Catalytic asymmetric synthesis of chiral azo compounds via interrupted Japp-Klingemann reaction with aryldiazonium salts

Asymmetric synthesis of enantioenriched azo compounds bearing tetrasubstituted stereocenter was achieved through chiral N,N′-dioxide/metal Lewis acid promoted interrupted Japp-Klingemann reaction of aryldiazonium tetrafluoroborate salts with nucleophiles under mild conditions. This protocol features wide substrate scope and good functional group compatibility.Azaarene-containing chiral azo compounds were stable enough in Japp-Klingemann reaction condition. The key to success of the reaction was the employment of metal salt/N,N′-dioxide ligand and the dual-task roles of the base. Moreover, the X-ray crystal structure of Ni(II)/N,N′-dioxide/substrate complex confirmed that the substrate was activated by bidentate coordination, which shed light on the origin of chiral control of the reaction.     

Altering elastic-plastic mechanical response of a series of isostructural metal-organic complex crystals

The mechanically compliant single crystals have attracted massive attention. However, the related reports on the single crystals composed of metal-organic complexes remain scarce. In this study, we synthesized a series of isostructural single crystals of Zn^II complexes that manifest mechanical bending in response to external stress. In these crystals, the mechanical responses can be shifted between elastic bending and plastic bending by the control of the intermolecular interactions through a rational structural modification in the substituent group of pyridine ligands. As the molecular reorientation corresponding to ligand variation elongates the interfacial distance between molecular slip planes, and the structural disorder of ligands disperses the interplanar intermolecular interactions, the shift from elastic bending to plastic bending of the metal-organic complex-based single crystal was realized. The different mechanical responses of single crystals were comprehensively investigated both experimentally and theoretically.

     

Advancing from unimechanism polymerization to multimechanism polymerization: binary polymerization

Polymerizations with multiple mechanisms performed simultaneously are promising but very challenging. As the key limitation,the complicated mutual influence between different mechanisms can be hardly defined and measured. Herein we establish a universal framework for the assessment of mutual influence between different mechanisms using binary polymerization for demonstration. The kinetics and thermodynamics of polymerization with two mechanisms are compared with the corresponding homopolymerization and the difference is expressed by a hybrid function. The hybrid function is composed of a hybrid parameter that describes the extent of mutual influence and a function that describes necessary conditions for mutual influence to occur. The extent of mutual influence can be calculated using kinetic and thermodynamic data without details of reaction mechanisms, for the first time providing a straightforward method to assess the mutual influence between different polymerization mechanisms.We envision that the method has potential in more complex systems with multiple mechanisms/monomers with mutual influence.     

Metformin booster adipocyte-targeted gene therapy for the treatment of obesity and related metabolic syndromes

Obesity has become an important public problem that endangers human conditions and urgently needs to be solved. However, most weight-loss drugs on the market have little effect and are accompanied by adverse effects such as strokes and heart attacks. Here, we construct an adipocyte-targeting polypeptide-based gene carrier consisting of an adipocyte-targeting peptide and p-toluylsulfonyl arginine-modified polylysine (ATS-PLL-RT), which can specifically bind to the prohibitin of mature adipocytes. We further construct a short hairpin RNA (shRNA) to simultaneously silence fatty acid binding proteins 4 and 5 (shFABP4/5). FABPs are molecular chaperones for fatty acid metabolism and storage in cells. Moreover, we introduce metformin for combined therapy. First, the metformin combination can effectively improve the efficiency of gene transfection. In addition, metformin itself has an alleviating effect on diet-induced obesity and relevant metabolic diseases. The combination treatment of obese mice with ATS-PLL-RT/shFABP4/5 and metformin achieves body weight reduction and metabolic recovery. This study provides a potentially effective strategy for the clinical treatment of obesity as well as mitigating obesity-induced metabolic syndromes.

     

Simple sulfone-bridged heterohelicene structure realizes ultraviolet narrowband thermally activated delayed fluorescence,circularly polarized luminescence,and room temperature phosphorescence

Due to narrowband emission and high quantum efficiencies, polycyclic aromatic heterocycles with multi-resonance thermally activated delayed fluorescence (MR-TADF) properties have recently gained considerable attention in the organic optoelectronic field. Albeit their great promise in the full visible region covering from blue to red, MR-TADF emitters with ultraviolet emission have been rarely reported. Through locking the two ortho-positions of a triphenylamine core by sulfone groups, a simple polycyclic aromatic heterocycle, BTPT, was facilely constructed, exhibiting 368 nm ultraviolet emission with a narrow full width at half maximum (FWHM) of 33 nm. Its neat film exhibited distinct TADF property with a main emission peak at 388 nm. Noteworthily, the enantiomeric crystals of BTPT not only demonstrated significant circularly polarized luminescence (CPL) with large luminescence dissymmetry factor in the 10^?3 order but also displayed obvious room temperature phosphorescence (RTP). The relationship between this innovative helical unit and unique photophysical properties, including ultraviolet MRTADF, CPL, and RTP, was reasonably revealed.

     

Palladium-catalyzed enantioselective carbonylation reactions

Carbonylation,one of the most powerful approaches to the preparation of carbonylated compounds,has received significant attention from researchers active in various fields.Indeed,impressive progress has been made on this subject over the past few decades.Among the various types of carbonylation reactions,asymmetric carbonylation is a straightforward methodology for constructing chiral compounds.Although rhodium-catalyzed enantioselective hydroformylations have been discussed in several elegant reviews,a general review on palladium-catalyzed asymmetric carbonylations is still missing.In this review,we summarize and discuss recent achievements in palladium-catalyzed asymmetric carbonylation reactions.Notably,this review’s contents are categorized by reaction type.     

Regulating the dimensionality of diphosphaperylenediimide-based polymers by coordinating the out-of-plane anisotropic π-framework toward Ag+

The development of hetero-π-conjugated molecules is of significance for constructing diverse assembling superstructures based on heteroatom-related bonded or nonbonded interactions. Herein, we developed one-pot P-heteroannulation via palladium-catalyzed dual P—C bonds formation and subsequent sulfidation to construct two isomeric diphosphaperylenediimides (cis-5 and trans-5). The unique out-of-plane anisotropic π-framework induced a cumulative anisotropy with a dipole moment of up to 8.82 D for cis-5, leading to distinct supramolecular packing arrangements. Optical and electrochemical characterizations demonstrated that they showed the largest redshifts extending to 574 nm and rather low-lying LUMO levels of ?4.41 eV. Furthermore, the introduced P=S moieties endowed these diphosphaperylenediimides with prominent coordination ability towards Ag⁺, thus the first example of perylene diimide (PDI) core-involved metal-organic coordination polymers (MOCPs) with tunable dimensionality varied from 1D, 2D, to 3D were tactfully achieved. In view of easy accessibility and 2D layered porous structure, thus 2D (trans-5)·(AgOTf) based MOCP showed high crystallinity and good CO₂ adsorption capacity with surface area of 112 m²/g. The result opens a span-new avenue for exploring rylene imide-based MOCPs and related properties by integrating P functionality.

     

Fluoro-substituted DPP-bisthiophene conjugated polymer with azides in the side chains as ambipolar semiconductor and photoresist

Photoresists are essential for the fabrication of flexible electronics through all-photolithographic processes. Single component semiconducting photoresist exhibits both semiconducting and photo-patterning properties, and as a result, the device fabrication process can be simplified. However, the design of semiconducting polymeric photoresist with ambipolar semiconducting property remains challenging. In this paper, we report a single component semiconducting photoresist (PFDPPF4T-N₃) by incorporating azide groups and noncovalent conformation locks into the side alkyl chains and conjugated backbones of a diketopyrrolopyrrole-based conjugated polymer, respectively. The results reveal that PFDPP4FT-N₃ exhibits ambipolar semiconducting property with hole and electron mobilities up to 1.12 and 1.17 cm² V^?1 s^?1, respectively. Moreover, field effect transistors with the individual photo-patterned thin films of PFDPPF4T-N₃ also show ambipolar semiconducting behavior with hole and electron mobilities up to 0.66 and 0.80 cm² V^?1 s^?1, respectively. These results offer a simple yet effective design strategy for high-performance single component semiconducting photoresists, which hold great potential for flexible electronics processed by all photolithography.

     

Spatially-separated and photo-enhanced semiconductor corrosion processes for high-efficient and contamination-free electrochemical nanoimprint lithography

Free of any thermoplastic or photocuring resists, electrochemical nanoimprint lithography (ECNL) has emerged as an alternative nanoimprint way to fabricate three-dimensional micro/nano-structures (3D-MNSs) directly on a semiconductor wafer by a spatially-confined corrosion reaction induced by the metal/semiconductor contact potential. However, the consumption of electron acceptors in the ultrathin electrolyte between imprint mold and semiconductor wafer will slow down or even cease the corrosion rate. To solve this problem, we change the short-circuited corrosion cell into a spatially-separated primary cell: the imprint mold compacted gallium arsenide (GaAs) wafer in the anodic chamber while the platinum (Pt) plate connected to the imprint mold in the cathodic chamber. Thus, the GaAs corrosion rate will be stabilized in its limiting steady-state current density because of the abundant source of electron acceptors in the catholic chamber. The corrosion processes can be photo-enhanced by white-light illumination. Consequently, both the accuracy and the efficiency are promoted dramatically, which are demonstrated by the excellent performance of the fabricated binary optical elements. Moreover, the contamination problem caused by the electron acceptors is totally avoided. All the results prove that this novel ECNL mode is competitive and prospective in imprinting 3D-MNSs directly on semiconductor wafer.

     

Catalyst-free multicomponent polymerization of sulfonyl azide,aldehyde and cyclic amino acids toward zwitterionic and amphiphilic poly(N-sulfonyl amidine) as nanocatalyst precursor

Polymers with metal coordination ability are outstanding precursors of nanocatalysts, attracting numerous attention in nanocatalysis area. It has been rarely reported for the poly(N-sulfonyl amidines) as macromolecular ligands for nanocatalysis. Herein, a catalyst-free multicomponent polymerization (MCP) strategy is developed to facilely prepare a library of amphiphilic poly(N-sulfonyl amidines) with zwitterionic properties starting from disulfonyl azide, hydrophilic dialdehyde and cyclic amino acids including proline and pipecolinic acid. Metals or additives can be thorougly avoided through this method. All the obtained polymers have well-defined structures, high yields and weight-average molecular weights (M_ws, up to 99,300 g/mol). The unique zwitterionic property, amphiphilicity and Cu(I) coordination ability of the obtained poly(N-sulfonyl amidines) endow them to form the polymer-Cu(I) complexes as nanocatalysts. Such nanocatalysts exhibite high catalytic efficiency in aqueous Cu-catalyzed azide-alkyne cycloaddition (CuAAC) reaction at a low Cu(I) loading of 50 ppm. Nanocatalysts with high ratio of polymers to Cu(I) have also been demonstrated with Cu(I) stabilization ability. This work provides a “green” MCP method toward zwitterionic and amphiphilic poly(N-sulfonyl amidines), and highlights their unique potentials for nanocatalysis.

     

Steric-switched defluorofunctionalization selectivity: controlled synthesis of monofluoroalkene-masked medium-sized heterocyclic lactams and lactones

The steric-switched ipso-defluoroamination-triggered and ipso-defluorooxylation-triggered cyclization of(trifluoromethyl)alkenes with amino alcohols and diamines are achieved under mild conditions. This regioselective strategy distinguishes the different nucleophilic heteroatom sites in amino alcohols and unsymmetric diamines by the sequential defluorinative functionalization of two C(sp³)–F bonds in a CF₃ group. Various attractive monofluoroalkene-masked medium-sized heterocyclic lactams and lactones are obtained in moderate to excellent yields. Simple derivation of these masked-heterocycles efficiently affords useful skeletons of lactams, lactones, and 1,4-oxazepanes in a single diastereoisomer. Mechanism studies indicate that a unique sequential ipso-/γ-selective defluorinative functionalization pathway is involved in these transformations.     

Organic white-light sources: multiscale construction of organic luminescent materials from molecular to macroscopic level

Organic luminescent materials play an integral role in the optoelectronic applications of displays and solid-state lighting. Nevertheless, high-performance organic luminescent materials require the efficient combination of two or more kinds of materials, which is extremely difficult owing to the completely different self-assembly behaviors of multicomponent molecules. Herein, based on a broad scale from the molecular, micro-/nano-scale, and macroscopic levels, we successfully demonstrate the multiscale construction of organic luminescent microwires of cocrystals, solid solutions, and core-shell microstructures. Through the wide selection of electron donor/acceptor pairs, a series of color-tunable charge-transfer (CT) cocrystals are formed via the intermolecular cooperative self-assembly process. On this basis, the high structural compatibility and perfect lattice mismatching (～1.1%) of cocrystals are critical factors that facilitate the combination of dissimilar materials to form solid solutions and core/shell microwires. Significantly, because of the full-spectrum light transport from 400 to 800 nm, the nano-micro-scaled solid solution microwires act as microscale white-light sources [CIE (0.32, 0.36)]. Meanwhile, the macroscopic-scale core/shell organic-microwires demonstrate tunable white-light emission with a high color-rendering index (CRI) of 83, whose CIE coordinates span from (0.37,0.39) to (0.40,0.31). Therefore, our work provides a feasible approach to the multiscale synthesis of novel luminescent organic semiconductor materials, which could lay a solid foundation for organic optoelectronics.

     

On the distinct reactivity of two isomers of [IrC4H2]+ toward methane and water

The gas-phase reactions of [IrC₄H₂]⁺ with methane and water have been explored by using mass spectrometry combined with quantum chemical calculations. Interestingly, under the employed conditions, two isomers of [IrC₄H₂]⁺ co-exist with different reactivity. One of them only activates methane while the other is solely reactive with water to produce CO. Apparently, upon varying the coordination patterns, the Ir center gains rather distinct capabilities of mediating the bond breaking and making processes. The reactivity toward methane mainly depends on the orbital orientation, while the π-aromaticity of the reaction complex matters for the conversion of water. The experimental and theoretical findings in this work do not only imply the promising role the Ir atom can play in the bulk-system methane conversion, but may also be instructive on how to construct a high-performance center for steam reforming of methane.

     

Scalable synthesis of multi-shelled hollow N-doped carbon nanosheet arrays with confined Co/CoP heterostructures from MOFs for pH-universal hydrogen evolution reaction

Developing low-cost but efficient hydrogen evolution reaction(HER)electrocatalysts over whole pH values is a significant but daunting task for the large-scale application of electrochemical hydrogen production.Herein,we develop,for the first time,a scalable MOF-assisted strategy for the fabrication and microstructural optimization of multi-shelled hollow N-doped carbon nanosheet arrays with confined Co/CoP heterostructures on carbon cloth(Co/CoP@NC/CC)for boosting HER performances.The key to this strategy is the step-by-step epitaxial growth of unprecedented multilayer ZIF-L arrays on carbon cloth,which are subsequently pyrolyzed and controllably phosphorized to achieve the precise control over the shell number and nanoarchitectures of the Co/CoP@NC/CC.Impressively,the HER performances can be significantly enhanced by increasing hollow shell number,and the optimal triple-shelled hollow Co/CoP@NC/CC exhibits low overpotentials of 86,78 and 145 mV in acidic,alkaline and neutral media to deliver a current density of 10 mA cm^-2,respectively,ranking as one of the best Co-based HER electrocatalysts over whole pH values.Further DFT calculations suggest that the Co/CoP heterostructures can effectively boost the cleavage of H–OH to generate protons and optimize the adsorption energy of hydrogen(ΔG_H*),which,together with the large electrode/electrolyte interface and accelerated charge/mass transfer of multi-shelled hollow array structure as well as the good conductivity and dispersity,are responsible for the remarkably improved HER performances.This study not only provides a new toolbox for enriching the family of multi-shelled nanoarchitecture materials,but also points out a general and effective route to develop highly efficient self-supported electrode materials for energy-related applications and beyond.     

Se-sensitized NIR hot band absorption photosensitizer for anti-Stokes excitation deep photodynamic therapy

Conventional anti-Stokes materials-involved deep photodynamic therapy(dPDT)requires much high-intensity irradiance due to low photosensitization efficiency.Herein,we proposed a"booster effector"approach to construct highly efficient hot band absorption phototherapeutics for low/biosafety power anti-Stokes light-triggered d PDT.Se,as"booster effector",was introduced into hot band absorption luminophores(HBAs),which not only significantly facilitated intersystem crossing,but also simultaneously enhanced hot band excitation efficiency atν808,as a result successfully enabling excellent photogenerated singlet oxygen capability of HBAs under ultra-low power anti-Stokes excitation(10 mW cm^-2in vitro).As far as we know,such low laser power-initiated photosensitization activity has never been reported in the existing anti-Stokes material systems.Importantly,FUC-Se ME can self-assemble into uniform nanospheres in water,greatly boosting cellular uptake(>25-fold larger than FUC-Se),and achieve superior cancer-killing effect(808 nm,10 mW cm^-2,5 min,the half-maximal inhibitory concentration IC50=1.36μM).After further PEGylation with folate-attached polymer,the resultant FUC-Se ME@FA can effectively enrich at the tumor(signal-to-background ratio,10).Under safety irradiation(330 mW cm^-2),FUC-Se ME@FA effectively inhibits deep-seated tumor progression(the tumor growth inhibition rate,84%).This work provides a successful paradigm,possibly being more clinically beneficial than conventional anti-Stokes materials.     

Non-contact biomimetic mechanism for selective hydrogenation of nitroaromatics on heterogeneous metal nanocatalysts

While the enzymatic reduction of unsaturated compounds usually has high specificity, highly selective reduction processes are hardly realized by heterogeneous industrial catalysts, which is critical for the green production of many fine chemicals. Here, we report an unexpected discovery of a biomimetic behavior of dicyandiamide (DICY)-modified Pt nanocatalysts for the green hydrogenation of a wide range of nitroaromatics. We demonstrate that the surface modification by DICY not only prevents the direct contact of nitroaromatic reactants with Pt surface but also induces an effective non-contact hydrogenation mechanism mediated by protons and electrons. In such a process, the DICY layer serves as a “semi-permeable membrane” to allow the permeation of H₂ molecules for being activated into electrons and protons at the Pt-DICY interface. With the generation of separated protons and electrons, the nitro group with strong electrophilic properties can be hydrogenated through the electron transfer followed by the proton transfer, which is facilitated by the hydrogen bonding network formed by protonated DICY. The unique mechanism makes it highly directional toward the hydrogenation of nitro groups without side reactions. Owing to its capability to largely eliminate the waste generation, the developed Pt-DICY catalysts have been successfully applied for the green industrial production of many important aniline intermediates.

     

Zinc–proline complex as a novel and efficient catalyst for the green synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones

A simple, efficient and green approach to the synthesis of 1H-pyrazolo[1,2-b]phthalazine-5,10-diones has been developed via one-pot three-component reaction of aromatic aldehyde, malononitrile and phthalhydrazide catalyzed by zinc–proline complex (Zn[L-proline]₂) using H₂O: PEG₄₀₀?=?6: 4 as solvent. Atom economy, good to excellent yield, operational simplicity and easy workup are important features of this method.

Graphical abstract

     

The Inverted Philosopher’s Stone: how to turn silver to a base metal

Metals often are classified as “noble” or “base”—characterizing their reduction potential as one of the most important chemical properties. We show that metals are only as noble as allowed by their environment, i.e. this is a relative term, and the “frame of reference” simply is the solvent in which the redox system is present. We prove that silver is a prime example for a noble metal that forfeits its noble character in the simple ionic liquid HMIM Br (1-hexyl-3-methylimidazolium bromide) as an example for such a solvent.

Graphical Abstract

     

A trinuclear {FeIII2FeII} complex involving both spin and non-spin transitions exhibits three-step and wide thermal hysteresis

The engineering of switchable molecules with magnetic multistability is lying on the cutting-edge research topics for integrating multi-switches and ternary memory devices. Here we presented a cyanide-bridged {Fe^III₂Fe^II} desolvated complex {[(pzTp)Fe^III-(CN)₃]₂[Fe^II(L)]} (1), obtained through single-crystal-to-single-crystal (SCSC) transformation from its solvated phase {[(pzTp)-Fe^III(CN)₃]₂[Fe^II(L)]}·2CH₃OH·5H₂O (1·sol). Remarkably, 1 exhibited unprecedented three-step transition in magnetization with wide thermal hysteresis (44, 40, and 36 K) in the temperature range of 80–320 K. The detailed studies demonstrated that the tristable character originates from both an order-disorder structural phase transition (SPT) and a strongly cooperative two-step spin crossover (SCO) process. This work thus provides a new promising strategy for realizing multiple bistablity in magnetization by introducing two different transitions.

     

Cellulose-g-tetraethylenepentamine dual-function imprinted polymers selectively and effectively adsorb and remove 4-nitrophenol and Cr(VI)

A cellulosic material has been synthesized that could efficiently and selectively adsorb organic and inorganic contaminants from aqueous solutions without interference from competing adsorption sites. Cellulose-graft-tetraethylenepentamine molecular imprinted polymer (C-TEPA-MIP) was synthesized by using 4-nitrophenol (4-NP) as the template. The C-TEPA-MIP adsorbent could adsorb 4-NP and Cr(VI) simultaneously and selectively, without being affected by the competitive adsorption sites of each of these pollutants. The adsorption of 4-NP was predominantly due to the imprinted sites of 4-NP in C-TEPA-MIP that were located inside of the adsorbent, whereas that of Cr(VI) was primarily due to the amine groups of TEPA found on the surface of the adsorbent. Compared with the non-imprint polymer synthesized without the template, C-TEPA-MIP showed higher selectivity for both 4-NP and Cr(VI) in unitary and binary systems. In addition, C-TEPA-MIP exhibited good stability and recyclability for 4-NP, which makes it a promising candidate material for applications concerning wastewater treatment.

Graphical abstract