Accounts of Chemical Research最新文献_第5页

Illuminating Palladium Catalysis.

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-26 DOI: 10.1021/acs.accounts.4c00815

Kelvin Pak Shing Cheung, Vladimir Gevorgyan

ConspectusThe past decade has witnessed significant advancements of visible-light-induced photocatalysis, establishing it as a powerful and versatile tool in organic synthesis. The major focus of this field has centered on the development of methodologies that either rely solely on photocatalysts or combine photocatalysis with other catalytic methods, such as transition metal catalysis, to address a broader and more diverse array of transformations. Within this rapidly evolving area, a subfield that we refer to as transition metal photocatalysis has garnered significant attention due to its growing impact and mechanistic uniqueness. A distinguishing feature of this subfield is the dual functionality of a single transition metal complex, which not only acts as a photocatalyst to initiate photochemical processes but also functions as a traditional catalyst, facilitating key bond-breaking and bond-forming events. As such, an exogenous photocatalyst is not required in transition metal photocatalysis. However, the implications of harnessing both the excited- and ground-state reactivities of the transition metal complex can extend beyond this simplification. One of the most compelling aspects of this area is that photoexcited transition metal complexes can exhibit unique reactivities inaccessible through conventional thermal or dual photocatalytic approaches. These distinct reactivities can be leveraged to accomplish novel transformations either by engaging an entirely different substrate pool or by unlocking new reactivities of known substrates.In 2016, our group pioneered the use of phosphine-ligated palladium catalysts that can be photoexcited upon visible-light irradiation to engage diverse substrates in radical reactions. In our initial discovery, we showed that photoexcitation can redirect the well-established oxidative addition of a Pd(0) complex into aryl iodides toward an unprecedented radical process, generating hybrid aryl Pd(I) radical species. We subsequently extended this novel strategy to the formation of alkyl radicals from alkyl halides. These reactive radical intermediates have been harnessed in a wide variety of transformations, including desaturation, alkyl Heck reactions, and alkene difunctionalization cascades, among others.Seeking to further expand this new avenue, we achieved the first example of asymmetric palladium photocatalysis in the context of allylic C-H amination, where the palladium catalyst now plays triple duty by additionally controlling the stereochemical outcome of the reaction. In parallel to reaction discovery, we have also established that diazo compounds, strained molecules, and electron-deficient alkenes can serve as alkyl radical precursors beyond organic halides and redox-active esters. Notably, the engagement of electron-deficient alkenes has been made possible by the photoinduced hydricity enhancement of Pd-H species, representing a new mode of photoexcited reactivity.This Account presents our discov

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引用次数: 0

Activation of Molecular Oxygen and Selective Oxidation with Metal Complexes

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-21 DOI: 10.1021/acs.accounts.4c0073110.1021/acs.accounts.4c00731

Chao Wang*, and , Jianliang Xiao*,

Selective oxidation with molecular oxygen is one of the most appealing approaches to functionalization of organic molecules and, yet at the same time, one of the most challenging reactions facing organic synthesis due to poor selectivity control. Molecular oxygen is a green and inexpensive oxidant, producing water as the only byproduct in oxidation. Not surprisingly, it has been used in the manufacturing of many commodity chemicals in the industry. It is also nature’s choice of oxidant and drives a variety of oxidation reactions critical to life and various other biologic processes. While the past decades have witnessed great progress in understanding, both structurally and mechanistically, how nature exploits metalloenzymes, i.e., monooxygenases and dioxygenases, to tackle some of the most challenging oxidation reactions, e.g., methane oxidation to methanol, there are only a small number of well-defined, man-made metal complexes that have been reported to enable selective oxidation with molecular oxygen of compounds more relevant to fine chemical and pharmaceutical synthesis.

In the past 10 years or so, our laboratories have developed several transition metal complexes and shown that they are capable of catalyzing selective oxidation under 1 atm of O₂. Thus, we have shown that an Fe(II)-bisimidazolidinyl-pyridine complex catalyzes selective oxygenation of C–H bonds in ethers with concomitant release of hydrogen gas instead of water, and when the iron center is replaced with Fe(III), selective oxidative cleavage of C═C bonds of olefins becomes feasible. To address the low activity of the iron complex in oxidizing less active olefins, we have developed a Mn(II)-bipyridine complex, which catalyzes oxidative cleavage of C═C bonds in aliphatic olefins, C–C bonds in diols, and carboxyl units in carboxylic acids under visible light irradiation. Light is necessary in the oxidation to cleave an off-cycle, inactive manganese dimer into a catalytically active Mn═O oxo species. Furthermore, we have found that a binuclear salicylate-bridged Cu(II) complex enables the C–H oxidation of tetrahydroisoquinolines as well as C═C bond cleavage, and when a catalytic vitamin B1 analogue is brought in, oxygenation of tetrahydroisoquinolines to lactams takes place via carbene catalysis. Still further, we have found that a readily accessible binuclear Rh(II)-terpyridine complex catalyzes the oxidation of alcohols, and being water-soluble, the catalyst can be easily separated and reused multiple times. In addition, we recently unearthed a simple protocol that allows waste polystyrene to be depolymerized to isolable, valuable chemicals. A cheap Brønsted acid acts as the catalyst, activating molecular oxygen to a singlet state through complexation with the polymer under light irradiation, thereby depolymerizing the polymer.

使用分子氧进行选择性氧化是有机分子功能化最有吸引力的方法之一，但同时也是有机合成面临的最具挑战性的反应之一，因为选择性控制不佳。分子氧是一种绿色、廉价的氧化剂，在氧化过程中产生的唯一副产物就是水。因此，它被用于制造工业中的许多商品化学品也就不足为奇了。它也是大自然选择的氧化剂，并驱动着对生命和其他各种生物过程至关重要的各种氧化反应。过去几十年来，人们在从结构和机理上理解自然界如何利用金属酶（即单氧酶和二氧酶）来处理一些最具挑战性的氧化反应（如甲烷氧化成甲醇）方面取得了巨大进步、在过去 10 年左右的时间里，我们的实验室开发了几种过渡金属配合物，并证明它们能够在 1 atm 的氧气环境下催化选择性氧化反应。因此，我们已经证明，Fe(II)-双咪唑烷基吡啶配合物能催化醚中 C-H 键的选择性加氧反应，同时释放出氢气而不是水；当铁中心被 Fe(III) 取代时，烯烃中 C═C 键的选择性氧化裂解变得可行。为了解决铁配合物在氧化活性较低的烯烃时活性较低的问题，我们开发了一种锰（II）-联吡啶配合物，它能在可见光照射下催化脂肪族烯烃中 C═C 键、二元醇中 C-C 键和羧酸中羧基单元的氧化裂解。在氧化过程中，光是将非循环、非活性锰二聚体裂解为具有催化活性的 Mn═O 氧化物的必要条件。此外，我们还发现，双核水杨酸盐桥接的 Cu（II）配合物能够使四氢异喹啉进行 C-H 氧化以及 C═C 键裂解，当加入催化维生素 B1 类似物时，四氢异喹啉通过碳烯催化作用氧合成为内酰胺。此外，我们还发现一种容易获得的双核 Rh(II)-terpyridine 复合物可以催化醇的氧化，而且这种催化剂具有水溶性，可以很容易地分离并多次重复使用。此外，我们最近发现了一种简单的方法，可以将废弃聚苯乙烯解聚成可分离的有价值化学品。一种廉价的布氏酸作为催化剂，在光照射下通过与聚合物络合，将分子氧活化为单线态，从而使聚合物解聚。

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引用次数: 0

Covalent Metal–Organic Frameworks: Fusion of Covalent Organic Frameworks and Metal–Organic Frameworks

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-21 DOI: 10.1021/acs.accounts.4c0077410.1021/acs.accounts.4c00774

Rong-Jia Wei, Xiao Luo, Guo-Hong Ning* and Dan Li*,

Metal–organic frameworks (MOFs) and covalent organic frameworks (COFs), as emerging porous crystalline materials, have attracted remarkable attention in chemistry, physics, and materials science. MOFs are constructed by metal clusters (or ions) and organic linkers through coordination bonds, while COFs are prepared by pure organic building blocks via covalent bonds. Because of the nature of linkages, MOFs and COFs have their own shortcomings. Typically, the relatively weak bond strengths of coordination bonds lead to poor chemical stability of MOFs, which limits their practical implementations. On the other hand, due to the strong covalent bonds, COFs exhibit rather higher stability under harsh conditions, compared to MOFs. However, the lack of open metal sites restricts their functionalization and application. Therefore, it is hypothesized that the “cream-skimming” of MOFs and COFs would address these drawbacks and produce a new class of crystalline porous material, namely, covalent metal–organic frameworks (CMOFs), with unprecedented structural complexity and advanced functionality. The CMOFs reveal a new synthetic approach for the preparation of reticular materials. Specifically, metal ions are reacted with chelating ligands to assemble metal complexes or clusters with functional reactive sites (e.g., −CHO, and −NH2), which can be further connected with organic linkers to form networked structures via dynamic covalent chemistry (DCC). The isolated metal complex or cluster precursors show enhanced stability which prevents structural decomposition and rearrangements during the self-assembly process of CMOFs. Since the topology of preassembled metal nodes is well-defined, the CMOFs structure can be readily predicted upon directed networking of covalent bonds. Unaccessible reticular materials from unstable or highly reactive metal ion/clusters under traditional conditions can be prepared via the DCC approach. Moreover, CMOFs synergize the advantages of MOFs and COFs, containing metal active sites ensuring various interesting properties, and covalent linkages that allow rather high chemical stability even under harsh conditions. In the past few years, our group has specifically focused on the development of general synthetic strategies for CMOFs by networking coinage metal (Cu, Ag, and Au)-based cyclic trinuclear units (CTUs) with DCC. The CTUs exhibit trigonal planar structures and can be functionalized with reactive sites, such as −NH2 and −CHO, that can further react with organic linkers to afford CMOFs. Notably, CTUs also features interesting properties including metallophilic attraction, π-acidity/basicity, luminescence, redox activity and catalytic activity, which can be incorporated into CMOFs. Therefore, we envision that CMOFs would be promising platforms not only for the development of novel reticular materials, but also for potential applications in many research fields including gas absorption/separation, sensin

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引用次数: 0

Buckybowl-Based Nanocarbons: Synthesis, Properties, and Applications

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-20 DOI: 10.1021/acs.accounts.4c0081210.1021/acs.accounts.4c00812

Yan Chen, and , Lei Zhang*,

The introduction of a five-membered ring into hexagon-fused networks typically induces strain that causes positive Gaussian curvature, leading to bowl-shaped polycyclic aromatic hydrocarbons (PAHs), often referred to as buckybowls or π-bowls. The interest in buckybowls is derived from their intriguing properties including, but not limited to, pyramidalized sp2 carbon atoms, low-lying lowest unoccupied molecular orbital (LUMO), surface charge stabilization, and bowl-to-bowl inversion. In recent years, investigations into the functionalization of buckybowls, as well as the structural aspects related to properties, have made significant progress. Indeed, the functionalization of buckybowls is a major route to increase structural diversity and fine-tune their properties. In particular, the fusion of aromatic rings to buckybowl rims (π-extension of buckybowls) has established a particularly promising synthetic strategy to access a wide range of buckybowl-based nanostructures with unique topologies and properties. A major obstacle, however, is the limited number of appropriate buckybowls, which could be suggested as potential frameworks for further functionalization. Moreover, buckybowls have been typically synthesized by ring-closing reactions, but many of these procedures suffer from the occurrence of considerable strain and lead to an undesired rearrangement. As a result, the development of buckybowl-based nanocarbons with desirable properties is still in its infancy due to the limited structural diversity, functionalization, and scalability.This Account describes our recent progress in the synthesis of buckybowls and buckybowl-based nanocarbons. In our study, diindeno[4,3,2,1-fghi:4′,3′,2′,1′-opqr]perylene (DIP), pyracyleno[6,5,4,3,2,1-pqrstuv]pentaphene (PP), tetracyclopenta[cd,fg,jk,mn]pyrene (TPP), and corannulene are employed as basic structural units, which exhibit a bowl-shaped geometry and offer an ideal platform for functionalization. General bottom-up approaches have been used to access buckybowl derivatives functionalized with peripheral alkynyl and aryl groups. These substituent groups significantly influence solubility, energy levels, and crystal packing, all of which impact their performance. These buckybowls are ultimately converted into π-extended nanocarbons with wide-ranging structural diversity, including doubly curved, rippled, and chiral nanocarbons. Chiral buckybowl-based nanocarbons, where chirality is introduced from quasi-[8]circulene moieties, have high enantiomerization barriers, enabling the separation of the enantiomers. Notably, the rippled nanocarbon containing 10 aromatic rings directly fused to the TPP core exhibits attractive electronic, magnetic, and mechanical properties, which can be further functionalized through the use of well-established chemistry, opening up many possibilities to access unusual carbon allotro

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引用次数: 0

Stereochemical Editing at sp3-Hybridized Carbon Centers by Reversible, Photochemically Triggered Hydrogen Atom Transfer

IF 18.3 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-19 DOI: 10.1021/acs.accounts.4c00830

Maximilian Iglhaut, Thorsten Bach

Millions of chiral compounds contain a stereogenic sp³-hybridized carbon center with a hydrogen atom as one of the four different substituents. The stereogenic center can be edited in an increasing number of cases by selective hydrogen atom transfer (HAT) to and from a photocatalyst. This Account describes the development of photochemical deracemization reactions using chiral oxazole-annulated benzophenones with a bonding motif that allows them to recognize chiral lactam substrates by two-point hydrogen bonding. The backbone of the catalysts consists of a chiral azabicyclo[3.3.1]nonan-2-one with a U-shaped geometry, which enables substrate recognition to occur parallel to the benzoxazole part of the aromatic ketones. The photocatalysts facilitate a catalytic photochemical deracemization of several compound classes including hydantoins, N-carboxyanhydrides, oxindoles, 2,5-diketopiperazines, and 4,7-diaza-1-isoindolinones. In addition, if more than one stereogenic center is present, the editing delivers a distinct diastereoisomer upon the appropriate selection of the respective photocatalyst enantiomer. The chiral photocatalysts operate via the benzophenone triplet that selectively abstracts a properly positioned hydrogen atom in exclusively one of the two substrate enantiomers. The photochemical step creates a planar carbon-centered radical and erases the absolute configuration at this position. While returning HAT to the same position would likely recreate the stereogenic center with the same absolute configuration, spectroscopic and quantum chemical studies suggest that the hydrogen atom is delivered from the photocatalyst to a heteroatom that is in conjugation to the radical center. Two scenarios can be distinguished for the hydrogen atom shuttling process. For hydantoins, N-carboxyanhydrides, and 4,7-diaza-1-isoindolinones, the back HAT occurs to a carbonyl oxygen atom or an imine-type nitrogen atom which is not involved in binding to the catalyst. For oxindoles and 2,5-diketopiperazines, a single lactam carbonyl group in the substrate is available to accept the hydrogen atom. It is currently assumed that back HAT occurs to this group, although the carbonyl oxygen atom is involved in hydrogen bonding to the catalyst. In comparison to the former reaction pathway, the latter process appears to be less efficient and more prone to side reactions. For both cases, an achiral enol or enamine is formed, which delivers upon dissociation from the catalyst statistically either one of the two stereoisomers of the substrate. Since only one substrate enantiomer (or diastereoisomer) is processed, a high enantioselectivity (or diastereoselectivity) results. Even though the editing is a contra-thermodynamic process, the described decoupling of a photochemical and a thermal step allows the usage of a single catalyst in loadings that vary between 2.5 and 10 mol % depending on the specific mode of action.

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引用次数: 0

Stereochemical Editing at sp3-Hybridized Carbon Centers by Reversible, Photochemically Triggered Hydrogen Atom Transfer

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-19 DOI: 10.1021/acs.accounts.4c0083010.1021/acs.accounts.4c00830

Maximilian Iglhaut, and , Thorsten Bach*,

Millions of chiral compounds contain a stereogenic sp³-hybridized carbon center with a hydrogen atom as one of the four different substituents. The stereogenic center can be edited in an increasing number of cases by selective hydrogen atom transfer (HAT) to and from a photocatalyst. This Account describes the development of photochemical deracemization reactions using chiral oxazole-annulated benzophenones with a bonding motif that allows them to recognize chiral lactam substrates by two-point hydrogen bonding. The backbone of the catalysts consists of a chiral azabicyclo[3.3.1]nonan-2-one with a U-shaped geometry, which enables substrate recognition to occur parallel to the benzoxazole part of the aromatic ketones. The photocatalysts facilitate a catalytic photochemical deracemization of several compound classes including hydantoins, N-carboxyanhydrides, oxindoles, 2,5-diketopiperazines, and 4,7-diaza-1-isoindolinones. In addition, if more than one stereogenic center is present, the editing delivers a distinct diastereoisomer upon the appropriate selection of the respective photocatalyst enantiomer. The chiral photocatalysts operate via the benzophenone triplet that selectively abstracts a properly positioned hydrogen atom in exclusively one of the two substrate enantiomers. The photochemical step creates a planar carbon-centered radical and erases the absolute configuration at this position. While returning HAT to the same position would likely recreate the stereogenic center with the same absolute configuration, spectroscopic and quantum chemical studies suggest that the hydrogen atom is delivered from the photocatalyst to a heteroatom that is in conjugation to the radical center. Two scenarios can be distinguished for the hydrogen atom shuttling process. For hydantoins, N-carboxyanhydrides, and 4,7-diaza-1-isoindolinones, the back HAT occurs to a carbonyl oxygen atom or an imine-type nitrogen atom which is not involved in binding to the catalyst. For oxindoles and 2,5-diketopiperazines, a single lactam carbonyl group in the substrate is available to accept the hydrogen atom. It is currently assumed that back HAT occurs to this group, although the carbonyl oxygen atom is involved in hydrogen bonding to the catalyst. In comparison to the former reaction pathway, the latter process appears to be less efficient and more prone to side reactions. For both cases, an achiral enol or enamine is formed, which delivers upon dissociation from the catalyst statistically either one of the two stereoisomers of the substrate. Since only one substrate enantiomer (or diastereoisomer) is processed, a high enantioselectivity (or diastereoselectivity) results. Even though the editing is a contra-thermodynamic process, the described decoupling of a photochemical and a thermal step allows the usage of a single catalyst in loadings that vary between 2.5 and 10 mol % depending on the specific mode of action.

数以百万计的手性化合物都含有一个以氢原子作为四个不同取代基之一的立体sp3杂化碳中心。在越来越多的情况下，可以通过选择性氢原子转移（HAT）在光催化剂之间进行编辑。本开户绑定手机领体验金介绍了使用手性噁唑annulated二苯甲酮进行光化学去甲基化反应的开发过程，这种二苯甲酮具有键合基团，可通过两点氢键识别手性内酰胺底物。催化剂的骨架由具有 U 型几何结构的手性氮杂双环[3.3.1]壬烷-2-酮组成，这使得底物识别与芳香酮的苯并恶唑部分平行进行。这种光催化剂可催化几类化合物的光化学去甲基化，包括海因、N-羧基酸酐、吲哚、2,5-二酮哌嗪和 4,7-二氮杂-1-异吲哚啉酮。此外，如果存在一个以上的立体中心，在适当选择相应的光催化剂对映体后，编辑会产生不同的非对映异构体。手性光催化剂通过二苯甲酮三重选择性地抽取两种底物对映体之一中位置合适的氢原子。光化学步骤会产生一个平面碳中心自由基，并消除该位置的绝对构型。虽然将 HAT 放回同一位置可能会重新生成具有相同绝对构型的立体中心，但光谱和量子化学研究表明，氢原子是从光催化剂传递到与自由基中心共轭的杂原子上的。氢原子穿梭过程可分为两种情况。对于 hydantoins、N-羧基酸酐和 4,7-二氮杂-1-异吲哚啉酮，后氢原子穿梭到一个羰基氧原子或一个亚胺型氮原子上，后者不参与与催化剂的结合。对于吲哚和 2,5-二酮哌嗪，底物中的单个内酰胺羰基可接受氢原子。尽管羰基氧原子参与了与催化剂的氢键结合，但目前认为该基团发生了反向氢键反应。与前一种反应途径相比，后一种过程似乎效率较低，而且更容易发生副反应。在这两种情况下，都会形成非手性的烯醇或烯胺，在与催化剂解离后，它们会从底物的两种立体异构体中任选一种进行统计传递。由于只处理一种底物对映体（或非对映异构体），因此对映选择性（或非对映选择性）很高。尽管编辑是一个反热力学过程，但所述的光化学步骤和热步骤的解耦允许使用单一催化剂，根据具体的作用模式，催化剂的负载量在 2.5 至 10 摩尔%之间。

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引用次数: 0

Skeletal Editing through Cycloaddition and Subsequent Cycloreversion Reactions.

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-18 Epub Date: 2025-01-28 DOI: 10.1021/acs.accounts.4c00813

Pengwei Xu, Armido Studer

ConspectusSkeletal editing, which involves adding, deleting, or substituting single or multiple atoms within ring systems, has emerged as a transformative approach in modern synthetic chemistry. This innovative strategy addresses the ever-present demand for developing new drugs and advanced materials by enabling precise modifications of molecular frameworks without disrupting essential functional complexities. Ideally performed at late stages of synthesis, skeletal editing minimizes the need for the cost- and labor-intensive processes often associated with de novo synthesis, thus accelerating the discovery and optimization of complex molecular architectures. While current efforts in skeletal editing predominantly focus on monatomic-scale modifications, editing molecules through cycloaddition followed by cycloreversion offers a unique strategy to manipulate molecular frameworks on a double-atomic scale. This introduces new possibilities for chemical transformations and enables transformations such as double-atom transmutation, formal single-atom transmutation, and atom insertion. Early examples of such skeletal editing processes often relied on the inherent high reactivity of the substrates, which needed to be sufficiently active to undergo cycloaddition and possess good leaving groups for the subsequent fragmentation (cycloreversion) step. Recently, however, the structural editing of relatively inert substrates has become achievable through substrate activation strategies designed to enhance either the cycloaddition or subsequent cycloreversion step.Along these lines, we recently developed a dearomative process for activating pyridines. In a simple high-yielding chemical operation, oxazinopyridines are readily obtained as activated dearomatized isolable intermediates. This method enabled us to achieve the transformation of pyridines into benzenes and naphthalenes through a cycloaddition/cycloreversion sequence. In this Account, related recent contributions from other research groups are highlighted as well, alongside early examples involving tetrazines, triazines, diazines, and other similar heterocycles as cycloaddition reaction partners. By offering a streamlined route to modify molecular structures, these approaches have demonstrated their ability to interconvert arenes and heteroarenes and have shown significant potential for late-stage editing applications as well as advancing drug discovery and the synthesis of bioactive molecules.In the future, these approaches will undoubtedly see broader development in the field of skeletal editing. New strategies for substrate activation should be devised to enable not only the incorporation of nitrogen and other heteroatoms into rings─rather than their deletion─but also to achieve ring contraction and expand the application of this strategy to non-aromatic rings. We hope that the advancements summarized in this Account will inspire chemists to explore and expand skeletal editing methodolog

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引用次数: 0

Aerolysin Nanopore Electrochemistry.

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-18 Epub Date: 2025-01-28 DOI: 10.1021/acs.accounts.4c00630

Jun-Ge Li, Yi-Lun Ying, Yi-Tao Long

ConspectusIons are the crucial signaling components for living organisms. In cells, their transportation across pore-forming membrane proteins is vital for regulating physiological functions, such as generating ionic current signals in response to target molecule recognition. This ion transport is affected by confined interactions and local environments within the protein pore. Therefore, the pore-forming protein can efficiently transduce the characteristics of each target molecule into ion-transport-mediated signals with high sensitivity. Inspired by nature, various protein pores have been developed into high-throughput and label-free nanopore sensors for single-molecule detection, enabling rapid and accurate readouts. In particular, aerolysin, a key virulence factor of Aeromonas hydrophila, exhibits a high sensitivity in generating ionic current fingerprints for detecting subtle differences in the sequence, conformation, and structure of DNA, proteins, polypeptides, oligosaccharides, and other molecules. Aerolysin features a cap that is approximately 14 nm wide on the cis side and a central pore that is about 10 nm long with a minimum diameter of around 1 nm. Its long lumen, with 11 charged rings at two entrances and neutral amino acids in between, facilitates the dwelling of the single analyte within the pore. This characteristic enables rich interactions between the well-defined residues within the pore and the analyte. As a result, the ionic current signal offers a unique molecular fingerprint, extending beyond the traditional volume exclusion model in nanopore sensing. In 2006, aerolysin was first reported to discriminate conformational differences of single peptides, opening the door for a rapidly growing field of aerolysin nanopore electrochemistry. Over the years, various mutant aerolysin nanopores have emerged, associated with advanced instrumentation and data analysis algorithms, enabling the simultaneous identification of over 30 targets with the number still increasing. Aerolysin nanopore electrochemistry in particular allows time-resolved qualitative and quantitative analysis ranging from DNA sequencing, proteomics, enzyme kinetics, and single-molecule reactions to potential clinical diagnostics. Especially, the feasibility of aerolysin nanopore electrochemistry in dynamic quantitative analysis would revolutionize omics studies at the single-molecule level, paving the way for the promising field of single-molecule temporal omics. Despite the success of this approach so far, it remains challenging to understand how confined interactions correlate to the distinguishable ionic signatures. Recent attempts have added correction terms to the volume exclusion model to account for variations in ion mobility within the nanopore caused by the confined interactions between the aerolysin and the analyte. Therefore, in this Account, we revisit the origin of the current blockade induced by target molecules inside the aerolysin

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引用次数: 0

Indirect Construction of Chiral Metal-Organic Frameworks for Enantioselective Luminescence Sensing.

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-18 Epub Date: 2025-02-02 DOI: 10.1021/acs.accounts.4c00795

Zongsu Han, Kun-Yu Wang, Mengmeng Wang, Wei Shi

ConspectusChiral metal-organic frameworks (MOFs) are promising candidates as luminescent sensing materials for chiral species, which are essential components in modern industries, pharmaceuticals, and biological processes. The discrimination of enantiomers with highly similar physical and chemical properties is crucial because they are often present concurrently in the same system but may feature distinct effects on living matters. While the rapid and precise sensing capabilities of chiral MOFs outshine traditional detection methods for chiral species in daily life, chemical production, and the natural environment, it requires well-matched chemical and electronic structures between MOFs and chiral species. Yet, conventional strategies to construct chiral luminescent MOFs are immensely challenging due to the crystallization difficulties based on low-symmetric building blocks.Recent advancements in MOF chemistry have led to novel pathways for synthesizing chiral MOFs for enantioselective sensing. Compared with direct synthesis using optically pure luminescent ligands, which are usually complex and costly, indirect synthesis has garnered significant attention for reduced costs, simplified synthesis, enhanced material stability, and broad application scope. In the past few years, our group has developed chiral guest ion exchange, chiral coordination modification, and chiral defect engineering for indirectly synthesizing chiral MOFs. The chiral guest ion exchange is cost-effective for introducing chiral ions into MOF pores but can be applied only in charged frameworks. In addition, it also faces limitations in chiral ion availability and the tendency toward chirality loss during the sensing process. Besides, compared with ion exchange, the chiral coordination modification can maintain the chemical stability of chiral MOFs due to the stronger coordination bonds. Still, it requires MOFs with accessible open metal sites that may bind disordered dangling molecules, complicating structural determination. Therefore, specific pathways such as chiral linker installation with dual-end coordination have been developed to afford well-defined crystal structures. While all aforementioned methods may decrease the MOFs' pore sizes to a certain degree, we further developed a chiral defect engineering approach to enlarge pore size and introduce chiral center simultaneously. Such a highly competitive strategy is facile and low-cost and can be expanded to many well-known stable MOFs.In this Account, we delve into the intricate evolution of indirect strategies for constructing chiral MOFs tailored for enantioselective sensing applications. We provide a detailed analysis of the progression and innovation within the field, tracing the development of MOF-based enantioselective luminescence sensors. By systematically reviewing the various synthetic approaches, this work highlights their respective strengths and limitations. Beyond reviewing the state of the art, this A

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引用次数: 0

Catalytic Hydrogenolysis of Lignin into Serviceable Products.

IF 16.4 1区化学 Q1 CHEMISTRY, MULTIDISCIPLINARY

Accounts of Chemical Research

Pub Date : 2025-02-18 Epub Date: 2025-02-05 DOI: 10.1021/acs.accounts.4c00644

Shuizhong Wang, Xiancheng Li, Rumin Ma, Guoyong Song

ConspectusLignin, a major component of lignocellulosic biomass, accounts for nearly 30% of organic carbon on Earth, making it the most abundant renewable source of aromatic carbon. The valorization of lignin beyond low-value heat and power has been one of the foremost challenges for a long time. On the other hand, aromatic compounds, constituting a substantial segment of the chemical industry and projected to reach a market value of $382 billion by 2030, are predominantly derived from fossil resources, contributing to increased CO2 emissions. Integrating lignin into the aromatic chemical supply chain will offer a promising strategy to reduce the carbon footprint and boost the economic viability of biorefineries. Thus, depolymerizing lignin biopolymers into aromatic chemicals suitable for downstream processing is an important starting point for its valorization. However, owing to lignin's complexity and heterogeneity, achieving efficient and selective depolymerization that yields desirable, isolable aromatic monomers remains a significant scientific challenge.The structure of lignins varies significantly in terms of subunits and linkages across plant species, leading to considerable differences in their reactivity, in the distribution of resulting monomers, and in their subsequent utilization. In this context, this Account highlights our recent studies on the catalytic hydrogenolysis of lignin into serviceable products for preparing valuable materials, fuels, and chemicals. First, we designed a series of catalytic systems for lignin hydrogenolysis specifically tailored to the structural features of lignin from wood, grass, and certain seed coats. To reduce reliance on expensive commercial catalysts like Pd/C, Ru/C, and Pt/C, we advanced heterogeneous metal catalysts by shifting from high-loaded nanostructured metals to low-loaded, atomically dispersed metals and replacing precious metals with nonprecious alternatives. This approach significantly reduces the cost of catalysts, enhances their atomic economy, and improves their catalytic activity and/or selectivity. Then, using the developed catalysts, phenolic monomers tethering a distinct side chain were selectively generated from the hydrogenolysis of lignin (from various plants), achieving yields close to the theoretical maximum. The high selectivity allowed the separation and purification of monomeric phenols from lignin reaction mixtures readily. To gain deeper insights into the cleavage of lignin C-O bonds, we designed deuterium-incorporated β-O-4 mimics (dimers and one polymer) for a mechanistic study, which excluded the pathways involving the loss of linkage protons and led to the proposal of a concerted hydrogenolysis process for β-O-4 cleavage. Finally, to enable the utilization of depolymerized lignin phenolic monomers, unconventional feedstocks in the current chemical industry, we developed a series of methods to transform them into valuable bioactive molecules, function

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引用次数: 0