Photoinduced Copper‐Catalyzed Asymmetric Decarboxylative Alkynylation with Terminal Alkynes

We describe a photoinduced copper‐catalyzed asymmetric radical decarboxylative alkynylation of bench‐stable N‐hydroxyphthalimide(NHP)‐type esters of racemic alkyl carboxylic acids with terminal alkynes, which provides a flexible platform for the construction of chiral C(sp³)?C(sp) bonds. Critical to the success of this process are not only the use of the copper catalyst as a dual photo‐ and cross‐coupling catalyst but also tuning of the NHP‐type esters to inhibit the facile homodimerization of the alkyl radical and terminal alkyne, respectively. Owing to the use of stable and easily available NHP‐type esters, the reaction features a broader substrate scope compared with reactions using the alkyl halide counterparts, covering (hetero)benzyl‐, allyl‐, and aminocarbonyl‐substituted carboxylic acid derivatives, and (hetero)aryl and alkyl as well as silyl alkynes, thus providing a vital complementary approach to the previously reported method.     

Three‐Dimensional Cuprous Lead Bromide Framework with Highly Efficient and Stable Blue Photoluminescence Emission

Considering the instability and low photoluminescence quantum yield (PLQY) of blue‐emitting perovskites, it is still challenging and attractive to construct single crystalline hybrid lead halides with highly stable and efficient blue light emission. Herein, by rationally introducing d¹⁰ transition metal into single lead halide as new structural building unit and optical emitting center, we prepared a bimetallic halide of [(NH₄)₂]CuPbBr₅ with new type of three‐dimensional (3D) anionic framework. [(NH₄)₂]CuPbBr₅ exhibits strong band‐edge blue emission (441 nm) with a high PLQY of 32 % upon excitation with UV light. Detailed photophysical studies indicate [(NH₄)₂]CuPbBr₅ also displays broadband red light emissions derived from self‐trapped states. Furthermore, the 3D framework features high structural and optical stabilities at extreme environments during at least three years. To our best knowledge, this work represents the first 3D non‐perovskite bimetallic halide with highly efficient and stable blue light emission.     

Enantioselective separation and dissipation of pydiflumetofen enantiomers in grape and soil by supercritical fluid chromatography–tandem mass spectrometry

Pydiflumetofen is registered in many countries and is widely used in crop production in the racemate form. However, the environmental behavior of the enantiomers has not been studied. An effective and sensitive chiral analytical method was first established for analyzing the pydiflumetofen enantiomers by supercritical fluid chromatography with tandem triple quadrupole mass spectrometry. The enantiomers could be separated and detected using the Chiralcel OD‐3 column in less than 3 min. The separation conditions were as follows: mobile phase, CO₂/methanol (80:20); flow rate, 1.0 mL/min; column temperature, 30°C, auto back‐pressure regulator pressure, 2000 psi with modified quick, easy, cheap, effective, rugged, and safe sample treatment method. The average recoveries of analytes from both matrices at three spiking levels were in the range of 84.1–103.0%. The limit of quantitation for each enantiomer was 0.005 mg/kg with a baseline resolution of approximately 1.64. The method was applied to monitor the enantioselective dissipation of pydiflumetofen in grape and soil. In grapes, (?)‐pydiflumetofen was degraded more rapidly than (+)‐pydiflumetofen. In soil, (+)‐pydiflumetofen was preferentially degraded. The data provided useful references for the risk assessment and rational use of pydiflumetofen in agriculture.     

Calcium ion pinned vanadium oxide cathode for high-capacity and long-life aqueous rechargeable zinc-ion batteries

Science China Chemistry - Rechargeable aqueous zinc ion batteries (ZIBs), with the easy operation, cost effectiveness, and high safety, are emerging candidates for high-energy wearable/portable...     

Tuning Magnetic Anisotropy in a Class of Co(II) Bis(hexafluoroacetylacetonate) Complexes

Tuning the magnetic anisotropy of metal ions remains highly interesting in the design of improved single‐molecule magnets (SMMs). We herein report synthetic, structural, magnetic, and computational studies of four mononuclear Co^II complexes, namely [Co(hfac)₂(MeCN)₂] ( 1 ), [Co(hfac)₂(Spy)₂] ( 2 ), [Co(hfac)₂(MBIm)₂] ( 3 ), and [Co(hfac)₂(DMF)₂] ( 4 ) (MeCN=acetonitrile, hfac=hexafluoroacetylacetone, Spy=4‐styrylpyridine, MbIm=5,6‐dimethylbenzimidazole, DMF=N,N‐dimethylformamide), with distorted octahedral geometry constructed from hexafluoroacetylacetone (hfac) and various axial ligands. By a building block approach, complexes 2 – 4 were synthesized by recrystallization of the starting material of 1 from various ligands containing solution. Magnetic and theoretical studies reveal that 1 – 4 possess large positive D values and relative small E parameters, indicating easy‐plane magnetic anisotropy with significant rhombic anisotropy in 1 – 4 . Dynamic alternative current (ac) magnetic susceptibility measurements indicate that these complexes exhibit slow magnetic relaxation under external fields, suggesting field‐induced single‐ion magnets (SIMs) of 1 – 4 . These results provide a promising platform to achieve fine tuning of magnetic anisotropy through varying the axial ligands based on Co(II) bis(hexafluoroacetylacetonate) complexes.     

Zero‐Dimensional Hybrid Cd‐Based Perovskites with Broadband Bluish White‐Light Emissions

Recently, low‐dimensional organic‐inorganic hybrid metal halide perovskites acting as single‐component white‐light emitting materials have attracted extensive attention, but most studies concentrate on hybrid lead perovskites. Herein, we present two isomorphic zero‐dimensional (0D) hybrid cadmium perovskites, (HMEDA)CdX₄ (HMEDA=hexamethylenediamine, X=Cl ( 1 ), Br ( 2 )), which contain isolated [CdX₄]^2? anions separated by [HMEDA]²⁺ cations. Under UV light excitation, both compounds display broadband bluish white‐light emission (515 nm for 1 and 445 nm for 2 ) covering the entire visible light spectrum with sufficient photophysical stabilities. Remarkably, compound 2 shows a high color rendering index (CRI) of 83 enabling it as a promising candidate for single‐component WLED applications. Based on the temperature‐dependent, powder‐dependent and time‐resolved PL measurements as well as other detailed studies, the broadband light emissions are attributed to self‐trapped excitons stemming from the strong electron‐phonon coupling.     

Hyperbranched Poly(ester‐enamine) from Spontaneous Amino‐yne Click Reaction for Stabilization of Gold Nanoparticle Catalysts

Hyperbranched polymers have garnered much attention due to attractive properties and wide applications, such as drug‐controlled release, stimuli‐responsive nano‐objects, photosensitive materials and catalysts. Herein, two types of novel hyperbranched poly(ester‐enamine) (hb‐PEEa) were designed and synthesized via the spontaneous amino‐yne click reaction of A₂ monomer (1, 3‐bis(4‐piperidyl)‐propane (A_2a) or piperazine (A_2b)) and B₃ monomer (trimethylolpropanetripropiolate). According to Flory's hypothesis, gelation is an intrinsic problem in an ideal A₂+B₃ polymerization system. By controlling the polymerization conditions, such as monomer concentration, molar ratio and rate of addition, a non‐ideal A₂+B₃ polymerization system can be established to avoid gelation and to synthesize soluble hb‐PEEa. Due to abundant unreacted alkynyl groups in periphery, the hb‐PEEa can be further functionalized by different amino compounds or their derivates. The as‐prepared amphiphilic PEG‐hb‐PEEa copolymer can readily self‐assemble into micelles in water, which can be used as surfactant to stabilize Au nanoparticles (AuNPs) during reduction of NaBH₄ in aqueous solution. As a demonstration, the as‐prepared PEG‐hb‐PEEa‐supported AuNPs demonstrate good dispersion in water, solvent stability and remarkable catalytic activity for reduction of nitrobenzene compounds.     

Vibro-impact analysis of two adjacent cantilever beams

Nonlinear Dynamics - This study analyzes the vibro-impact behavior of two adjacent cantilever beams subjected to vibration generated by applying harmonic excitation to their rigid base. For the...     

Compensation method for complex hysteresis characteristics on piezoelectric actuator based on separated level-loop Prandtl–Ishlinskii model

Nonlinear Dynamics - Piezoelectric ceramic actuators show nonlinear hysteresis characteristics due to material properties. In order to modify the inverse piezoelectric effect as an ideal linear...     

Fixed-time disturbance observer-based robust fault-tolerant tracking control for uncertain quadrotor UAV subject to input delay

Nonlinear Dynamics - This study focuses on the design of a fixed-time disturbance observer-based robust fault-tolerant tracking control scheme for an uncertain quadrotor unmanned aerial vehicle...