A visible‐light‐driven, copper‐catalyzed three‐component radical cross‐coupling of oxime esters, styrenes, and boronic acids has been developed. Key steps of this protocol involve catalytic ...generation of an iminyl radical from a redox‐active oxime ester and subsequent C−C bond cleavage to generate a cyanoalkyl radical. Upon its addition to styrene, the newly formed benzylic radical undergoes coupling with a boronic‐acid‐derived ArCuII complex to achieve 1,1‐diarylmethane‐containing alkylnitriles.
Key steps of the visible‐light‐driven title reaction involve catalytic generation of an iminyl radical from a redox‐active oxime ester and subsequent C−C bond cleavage to give a cyanoalkyl radical. Upon its addition to styrene, a benzylic radical is formed that undergoes coupling with a boronic‐acid‐derived ArCuII complex to give 1,1‐diarylmethane‐containing alkylnitriles. The method features the use of readily available substrates and high functional‐group tolerance.
We herein report a new coordination network that deforms in a smooth and reversible manner under either thermal or pressure stimulation. Concomitantly, the organic fluorophores coordinatively bound ...to the channel in a face‐to‐face arrangement respond to this structural deformation by finely adapting their conformation and arrangement. As a result, the material exhibits a remarkable dual‐stimuli‐responsive luminescence shift across almost the entire visible region: The emission color of the crystal gradually changes from cyan to green upon heating and then to red upon pressure compression. Furthermore, each stage exhibits a linear dependence of both the emission maximum and intensity on the stimulus and is fully reversible.
Coping with pressure and heat: In response to changes in temperature and pressure, the flexible scaffold of a luminescent coordination network underwent smooth and reversible structural deformation that regulated the conformation and arrangement of the emissive organic molecules coordinatively bound to the channel in the structure. As a result, a reversible fluorescence shift across almost the entire visible region was observed (see picture).
A reliable and low‐cost solution‐processing procedure to synthesize a highly adhesive flexible metal antenna with low resistivity for radio‐frequency identification device (RFID) tags on paper ...substrates via inkjet printing combined with surface modification and electroless deposition (ELD) is demonstrated in this paper. Through the surface modification of colloidal solution of hydrolyzed stannous chloride and chitosan solution, the paper‐based substrate is able to reduce the penetration rate of ink and further increase the adsorption amount of silver ions, which could create a catalytic activating layer to catalyze the subsequent ELD of a conductive deposited metal antenna. The resulting metal antenna for RFID tags presents good adhesive strength and low resistivity of 2.58 × 10−8 Ω·m after 40 min of ELD, and maintains a reliable reading range of RFID tags even after over 1000 times of bending and mechanical stress. Consequently, the developed technology proposed allows for cheap, efficient, and massive production of metal antenna for paper‐based RFID tags with excellent mechanical and electrical properties. Furthermore, this process is especially advantageous for the fabrication of next‐generation flexible electronic devices based on paper substrates.
A novel and efficient solution‐processing procedure combined with inkjet printing, surface modification, and electroless deposition is proposed for the fabrication of an outstanding flexible radio‐frequency identification device (RFID) tag metal antenna on a paper‐based substrate without high temperature or sophisticated manufacturing equipment. This method is a low‐cost and portable fabrication route for RFID antennas, which is promising for large‐scale commercial manufacturing.
Atomic‐molecular engineering is an effective way to accurately tailor the microstructures and components of materials at the micro‐nano scale, which can be applied to flexibly manipulate their ...electromagnetic (EM) response. Herein, graphene microlaminates with multi‐layer structure are fabricated by atomic cluster engineering and oxidative molecular layer deposition for the first time. The microlaminates enable a tunable EM loss (from 0.93 to 3.94 for imaginary permittivity and from 0.17 to 0.25 for imaginary permeability) by changing poly(3,4‐ethylenedioxythiophene) cycles, and the attenuation constant reaches 160. On this basis, multifunctional antennas are conceived, achieving frequency‐selective response that enables steady harvest of > 90% of EM energy from signal source, and tactfully recycling waste heat energy and mechanical energy. This study will furnish a new horizon for information transmission and artificial intelligence in the future.
Atomic‐molecular engineering is employed to fabricate graphene microlaminate with multi‐layer structure. The microlaminate exhibits excellent electromagnetic losses and high energy attenuation. Importantly, multifunctional antenna is further conceived, with integrated functions including frequency‐selective response and waste energy recycling, which will promote the development of an intelligent society.
Two pure silver nanoparticles (Ag210(iPrPhS)71(Ph3P)5Cl and Ag211(iPrPhS)71(Ph3P)6Cl labeled as SD/Ag210 and SD/Ag211 (SD=SunDi), were found to co‐crystallize in forming compound 1. Single‐crystal ...X‐ray diffraction (SCXRD) revealed that they differ by only one Ag(PPh3). Their four‐shell nanoparticles consist of three pure Ag metal shells (Ag19@Ag52@Ag45) shielded by a silver‐organic Ag89(iPrPhS)71ClAg(Ph3P)n outermost shell. The number (n) of Ag(Ph3P) is five for SD/Ag210 and six for SD/Ag211. The pseudo‐fivefold symmetric Ag nanoparticles exhibit surface plasmon absorption similar to a true metallic state but at the nanoscale. This work exemplifies the important effects of phosphine in stabilizing large silver nanoparticles; and offers a platform to investigate the origin of differences in nanoscale metal materials, even differing by only one metal atom; it also sheds light on the regioselective binding of auxiliary Ph3P on the surface of silver nanoparticles.
Two in one: Two different silver nanoparticles, Ag210(iPrPhS)71(Ph3P)5Cl and Ag211(iPrPhS)71(Ph3P)6Cl, differing by one Ag center, co‐crystallize in a single crystal. Both silver nanoparticles share the same Russian‐doll Ag19@Ag52@Ag45@Ag89 four‐shell motif covered by the same number of iPrPhS− and Cl− ligands.
Conspectus Nitrogen-centered radicals (NCRs) are a versatile class of highly reactive species that have a longer history than the classical carbon-based radicals in synthetic chemistry. Depending on ...the N-hybridization and substitution patterns, NCRs can serve as electrophiles or nucleophiles to undergo various radical transformations. Despite their power, progress in nitrogen-radical chemistry is still slow compared with the popularity of carbon radicals, and their considerable synthetic potential has been largely underexplored, which is, as concluded by Zard, mainly hampered by “a dearth of convenient access to these species and a lack of awareness pertaining to their reactivity”. Over the past decade, visible-light photoredox catalysis has been established as a powerful toolbox that synthetic chemists can use to generate a diverse range of radical intermediates from native organic functional groups via a single electron transfer process or energy transfer under mild reaction conditions. This catalytic strategy typically obviates the need for external stoichiometric activation reagents or toxic initiators and often enables traditionally inaccessible ionic chemical reactions. On the basis of our long-standing interest in nitrogen chemistry and catalysis, we have emphasized the use of visible-light photoredox catalysis as a tactic to discover and develop novel methods for generating NCRs in a controlled fashion and synthetic applications. In this Account, we describe our recent advances in the development of visible-light-driven photoredox-catalyzed generation of NCRs and their synthetic applications. Inspired by the natural biological proton-coupled electron transfer (PCET) process, we first developed a strategy of visible-light-driven photoredox-catalyzed oxidative deprotonation electron transfer to activate the N–H bonds of hydrazones, benzamides, and sulfonamides to give the corresponding NCRs under mild reaction conditions. With these reactive species, we then achieved a range of 5-exo and 6-endo radical cyclizations as well as cascade reactions in a highly regioselective manner, providing access to a variety of potentially useful nitrogen heterocycles. To further expand the repertoire of possible reactions of NCRs, we also revealed that iminyl radicals, derived from O-acyl cycloalkanone oxime esters, can undergo facile ring-opening C–C bond cleavage to give cyanoalkyl radicals. These newly formed radical species can further undergo a variety of C–C bond-forming reactions to allow the synthesis of diverse distally functionalized alkyl nitriles. Stimulated by these studies, we further developed a wide variety of visible-light-driven copper-catalyzed radical cross-coupling reactions of cyanoalkyl radicals. Because of their inherent highly reactive and transient properties, the strategy of heteroatom-centered radical catalysis is still largely underexplored in organic synthesis. Building on our understanding of the fundamental chemistry of NCRs, we also developed for the first time the concept of NCR covalent catalysis, which involves the use of in situ-photogenerated NCRs to activate allyl sulfones, vinylcyclopropanes, and N-tosyl vinylaziridines. This catalytic strategy has thus enabled efficient difunctionalization of various alkenes and late-stage modification of complex biologically active molecules. In this Account, we describe a panoramic picture of our recent contributions since 2014 to the development and application of the visible-light-driven photoredox systems in the field of NCR chemistry. These studies provide not only efficient methods for the synthesis of functionally rich molecules but also some insight into the exploration of new reactivity or reaction modes of NCRs.
Developing universal stimuli‐responsive materials capable of emitting a broad spectrum of colors is highly desirable. Herein, we deliberately grafted a conformation‐adaptable organic chromophore into ...the established coordination space of a flexible metal–organic framework (MOF). In terms of the coupled structural transformations and the space confinement, the chromophore in the MOF matrix underwent well‐regulated conformational changes under physical and chemical stimuli, simultaneously displaying thermo‐, piezo‐, and solvato‐fluoro‐chromism with color tunability over the visible range. Owing to the resilient nature and the reduced dimensionality of the selected coordination space, all three color modulations behaved in a sensitive and self‐reversible manner, each following a linear correlation of the emission maximum with stimulus. Single‐crystal X‐ray diffraction of the variable‐temperature structures and solvent‐inclusion crystals elucidated the intricate color varying mechanisms.
A smart luminescent material was constructed by anchoring an organic chromophore into the 2D coordination space of a flexible metal–organic framework. Thermo‐, piezo‐, and solvato‐fluoro‐chromisms were simultaneously achieved within a single material, featuring dynamic full‐color tunability, excellent reversibility, and linear sensor response.
Peroxymonosulfate (PMS) is extensively used as an oxidant to develop the sulfate radical-based advanced oxidation processes in the decontamination of organic pollutants and various PMS activation ...methods have been explored. Visible-light-assisted PMS activation to construct a Fenton-like process has shown a great potential for pollution control. In our work, BiVO4 nanosheets were prepared using a hydrothermal process and used to activate PMS under visible light. A rapid degradation of ciprofloxacin (CIP) was achieved by dosing PMS (0.96 g/L), BiVO4 (0.32 g/L) under visible light with a reaction rate constant of 77.72-fold higher than that in the BiVO4/visible light process. The electron spin resonance and free radical quenching experiments indicate that reactive species of •O2−, h+, •OH and SO4•− all worked, where h+, •OH and SO4•− were found as the dominant contributors to the CIP degradation. The spectroscopic analyses further demonstrate that the photoinduced electrons were directly involved in the PMS activation process. The generated •O2− was partially utilized to activate PMS and more •OH was produced because of the chain reactions between SO4•− and H2O/OH−. In this process, PMS acted as an electron acceptor to transfer the photo-induced charges from the conduction band of BiVO4 and PMS was successfully activated to yield the high-powered oxidative species. From the degradation intermediates of CIP detected by a liquid-chromatography-mass spectrometer, the possible degradation pathways were proposed. The substantially decreased toxicity of CIP after the reaction was also observed. This work might provide new insights into the visible-light-assisted PMS activation mechanisms and is useful to construct environmentally-friendly catalytic processes for the efficient degradation of organic pollutants.
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•PMS was effectively activated by BiVO4 nanosheets for water purification under visible light.•Separation of electron/hole pairs and generation of oxidative species were enhanced.•Visible-light-assisted PMS activation Fenton-like mechanism was elucidated.•High mineralization and low biotoxicity validated the application potential of the system.
Lanthanide metal–organic frameworks (Ln‐MOFs) are promising for luminescence detection of volatile organic compound (VOC) vapors, but usually suffer from the silent or quenched Ln3+ emission. Herein, ...we report a new dual‐emissive Eu‐MOF composed of the coordinatively unsaturated Eu9 clusters that afford abundant open metal sites to form a confined “binding pocket” to facilitate the preconcentration and recognition of VOCs. Single‐crystal structural analyses reveal that specific analytes can replace the OH oscillators in the first coordination sphere of Eu3+ and form a unique hydrogen‐bonding second‐sphere adduct tying adjacent Eu9 clusters together to minimize their nonradiative vibrational decay. With the promoted Eu3+ luminescence, the MOF realizes real‐time in situ visual sensing of THF vapor (<1 s) and shows a quantitative ratiometric response to the vapor pressure with a limit of detection down to 17.33 Pa. Also, it represents a top‐performing ratiometric luminescent thermometer.
A dual‐emissive polynuclear Eu‐MOF enriched with abundant potential open metal sites was constructed. In terms of a novel recognition‐transduction protocol, this material realized real‐time in situ visual detection of THF vapor (<1 s) while showing a quantitative ratiometric response to vapor pressure with an ultralow limit of detection.
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