Enantioselective Synthesis of C−O Axially Chiral Diaryl Ethers by NHC‐Catalyzed Atroposelective Desymmetrization**Shee, Sayan; Shree Ranganathappa, Sowmya; Gadhave, Mahesh S.; Gogoi, Romin; Biju, Akkattu T.
doi: 10.1002/anie.202311709pmid: 37986240
Axially chiral diaryl ethers, a distinguished class of atropisomers possessing unique dual C−O axis, hold immense potential for diverse research domains. In contrast to the catalytic enantioselective synthesis of conventional single axis bearing atropisomers, the atroposelective synthesis of axially chiral ethers containing flexible C−O axis remains a significant challenge. Herein, we demonstrate the first N‐heterocyclic carbene (NHC)‐catalyzed synthesis of axially chiral diaryl ethers via atroposelective esterification of dialdehyde‐containing diaryl ethers. Mechanistically, the reaction proceeds via NHC‐catalyzed desymmetrization strategy to afford the corresponding axially chiral diaryl ether atropisomers in good yields and high enantioselectivities under mild conditions. The derivatization of the synthesized product expands the utility of present strategy via access to a library of C−O axially chiral compounds. The temperature dependency and preliminary investigations on the racemization barrier of C−O bonds are also presented.
Mechanochemistry in Block Copolymers: New Scission Site due to Dynamic Phase SeparationZhang, Hang; Zoubi, Alan Z.; Silberstein, Meredith N.; Diesendruck, Charles E.
doi: 10.1002/anie.202314781pmid: 37962518
Mechanochemistry can lead to the degradation of the properties of covalent macromolecules. In recent years, numerous functional materials have been developed based on block copolymers (BCPs), however, like homopolymers, their chains could undergo mechanochemical damage during processing, which could have crucial impact on their performance. To investigate the mechanochemical response of BCPs, multiple polymers comprising different ratios of butyl acrylate and methyl methacrylate were prepared with similar degree of polymerization and stressed in solution via ultrasonication. Interestingly, all BCPs, regardless of the amount of the methacrylate monomer, presented a mechanochemistry rate constant similar to that of the methacrylate homopolymer, while a random copolymer reacted like the acrylate homopolymer. Size‐exclusion chromatography showed that, in addition to the typical main peak shift towards higher retention times, a different daughter fragment was produced indicating a secondary selective scission site, situated around the covalent connection between the two blocks. Molecular dynamics modeling using acrylate and methacrylate oligomers were carried out and indicated that dynamic phase separation occurs even in a good solvent. Such non‐random conformations can explain the faster polymer mechanochemistry. Moreover, the dynamic model for end‐to‐end chain overstretching supports bond scission which is not necessarily chain‐centered.
Excitation Wavelength‐Dependent Fluorescence of a Lanthanide Organic Metal Halide Cluster for Anti‐Counterfeiting ApplicationsZhao, Hongyuan; Wang, Qiujie; Wen, Ziying; Sun, Haibo; Ji, Sujun; Meng, Xuan; Zhang, Ruiling; Jiang, Junke; Tang, Zhe; Liu, Feng
doi: 10.1002/anie.202316336pmid: 37966337
The achievement of significant photoluminescence (PL) in lanthanide ions (Ln3+) has primarily relied on host sensitization, where energy is transferred from the excited host material to the Ln3+ ions. However, this luminous mechanism involves only one optical antenna, namely the host material, which limits the accessibility of excitation wavelength‐dependent (Ex‐De) PL. Consequently, the wider application of Ln3+ ions in light‐emitting devices is hindered. In this study, we present an organic–inorganic compound, (DMA)4LnCl7 (DMA+=[CH3NH2CH3]+, Ln3+=Ce3+, Tb3+), which serves as an independent host lattice material for efficient Ex‐De emission by doping it with trivalent antimony (Sb3+). The pristine (DMA)4LnCl7 compounds exhibit high luminescence, maintaining the characteristic sharp emission bands of Ln3+ and demonstrating a high PL quantum yield of 90–100 %. Upon Sb3+ doping, the compound exhibits noticeable Ex‐De emission with switchable colors. Through a detailed spectral study, we observe that the prominent energy transfer process observed in traditional host‐sensitized systems is absent in these materials. Instead, they exhibit two independent emission centers from Ln3+ and Sb3+, each displaying distinct features in luminous color and radiative lifetime. These findings open up new possibilities for designing Ex‐De emitters based on Ln3+ ions.
Ultrafluorogenic Monochromophore‐Type BODIPY‐Tetrazine Series for Dual‐Color Bioorthogonal Imaging with a Single ProbeKim, Dahham; Son, Hayoung; Park, Seung Bum
doi: 10.1002/anie.202310665pmid: 37749957
Various fluorogenic probes utilizing tetrazine (Tz) as a fluorescence quencher and bioorthogonal reaction partner have been extensively studied over the past few decades. Herein, we synthesized a series of boron‐dipyrromethene (BODIPY)‐Tz probes using monochromophoric design strategy for bioorthogonal cellular imaging. The BODIPY‐Tz probes exhibited excellent bicyclo[6.1.0]nonyne (BCN)‐selective fluorogenicity with three‐ to four‐digit‐fold enhancements in fluorescence over a wide range of emission wavelengths, including the far‐red region. Furthermore, we demonstrated the applicability of BODIPY‐Tz probes in bioorthogonal fluorescence imaging of cellular organelles without washing steps. We also elucidated the aromatized pyridazine moiety as the origin of BCN‐selective fluorogenic behavior. Additionally, we discovered that the fluorescence of the trans‐cyclooctene (TCO) adducts was quenched in aqueous media via photoinduced electron transfer (PeT) process. Interestingly, we observed a distinctive recovery of the initially quenched fluorescence of BODIPY‐Tz‐TCO upon exposure to hydrophobic media, accompanied by a significant bathochromic shift of its emission wavelength relative to that exhibited by the corresponding BODIPY‐Tz‐BCN. Leveraging this finding, for the first time, we achieved dual‐color bioorthogonal cellular imaging with a single BODIPY‐Tz probe.
Efficient Visible‐Light‐Activated Ultra‐Long Room‐Temperature Phosphorescence Triggered by Multi‐EsterificationYu, Jiahong; Sun, Zhiyu; Ma, Huili; Wang, Chengyun; Huang, Wenbin; He, Zikai; Wu, Wenjun; Hu, Honglong; Zhao, Weijun; Zhu, Wei‐Hong
doi: 10.1002/anie.202316647pmid: 37968887
The development of ultra‐long room‐temperature phosphorescence (UL‐RTP) in processable amorphous organic materials is highly desirable for applications in flexible displays, anti‐counterfeiting, and bio‐imaging. However, achieving efficient UL‐RTP from amorphous materials remains a challenging task, especially with activation by visible light and a bright afterglow. Here we report a general and rational molecular‐design strategy to enable efficient visible‐light‐excited UL‐RTP by multi‐esterification of a rigid large‐plane phosphorescence core. Notably, multi‐esterification minimizes the aggregation‐induced quenching and accomplishes a ′four birds with one stone′ possibility in the generation and radiation process of UL‐RTP: i) shifting the excitation from ultraviolet light to blue‐light through enhancing the transition dipole moment of low‐lying singlet‐states, ii) facilitating the intersystem crossing process through the incorporation of lone‐pair electrons, iii) boosting the decay process of long‐lived triplet excitons resulting from a significantly increased transition dipole moment, and iv) reducing the intrinsic triplet nonradiative decay by substitution of high‐frequency vibrating hydrogen atoms. All these factors synergistically contribute to the most efficient and stable visible‐light‐stimulated UL‐RTP (lifetime up to 2.01 s and efficiency up to 35.4 % upon excitation at 450 nm) in flexible films using multi‐esterified coronene, which allows high‐tech applications in single‐component time‐delayed white light‐emitting diodes and information technology based on flashlight‐activated afterglow encryption.
0D Pyramid‐intercalated 2D Bimetallic Halides with Tunable Electronic Structures and Enhanced Emission under PressureLiu, Yang; Liang, Jiayuan; Deng, Zeyu; Guo, Songhao; Ji, Xiaoqin; Chen, Congcong; Canepa, Pieremanuele; Lü, Xujie; Mao, Lingling
doi: 10.1002/anie.202314977pmid: 37991471
Hybrid metal halides are emerging semiconductors as promising candidates for optoelectronics. The pursuit of hybridizing various dimensions of metal halides remains a desirable yet highly complex endeavor. By utilizing dimension engineering, a diverse array of new materials with intrinsically different electronic and optical properties has been developed. Here, we report a new family of 2D‐0D hybrid bimetallic halides, (C6N2H14)2SbCdCl9 ⋅ 2H2O (SbCd) and (C6N2H14)2SbCuCl9 ⋅ 2H2O (SbCu). These compounds adopt a new layered structure, consisting of alternating 0D square pyramidal [SbCl5] and 2D inorganic layers sandwiched by organic layers. SbCd and SbCu have optical band gaps of 3.3 and 2.3 eV, respectively. These compounds exhibit weak photoluminescence (PL) at room temperature, and the PL gradually enhances with decreasing temperature. Density functional theory (DFT) calculations reveal that SbCd and SbCu are direct gap semiconductors, where first‐principles band gaps follow the experimental trend. Moreover, given the different pressure responses of 0D and 2D components, these materials exhibit highly tunable electronic structures during compression, where a remarkable 11 times enhancement in PL emission is observed for SbCd at 19 GPa. This work opens new avenues for designing new layered bimetallic halides and further manipulating their structures and optoelectronic properties via pressure.
Mobility‐Modulated Sequential Dissociation Analysis Enables Structural Lipidomics in Mass Spectrometry ImagingQian, Yao; Guo, Xiangyu; Wang, Yunfang; Ouyang, Zheng; Ma, Xiaoxiao
doi: 10.1002/anie.202312275pmid: 37946693
Spatial lipidomics based on mass spectrometry imaging (MSI) is a powerful tool for fundamental biology studies and biomarker discovery. But the structure‐resolving capability of MSI is limited because of the lack of multiplexed tandem mass spectrometry (MS/MS) method, primarily due to the small sample amount available from each pixel and the poor ion usage in MS/MS analysis. Here, we report a mobility‐modulated sequential dissociation (MMSD) strategy for multiplex MS/MS imaging of distinct lipids from biological tissues. With ion mobility‐enabled data‐independent acquisition and automated spectrum deconvolution, MS/MS spectra of a large number of lipid species from each tissue pixel are acquired, at no expense of imaging speed. MMSD imaging is highlighted by MS/MS imaging of 24 structurally distinct lipids in the mouse brain and the revealing of the correlation of a structurally distinct phosphatidylethanolamine isomer (PE 18 : 1_18 : 1) from a human hepatocellular carcinoma (HCC) tissue. Mapping of structurally distinct lipid isomers is now enabled and spatial lipidomics becomes feasible for MSI.