R&D｜CCS Chemistry 近期报道
引言
1
Plasmonic metal nanostructures, possessing unique surface plasmon resonance properties, show excellent capabilities for light trapping and coupling. On this basis, various plasmonic metal nanostructures offer extraordinary opportunities to promote the conversion efficiency of solar energy to electric energy, hydrogen energy or thermal energy, and so on. In this review article, we highlight a number of recent research achievements on the rational design of plasmonic metal nanostructures so as to maximize the utilization of the entire solar spectrum. Compared with single metal nanoparticles, multiplex (such as multicompositions, sizes, or shapes) nanoparticle structures emphasize advantages in broadening the absorption range and improving light-utilization efficiency. This review concludes with discussions regarding challenges in this research field and proposals of prospects for future directions.
2
The copper-catalyzed, highly enantioselective 1,4-protoboration of terminal 1,3-dienes with proton source and B2Pin2 has been developed. Chiral allylic boronate reagents, which are significant precursors for many well-established transformations, were prepared by this novel method with good functional group tolerance and enantioselectivity. Further studies indicated the products could be used as versatile precursors for asymmetric transformations and natural products syntheses. The mechanism of this reaction was investigated by control and reaction monitoring experiments.
3
A biphenyl-bridged bis-tris(urea) ligand L was rationally designed with a favorable angle to construct a hexagon-shaped A6L6 (A = anion) complex upon assembly with phosphate anions (PO43−) via anion-coordination-driven assembly (ACDA). Due to the moderate flexibility of L, another well-defined discrete architecture, a square-like A4L4 complex, has also been obtained from ligand L and PO43−. Interconversion between these two self-assemblies can be readily realized by solvent regulation. In addition, the two anionic architectures display different binding abilities for selected cationic guest molecules, enabling the uptake of a desired guest from a mixture of guests.
4
The development and enrichment of organic materials with narrowband emission in longer wavelength regions beyond 515 nm still remains a great challenge. Herein, a synthetic methodology for narrowband emission materials has been proposed to functionalize multiple resonance (MR) skeletons and generate a universal building block, namely, the key intermediate DtCzB-Bpin, which can be utilized to construct multifarious thermally activated delayed fluorescence (TADF) materials with high color purity through a simple one-step Suzuki coupling reaction. Based on this unique synthetic strategy, a series of efficient narrowband green TADF emitters has been constructed by localized attachment of 1,3,5-triazine and pyrimidine derivatives-based acceptors onto B–N-containing MR frameworks with 1,3-bis(3,6-di-tert-butylcarbazol-9-yl)benzene (DtCz) as the ligand. The precise modulation of the acceptor is an intelligent approach to achieve bathochromic shift and narrowband emission simultaneously. The DtCzB-TPTRZ-based organic light-emitting diode (OLED) exhibits pure green emission with Commission Internationale de L’Eclairage (CIE) coordinates of (0.23, 0.68), a maximum external quantum efficiency (EQE) of 30.6%, and relatively low efficiency roll-off.
5
Discrete Pt(II) metallacycles have attracted particular attention for the chemotherapeutic treatment of cancer. However, a single chemotherapy cannot simultaneously balance efficiency and safety because the continuous administration throughout the entire therapy period will lead to inefficient therapy and potentially long-term systemic toxicity. Therefore, the development of a novel organoplatinum(II) metallacycle with multimodal treatment capabilities is urgently needed to overcome these issues. Herein, a discrete Pt(II) metallacycle ( SCY) bearing the near-infrared (NIR) photosensitizer heptamethine cyanine was fabricated and further encapsulated by amphiphilic 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-methoxy(polyethyleneglycol) (DSPE-mPEG) to form P@SCY nanoparticles. Heptamethine cyanine, which has excellent photoconversion efficiency, can generate reactive oxygen species (ROS) and heat simultaneously, and the cyanine moiety can target mitochondria in cancer cells due to their quaternary ammonium salt cations, which improve the effect of phototherapy. Due to its excellent phototherapy and chemotherapy properties, P@SCY exhibited remarkable trimodal therapeutic effects [chemo-/photodynamic therapy (PDT)/photothermal therapy (PTT)] against cancer cells (HepG2 cells, MCF-7 cells, and 4T1 cells) in vitro. Furthermore, in vivo results also confirmed that P@SCY had superior antitumor properties with minimal side effects in the 4T1 tumor model. This work presents a practicable approach to develop a multifunctional organoplatinum(II) metallacycle for multimodal tumor therapy.
6
The transition-metal-catalyzed cyanations of aryl halides are among the most used methods for synthesizing aryl nitriles. Despite tremendous advances, cyanating an aryl halide in a facile and benign fashion has generally been unsuccessful. The challenge in this significant transformation is the strong affinity of cyanide for metals, which hampers oxidative addition (OD) and reductive elimination (RE) making organometallic catalysis elusive. Herein, we demonstrate for the first time that photoredox–nickel-catalyzed cyanations of aryl halides are readily enabled by visible light, in which Ni(II) species are transiently oxidized to Ni(III) species, thereby facilitating subsequent cyanide transfer and RE. Using this dual catalysis strategy, we cyanated aryl and alkenyl halides at room temperature in a highly benign manner (30 examples, 53–93% yield) by avoiding the use of air-sensitive ligands, Ni(0) precursors, and hypertoxic cyanation reagents, while also limiting excess metal waste. Computational studies were also used to help understand the present transformation.
7
Ambient electrochemical nitrogen fixation is a promising and environmentally benign route for producing sustainable ammonia, but has been limited by the poor performance of existing catalysts that promote the balanced chemisorption of N2 and subsequent electrochemical activation and hydrogenation. Herein, we describe the highly selective and efficient electrohydrogenation of nitrogen to ammonia using a hollow nanorod-based hierarchically graphitic carbon electrocatalyst with abundant atomically dispersed Mn sites. We discovered that the electron interactions strengthen the interfacial binding between nitrogen and active Mn Lewis acidic hotspots. The Lewis acid–base interactions promote the chemisorption and lock up nitrogen on the active sites and suppress proton adsorption. The proton-coupled electron transfer cleavage of the nitrogen triple bond through an associative mechanism was confirmed under lower overpotential, which delivered high ammonia yield of 67.5 μg h−1 mgcat.−1 and Faradaic efficiency of 13.7% at −0.25 V versus the reversible hydrogen electrode, along with ∼100% selectivity and significantly enhanced electrochemical stability (about 88.8% current retention over 50 h potentiostatic test) under mild conditions. Our strategy is versatile to tailor the nitrogen fixation performance of single-atom catalysts with atomic accuracy.
8
Mechanically interlocked molecules (MIMs) and host–guest chemistry have received great attention in the past few decades. However, it remains challenging to design architectures with mechanically interlocked features and construct cavities for guest molecule recognition using similar building blocks. In this study, we designed and constructed a series of novel twisted supramolecular structures by assembling various multitopic terpyridine (tpy) ligands with the same diameter and Zn(II) ions. The obtained complexes exhibited evolutional architectures and showed distinctively different space-constraint effects. Specifically, the assembled dimer SA, SB, and SBH displayed mechanically interlocked phenomena, including [2]catenane and [3]catenane, with an increase in concentration. However, no interlocked structures were observed in complexes SC and SCH constructed by hexatopic tpy ligands due to the significant space constraints. The single-crystal data of complex SCH further proved significant space constraints and illustrated the formation of a relatively closed cavity, which showed excellent host–guest properties for different calixarenes, especially high affinity for calix[6]arene.
9
Molecular nanotopology—a term we coined recently—is a rapidly developing field of research that is emerging out of the confluence of chemical topology with the mechanical bond. When perusing the increased research activities in this field, it is clear that a new discipline is ready to receive recognition in its own right. In this Mini-Review, we address the historical development of chemical topology and describe how the rational design and practical synthesis of molecular links and knots with mechanical bonds, together with interwoven extended frameworks, have led to the rapid establishment of molecular nanotopology as a discipline. Representative examples are highlighted to offer the reader an extensive overview of ongoing research. We spotlight the major challenges facing chemists and materials scientists and provide some indications as to how molecular nanotopology is going to develop in the years ahead.
10
Catalytic asymmetric aza-Michael represents one of the most convenient and atom-economical approaches for the rapid construction of biologically active chiral β-amino acid frameworks. However, the direct enantioselective addition of nitrogen-based nucleophiles to intrinsically low reactivity of α,β-unsaturated carboxylic acid, ester, and amide, as well as simple α,β-unsaturated nitrile, remains a long-standing challenge. Herein, we report a unified Cu-catalyzed asymmetric reversal hydroamination, capable of direct preparation of a series of β-amino acid, ester, amide, and nitrile in a highly regio- and enantioselective manner, without the requirement of traditional preinstallation of stoichiometric quantities of auxiliaries.
11
Asymmetric nucleophilic addition of 3-substituted N-Boc oxindoles to 3-bromooxindoles was designed to directly construct hetero-3,3′-bisoxindoles, with varying vicinal quaternary carbon stereocenters and N-substituents. The reaction progressed efficiently with high yields, good diastereo- and enantioselectivity (up to >99% ee) under mild reaction conditions catalyzed by chiral N,N′-dioxide/metal complexes. This methodology enabled the facile transformation of the generated hetero-3,3’-bisoxindoles into diverse hexahydropyrroloindole alkaloids with potential antiparasitic and anticancer properties.
12
A catalytic, enantioselective spirocyclization of formanilides or formylindolines and enamides has been developed herein. The reaction proceeds through a sequential iridium-catalyzed hydrosilylation of tertiary formanilides and a chiral phosphoric acid-catalyzed formal cycloaddition of exocyclic enamides, thus providing straightforward access to a diverse array of enantioenriched azaspirocycles under mild conditions. A new bowl-shaped phosphoric acid bearing an o-CF3-aryl on the H8-BINOL-framework OCF-CPA (CPA18) has been developed as an effective, multipoint-controlled chiral catalyst for the reaction. And mechanistic investigations reveal the presence of crucial C–H⋯F hydrogen bonding in the enantiodetermining transition states.
13
Despite the significant progress in carbohydrate chemistry, there remains a pressing need for efficient and practical glycosylation methods using simple glycosyl donors and with high atom economy. Herein, a new protocol for glycosylation with glycosyl chloride donors under palladium-catalyzed conditions is developed. PdII complex serves as a Lewis acid to promote the activation of glycosyl chloride for the formation of oxocarbenium ion intermediate. This new method is operationally simple, robust, and enables efficient synthesis of both O- and N-glycosides with a broad substrate scope. In particular, it offers an easy access to a range of N-ribonucleoside analogs.
14
Catenated cages are generally considered thermodynamically more stable than their constituent monomeric cages. However, the catenation mechanism is yet to be elucidated; it would require systematic investigation into the structural effects of the building blocks, their enthalpic and entropic contributions, and the effect of solvents. By inspecting these factors, we rationalized some design principles for the efficient construction of catenated cages. Our study revealed that a steric hindrance linker and a rigid panel led to the formation of an enthalpy-favored encapsulated intermediate before catenation occurred. The stability of this enthalpic intermediate was crucial for cage catenation, as the reactions were otherwise outcompeted by an entropy-favored intermediate. The formation of the latter was facilitated significantly by a flexible panel and solvent molecules that stably resided within the monomeric cage. This study provides a guideline for the elaboration of catenated cages with more sophisticated topologies, which could be extended to other complex supramolecular assemblies.
15
In order to develop pure organic single-molecule white-light emitters (SMWLE), the oxidation of thianthrene (TA) was performed on sulfur atoms at different degrees to tune room temperature phosphorescence (RTP) emission. With increasing degrees of oxidation from 1OTA, 2OTA, 3OTA, to 4OTA, monomeric and aggregative RTP emission was gradually suppressed, due to the gradual disappearance of lone pair electrons on sulfur atoms. Among these compounds, monomers and aggregates of 1OTA demonstrated a better intensity match between fluorescence and RTP. Through partial oxidation of TA, 1OTA exhibited the simultaneous ternary emissions from the lowest singlet state (S1), the lowest triplet state (T1), and the high-lying triplet state (Tn) in doped film. The single-molecule white-light emission was achieved in 1OTA crystal with a photoluminescence quantum yield (PLQY) of 47.1%. This work not only reports the RTP behavior of TA with different degrees of oxidation, but also provides an example of excited-state modulation to harvest an efficient SMWLE material.
16
Herein, we report a mild and practical protocol for the copper-catalyzed chlorofluoromethylthiolation of (hetero)aryl boronic acids with the novel reagent PhSO2SCFClH. The resulting products are amenable to halogen-exchange 18F-fluorination with cyclotron-produced [18F]fluoride affording [18F]ArSCF2H. This process highlights the combined value of reagent development and (hetero)aryl boron precursors for radiochemistry by adding the [18F]SCF2H group to the list of 18F-motifs within reach for positron emission tomography studies.
17
Light-driven carbon dioxide (CO2) capture and utilization is one of the most fundamental reactions in Nature. Herein, we report the first visible-light-driven photocatalyst-free hydrocarboxylation of alkenes with CO2. Diverse acrylates and styrenes, including challenging tri- and tetrasubstituted ones, undergo anti-Markovnikov hydrocarboxylation with high selectivities to generate valuable succinic acid derivatives and 3-arylpropionic acids. In addition to the use of stoichiometric aryl thiols, the thiol catalysis is also developed, representing the first visible-light-driven organocatalytic hydrocarboxylation of alkenes with CO2. The UV–vis measurements, NMR analyses, and computational investigations support the formation of a novel charge-transfer complex (CTC) between thiolate and acrylate/styrene. Further mechanistic studies and density functional theory (DFT) calculations indicate that both alkene and CO2 radical anions might be generated, illustrating the unusual selectivities and providing a novel strategy for CO2 utilization.
18
The utilization of economic and practical trifluoromethyl reagents to introduce trifluoromethyl (CF3) groups into organic molecules is an important research focus due to their role as vital structural motifs in the pharmaceutical and agricultural industries. Herein, we disclose a cost-efficient and practical approach of photoinduction of a radical relay process for the synthesis of α-CF3 ketones. We showed that trifluoromethylation reagents such as TES-OTf, Tf2O, TMS-OTf, TBS-OTf, H-OTf, and others, could be used successfully as inexpensive CF3 precursors under metal-free and redox-neutral conditions. The potential application of this protocol was highlighted further by late-state modification of drug segments and gram-scale synthesis. Our mechanistic studies revealed that this transformation might involve a radical process, and acetic acid (CH3COOH) not only promoted the formation of enol triflates, but also accelerated the in situ conversion from enol triflates to α-CF3 ketones.