Zero-valent Palladium Single-Atoms Catalysts Confined in Black Phosphorus for Efficient Semi-hydrogenation

Single-atom catalysts (SACs) represent a new frontier in heterogeneous catalysis due to their remarkable catalytic properties and maximized atomic utilization. However, single atoms often bond to the support with polarized electron density and thus exhibit a high valence state, limiting their catalytic scopes in many chemical transformations. Here, we demonstrated that two-dimensional (2D) black phosphorus (BP) act as giant phosphorus (P) ligand to confine a high density of single atoms (eg, Pd1, Pt1) via atomic layer deposition. Unlike other 2D materials, BP with relatively low electronegativity and buckled structure favors the strong confinement of robust zero-valent palladium SACs in the vacancy site. Metallic Pd1/P SAC shows a highly selective semi-hydrogenation of phenylacetylene towards styrene, outperforming high-valence Pt1/P SAC, and also distinct from metallic Pd nanoparticles that facilitate the formation of fully hydrogenated products. Our DFT calculations reveal that Pd atom forms covalent-like bonding with adjacent P atoms, wherein H atoms tend to adsorb over electron-rich region for the subsequent hydrogenation. Zero-valent Pd in the confined space favors a larger energy gain for the synthesis of partially-hydrogenated product over the fully-hydrogenated one. Our work provides a new route towards the synthesis of zero-valent SACs on BP for a wide range of organic transformations.

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Atomic layer deposition of nanoparticles on self-assembled monolayer modified silicon substrate

MRS Proceedings ◽

10.1557/opl.2013.631 ◽

2013 ◽

Vol 1546 ◽

Author(s):

Kun Cao ◽

Zhilong Ren ◽

Shengmei Xiang ◽

Bin Shan ◽

Rong Chen

Keyword(s):

Atomic Layer Deposition ◽

Silicon Substrate ◽

Particle Diameter ◽

Atomic Layer ◽

Pd Nanoparticles ◽

Noble Metal Nanoparticles ◽

Self Assembled Monolayer ◽

Layer Deposition ◽

Wide Range ◽

Self Assembled

ABSTRACTAtomic layer deposition has attracted much attention recently in fabricating noble metal nanoparticles for a wide range of applications. We have explored synthesizing palladium nanoparticles via atomic layer deposition on self-assembled monolayers modified silicon substrate. Using alkyltrichlorosilanes as the passivating agents, our results show the method is capable of fabricating Pd nanoparticles with well controlled density and particle diameter on the modified silicon substrate.

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Tunable Carbon Surface from Mono- to Multi-Metallic Single Atoms

10.26434/chemrxiv.12264083 ◽

2020 ◽

Author(s):

Weihong Lai ◽

Heng Wang ◽

Quan jiang ◽

Zichao Yan ◽

Hanwen Liu ◽

...

Keyword(s):

Synergistic Effects ◽

Structural Evolution ◽

Charge Compensation ◽

Catalytic Reactions ◽

Single Atom ◽

Carbon Surface ◽

Hydrogen Electrode ◽

Single Atoms ◽

Mass Activity ◽

Co Doped

Herein, we develop a non-selective charge compensation strategy to prepare multi-single-atom doped carbon (MSAC) in which a sodium p-toluenesulfonate (PTS-Na) doped polypyrrole (S-PPy) polymer is designed to anchor discretionary mixtures of multiple metal cations, including iron (Fe3+), cobalt (Co3+), ruthenium (Ru3+), palladium (Pd2+), indium (In3+), iridium (Ir2+), and platinum (Pt2+) . As illustrated in Figure 1, the carbon surface can be tuned with different level of compositional complexities, including unary Pt1@NC, binary (MSAC-2, (PtFe)1@NC), ternary (MSAC-3, (PtFeIr)1@NC), quaternary (MSAC-4, (PtFeIrRu)1@NC), quinary (MSAC-5, (PtFeIrRuCo)1@NC), senary (MSAC-6, (PtFeIrRuCoPd)1@NC), and septenary (MSAC-7, (PtFeIrRuCoPdIn)1@NC) samples. The structural evolution of carbon surface dictates the activities of both ORR and HER. The senary MSAC-6 achieves the ORR mass activity of 18.1 A·mgmetal-1 at 0.9 V (Vs reversible hydrogen electrode (RHE)) over 30K cycles, which is 164 times higher than that of commercial Pt/C. The quaternary MSAC-4 presented a comparable HER catalytic capability with that of Pt/C. These results indicate that the highly complexed carbon surface can enhance its ability over general electrochemical catalytic reactions. The mechanisms regarding of the ORR and HER activities of the alternated carbon surface are also theoretically and experimentally investigated in this work, showing that the synergistic effects amongst the co-doped atoms can activate or inactivate certain single-atom sites.

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Strongly Coupled Redox-Linked Conformational Switching at the Active Site of the Non-Heme Iron-Dependent Dioxygenase, TauD

10.26434/chemrxiv.9461462 ◽

2019 ◽

Author(s):

Christopher John ◽

Greg M. Swain ◽

Robert P. Hausinger ◽

Denis A. Proshlyakov

Keyword(s):

Active Site ◽

Structural Model ◽

Heme Iron ◽

Chemical Transformations ◽

Experimental Conditions ◽

Strongly Coupled ◽

Non Heme Iron ◽

Reversible Redox ◽

Wide Range ◽

Complex Structural

2-Oxoglutarate (2OG)-dependent dioxygenases catalyze C-H activation while performing a wide range of chemical transformations. In contrast to their heme analogues, non-heme iron centers afford greater structural flexibility with important implications for their diverse catalytic mechanisms. We characterize an in situ structural model of the putative transient ferric intermediate of 2OG:taurine dioxygenase (TauD) by using a combination of spectroelectrochemical and semi-empirical computational methods, demonstrating that the Fe (III/II) transition involves a substantial, fully reversible, redox-linked conformational change at the active site. This rearrangement alters the apparent redox potential of the active site between -127 mV for reduction of the ferric state and 171 mV for oxidation of the ferrous state of the 2OG-Fe-TauD complex. Structural perturbations exhibit limited sensitivity to mediator concentrations and potential pulse duration. Similar changes were observed in the Fe-TauD and taurine-2OG-Fe-TauD complexes, thus attributing the reorganization to the protein moiety rather than the cosubstrates. Redox difference infrared spectra indicate a reorganization of the protein backbone in addition to the involvement of carboxylate and histidine ligands. Quantitative modeling of the transient redox response using two alternative reaction schemes across a variety of experimental conditions strongly supports the proposal for intrinsic protein reorganization as the origin of the experimental observations.

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The Synthesis and Application of Functionalized Mesoporous Silica SBA-15 as Heterogeneous Catalyst in Organic Synthesis

Current Organic Chemistry ◽

10.2174/1385272824999201210194444 ◽

2020 ◽

Vol 24 ◽

Author(s):

Ghodsi Mohammadi Ziarani ◽

Shima Roshankar ◽

Fatemeh Mohajer ◽

Alireza Badiei

Keyword(s):

Mesoporous Silica ◽

Heterogeneous Catalyst ◽

Organic Synthesis ◽

Lewis Acid ◽

Heterogeneous Catalysts ◽

Organic Transformations ◽

Functionalized Mesoporous Silica ◽

Silica Nanomaterials ◽

Wide Range ◽

Target Molecules

Abstract:: Mesoporous silica nanomaterials provide an extraordinary advantage for making new and superior heterogeneous catalysts because of their surface silanol groups. The functionalized mesoporous SBA-15, such as acidic, basic, BrÖnsted, lewis acid, and chiral catalysts, are used for a wide range of organic synthesis. The importance of the chiral ligands, which were immobilized on the SBA-15, was mentioned in this review to achieve chiral products as valuable target molecules. Herein, their synthesis and application in different organic transformations are reviewed from 2016 till date 2020.

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α-Alkoxyalkyl Triphenylphosphonium Salts: Synthesis and Reactions

Current Organic Chemistry ◽

10.2174/1385272823666190926092242 ◽

2019 ◽

Vol 23 (16) ◽

pp. 1738-1755

Author(s):

Humaira Y. Gondal ◽

Zain M. Cheema ◽

Abdul R. Raza ◽

Ahmed Abbaskhan ◽

M. I. Chaudhary

Keyword(s):

Carbonyl Compounds ◽

Claisen Rearrangement ◽

Alder Reaction ◽

Coupling Reactions ◽

Phosphonium Salts ◽

Organic Transformations ◽

Enol Ethers ◽

Wide Range ◽

Synthetic Methodologies ◽

Alkoxy Groups

Following numerous applications of Wittig reaction now functionalized phosphonium salts are gaining attention due to their characteristic properties and diverse reactivity. This review is focused on α-alkoxyalkyl triphenylphosphonium salts: an important class of functionalized phosphonium salts. Alkoxymethyltriphenylphosphonium salts are majorly employed in the carbon homologation of carbonyl compounds and preparation of enol ethers. Their methylene insertion strategy is extensively demonstrated in the total synthesis of a wide range of natural products and other important organic molecules. Similarly enol ethers prepared thereof are important precursors for different organic transformations like Diels-Alder reaction, Claisen rearrangement, Coupling reactions, Olefin metathesis and Nazarov cyclization. Reactivity of these α-alkoxyalkylphosphonium salts have also been studied in the nucleophilic substitution reactions. A distinctive application of this class of phosphonium salts was recently reported in the phenylation of carbonyl compounds under very mild conditions. Synthesis of structurally diverse alkoxymethyltriphenylphosphonium salts with variation in alkoxy groups as well as counter anions are reported in literature. Here we present a detailed account of different synthetic methodologies for the preparation of this unique class of quaternary phosphonium salts and their applications in organic synthesis.

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Recent Application of Polystyrene-supported Triphenylphosphine in Solid-Phase Organic Synthesis

Current Organic Chemistry ◽

10.2174/1385272822666181026115752 ◽

2019 ◽

Vol 23 (6) ◽

pp. 643-678

Author(s):

Lalthazuala Rokhum ◽

Ghanashyam Bez

Keyword(s):

Organic Synthesis ◽

Combinatorial Chemistry ◽

Solid Phase ◽

Recent Application ◽

Organic Transformations ◽

Solid Phase Organic Synthesis ◽

Wide Range ◽

Fast Development ◽

Polymer Supported

Recent years have witnessed a fast development of solid phase synthetic pathways, a variety of solid-supported reagent and its applications in diverse synthetic strategies and pharmaceutical applicability’s. Polymer-supported triphenylphosphine is getting a lot of applications owing to the speed and simplicity in the process. Furthermore, ease of recyclability and reuse of polymer-supported triphenylphosphine added its advantages. This review covers a wide range of useful organic transformations which are accomplished using cross-linked polystyrene-supported triphenylphosphine with the aim of giving renewed interest in the field of organic and medicinal-combinatorial chemistry.

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Organocatalyzed Heterocyclic Transformations In Green Media: A Review

Current Organocatalysis ◽

10.2174/2213337207999200805115813 ◽

2020 ◽

Vol 07 ◽

Author(s):

Neslihan Demirbas ◽

Ahmet Demirbas

Keyword(s):

Hydrogen Bonding ◽

Phase Transfer ◽

Noncovalent Interactions ◽

Binding Capacity ◽

Chemical Transformations ◽

Organic Transformations ◽

Phase Transfer Catalysts ◽

Waste Production ◽

Synthetic Methodologies ◽

Organocatalytic Reactions

Background: Since the discovery of metal-free catalysts or organocatalysts about twenty years ago, a number of small molecules with different structures have been using to accelerate organic transformations. With the development of environmental awareness, in order to obtain highly privileged scaffolds, scientists have directed their studies towards the synthetic methodologies which minimize or preferably eliminate the formation of waste, avoid from toxic solvents and reagents and use renewable starting materials as far as possible. Methods: In this connection, the organocatalytic reactions providing efficiency and selectivity for most of case have become an endless topic in organic chemistry since several advantages from both practical and environmental standpoints. Organocatalysts supplying transformation of reactants into products with the least possible waste production have been serving to the concept of green chemistry. Results and Conclusion: Organocatalysts have been classified on the basis of their binding capacity to the substrate with covalently or noncovalent interactions involving hydrogen bonding and electrostatic interaction. Diverse types of small organic compounds including proline and its derivatives, phase-transfer catalysts, (thio)urease, phosphoric acids, sulfones, N-oxides, guanidines, cinchona derivatives, aminoindanol and amino acids have been utilized as hydrogen bonding organocatalysts in different chemical transformations.

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