Chemistry - An Asian Journal最新文献

Ammonia is a dynamic chemical precursor and energy carrier, traditionally manufactured through the Haber–Bosch process, which is an energy-intensive and carbon-emissive. As an alternative, the electrochemical nitrate reduction reaction to ammonia under ambient conditions has gained significant attention for its dual benefits of sustainable ammonia synthesis and nitrate pollutant remediation. Recent studies have shown that the electronic structure of the catalyst material strongly influences the catalytic efficiency of nitrate reduction. Modulation of the electronic structure via heteroatom doping, alloy formation, introduction of oxygen vacancies, strain engineering, and construction of phase boundaries alters the adsorption energies of key intermediates. Current studies on nitrate reduction to ammonia mostly focus on enhancing the Faradaic efficiency (FE) and yield rate up to industrial scale under harsh condition. However, the direct or indirect influence of ligand modulation, coordination engineering, and the introduction of a guest molecule into a host matrix toward electronic structure has rarely been discussed thoroughly. This review critically summarizes recent advances in electronic structure engineering for NO₃RR catalysts and elucidates the mechanistic role of electronic modulation in ammonia selectivity discussing the experimental and computational insights. By correlating chemical structure with catalytic performance, we provide a roadmap for designing next-generation electrocatalysts with superior nitrate-to-ammonia conversion efficiency.

Developing efficient orange-red emitters based on donor–acceptor (D−A) π conjugates with thermally activated delayed fluorescence (TADF) remains a significant challenge. Herein, we designed a series of donor-acceptor emitters (3,6-Az-DBP, 2,7-Az-DBP, and 2-Az-DBP) by incorporating twisted 10,11-dihydro-5H-dibenzo[b,f]azepine (Az) as a donor alongside the rigid and planar dibenzo[a,c]phenazine (DBP) acceptor core molecule at different sites viz., 3,6-, 2,7-, and 2- positions. As a result of site-specific substitution, considerable alteration in electronic properties was observed. For 3,6-Az-DBP, the energy gap between singlet and triplet states (ΔE_ST) was found to be 0.42 eV, which is much higher than that for 2-Az-DBP (0.25 eV) and 2,7-Az-DBP (0.06 eV). Owing to miniscule ΔE_ST, 2-Az-DBP and 2,7-Az-DBP showed orange and red TADF, respectively, in CBP blend. Both these compounds also showed red room temperature phosphorescence in powder samples having lifetimes in milliseconds time regime. Further, organic light emitting diode (OLED) of CBP doped 2-Az-DBP showed a high luminance of 6 × 10³ Cd/m² @ current density of 50 mA/cm²with EQE_max of about 12.3%. These studies provide a promising strategy, site selective substitution of donor on acceptor core, to improve the emission properties for red TADF emitters.

Guanosine (G) self-assembles into metal-stabilized architectures such as G-quartets (G₄·Mⁿ⁺) with metal ions, including Na⁺, K⁺, Rb⁺ and Cu⁺, and G-dimers G₂·(Mⁿ⁺)₂ with Ag⁺. Here, we show that Cu²⁺ forms a stable G₂·(Cu²⁺)₂ dimer-based gel at elevated temperatures. This gel exhibits self-healing and time-dependent syneresis behavior. In situ reduction of Cu²⁺ to Cu⁺ by ascorbic acid converts the G₂·(Cu²⁺)₂ dimeric gel to a G₄·Cu⁺ G-quadruplex gel, enabling a redox-controlled gel-to-gel transformation. The G₂·(Cu²⁺)₂ gel is mechanically stronger but dilution-sensitive, whereas the G₄·Cu⁺ gel is weaker yet more dilution-tolerant. These results establish copper oxidation states as determinants of G-based assembly and demonstrate a redox-triggered route to adaptive, stimuli-responsive soft materials.

Cyclic peptides are peptidic macrocycles with ring-constrained backbones that have distinct physicochemical and biological properties, with the simplest being cyclic dipeptides. Four cyclic dipeptides, cyclo(Pro-Pro), cyclo(Pip-Pip), cyclo(PrS-PrS), and the unique sulfur-rich cyclo(PipS-PipS), were synthesized from unprotected amino acids by using a one-pot thionyl chloride-mediated cyclization process, producing 19%–40% without the use of protective-group strategies. FTIR, NMR, and high-resolution mass spectrometry (HRMS) were used to confirm the structures. The 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay was used to assess antioxidant activity, and it was discovered that sulfur incorporation and six-membered ring size significantly increase radical quenching. A cloud-based platform was used to predict electronic properties, such as HOMO-LUMO gaps, dipole moments, and oxidation potential. Compounds with smaller HOMO-LUMO gaps and lower oxidation potentials had higher DPPH scavenging efficiencies, establishing a clear structure-property-activity relationship. This study identifies promising sulfur-containing cyclic dipeptides for future development as antioxidant therapeutics and presents a scalable pathway to diverse cyclic dipeptides.

The electrochemical nitrate reduction reaction (NO₃RR) has attracted considerable attention for the sustainable production of NH₃, urea, amino acids, and other value-added chemicals. Among these, NH₃ is particularly significant due to its large-scale industrial synthesis via the Haber–Bosch process. Herein, we report the design of an efficient NO₃RR catalyst prepared through a simple synthesis route. Fe₂O₃ clusters (2–5 nm) were uniformly deposited on iron phthalocyanine (FePc)-modified N-doped carbon nanotubes (Fe₂O₃/FePc/CNT), yielding a high NH₃ production rate of 58.67 mg h⁻¹ cm⁻² with a Faradaic efficiency (FE) of 81.89% at −1.0 V versus RHE. Comparative studies with FePc/CNT, Pc/CNT, and Fe₂O₃/CNT confirmed the synergistic effect between Fe₂O₃ clusters and FePc, with the optimized Fe₂O₃/FePc/CNT catalyst showing superior activity and selectivity. Furthermore, the optimized catalyst exhibited excellent stability for 24 h. A possible mechanism for NH₃ formation is proposed on the basis of the reaction intermediates identified by ex situ FTIR and x-ray photoelectron spectroscopy (XPS) analyses.