Bulletin of the Korean Chemical Society最新文献

The photoexcitation dynamics of N₃⁻-bound ferric myoglobin (MbN₃) were investigated after exciting MbN₃ in D₂O at 283 K with a 575 nm pulse by probing the anti-symmetric stretching mode of the azide. Global fitting of the overall time-resolved spectra revealed that thermal relaxation of two stretching bands proceeded with a time constant of 6 ps, and that a new absorption band formed and decayed with time constants of 0.6 and 23 ps, respectively. The new absorption near 2040 cm⁻¹ was attributed to the high-spin species 2.4 kJ/mol above the low-spin species, as the excited low-spin relaxes thermally via the high-spin species. However, this absorption could also arise from deligated N₃̄ remaining within the protein. The decay of this absorption can be interpreted as either spin transition of the high-spin species into the low-spin species or geminate recombination of the dissociated N₃̄. The implications of both interpretations are discussed.

The cover picture illustrates the design process of a new 5-LO inhibitor through molecular hybridization. The highlighted portions in each chemical structure represent the regions where structural fusion is applied, and the sparks depict the process of fusion. The target compound acts on the 5-LO protein in mouse, relieving the ear edema. The drugs indicated by the prohibition sign in the bottom right corner are steroid-based drug and a 5-LO target drug called Zeiluton, both have toxicity issues. More details are available in the article by Young-Chang Kim, Aizhan Abdildinova, Ye Jin Shin, Dong Kyun Han, Jong Yeon Hwang, Hyae Gyeong Cheon, Young-Dae Gong.

Interferometric scattering (iSCAT) microscopy, label-free high-speed (up to ~1000 frames per second) imaging and tracking technique, has proven to be a versatile tool by measuring the mass and 3D position of nanoparticles and biomolecules as well as visualizing real-time dynamics of nanoscale events in complex cellular environments. However, the quantification of iSCAT signals has not been straightforwardly defined in practical terms. We delve into several issues associated with signal processing in iSCAT: error-prone post-processing routine and lack of statistical reliability in the convention of iSCAT contrast. After providing a brief account of concepts and principles of correlation spectroscopy, we here discuss an alternative ensemble (higher number density of scatterers) statistical analysis that can be used to extract the dynamic information of scattering particles from fluctuating iSCAT signals. Finally, our perspective on the correlation approach toward time-correlated iSCAT technique will be presented.

Ammonia borane (AB) has garnered significant attention as a high-efficiency energy source, prompting extensive investigations into its electrochemical oxidation. One prominent avenue of research focuses on the development of electrocatalysts to enhance the oxidation of AB. Employing the novel approach of single-entity electrochemistry (SEE), the electrocatalytic properties of gold (Au), silver (Ag), and palladium (Pd) nanoparticles (NPs) for AB oxidation were explored. In the case of Au and Ag NPs, SEE experiments yielded no discernible current signal, in contrast to the electrocatalytic currents observed with bulk electrodes. However, when Pd NPs were utilized, characteristic staircase signals in the SEE measurements were observed. The variation of the SEE current signal for Pd NPs under different applied potentials, AB concentrations, and NP concentrations was further investigated. An analysis of the SEE signal elucidated the conditions under which Pd NPs can effectively catalyze AB oxidation at the single NP level.

Lithium–sulfur batteries (LSBs) have gained remarkable attention over the past several years, however, their inherent limitations, such as the poor interfacial stability of their Li anodes and the severe dissolution of polysulfide, are regarded as bottlenecks that prevent these batteries from entering commercial markets. In this study, a 1,1-diethoxyethane (DEE), which has been functionalized with acetal groups, is proposed as an electrolyte cosolvent to complement the limitations of the electrode materials of LSBs. In Li/Li symmetric cells, the DEE cosolvent exhibited stable cycling behavior, whereas the cell with the baseline electrolyte exhibited rapidly increasing polarization, even after 650 h. In LSB cells, the electrolyte that contains 50% DEE exhibits the highest cycling retention (65.0%) compared to the baseline electrolyte (49.8%) because it effectively protects the interface of the Li anode, but also suppresses the dissolution of polysulfide species.

Cobalt (Co) has played an important role in nickel (Ni)-rich cathode materials in terms of improving electrochemical performance, boosting energy density, and improving cycling life for lithium-ion batteries (LIBs). While Co resources are becoming more cost-effective, they pose environmental challenges that can lead to limitations in production and indicate the need for alternative Co-free, Ni-rich cathodes. This review aims to compile some of the concepts established in recent years to overcome the electrochemical disadvantages of Ni-rich cathodes without Co. With the development of strategies involving single-crystals, core-shell structures, and substitution of Co by other metal ions, problems associated with capacity reduction and the underlying structure degradation mechanism have been resolved. Therefore, structural transformation strategies focusing on potential cathodes with improved energy density and lifetime have been pursued for safe LIBs. We also address possible issues and some new insights to improve the performance of Co-free, Ni-rich cathodes for practical applications.

A myriad of metal ions and organic linkers can be used to produce metal–organic frameworks (MOFs) with varied functionalities, porosities, and dimensionalities. Such diversity has garnered significant research interest, particularly in leveraging MOFs as proton conductors for fuel cells. One effective approach involves introducing guest molecules into MOF pores. These molecules serve either as proton carriers or as proton-conducting media through potential hydrogen bonding networks. This review offers an organized overview of key methodologies historically employed to achieve superprotonic conductivity in MOFs. The article systematically categorizes these tactics into three primary groups: guest molecule encapsulation, modulation at metal-coordination sites, and ligand functionalization. We succinctly discuss the roles of proton carriers, conducting media, and the overall MOF framework, emphasizing the significance of each strategy's application. In conclusion, we provide insights into the future development of MOFs as proton conductors, rooted in the categorization and conceptual understanding of these strategies.

The oxygen reduction reaction (ORR) is a kinetically sluggish reaction because it requires the transfer of four electrons. In this work, one-pot process involving thermal treatment of Co(II) acetylacetonate is developed. The resulting core–shell material (Co@C-800) consists of metallic Co cores encapsulated by carbon-based layered shells. Morphological analysis reveals the core–shell structures, with core particles surrounded by carbon networks. Chemical characterization using various spectroscopic techniques indicates the presence of metallic Co as the major component in Co@C-800, with minor Co species exhibiting higher oxidation states. Raman spectroscopy confirms the formation of sp2-hybridized carbon shells. Co@C-800 displays efficient electrocatalytic ORR performance, evidenced by high onset and half-wave potentials. The excellent durability and stability of Co@C-800, demonstrated through resistance to methanol poisoning and cyclic testing, suggest the potential of core–shell materials as a practical electrocatalyst.

This study focuses on the utilization of two-dimensional Ti₃C₂ MXene as a catalyst for photocatalytic hydrogen production. MXenes, a class of transition metal carbides/nitrides, exhibit exceptional properties conducive to enhancing photocatalytic reactions. This research explores the performance of Ti₃C₂ MXene as a cocatalyst in photocatalytic systems, aiming to improve charge separation, inhibit recombination, and facilitate efficient hydrogen evolution from water under light irradiation. The synthesis methods, catalyst-loading strategies, and overall photocatalytic mechanisms are investigated, shedding light on the potential of Ti₃C₂ MXene as a promising material for advancing hydrogen production through sustainable means.

γ-butyrolactones and their derivatives serve as the fundamental building blocks for a wide range of biologically significant and synthetically challenging natural products, which find extensive applications in various high-demand chemicals. In this study, we have successfully established a facile and atom-efficient synthesis of γ-butyrolactones through the carbonylative ring expansion of oxetanes. We employed both homogeneous and heterogenized bimetallic catalysts ([HCP-TPPM][Co(CO)₄], where HCP refers to hyper cross-linked polymer and TPP denotes tetraphenylporphyrin, with M = Cr³⁺ and Al³⁺). While the homogeneous catalysts exhibited remarkable activity, the heterogeneous catalysts offered the distinct advantages of facilitating product separation and enabling catalyst recycling. Notably, during the catalyst recycling studies, we observed a decrease in catalytic activity attributed to cobaltate leaching. The hypothesis of cobaltate leaching through β-hydrogen elimination was validated by comparative studies using substrates with and without β-hydrogen in both batch and continuous flow catalytic processes.