Journal of Chemical Sciences最新文献

The misfolding and subsequent brain accumulation of two intrinsically disordered proteins, amyloid-beta (Aβ) and tau, are considered major hallmarks of Alzheimer's disease (AD), a neurodegenerative disorder characterized by cognitive decline and memory loss. Aβ accumulates extracellularly in the brain parenchyma, while tau aggregates intracellularly within neurons. Understanding the underlying molecular mechanisms is essential for uncovering the origins of AD and has remained an active area of research for over three decades, with the aim of developing therapeutics to mitigate or prevent disease progression. Our research group has made significant contributions over the years to explore the Aβ aggregation process, with particular emphasis on unraveling the role played by the solvent in guiding the process using large-scale atomistic molecular dynamics simulations. More recently, we have expanded our focus to probe the microscopic mechanism of aggregation of the tau protein. Some of the important findings that originated from our work have been presented in this review.

Graphical abstract

Alzheimer's disease is caused due to aggregation of two intrinsically disordered proteins (IDP), amyloid-β and tau. Simulation studies have unravelled that water plays a pivotal role in the aggregation process. A schematic image depicting water molecules confined within the core and at the surface of an IDP aggregate is shown.

The microscopic understanding of the morphology and ion/proton dynamics in hydrated Nafion systems is extremely essential for optimizing the efficiency of thermochemical/electrochemical processes like the Cu–Cl thermodynamic cycle for hydrogen generation. The present study addresses the gap in theoretical investigations on the structure and proton dynamics in aqueous Nafion systems, focusing on Cu⁺/Cu²⁺ and proton dynamics using robust MD simulations. We report a systematic investigation of the structure, transport and dynamics of protons and copper ions by varying water content, temperature and copper ion concentration. The present study captures the formation of continuous water channels within the hydrophobic Nafion matrix as observed in many experimental findings. Simulations are also conducted with 10% hydrated Nafion in contact with 11 N HCl and 1 M copper ions to represent the real composition of Cu–Cl electrolyzer. The MD analyses demonstrated that the highly acidic environment (11 N HCl) of the Cu–Cl electrolyzer would boost the swelling of Nafion membrane with reduced water–water interactions. On the other hand, the pairing of Cu–Cl ions would enhance the Nafion–hydronium ion interactions in the presence than in the absence of acid. The augmented interaction of hydronium ions with the sulfonic acid group of Nafion, would in due course, assist in faster transport of hydronium ions following Grotthuss mechanism. The hydrogen-bond life time of Nafion hydrated water was higher than that of bulk water due to the formation of separate water clusters within the Nafion membrane. The pores of Nafion allows only the transport of hydronium ions and water molecules whereas copper and chloride ions are restricted. The present findings on the structure and proton dynamics of the polymeric Nafion membranes might contribute towards the optimization of Cu–Cl electrolyzer for efficient and trouble free hydrogen production.

Graphical abstract

The effects of water content, temperature, presence of Cu⁺/Cu²⁺ ions and acidity in Nafion membrane were investigated. The increasing water content led to the formation of water channels within the membrane. Swelling, formation of channels and enhanced hydrogen bonding were observed at higher water content.

Traditionally, thermally activated delayed fluorescence (TADF) molecular design has focused on donor–acceptor (D–A) structures. However, this study explores alternate molecular configurations that extend beyond the conventional models. Using density functional theory (DFT) and time-dependent DFT calculations, we systematically investigated the impact of various donor and acceptor arrangements, such as D_A, D_A_D, A_D_A, D_A_D_A, and D_A_A_D, on the TADF properties of emitters using 5,10-dihydrophenazine (DHPZ) as the donor and benzophenone (BP) as the acceptor. In tetrad systems, the electronic structure of TADF emitters strongly depends on the spatial arrangement of the donor and acceptor units. For instance, in the D_A_D_A configuration, the lowest three singlet and triplet states exhibit charge transfer character. In contrast, the D_A_A_D configuration reveals significant Frenkel-type character in T₃ and T₄ states. The involvement of these higher triplet states enhances the spin–orbit coupling value and improves the reverse intersystem crossing (RISC) rates. Additionally, the configuration of donor and acceptor units influences the number of potential RISC channels. Overall, the D_A_A_D configuration emerges as a promising design, demonstrating superior TADF performance through multiple efficient exciton utilization pathways (up to 10 RISC channels) and faster RISC rates (> 10⁵ to 10⁸ s^–1) compared to D_A_D_A.

Graphical abstract

The D_A_A_D configuration emerged as a promising design, demonstrating superior TADF character through multiple efficient exciton utilization pathways (10 channels) and faster RISC (> 10⁵ to 10⁸ s⁻¹) rates compared to D_A_D_A.

Using the accurate quantum chemical calculations, the origin behind the hydrophobicity/hydrophilicity of two similar ionic liquids (ILs), 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]⁺[PF₆]⁻) and 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]⁺[BF₄]⁻) is thoroughly investigated. The structure of all the species and their corresponding interaction energies with water are computed by employing the wB97XD functional and 6-311G++(d,p) basis set. The use of the functional and basis set has been benchmarked either considering the experimental data or predictions from the sophisticated ab initio calculations. A continuum solvation model is utilized initially to understand the hydration (solvation) behaviour of the ILs as well as the hydration of the constituent ions. The explicit solvation has also been performed to monitor the effects of each molecular water addition to IL ion pairs and their anionic counterparts. This is done by calculating the interaction energy profiles as well as their charge distributions. It is found that anions and their charges transfer to cations or surroundings play a decisive role in this qualitatively different behaviour of these two ILs towards water. In addition, classical molecular dynamics simulations have been performed to investigate the hydration structure of the ions in the bulk water. The quantum chemical calculations presented here demonstrate the importance of anion-medium interactions in determining the hydrophobicity/hydrophilicity character of these two ILs.

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This paper investigates quantum mechanical origin of hydrophobicity by considering two ionic liquids, differing only in anions, as representative systems. The non-ionic interaction was found play an important role. The Gradient isosurfaces and the corresponding RDG plots for both the represenattive ILs in water are also shown

The role of intermolecular hydrogen bonds in photoinduced electron transfer (PET) between coumarin 153 (C153) and N,N-dimethylaniline (DMA) was investigated using DFT and TDDFT. Calculations revealed that two intermolecular hydrogen bonds significantly strengthen in the excited state (S₂), with hydrogen-bond binding energy increasing from 8.24 kJ/mol to 157.35 kJ/mol, and dipole moment rising from 7.25 D to 23.43 D. Frontier molecular orbital analysis confirmed that the S₁ state is an intermolecular charge transfer (CT) state, facilitated by enhanced hydrogen bond coupling. Spectral shifts in C–H stretching vibrations validated hydrogen bond dynamics. These findings demonstrate that the reinforcement of hydrogen bonds in the excited state accelerates PET, offering valuable insights for the design of efficient photoactive materials.

Graphical Abstract

This study shows that the S excited state of the C153/DMA complex is a locally excited state on C153 with partial intramolecular charge transfer (CT) from N to the C=O group. The S₁ state, in contrast, is an intermolecular CT state involving photoinduced electron transfer (PET) from DMA to C153 and has low oscillator strength. Hydrogen bonds between molecules are stronger in the S₂ state, supporting this electron transfer.

We have witnessed a recent surge in the development and application of the information-theoretic approach in density functional theory. In this article, by focusing on our own work in recent years, we highlight its theoretical framework, including four representations, three principles and two identities, illustrate four examples of its applications in determining electrophilicity, nucleophilicity, regioselectivity and stereoselectivity, and then overview a few advances in the recent literature such as topological analysis, energetic information, excited states and machine learning. We conclude by providing a few remarks about its future developments and possible applications.

Graphical abstract

Strong linear correlations of experimental scales of electriphilicity and nucleophilicity with theoretical quantities such as information gain and Hirshfeld charge from information-theoretic approach were showcases.

Deep eutectic solvents (DESs) offer a sustainable alternative to conventional ionic liquids through their cost-effective synthesis and benign constituents. In this study, we employed all-atom molecular dynamics simulations to investigate how the alkyl chain length of DES constituents influences microscopic diffusion and complexation dynamics in systems composed of lithium perchlorate with acetamide and propanamide. Our analysis identifies distinct diffusion regimes – ranging from ballistic to sub-diffusive and Fickian behaviour – with dynamic heterogeneity becoming more pronounced as the alkyl chain length increases. Importantly, the study reveals that this enhanced dynamical heterogeneity is strongly linked to the stability and extended lifetimes of Li⁺-alkylamide complexes, as evidenced by elevated non-Gaussian parameters, delayed transition to Gaussian dynamics, and reinforced radial distribution peaks. These insights highlight the critical interplay between molecular architecture and complexation dynamics, paving the way for the rational design of DESs for advanced electrochemical and catalytic applications.

Graphical Abstract

This study reveals that increasing the alkyl chain length in DESs strengthens Li⁺-amide complexation, leading to longer lifetimes. This enhanced complex stability directly induces pronounced dynamical heterogeneity, as evidenced by delayed Fickian diffusion and elevated non-Gaussian behaviour, highlighting the intricate link between complex stability and microscopic transport properties.

In this study, we utilize a promoter, specifically zinc, in varying concentrations to examine its promoting effects. This series of catalysts was prepared using a co-impregnation method involving zinc and platinum on titanium dioxide (TiO₂). The material was then dried at 100 °C and calcinated at 400 °C for 4 hours. The samples were subjected to a prolonged reduction at 300 °C for four hours. The physicochemical characteristics of the x Zn–Pt/TiO₂ P25 samples, each with distinct weight percentages of x Zn, were evaluated using a comprehensive array of analytical techniques. These methods included elemental analysis, X-ray diffraction, nitrogen sorption, hydrogen chemisorption, transmission electron microscopy, and cyclohexane dehydrogenation. This specific reaction has been utilized as a model to evaluate the accessibility of platinum and the degree of zinc coverage. An investigation into the performance and selectivity of the catalysts was conducted during the hydrogenation of citral, which was performed at a temperature of 70 °C and a hydrogen pressure of 7 MPa. The reaction occurred in isopropanol as the solvent and lasted for 120 minutes. A higher concentration of zinc in the materials was correlated with a reduced accessibility of platinum metal within the catalysts. This specific reaction has been utilized as a model to evaluate the accessibility of platinum and the degree of zinc coverage.

Graphical Abstract

The synthesis of x% Zn–Pt/TiO₂ catalysts (x between 0 and 0.3 wt%), for further application in the selective hydrogenation of citral in the liquid phase. The catalytic systems were deeply characterized by several physico-chemical techniques. We clearly evidenced the existence of an interaction between Pt and Zn with the formation problem of alloy, leading to an inhibition of the Pt hydrogenating activity but contributing to a remarkable increase in the selectivity to unsaturated alcohols due to a better activation of the C=O bond of citral. A maximum value of 81% for the unsaturated alcohols selectivity was reached with the bimetallic 0.3% Zn–Pt/TiO₂ catalyst.