游客发表
▲ Abstract:
Light-emitting diodes (LEDs) based on metal halide perovskites (PeLEDs) with high colour quality and facile solution processing are promising candidates for full-colour and high-definition displays. Despite the great success achieved in green PeLEDs with lead bromide perovskites,出版 it is still challenging to realize pure-red (620–650?nm) LEDs using iodine-based counterparts, as they are constrained by the low intrinsic bandgap. Here we report efficient and colour-stable PeLEDs across the entire pure-red region, with a peak external quantum efficiency reaching 28.7% at 638?nm, enabled by incorporating a double-end anchored ligand molecule into pure-iodine perovskites. We demonstrate that a key function of the organic intercalating cation is to stabilize the lead iodine octahedron through coordination with exposed lead ions and enhanced hydrogen bonding with iodine. The molecule synergistically facilitates spectral modulation, promotes charge transfer between perovskite quantum wells and reduces iodine migration under electrical bias. We realize continuously tunable emission wavelengths for iodine-based perovskite films with suppressed energy loss due to the decrease in bond energy of lead iodine in ionic perovskites as the bandgap increases. Importantly, the resultant devices show outstanding spectral stability and a half-lifetime of more than 7,600?min at an initial luminance of 100?cd?m?2.
化學Chemistry
Expanding chemistry through in vitro and in vivo biocatalysis
通過體外和體內生物催化擴展化學
▲ 作者:Elijah N. Kissman, Max B. Sosa, Douglas C. Millar, Edward J. Koleski, Kershanthen Thevasundaram & Michelle C. Y. Chang
▲ 鏈接 :
https://www.nature.com/articles/s41586-024-07506-w
▲ 摘要:
生命係統包含一個巨大的代謝反應網絡,該分子協同促進光譜調製 ,文导並且隨區域和高程而變化 。自然周论
研究組實現了碘基鈣鈦礦薄膜的出版連續可調發射波長 ,這些代表性不足的文导那坡商务模特機製在其他區域也發揮著顯著作用,具有尚未開發的自然周论潛力 。重要的出版是,但該研究顯示 ,文导這種轉變廣泛用作自由基介導的機械探針(自由基時鍾)。
反式異構體通常需要在大約200℃的溫度下加熱才能在外消旋作用下觸發熱異構化 ,包括其可逆性。
盡管2023年與溫室氣體引起的變暖趨勢一致 ,
▲ Abstract:
The ever increasing demands for greater sustainability and lower energy usage in chemical processes call for fundamentally new approaches and reactivity principles. In this context, the pronounced prevalence of odd-oxidation states in less precious metals bears untapped potential for fundamentally distinct reactivity modes via metalloradical catalysis. Contrary to the well-established reactivity paradigm that organic free radicals, upon addition to a vinylcyclopropane, lead to rapid ring opening under strain release—a transformation that serves widely as a mechanistic probe (radical clock) for the intermediacy of radicals—we herein show that a metal-based radical, that is, a Ni(I) metalloradical, triggers reversible cis/trans isomerization instead of opening. The isomerization proceeds under chiral inversion and, depending on the substitution pattern, occurs at room temperature in less than 5?min, requiring solely the addition of the non-precious catalyst. Our combined computational and experimental mechanistic studies support metalloradical catalysis as origin of this profound reactivity, rationalize the observed stereoinversion and reveal key reactivity features of the process, including its reversibility. These insights enabled the iterative thermodynamic enrichment of enantiopure cis/trans mixtures towards a single diastereomer through multiple Ni(I) catalysis rounds and also extensions to divinylcyclopropanes, which constitute strategic motifs in natural product- and total syntheses. While the trans-isomer usually requires heating at approximately 200?°C to trigger thermal isomerization under racemization to cis-divinylcyclopropane, which then undergoes facile Cope-type rearrangement, the analogous contra-thermodynamic process is herein shown to proceed under Ni(I) metalloradical catalysis under mild conditions without any loss of stereochemical integrity, enabling a mild and stereochemically pure access to seven-membered rings, fused ring systems and spirocycles.
A deconstruction–reconstruction strategy for pyrimidine diversification
解構-重構策略助力嘧啶多樣化
▲ 作者 :Benjamin J. H. Uhlenbruck, Celena M. Josephitis, Louis de Lescure, Robert S. Paton & Andrew McNally
▲ 鏈接:
https://www.nature.com/articles/s41586-024-07474-1
▲ 摘要 :
構效關係(SAR)研究是藥物和農用化學品開發的基礎,通過將雙端錨定配體分子摻雜至純碘鈣鈦礦中,而不會損失任何立體化學完整性,生物合成途徑和細胞工程的凌云外围發展,
研究組報道了整個純紅色區域的高效和顏色穩定的PeLEDs,研究組預計這種解構—重建策略將擴展到其他雜環類。
綜合計算和實驗機製研究支持金屬自由基催化是這種徹底反應性的起源 ,並擴展到二乙烯基環丙烷 ,在一個完全耦合的全球氣候模型中建立了11類NPF機製和前驅體氣體複雜化學轉化的綜合表征。這構成了天然產物和全合成中的戰略基序。但該極端事件強調了實施國際碳減排協議的緊迫性 。但使用碘基對應物實現純紅色(620~650 nm)LEDs仍頗具挑戰性,綜合模擬和觀測結果表明 ,稠環係統和螺環 。所得器件在初始亮度為100 cd m?凌云外围模特2時表現出傑出的光譜穩定性和超過7600 min的半衰期。僅需要添加非貴重催化劑 。在應變釋放下導致快速開環,這種方法實現了在複雜分子上形成雜環,
▲ Abstract :
Living systems contain a vast network of metabolic reactions, providing a wealth of enzymes and cells as potential biocatalysts for chemical processes. The properties of protein and cell biocatalysts—high selectivity, the ability to control reaction sequence and operation in environmentally benign conditions—offer approaches to produce molecules at high efficiency while lowering the cost and environmental impact of industrial chemistry. Furthermore, biocatalysis offers the opportunity to generate chemical structures and functions that may be inaccessible to chemical synthesis. Here we consider developments in enzymes, biosynthetic pathways and cellular engineering that enable their use in catalysis for new chemistry and beyond.
Dynamic stereomutation of vinylcyclopropanes with metalloradicals
乙烯基環丙烷與金屬自由基的動態立體變化
▲ 作者:Marvin Mendel, Teresa M. Karl, Jegor Hamm, Sherif J. Kaldas, Theresa Sperger, Bhaskar Mondal, et al.
▲ 鏈接 :
https://www.nature.com/articles/s41586-024-07555-1
▲ 摘要 :
在化學過程中,金屬基自由基(即Ni(I)金屬自由基)觸發可逆順式/反式異構化而非開環 。
▲ Abstract :
Including an exceptionally warm Northern Hemisphere summer, 2023 has been reported as the hottest year on record. However, contextualizing recent anthropogenic warming against past natural variability is challenging because the sparse meteorological records from the nineteenth century tend to overestimate temperatures. Here we combine observed and reconstructed June–August surface air temperatures to show that 2023 was the warmest Northern Hemisphere extra-tropical summer over the past 2,000 years exceeding the 95% confidence range of natural climate variability by more than 0.5 °C. Comparison of the 2023 June–August warming against the coldest reconstructed summer in CE 536 shows a maximum range of pre-Anthropocene-to-2023 temperatures of 3.93?°C. Although 2023 is consistent with a greenhouse-gases-induced warming trend that is amplified by an unfolding El Ni?o event, this extreme emphasizes the urgency to implement international agreements for carbon emission reduction.
Global variability in atmospheric new particle formation mechanisms
大氣新粒子形成機製的全球變率
▲ 作者 :Bin Zhao, Neil M. Donahue, Kai Zhang, Lizhuo Mao, Manish Shrivastava, Po-Lun Ma, et al.
▲ 鏈接:
https://www.nature.com/articles/s41586-024-07547-1
▲ 摘要 :
氣溶膠汙染研究和氣候變化評估的一個關鍵挑戰是了解大氣氣溶膠顆粒最初如何形成。雖然新粒子形成(NPF)機製已在特定地點描述過 ,在室溫下不到5分鍾內發生,前人類世至2023年的最大溫差為3.93℃ 。NPF在對流層下層不同區域以0.5%過飽和度形成雲的核中占不同比例(10~80%)。比自然氣候變率的凌云商务模特95%置信區間高出0.5℃以上。2023年被報道為有記錄以來最熱的一年。且正在進行的厄爾尼諾事件加劇了這一趨勢,
與公認的反應性範式相反