Monthly Archives: September 2023

Structure‐property Relationship of Double Perovskite Oxide towards Trifunctional Electrocatalytic Activity: Strategy for Designing and Development

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Structure-property Relationship of Double Perovskite Oxide towards Trifunctional Electrocatalytic Activity: Strategy for Designing and Development

The present review emphases on the strategy for development of trifunctional double perovkite electrocatalysts for water splitting reaction. Synergistic effect of multiple cationic redox sites and structural distortions in double perovskites can tailor the ORR/OER/HER activities concurrently in single material. This review highlights recent observations of trifunctional activity of few double perovskite and motivate further to obtain improved efficiency.


Abstract

In the present scenario, the paramount significant roles of various heterogeneous catalysts stimulate the modern technologies to underpin the benchmark requirements for the generation of sustainable energy by reducing toxic fossil fuel emissions. Such critical role necessitates further development of cost-effective highly efficient and earth-abundant multifunctional or trifunctional electrocatalysts to promote the advancement of electrochemical overall water splitting performances, yet it is extremely desirable. In this review context, we present the development of double perovskite (DP) oxides as robust trifunctional catalysts for electrochemical oxygen evolution reaction (OER), oxygen reduction reaction (ORR) and hydrogen evolution reactions (HER) by rational design of multiple cationic redox sites with stoichiometric oxygen amount. Particularly, we highlight the importance of the structural modifications via doping, surface structure and oxygen stoichiometry as key parameters to tune the electrocatalytic activities and understand the insight into activity and mechanism of this oxide family. This perspective also describes controlled synthesis protocols including the surface structure of double perovskite oxides are key techniques for realizing a correlation between structure-activity relationships of these materials. Finally, it is concluded by outlining the several aspects of optimization strategies and computational opportunities can expand the future scope of double perovskite oxides as robust trifunctional electrocatalysts.

Macrocyclization of Dienes under Confinement with Cationic Tungsten Imido/Oxo Alkylidene N‐Heterocyclic Carbene Complexes

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Macrocyclization of Dienes under Confinement with Cationic Tungsten Imido/Oxo Alkylidene N-Heterocyclic Carbene Complexes

Two tungsten-based catalysts have been selectively immobilized within the pores of ordered mesoporous silica materials. X-ray absorption spectroscopy confirm the structural integrity of the catalysts. Compared to the homogenous analogues, the immobilized tungsten-catalysts exhibit a substantially increased macrocyclization- and Z-selectivity, which allow for the use of high substrate concentrations.


Abstract

Macrocyclization reactions are still challenging due to competing oligomerization, which requires the use of small substrate concentrations. Here, the cationic tungsten imido and tungsten oxo alkylidene N-heterocyclic carbene complexes [[W(N-2,6-Cl2-C6H3)(CHCMe2Ph(OC6F5)(pivalonitrile)(IMes)+ B(ArF)4 −] (W1) and [W(O)(CHCMe2Ph(OCMe(CF3)2)(IMes)(CH3CN)+ B(ArF)4 −] (W2) (IMes=1,3-dimesitylimidazol-2-ylidene; B(ArF)4 −=tetrakis(3,5-bis(trifluoromethyl)phenyl borate) have been immobilized inside the pores of ordered mesoporous silica (OMS) with pore diameters of 3.3 and 6.8 nm, respectively, using a pore-selective immobilization protocol. X-ray absorption spectroscopy of W1@OMS showed that even though the catalyst structure is contracted due to confinement by the mesopores, both the oxidation state and structure of the catalyst stayed intact upon immobilization. Catalytic testing with four differently sized α,ω-dienes revealed a dramatically increased macrocyclization (MC) and Z-selectivity of the supported catalysts compared to the homogenous progenitors, allowing high substrate concentrations of 25 mM. With the supported complexes, a maximum increase in MC-selectivity from 27 to 81 % and in Z-selectivity from 17 to 34 % was achieved. In general, smaller mesopores exhibited a stronger confinement effect. A comparison of the two supported tungsten-based catalysts showed that W1@OMS possesses a higher MC-selectivity, while W2@OMS exhibits a higher Z-selectivity which can be rationalized by the structures of the catalysts.

Ag6Cu8(C≡CAr)14(DPPB)2: Rigid Ligands Co‐Protected Bimetallic Silver(I)‐Copper(I) Cluster with Room‐Temperature Luminescent

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Metal clusters have become increasingly important in various applications, with ligands playing a crucial role in their construction. In this study, we synthesized a bimetallic cluster, Ag6Cu8(C≡CAr)14(DPPB)2 (Ag6Cu8), using a rigid acetylene ligand, 3,5-bis(trifluoromethyl)phenylacetylide. Through single-crystal structure characterization, we discovered that the butterfly-shaped Ag2Cu2 motifs were subject to distortion due to steric hindrance imposed by the rigid ligand. These motifs assembled together through shared vertices and edges. Mass spectrometry analysis revealed that the primary fragments detected during electrospray ionization (ESI) testing corresponded to the Ag2Cu2 motifs. Furthermore, we conducted a comprehensive investigation of the cluster’s solution properties employing 31P NMR, UV-vis absorption, and photoluminescent measurements. In contrast to previously reported Ag/Cu bimetallic clusters protected by flexible ligands, Ag6Cu8 protected by rigid ligands exhibited intriguing room temperature fluorescence properties alongside excellent thermal stability. DFT calculations of the energy levels of Ag6Cu8 and Ag6Cu8 removing aromatic ring revealed that the presence of the aromatic ring can lower the electronic energy levels of the cluster molecule, and reduce the energy gap from 4.05 eV to 3.45 eV. Moreover, the rigid ligand further suppressed the non-radiative transition process, leading to room temperature fluorescence emission.

Copper‐Catalyzed α,β‐Regioselective (2+4) Cycloaddition of Propargylic Esters

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A copper-catalyzed α,β-regioselective (2+4) cycloaddition of propargylic esters with o-hydroxyphenyl substituted secondary phosphine oxides (SPOs) was established, which afforded a series of phosphorus-containing six-membered heterocycles in high yields (up to 99 % yield). This reaction represents the first α,β-regioselective (2+n) cycloaddition of propargylic esters via the intermediates of copper−allenylidenes, which will enrich the chemistry of propargylic esters and copper−allenylidenes. Moreover, this work also represents the first application of o-hydroxyphenyl substituted SPOs as 1,4-dinucleophiles in (2+4) cycloadditions, which provides a useful protocol for the synthesis of phosphorus-containing six-membered heterocycles with potential bioactivity.

One‐Pot Synthesis of Fused Tetrahydroquinoline‐Iminosugar Derivatives

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An efficient and simple one-pot synthesis of structurally diverse novel tetrahydroquinolin fused iminosugars was developed through the aza-Diels-Alder mechanism. The adaptability of this method has been demonstrated by a variety of imines and D/L-ribose tosylates, and both electron-donating and withdrawing substituted imines are employed in reaction well. In addition, this reaction is characterized by simple operation, good yield, and high atom economy. Some synthetic iminosugars showed moderate anti proliferation of HCT116 tumor cells.

Efficient Synthesis of Fully Substituted and Diversely Functionalized Pyrazoles through p‐TSA Catalyzed One‐Pot Condensation of Cyclic β‐Diketones, Arylglyoxals and Arylhydrazones

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Efficient Synthesis of Fully Substituted and Diversely Functionalized Pyrazoles through p-TSA Catalyzed One-Pot Condensation of Cyclic β-Diketones, Arylglyoxals and Arylhydrazones

An acid catalyzed one-pot condensation of readily available cyclic β-diketones, arylglyoxals and arylhydrazones produces a library of diversely functionalized pyrazole derivatives in excellent yield under metal-catalyst-free benign conditions.


Abstract

A one-pot, three-component, and atom economic synthesis of biologically and pharmaceutically important fully substituted and functionalized pyrazole derivatives has been accomplished under metal-catalyst-free benign conditions. The strategy involves early condensation of readily available cyclic β-diketones (dimidone, 4-hydroxycoumarin and 2-hydroxy-1,4-naphthoquinone) and arylglyoxals to generate a chalcone type intermediate which upon acid catalyzed condensation with ambident nucleophile arylhydrazones produces various aryl and cyclic β-diketone substituted pyrazole derivatives. The synthesis embraces high functional group tolerance, broad substrate scope, excellent yield of the products, short reaction time and operationally simple and mild reaction conditions. The synthesis provides an easy opportunity of incorporating biologically important N-diarylsulfide/selenide functionality, various enolisable cyclic β-diketones and other bioactive heterocycles concurrently to pyrazole, which may help in designing and development of pyrazole derivatives of pharmacological significance.