Palladium-bearing intermetallic electride as an efficient and stable catalyst for Suzuki cross-coupling reactions

Electron Deficient Ir-O Bonds Promote Heterogeneous Ir-Catalyzed Anti-Markovnikov Hydroboration of Alkenes under Mild Neat Conditions

Tuning electronic characteristics of metal-ligand bonds based on reaction pathways to achieve efficient catalytic processes has been widely studied and proven to be feasible in homogeneous catalysis, but it is scarcely investigated in heterogeneous catalysis. Herein, we demonstrate the regulation of the electronic configuration of Ir-O bonds in an Ir single-atom catalyst according to the borane activation mechanism. Ir-O bonds in Ir1/Ni(OH)x are found to be more electron-poor than those in Ir1/NiOx. Despite the mild solvent-free conditions and ambient temperature, Ir1/Ni(OH)x exhibits outstanding performance for the hydroboration of alkenes, furnishing the desired alkylboronic esters with a turnover frequency value of ≤3060 h-1 and 99% anti-Markovnikov selectivity, which is significantly better than that of Ir1/NiOx (42 h-1). It is further proven that the more electron-poor Ir-O bonds as active centers are more oxidative and so benefit the activation of the H-B bond in the reductive pinacolborane.

Pyrimidine-morpholine hybrids as potent druggable therapeutics for Alzheimer's disease: Synthesis, biochemical and in silico analyses

The identification of effective and druggable cholinesterase inhibitors to treat progressive neurodegenerative Alzheimer's disorder remains a continuous drug discovery hunt. In this perspective, the present study investigates the design and discovery of pyrimidine-morpholine hybrids (5a-l) as potent cholinesterase inhibitors. Palladium-catalyzed Suzuki-Miyaura cross-coupling reaction was employed to introduce the structural diversity on the pyrimidine heterocyclic core. A range of commercially available boronic acids was successfully coupled showing a high functional group tolerance. In vitro cholinesterase inhibitory potential using Ellman's method revealed significantly strong potency. Compound 5h bearing a meta-tolyl substituent at 2-position of pyrimidine ring emerged as a lead candidate against AChE with an inhibitory potency of 0.43 ± 0.42 µM, ∼38-fold stronger value than neostigmine (IC50 = 16.3 ± 1.12 µM). Compound 5h also showed the lead inhibition against BuChE with an IC50 value of 2.5 ± 0.04 µM. The kinetics analysis of 5h revealed the non-competitive mode of inhibition against AChE whereas computational modelling results of potent leads depicted diverse contacts with the binding site amino acid residues. Molecular dynamics simulations revealed the stability of biomolecular system, while, ADME analysis demonstrated druglikeness behaviour of potent compounds. Overall, the investigated pyrimidine-morpholine scaffold presented a remarkable potential to be developed as efficacious anti-Alzheimer's drugs.

Hierarchical NiZn Solid Solution as a Highly Efficient Palladium Free Heterogeneous Catalyst for Suzuki-Miyaura Cross-Coupling Reaction

In this report, surfactant free solid solution of NiZn with a hierarchical architecture was synthesized via a one-pot colloidal approach. Evidence supporting hierarchical crystal growth and alloying of metals at the atomic level was obtained from field emission scanning electron microscopy and transmission electron microscopy-energy-dispersive X-ray data. Lattice sites of face-centered metallic Ni were found to be occupied by Zn as evident from powder X-ray diffraction where a gradual shift in the peak position and increase in the average lattice parameter upon reduction of the Ni content in the alloy samples can be observed. This well-alloyed, magnetically separable, non-noble metal-based solid solution has the potential to replace the palladium-based catalyst in the Suzuki-Miyaura cross-coupling of aryl halides (-Cl/-Br) and phenylboronic acid. The nanostructured catalyst was formed through the assembly of a triangular spiked and sheet-like structure and is magnetically well separable that is stable enough under the catalytic reaction condition. The developed heterogeneous catalyst and the designed economical catalytic model are the first ever reported work. The catalytic results outperformed most of the reported state-of-the-art works involving the transition metal-based catalyst.

Berry curvature contributions of kagome-lattice fragments in amorphous Fe-Sn thin films

Amorphous semiconductors are widely applied to electronic and energy-conversion devices owing to their high performance and simple fabrication processes. The topological concept of the Berry curvature is generally ill-defined in amorphous solids, due to the absence of long-range crystalline order. Here, we demonstrate that the Berry curvature in the short-range crystalline order of kagome-lattice fragments effectively contributes to the anomalous electrical and magneto-thermoelectric properties in Fe-Sn amorphous films. The Fe-Sn films on glass substrates exhibit large anomalous Hall and Nernst effects comparable to those of the single crystals of topological semimetals Fe₃Sn₂ and Fe₃Sn. With modelling, we reveal that the Berry curvature contribution in the amorphous state likely originates from randomly distributed kagome-lattice fragments. This microscopic interpretation sheds light on the topology of amorphous materials, which may lead to the realization of functional topological amorphous electronic devices.

Single-Atom Catalysts for Hydrogen Activation

Selective hydrogenation is one of the most important reactions in fine chemical industry, and the activation of H₂ is the key step for hydrogenation. Catalysts play a critical role in selective hydrogenation, and some single-atom catalysts (SACs) are highly capable of activating H₂ in selective hydrogenation by virtue of the maximized atom utilization and the highly uniform active sites. Therefore, more research efforts are needed for the rational design of SACs with superior H₂ -activating capabilities. Herein, the research progress on H₂ activation in typical hydrogenation systems (such as alkyne hydrogenation, hydroformylation, hydrodechlorination, hydrodeoxygenation, nitroaromatics hydrogenation, and polycyclic aromatics hydrogenation) is reviewed, the mechanisms of SACs for H₂ activation are summarized, and the structural regulation strategies for SACs are proposed to promote H₂ activation and provide schemes for the design of high-selectivity hydrogenation catalysts from the atomic scale. At the end of this review, an outlook on the opportunities and challenges for SACs to be developed for selective hydrogenation is presented.

Multifold Fermions and Fermi Arcs Boosted Catalysis in Nanoporous Electride 12CaO·7Al2 O3

Topological materials have been recently regarded as ideal catalysts for heterogeneous reactions due to their surface metallic states and high carrier mobility. However, the underlying relationship between their catalytic performance and topological states is under debate. It has been discovered that the electride 12CaO·7Al₂ O₃ (C12A7:4e^- ) hosts multifold fermions and Fermi arcs on the (001) surface near the Fermi level due to the interstitial electrons. Through the comparison of catalytic performance under different doping and strain conditions, based on the hydrogen evolution process, it has been demonstrated that the excellent catalytic performance indeed originates from topological properties. A linear relationship between the length of Fermi arcs, and Gibbs free energy (ΔG_H* ) has been found, which not only provides the direct evidence to link the enhanced catalytic performance and surface Fermi arc states, but also fully clarifies the fundamental mechanism in topological catalysis.

Catalysis of Alloys: Classification, Principles, and Design for a Variety of Materials and Reactions

Alloying has long been used as a promising methodology to improve the catalytic performance of metallic materials. In recent years, the field of alloy catalysis has made remarkable progress with the emergence of a variety of novel alloy materials and their functions. Therefore, a comprehensive disciplinary framework for catalytic chemistry of alloys that provides a cross-sectional understanding of the broad research field is in high demand. In this review, we provide a comprehensive classification of various alloy materials based on metallurgy, thermodynamics, and inorganic chemistry and summarize the roles of alloying in catalysis and its principles with a brief introduction of the historical background of this research field. Furthermore, we explain how each type of alloy can be used as a catalyst material and how to design a functional catalyst for the target reaction by introducing representative case studies. This review includes two approaches, namely, from materials and reactions, to provide a better understanding of the catalytic chemistry of alloys. Our review offers a perspective on this research field and can be used encyclopedically according to the readers' individual interests.

One-step synthesis of PdCu@Ti3C2 with high catalytic activity in the Suzuki-Miyaura coupling reaction

Owing to their enhanced catalytic stability and cyclability, two-dimensional (2D) material-supported Pd-based bimetallic alloys have promising applications for catalytic reactions. Furthermore, the alloying strategy can effectively reduce costs and improve catalytic performance. In this paper, we report a one-step reduction method to synthesize a novel heterogeneous catalyst, PdCu@Ti₃C₂, with good catalytic performance. The composition and structure of the as-prepared catalyst were characterized by inductively coupled plasma-mass spectrometry (ICP-MS), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and X-ray photoelectron spectroscopy (XPS). The catalyst particles, which were identified as a PdCu bimetallic alloy, exhibited good dispersion on the substrate. The performance of the catalyst in the Suzuki-Miyaura coupling reaction was studied, and the results showed that PdCu@Ti₃C₂ had excellent catalytic activity, similar to that of homogeneous Pd catalysts such as Pd(PPh₃)₄. Moreover, the prepared catalyst could be reused at least 10 times in the Suzuki-Miyaura coupling reaction with high yield.

Molecular Electrides: An In Silico Perspective

Electrides are defined as the ionic compounds where the electron(s) serves as an anion. These electron(s) is (are) not bound to any atoms, bonds, or molecules rather than they are localized into the space, crystal voids, or interlayer between two molecular slabs. There are three major categories of electrides, known as organic electriades, inorganic electrides, and molecular electrides. The computational techniques have proven as a great tool to provide emphasis on the electride materials. In this review, we have focused on the computational methodologies and criteria that help to characterize molecular electrides. A detailed account of the computational methods and basis sets applicable for molecular electrides have been discussed along with their limitation(s) in this field. The main criterion for the identification of the electrides has also been discussed thoroughly with proper examples. The molecular electrides presented here have been justified with all the required criteria that support and proved their electride characteristics. We have also presented a few systems which have similar properties but are not considered as molecular electrides. Moreover, the applicability of the electrides in catalytic processes has also been presented.

Intermetallic YIr2 nanoparticles with negatively charged Ir active sites for catalytic hydrogenation of cyclohexanone to cyclohexanol

Negatively charged iridium species in Laves phase YIr2 as highly active sites for hydrogenation of cyclohexanone to cyclohexanol.

Intermetallic Nanocatalyst for Highly Active Heterogeneous Hydroformylation

Hydroformylation is an imperative chemical process traditionally catalyzed by homogeneous catalysts. Designing a heterogeneous catalyst with high activity and selectivity in hydroformylation is challenging but essential to allow the convenient separation and recycling of precious catalysts. Here, we report the development of an outstanding catalyst for efficient heterogeneous hydroformylation, RhZn intermetallic nanoparticles. In the hydroformylation of styrene, it shows three times higher turnover frequency (3090 h^-1) compared to the benchmark homogeneous Wilkinson's catalyst (966 h^-1), as well as a high chemoselectivity toward aldehyde products. RhZn is active for a variety of olefin substrates and can be recycled without a significant loss of activity. Density functional theory calculations show that the RhZn surfaces reduce the binding strength of reaction intermediates and have lower hydroformylation activation energy barriers compared to pure Rh(111), leading to more favorable reaction energetics on RhZn. The calculations also predict potential catalyst design strategies to achieve high regioselectivity.

How Many Electrons Does a Molecular Electride Hold?

Electrides are very peculiar ionic compounds where electrons occupy the anionic positions. In a crystal lattice, these isolated electrons often form channels or surfaces, furnishing electrides with many traits with promising technological applications. Despite their huge potential, thus far, only a few stable electrides have been produced because of the intricate synthesis they entail. Due to the difficulty in assessing the presence of isolated electrons, the characterization of electrides also poses some serious challenges. In fact, their properties are expected to depend on the arrangement of these electrons in the molecule. Among the criteria that we can use to characterize electrides, the presence of a non-nuclear attractor (NNA) of the electron density is both the rarest and the most salient feature. Therefore, a correct description of the NNA is crucial to determine the properties of electrides. In this paper, we analyze the NNA and the surrounding region of nine molecular electrides to determine the number of isolated electrons held in the electride. We have seen that the correct description of a molecular electride hinges on the electronic structure method employed for the analyses. In particular, one should employ a basis set with sufficient flexibility to describe the region close to the NNA and a density functional approximation that does not suffer from large delocalization errors. Finally, we have classified these nine molecular electrides according to the most likely number of electrons that we can find in the NNA. We believe this classification highlights the strength of the electride character and will prove useful in designing new electrides.

A Hierarchical-Structured Impeller with Engineered Pd Nanoparticles Catalyzing Suzuki Coupling Reactions for High-Purity Biphenyl

Suzuki cross-coupling reactions catalyzed by palladium are authoritative protocols in fine-chemical synthesis. Mass transfer and catalyst activity are both significant factors affecting the reaction efficiency in heterogeneous reactions. Although the holistic catalysts hold great promise in heterogeneous reactions due to the enhanced mass transport and convenient recycling, the unsatisfied catalytic activity has impeded further large-scale applications. In addition, another pronounced barrier is the product separation in the intricate system. Here, the catalytic production and separation of biphenyl (purity of 99.7%) were achieved by integrating the Suzuki cross-coupling reactions and the crystallization separation for the first time. A hierarchical-structured impeller with Pd nanoparticles (NPs) loaded on the Ni(OH)₂ nanosheets was prepared to catalyze the Suzuki reactions for bromobenzene, which exhibits a high turnover frequency (TOF) value of 25,976 h^-1 and a yield of 99.5%. The X-ray absorption fine structure (XAFS) analysis has unveiled that the electron transfer between the Pd NPs and Ni(OH)₂ accounts for the greatly enhanced catalytic activity. The findings inspire new insights toward rational engineering of highly efficient holistic catalysts for Suzuki reaction, and the innovative integrated technology offers an avenue for the separation and collection of products.

Designed electron-deficient gold nanoparticles for a room-temperature Csp3-Csp3 coupling reaction

Stille cross-coupling reactions catalysed by an ideal catalyst combining the high activity of homogeneous catalysts and the reusability of heterogeneous catalysts are of great interest for C-C bond formation, which is a widely used reaction in fine chemistry. Despite great effort to increase the utilization ratio of surface metal atoms, the activity of heterogeneous catalysts under mild conditions remains unsatisfactory. Herein, we design a proof-of-concept strategy to trigger the room-temperature activity of heterogeneous Au catalysts by decreasing the electron density at the interface of a rationally designed Schottky heterojunction of Au metals and boron-doped carbons. The electron-deficient Au nanoparticles formed as a result of the rectifying contact with boron-doped carbons facilitate the autocleavage of C-Br bonds for highly efficient C-C coupling reactions of alkylbromides and allylstannanes with a TOF value of 5199 h-1 at room temperature, surpassing that of the state-of-the-art homogeneous catalyst.

Suzuki–Miyaura cross coupling reaction: recent advancements in catalysis and organic synthesis

Suzuki–Miyaura cross coupling reaction (SMCR) – A milestone in the synthesis of C–C coupled compounds.