher emission energies, with certain configurations yielding emissions within the visible range. By elucidating how quantum confinement effects, symmetry breaking and dopant-induced modifications govern GQD optical properties, we provide practical design rules for tailoring emission spectra for next-generation optoelectronic, bioimaging and sensing applications.

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The compound, Bi₂ZnB₂O₇, stabilized in the melilite structure, has been prepared and characterized. The partial substitution of transition elements (Co²⁺, Ni²⁺ and Cu²⁺ ions) in place of tetrahedral Zn²⁺ ions gave rise to colored compounds. The origin of the color in the compounds was understood based on the allowed d-d transitions. The near-IR reflectivity studies indicate reasonable NIR reflectivity with values in the range of 50–65%. The tetrahedral B³⁺ ions were partially replaced by Al³⁺ ions, giving rise to a new melilite analogue, Bi₂Zn(B_1.5Al_0.5)O₇. The Bi³⁺ ions, substituted by rare-earth ions (Eu³⁺, Tb³⁺ and Tm³⁺), resulted in compounds exhibiting intense red, green and blue emissions. The life-time studies indicated an average life time in the milliseconds region for all three substituted compounds. The substitution of the same ions in place of Y³⁺ ions in (Bi_1.9Y_0.1)ZnB₂O₇ compounds also resulted in a similar behaviour. The compounds, Bi₂ZnB₂O₇, Bi₂Zn(B_1.5Al_0.5)O₇, (Bi_1.75Y_0.25)ZnB₂O₇ and (Bi_1.75La_0.25)ZnB₂O₇, were examined for their dielectric behaviour at room temperature, which gave reasonably good values with minimal dielectric loss. The present studies clearly indicates that the melilite structure could be adaptable, though in a limited way, resulting in new colored compounds and excellent luminescence behaviour.

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The compound, Bi₂ZnB₂O₇, was explored towards new colored compounds by substituting divalent transition metal ions Co²⁺/Ni²⁺/Cu²⁺ in place of Zn²⁺ ion in the compound. Substitution of rare-earth ions at the bismuth site gives rise to intense characteristic emission.

A bis-pyridinium calix[4]pyrrole derivative has been synthesized and investigated for its supramolecular interactions with nerve agent surrogates. The receptor promotes the degradation of organophosphorus nerve agent surrogates by facilitating the release of fluoride and cyanide leaving groups. The released anions are subsequently detected via fluorescence response, enabling dual functionality in degradation and sensing. The binding interactions and mechanistic insights were elucidated through NMR spectroscopy, fluorescence titration, and computational studies, confirming the receptor’s role in modulating leaving group dissociation. These findings contribute to the development of supramolecular strategies for chemical defence and environmental detoxification.

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A bis-pyridinium calix[4]pyrrole derivative promotes the degradation of organophosphorus nerve agent surrogates by facilitating the release of fluoride and cyanide leaving groups. The released anions are subsequently detected via fluorescence response, enabling dual functionality in degradation and sensing. This supramolecular approach provides insights into molecular recognition and chemical detoxification strategies.

Supercapacitors are among the most promising electrochemical energy-storage devices, bridging the gap between traditional capacitors and batteries in terms of power and energy density. Their charge-storage performance is largely influenced by the properties of electrode materials, electrolytes and the underlying charge-storage mechanisms. This review provides an overview of the fundamental principles of electrochemical energy storage in supercapacitors, highlighting various energy-storage materials and strategies for enhancing their performance, with a focus on manganese- and nickel-based materials. Key factors, such as electrode surface area, porosity and electrical conductivity are identified as critical contributors to performance. Approaches, such as nanostructuring, chemical activation and integration with conductive graphitic carbon or conducting polymers are extensively utilized to optimize these properties. The charge-storage performance of nanostructured Mn- and Ni-based materials investigated in our laboratory and the charge storage in nanoporous electrode are presented. Finally, the challenges and prospects of these materials for practical applications, including wearable and flexible supercapacitors, are discussed.

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Electrochemical energy storage with supercapacitors using rationally designed electrode materials is reviewed.

Krossing et al. reported a new method for the synthesis and characterization of a cationic [Mn(CO)₅(n-pentane)]⁺ complex in both solution and solid state. The elegant strategy significantly improved the lifetime of the σ-pentane complex in solution at room temperature and allowed crystallization at 0 °C.

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This news story article summarizes the development of various strategies for the characterization (NMR, X-ray) of sigma-alkane complexes. Most notably, a recently discovered route by Krossing and coworkers to make a n-pentane C-H bond ligated onto a highly electron-deficient cationic manganese(I) carbonyl centre is highlighted.