Plastic Chip Electrode: An Emerging Multipurpose Electrode Platform

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Plastic Chip Electrode: An Emerging Multipurpose Electrode Platform

Conventional electrodes are now falling behind in meeting the increasing technological demands. Innovative and tailored electrodes are believed to be the most promising solution to the problem. Polymer composite electrodes are an optimistic class of tailored electrodes. This review outlines a bird-eye account of the carbon polymer composites and discusses the state-of-the-art on the Plastic Chip Electrode (PCE) comprehensively. PCE is a bulk conducting, self-standing, composite electrode fabricated by a spontaneous solvent-based method. The application of PCE as a multipurpose electrode platform is discussed here.


Abstract

The properties of electrodes play a crucial role in the processes occurring on them. Therefore, a variety of materials have been tried as electrodes. Carbon composite materials are among the most admired ones. Use of composites as electrode material dates back to the mid of the last century when polymer-carbon composites were tried as general-purpose electrode platforms and epoxy impregnated graphite paste/ solid electrodes were tried in polarography. Later the composite electrodes have seen several phases of development. Plastic Chip Electrode (PCE) is a class of polymer composite electrode developed by our group. This monographic review gives a bird‘s eye account of polymer composite electrodes and appurtenant work, followed by elaborating on various aspects and state-of-the-art plastic chip electrodes.

Isolation of a Dodecanuclear Polyoxo Cluster {Nb12O21} Showing a Rare Case of Five‐fold Coordinated Niobium(V) Centers with a Square Pyramidal Geometry

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Isolation of a Dodecanuclear Polyoxo Cluster {Nb12O21} Showing a Rare Case of Five-fold Coordinated Niobium(V) Centers with a Square Pyramidal Geometry

Isolation of two large dodecameric {Nb12O21} clusters in the same lattice was achieved by combination of NbCl4 ⋅ 2THF with anthracene-9-carboxylic acid. The clusters are constituted of octahedral niobium(V) centers associated with rarely seen square pyramidal niobium(V) cations.


Abstract

The reactivity of the complexing anthracene-9-carboxylate ligand has been investigated with a niobium(IV) tetrachloride precursor (NbCl4 ⋅ 2THF) in isopropanol solvent. This resulted in the crystallization of a molecular assembly containing two distinct {Nb12O21} cores surrounded by multiple isopropanolate and anthracenoate ligands. The compound is formulated [Nb12((μ3-O)3(μ-O)18(C15H9O2)8(OiPr)10] ⋅ [Nb12(μ3-O)2(μ-O)19(C15H9O2)8(OiPr)10] illustrating the two different dodecameric oxo-clusters, for which the niobium(IV) precursor was oxidized in the niobium(V) state during the reactional process. The two distinct {Nb12O21} units mainly differs by the environment of the niobium centers, which exhibits unexpected five-fold coordination (square pyramid) for some of them, together with the classical six-fold coordination (octahedron) as usually found for niobium(V). In the crystallization process, the. IR spectroscopy was used to analyze the esterification reaction occurring between the anthracene acid an isopropanolate ligands responsible of the production of water used in the oxo-condensation of the niobium centers. 93Nb Solid state NMR was tentatively used to assess the occurrence of the different niobium environments.

Protonation Behavior of a Tetrahydrido Molybdenum(IV) Complex with Organic and Inorganic Acids

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Protonation Behavior of a Tetrahydrido Molybdenum(IV) Complex with Organic and Inorganic Acids

Protonation of polyhydride complexes: conjugated base matters! The protonation of a neutral molybdenum(IV) tetrahydride complex was investigated using a range of proton sources. Whereas simple acid-base process was achieved in the case of a phosphonium, subsequent reactivity of the resulting cationic pentahydride species with conjugated base was typically observed.


Abstract

The reaction of [MoH4(depe)2] (1) (depe=1,2-bis(diethylphosphino)ethane) with different proton sources (HPtBu3 +, C6H5COOH, C6F5COOH, H2SO4) was investigated. Whereas complete conversion of 1 into its protonated form is observed in the presence of the phosphonium salt, [MoH5(depe)2]+ only transiently forms upon treatment with the other acids. Further reactivity of the pentahydride complex is indeed noticed with the conjugated base, typically resulting in the formation of neutral (C6F5COOH, H2SO4) or cationic (PhCOOH) molybdenum dihydride complexes. The compounds were characterized by NMR spectroscopy and X-ray crystallographic studies were performed when suitable crystals were obtained.

Variation of Clasper Scent Gland Composition of Heliconius Butterflies from a Biodiversity Hotspot

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Variation of Clasper Scent Gland Composition of Heliconius Butterflies from a Biodiversity Hotspot

Male Heliconius butterflies, which occur locally in three mimicry groups, show an extremely high diversity of compounds in their clasper scent glands. The more than 1,000 different compounds identified in 17 species are used for species-specific mixtures of volatile and non-volatile compounds, presumably used for chemical communication. (Photos: C. Jiggins)


Abstract

Male Heliconius butterflies possess two pheromone emitting structures, wing androconia and abdominal clasper scent glands. The composition of the clasper scent gland of males of 17 Heliconius and Eueides species from an overlapping area in Ecuador, comprising three mimicry groups, was investigated by GC/MS. The chemical signal serves as an anti-aphrodisiac signal that is transferred from males to females during mating, indicating the mating status of the female to prevent them from harassment by other males. In addition, the odour may also serve in predator defence. There is potential for convergence driven by mimicry, although, such convergence might be detrimental for species recognition of the butterflies within the mimicry ring, making mating more difficult. More than 500 compounds were detected, consisting of volatile, semi-volatile or non-volatile compounds, including terpenes, fatty acid esters or aromatic compounds. Several novel esters were identified by GC/MS and GC/IR data, microderivatisation and synthesis, including butyl (Z)-3-dodecenoate and other (Z)-3-alkenoates, 3-oxohexyl citronellate and 5-methylhexa-3,5-dienyl (E)-2,3-dihydrofarnesoate. The secretions were found to be species specific, potentially allowing for species differentiation. Statistical analysis of the compounds showed differentiation by phylogenetic clade and species, but not by mimicry group.

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.