Bulletin of the Korean Chemical Society最新文献

Mid-infrared (MIR) spectroscopy has emerged as a pivotal tool for studying molecular dynamics with ultrafast time resolution, allowing precise investigations into structural changes, chemical reactions, and energy transfer processes. This review explores the transformative capabilities of femtosecond MIR spectroscopy techniques such as pump-probe (PP) and two-dimensional infrared (2DIR) spectroscopy, which offer unparalleled specificity in probing molecular vibrations and exploring complicated energy landscapes across diverse scientific fields. Advanced laser technologies, including pulse shapers and asynchronous optical sampling (ASOPS), have significantly enhanced the precision and efficiency of MIR spectroscopic methods. ASOPS, in particular, has revolutionized time-resolved studies by mitigating traditional mechanical delay stage limitations, enabling robust femtosecond-to-nanosecond dynamics investigations with enhanced noise reduction and long-term stability. This review provides a comprehensive overview of the evolution and strengths of MIR-based PP and 2DIR spectroscopy, emphasizing the pivotal role of ASOPS in overcoming technical challenges. By delineating current methodologies, this review aims to guide researchers in selecting and optimizing experimental configurations tailored to their scientific inquiries.

Recent advances have established solar energy as a major source of nearly inexhaustible renewable energy and a viable method for water purification. This review focuses on the utilization of transition metal-based materials to create efficient photocatalysts for harnessing solar energy. Additionally, it highlights the crucial role of mass spectrometry (MS) in enhancing the efficiency of renewable energy and water purification processes. The various photocatalysts discussed in this review demonstrate significant efficacy in solar-driven water evaporation and the degradation of organic pollutants in wastewater. Solar energy is also harnessed for the production of ammonia through N₂ reduction and for converting CO₂ into valuable carbon fuels. Integrating MS analysis into these processes allows for the precise quantification of residual contaminants in aqueous samples, thereby ensuring environmental safety. Moreover, MS analysis can improve overall process efficiency by evaluating products and by-products and comparing energy conversion rates. These advances underscore the critical importance of MS analysis in promoting sustainable energy and environmental solutions through the development of transition metal-based photocatalysts.

X-ray imaging is transforming battery research by delivering multiscale insights into structure, composition, and chemistry, spanning micrometer to nanometer scales. As indispensable components of energy storage, electric vehicles, and mobile devices, batteries face significant challenges due to their intricate electrochemical processes, hierarchical architectures, and inaccessible components such as buried interfaces and air-sensitive materials. These complexities demand advanced techniques capable of uncovering localized effects and addressing the heterogeneity that often obscures critical phenomena. Advanced x-ray imaging techniques are rising to meet these demands, bridging knowledge gaps by providing detailed visualization of battery processes in ways that conventional methods cannot. Operando x-ray imaging, in particular, captures real-time changes during battery cycling; enabling researchers to observe dynamic processes and material transformations that are otherwise inaccessible. This approach overcomes the limitations of traditional destructive post-mortem analyses by offering a non-invasive, real-time window into battery operation. Recent advances in spatial resolution, computational power, and data analysis tools have made x-ray imaging increasingly accessible and effective for studying critical phenomena, such as buried interfaces, phase transitions, and surface-bulk differences. This work introduces four advanced x-ray imaging techniques, outlining their principles, capabilities, and contributions to battery research. These methods illuminate key processes, advance our understanding of battery behavior, and guide targeted performance improvements. Finally, we explore the future of x-ray imaging as a mainstream tool for addressing the pressing challenges in energy storage systems, emphasizing its pivotal role in guiding innovations for next-generation batteries.

Polyethylene glycol (PEG) has been globally recognized as an environmentally-friendly chemical solvent used in many disciplines for various purposes. In this work, intelligent models are constructed based upon least squares support vector machine (LSSVM) and adaptive neuro-fuzzy inference system (ANFIS) methodologies optimized with either genetic algorithm (GA), coupled simulated annealing (CSA) or particle swarm optimization (PSO) to estimate PEG density in terms of PEG molecular weight, temperature, and pressure based upon data gathered from experimental works delineated in the published literature. Leverage method is performed on the acquired dataset to explore it in terms of outlier datapoints, and relevancy factor is used to perform sensitivity analysis. Graphical and statistical indexes are used to evaluate the authenticity of the developed models. The results show that nearly all intelligent models are accurate, with LSSVM-CSA being the most accurate model, which outperforms the modified Tait equation as outlined by the calculated mean square error, average absolute relative error, and R-squared values. In addition, the performed sensitivity analysis indicates that temperature is the most effective input variable with an indirect relationship. The developed intelligent models, particularly the LSSVM-CSA model, are highly capable of predicting PEG density without needing experimental approaches that are known to be arduous and laborious.

This Personal Account highlights the research contributions of the Kim and Oh groups in molecular oxygen-promoted reactions since 2016, focusing on aerobic oxidation and radical chemistry. The groups' early work involved copper catalysts, leading to the discovery of the aerobic oxidation of 2-naphthols to form ortho-naphthoquinones (o-NQ), which were later used as organocatalysts. Over time, research expanded from metal catalysis to organocatalysis and photochemistry, achieving breakthroughs in reaction pathways and radical chemistry under aerobic conditions. The Account first discusses metal-catalyzed aerobic oxidation reactions, including copper-catalyzed transformations of 2-naphthol derivatives, palladium-catalyzed hydroamination, and rhodium-catalyzed decarbonylative oxidation. Other reactions include copper-catalyzed oxidation of amines to nitrogen compounds, as well as the synthesis of isoquinolones and benzothiazoles. These methodologies highlight the broad applicability of molecular oxygen in metal catalysis, enabling efficient and selective transformations in organic synthesis. Next, the Account summarizes o-NQ-based aerobic oxidation protocols, including the dehydrogenation of amines to form (ket)imines and a deamination method converting amines into carbonyl compounds. The application of o-NQ catalysts led to the formation of indole-3-carboxylates and fused pyrimidin-4(3H)-ones, along with one-pot deaminative oxidation converting primary amines into carboxylic acids. The alcohol dehydrogenase-like activity of o-NQ catalysts was also used to oxidize alcohols to aldehydes and ketones. Additionally, a water-soluble redox-active amine oxidase-like catalyst, cacotheline, derived from a natural source, was identified. The catalytic versatility of o-NQ catalysts was demonstrated in the selective activation of amines and nitroalkanes for deaminative cross-coupling and N-nitrosation reactions, as well as novel catalytic methods for the hydrodeamination of aryl amines. The last section discusses visible-light-induced photochemistry of N-nitrosamines, generating aryl cations that underwent aromatic nucleophilic substitution. A redox-neutral selenofunctionalization method, regenerating diselenides from selenols using molecular oxygen without external catalysts, was also presented. The presented work highlights the development of novel and efficient catalytic reactions utilizing aerobic oxidation processes, enabling effective functional group transformations and the creation of diverse heterocyclic compounds.

Titanium dioxide (TiO₂) has received significant attention due to its importance in a wide range of applications, including photocatalysis, solar energy conversion, and chemical sensing. The physicochemical properties of TiO₂ can be finely tuned using a novel platform of ultrathin oxide films. In this study, a computational study based on density functional theory (DFT) calculations is performed to investigate the thickness-dependent geometric and electronic properties of ultrathin rutile-phase TiO₂(110) films supported by five body-centered cubic metal substrates: W, Mo, Ta, Nb, and V, oriented along the (100) plane. The DFT calculations suggest that W and Mo may serve as optimal metal substrates for the formation of ultrathin TiO₂ films, in which lattice mismatch along the long axis plays a significant role. Furthermore, the interfacial electronic structure of the TiO₂ film, primarily characterized by charge transfer from metal to the TiO₂ layer and the formation of metal-included gap states (MIGS), can be used to rationalize the thickness-dependent variation in the work function of ultrathin TiO₂ films on metal substrates. Our results provide valuable insights into the effect of the film thickness on the geometric and electronic properties of TiO₂ films grown on metal substrates.

The cover illustration depicts StayGOLD fluorescent proteins coupled to streptavidin, enabling DNA labeling. The biotin-labeled DNA, shown in the upper left of the DNA structure, specifically interacts with streptavidin, directing fluorescent proteins to precise locations on the DNA. A more detailed analysis of StayGOLD fluorescent protein can be found in the article by Yurie Tehee Kim, Joohee Choe, Kyubong Jo.

Quantum chemical theories are essential tools for predicting the properties of complex quantum systems without the need for prior empirical data. While traditional theories have long dominated the field, their applicability is often limited in complex scenarios, particularly for systems involving excited states. Mixed-Reference Spin-Flip Time-Dependent Density Functional Theory (MRSF-TDDFT) addresses these challenges, offering a robust, accurate, and computationally efficient framework for studying both ground and excited states of large molecular systems. MRSF-TDDFT achieves predictive accuracy on par with much more computationally intensive quantum chemical methods. Notably, it successfully describes the doubly excited states, a limitation of conventional TDDFT, by naturally incorporating key doubly excited configurations within its response space. This capability also enables MRSF-TDDFT to accurately reproduce the correct asymptotic behavior of bond-breaking potential energy surfaces. Furthermore, it resolves critical photochemical features, such as the conical intersections, which elude both TDDFT and Complete Active Space Self-Consistent Field (CASSCF) methods. Despite its advanced predictive power, MRSF-TDDFT retains computational efficiency comparable to traditional TDDFT. With the development of custom-tailored functionals, its accuracy can be further enhanced, extending its potential applications. This innovation represents a significant advancement, empowering researchers to uncover intricate molecular behaviors and facilitate the design of novel materials with unprecedented precision.

Parkinson's disease (PD) is a progressive neurodegenerative disease caused by a loss of dopaminergic neurons in the substantia nigra. Monoamine oxidase-B (MAO-B) inhibition is a promising strategy for disease modification. Here, we synthesized a series of 2,6-diarylbenzo[d]oxazoles and identified two potent and selective hMAO-B inhibitors: 4,4′-(benzo[d]oxazole-2,6-diyl)diphenol 4a (IC₅₀ = 0.182 μM) and 4-(2-(3-fluorophenyl)benzo[d]oxazol-6-yl)phenol 4f (IC₅₀ = 0.184 μM). Molecular modeling indicated that the benzoxazole core interacts hydrophobically within the active site, contributing to their inhibitory potency. Both compounds demonstrated reversible or partially reversible inhibition of hMAO-B and neuroprotective effects in the MPP⁺-induced neurotoxicity assay using human neuroblastoma cells. Additionally, both compounds exhibited good microsomal stability and lacked significant perturbation of hERG channel activity. While 4a showed CYP inhibition against some isozymes, 4f had minimal effects on CYP isozyme activities, suggesting a more favorable pharmacokinetic profile. Based on these findings, 4f presents a promising therapeutic candidate for the treatment of PD.

Photocatalytic conversion of waste carbon dioxide (CO₂) into fine chemicals is crucial for solar energy utilization and mitigating the global climate crisis. Artificial photocatalysis based on the integrated biocatalyst offers a promising approach for converting CO₂ into high-value chemicals. The development of metal-free heterogeneous photocatalysts has gained significant attention as a sustainable platform for practical artificial photocatalytic systems. In this study, we report a one-pot synthesis of covalent triazine-based photocatalysts (CTPs) and their photocatalytic applications. The as-synthesized CTPs exhibit excellent photocatalytic performance, achieving the generation of HCOOH from CO₂ with a yield of 224.85 μM. The underlying photo-physical properties of CTPs were investigated by using systematic time-resolved laser spectroscopies. These measurements reveal that the formation of a long-lived charge transfer state in CTPs at the late time window is strongly correlated with the enhanced photocatalytic efficiency by delaying the ultrafast charge recombination. This study will serve as a benchmark example of heterogeneous photocatalysts and their wide applications for CO₂ fixation and solar chemical production.