Turnover Frequency Research Articles

Ruthenium‐Catalyzed Methanol Production from Aqueous Paraformaldehyde and Mechanistic Study

AbstractA series of water‐soluble arene‐Ru(II) complexes, [(η6‐p‐cymene)RuCl(L)]+Cl‒ ([Ru]‐7 – [Ru]‐12) (L = substituted bis‐imidazole methane) exhibited efficient and selective methanol production from paraformaldehyde in water. The findings inferred a crucial role of the ligand in tuning the catalytic performance. A pH‐dependent behavior of this series of catalysts was observed, where the amount of base was influential in methanol production from paraformaldehyde. The catalyst [Ru]‐7 (L1 = 4,4′‐((2‐hydroxyphenyl)methylene)bis(2‐ethyl‐5‐methyl‐1H‐imidazole) was the most efficient among the explored catalysts giving a turnover number (TON) of 1200 at 90 °C. A mechanistic cycle has also been proposed for the catalytic reaction based on the mass and NMR investigations including those using deuterium‐labelled molecules.

A Two‐in‐One Strategy to Simultaneously Boost the Site Density and Turnover Frequency of Fe−N−C Oxygen Reduction Catalysts

Site density and turnover frequency are the two fundamental kinetic descriptors that determine the oxygen reduction activity of iron‐nitrogen‐carbon (Fe−N−C) catalysts. However, it remains a grand challenge to simultaneously optimize these two parameters in a single Fe−N−C catalyst. Here we show that treating a typical Fe−N−C catalyst with ammonium iodine (NH4I) vapor via a one‐step chemical vapor deposition process not only increases the surface area and porosity of the catalyst (and thus enhanced exposure of active sites) via the etching effect of the in‐situ released NH3, but also regulates the electronic structure of the Fe−N4 moieties by the iodine dopants incorporated into the carbon matrix. As a result, the NH4I‐treated Fe−N−C catalyst possesses both high values in the site density of 2.15×1019 sites g−1 (×2 enhancement compared to the untreated counterpart) and turnover frequency of 3.71 electrons site−1 s−1 (×3 enhancement) that correspond to a high mass activity of 12.78 A g−1, as determined by in‐situ nitrite stripping technique. Moreover, this catalyst exhibits an excellent oxygen reduction activity in base with a half‐wave potential (E1/2) of 0.924 V and acceptable activity in acid with E1/2 = 0.795 V, and superior power density of 249.1 mW cm−2 in zinc‐air batteries.

A Two-in-One Strategy to Simultaneously Boost the Site Density and Turnover Frequency of Fe-N-C Oxygen Reduction Catalysts.

Site density and turnover frequency are the two fundamental kinetic descriptors that determine the oxygen reduction activity of iron-nitrogen-carbon (Fe-N-C) catalysts. However, it remains a grand challenge to simultaneously optimize these two parameters in a single Fe-N-C catalyst. Here we show that treating a typical Fe-N-C catalyst with ammonium iodine (NH4I) vapor via a one-step chemical vapor deposition process not only increases the surface area and porosity of the catalyst (and thus enhanced exposure of active sites) via the etching effect of the in-situ released NH3, but also regulates the electronic structure of the Fe-N4 moieties by the iodine dopants incorporated into the carbon matrix. As a result, the NH4I-treated Fe-N-C catalyst possesses both high values in the site density of 2.15×1019 sites g-1 (×2 enhancement compared to the untreated counterpart) and turnover frequency of 3.71 electrons site-1 s-1 (×3 enhancement) that correspond to a high mass activity of 12.78 A g-1, as determined by in-situ nitrite stripping technique. Moreover, this catalyst exhibits an excellent oxygen reduction activity in base with a half-wave potential (E1/2) of 0.924 V and acceptable activity in acid with E1/2 = 0.795 V, and superior power density of 249.1 mW cm-2 in zinc-air batteries.

3d-5d Orbital Hybridization in Nanoflower-Like High-Entropy Alloy for Highly Efficient Overall Water Splitting at High Current Density.

Exploring highlyefficient electrocatalysts for overall water splitting is a challenging butnecessary task for development of green and renewable energy. Herein, PtIrFeCoNi high-entropy alloy nanoflowers (HEA NFs) withstrong 3d-5d orbital hybridization were fabricated to achieve highly efficientoverall water splitting at high current density. The Pt26Ir7Fe13Co22Ni32 HEA NFs achieved a 57.52-fold higher than commercial IrO2 in turnoverfrequency (TOF) for oxygen evolution reaction (OER). Besides, its TOF value forhydrogen evolution reaction (HER) was 2.11-fold higher than that of commercialPt/C. The cell voltages based on Pt26Ir7Fe13Co22Ni32 HEA NFs for overall water splitting were only 1.594 V and 1.861 V at currentdensities of 100 mA cm-2 and 500 mA cm-2, which weresignificantly lower than those of Pt/C.

Adaptable Blueprint for Non-metal Near-Infrared Organic Photocatalysts by Aromatic Sulfones.

We present a versatile approach to designing and utilizing high-performance nonmetal near-infrared (NIR) organic photocatalysts based on aromatic sulfones. Current NIR photocatalysts are mainly metal complexes and inorganic materials, while the few reported nonmetal organic NIR photocatalysts primarily use photosensitization to produce active species such as singlet oxygen. Our sulfone-rosamine-based redox photocatalyst 3 demonstrates exceptional capabilities, including high ability for metal-free photo-oxidative bromination, intrinsically oxygen-independent redox reactions, and remarkable photostability with a turnover number (TON) exceeding 2800. We showcase the photocatalyst's efficacy in photo-oxidative bromination of aromatic compounds under 738 nm illumination. The reaction mechanism is elucidated through electrochemical studies, time-resolved spectral measurements, and DFT calculations. Transient absorption measurements using the randomly interleaved pulse train (RIPT) method reveal the photoexcited state of 3 in the reaction. The photocatalyst 3 demonstrated its versatility for several aromatic substances, including those exhibiting strong light absorption in the visible region. This aromatic sulfone-based approach offers a robust blueprint for developing nonmetal NIR organic photocatalysts with superior photo-oxidation ability and stability, addressing key limitations of conventional organic NIR photocatalysts.

Zero-Valent Copper Catalysis Enables Regio- and Stereoselective Difunctionalization of Alkynes.

The development of a metallic copper-based catalyst system remains a significant challenge. Herein, we report the synthesis of highly stable, active, and reusable Cu0 catalyst for the carboboration of alkynes using carbon electrophiles and bis(pinacolato)diboron (B2pin2) as chemical feedstocks to afford di- and trisubstituted vinylboronate esters in a regio- and stereoselective manner with appreciable turnover number (TON) of up to 2535 under mild reaction conditions. This three-component coupling reaction works well with a variety of substituted electrophiles and alkynes with broad functional group tolerance. In addition, a wide range of terminal and challenging internal alkynes were efficiently converted into hydroborated products in up to >99% yield with excellent regioselectivity in the absence of carbon electrophiles. X-ray photoelectron spectroscopy and X-ray absorption near-edge spectroscopy (XANES) analysis confirm that the oxidation state of the copper in the catalyst is zero. The broad range of organic transformations, effectiveness, and recyclability of this Cu0 catalyst are the major achievements that provide an environmentally friendly route for the efficient production of tri- and tetrasubstituted olefins, key intermediates in organic synthesis. The gram-scale reaction and synthetic transformations further highlights the usefulness of these methods.

Zero‐Valent Copper Catalysis Enables Regio‐ and Stereoselective Difunctionalization of Alkynes

The development of a metallic copper‐based catalyst system remains a significant challenge. Herein, we report the synthesis of highly stable, active, and reusable Cu0 catalyst for the carboboration of alkynes using carbon electrophiles and bis(pinacolato)diboron (B2pin2) as chemical feedstocks to afford di‐ and trisubstituted vinylboronate esters in a regio‐ and stereoselective manner with appreciable turnover number (TON) of up to 2535 under mild reaction conditions. This three‐component coupling reaction works well with a variety of substituted electrophiles and alkynes with broad functional group tolerance. In addition, a wide range of terminal and challenging internal alkynes were efficiently converted into hydroborated products in up to >99% yield with excellent regioselectivity in the absence of carbon electrophiles. X‐ray photoelectron spectroscopy and X‐ray absorption near‐edge spectroscopy (XANES) analysis confirm that the oxidation state of the copper in the catalyst is zero. The broad range of organic transformations, effectiveness, and recyclability of this Cu0 catalyst are the major achievements that provide an environmentally friendly route for the efficient production of tri‐ and tetrasubstituted olefins, key intermediates in organic synthesis. The gram‐scale reaction and synthetic transformations further highlights the usefulness of these methods.

Tuning Hydrogen Binding on Ru Sites by Ni Alloying on MoO2 Enables Efficient Alkaline Hydrogen Evolution for Anion Exchange Membrane Water Electrolysis.

Ruthenium (Ru)-based electrocatalysts have shown promise for anion exchange membrane water electrolysis (AEMWE) due to their ability to facilitate water dissociation in the hydrogen evolution reaction (HER). However, their performance is limited by strong hydrogen binding, which hinders hydrogen desorption and water re-adsorption. This study reports the development of RuNi nanoalloys supported on MoO2, which optimize the hydrogen binding strength at Ru sites through modulation by adjacent Ni atoms. Theoretical simulations reveal that substituting Ni atoms for adjacent Ru atoms reduces the high hydrogen adsorption Gibbs free energy on Ru while maintaining a low energy barrier for water dissociation. As a result, the RuNi/MoO₂ catalyst shows excellent HER performance with a low overpotential of 51mV at a current density of 100mAcm⁻2, outperforming commercial Pt/C. Furthermore, RuNi/MoO₂ demonstrates high turnover frequency (7.06s-1), mass activity (13.4Amg-1), and price activity (1030.77Adollar-1). In an AEMWE cell, RuNi/MoO₂ as the cathode catalyst achieves a current density of 1Acm-2 at 60°C with just 1.7V using 1m KOH. This work highlights the potential of RuNi/MoO₂ for ultra-high mass activity in efficient AEMWE applications.

Boosting the Hydrogen Evolution Activity of a Low-Coordinated Co─N─C Catalyst via Vacancy Defect-Mediated Alteration of the Intermediate Adsorption Configuration.

The cobalt-nitrogen-carbon (Co─N─C) single-atom catalysts (SACs) are promising alternatives to precious metals for catalyzing the hydrogen evolution reaction (HER) and their activity is highly dependent on the coordination environments of the metal centers. Herein, a NaHCO3 etching strategy is developed to introduce abundant in-plane pores within the carbon substrates that further enable the construction of low-coordinated and asymmetric Co─N3 sites with nearby vacancy defects in a Co─N─C catalyst. This catalyst exhibits a high HER activity with an overpotential (η) of merely 78mV to deliver a current density of 10mA cm-2, a Tafel slope of 45.2mV dec-1, and a turnover frequency of 1.67 s-1 (at η = 100mV). Experimental investigations and theoretical calculations demonstrate that the vacancy defects neighboring the Co─N3 sites can modulate the electronic structure of the catalyst and alter the adsorption configuration of the H intermediate from the typical atop mode to the side mode, resulting in weakened H adsorption strength and thus improved HER activity. This work provides an efficient strategy to regulate the coordination environment of SACs for improved catalytic performance and sheds light on the atomic-level understanding of the structure-activity relationships.

Functional Characterization of the SHIP1-Domains Regarding Their Contribution to Inositol 5-Phosphatase Activity

The Src homology 2 domain-containing inositol 5-phosphatase 1 (SHIP1) is a multidomain protein consisting of two protein–protein interaction domains, the Src homology 2 (SH2) domain, and the proline-rich region (PRR), as well as three phosphoinositide-binding domains, the pleckstrin homology-like (PHL) domain, the 5-phosphatase (5PPase) domain, and the C2 domain. SHIP1 is commonly known for its involvement in the regulation of the PI3K/AKT signaling pathway by dephosphorylation of phosphatidylinositol-3,4,5-trisphosphate (PtdIns(3,4,5)P3) at the D5 position of the inositol ring. However, the functional role of each domain of SHIP1 for the regulation of its enzymatic activity is not well understood. To determine the contribution of the individual domains to catalytic activity, the full-length protein was compared with truncated constructs lacking one or more domain(s), regarding the substrate turnover (kcat) and catalytic efficiency (kcat/Km) towards ci8-PtdIns(3,4,5)P3. With this approach, it was possible to verify the allosteric activation of SHIP1 mediated by the C2 domain as described previously, while the PHL domain seemed instead to have a negative effect regarding catalytic efficiency. The full-length SHIP1 clearly displayed the highest turnover and the second-highest catalytic efficiency, showing the role of the SH2 domain and PRR not only in protein–protein interactions but also in catalysis. The SH2 domain increased substrate turnover but negatively affected catalytic efficiency. The linker between the SH2 and the PHL domains decreased the turnover number but positively influenced the catalytic efficiency. The PRR increased both the substrate turnover and the protein’s catalytic efficiency. The regression analysis of the Michaelis–Menten graph revealed SHIP1 to be an allosteric enzyme, with the PRR and the linker being the most involved domains in that regard. In summary, our data indicate a complex regulation of the enzymatic activity of SHIP1 by its individual domains. While the C2 domain and PRR at the carboxy-terminus have a positive effect on enzymatic activity, the SH2 and PHL domain at the amino-terminus inhibit catalytic efficiency.

Overcoming the Tradeoff Between Reaction Rate and Overpotential in Dinuclear Cobalt Complex Catalyzed Electrochemical Water Oxidation

This study focuses on enhancing the water oxidation reaction (WOR) efficacy of dinuclear cobalt complex catalysts from both kinetic (turnover frequency, TOF) and thermodynamic (overpotential, η) perspectives. For this purpose, we synthesized six dinuclear cobalt complexes 1–6 comprising non‐innocent ligands with different electronically active substituents (‐OMe (1), ‐Me (2), ‐H (3), ‐F (4), ‐Cl (5), and ‐CN (6)). The electronic effects on the electrochemical WOR under neutral, acidic, and alkaline conditions were investigated experimentally and computationally. X‐ray crystallography revealed that the valence state of the cobalt complexes was affected by electronic effects, affording different catalytic potentials, as evidenced by electrochemical measurements. Kinetic and spectroscopic studies confirmed that the synergistic effect of catalyst identity and reaction media changes the reaction mechanism of each catalyst. The WOR performance of 1–6 was tunable through ligand electronics and solvent effects, with the log(TOF)‐η analysis highlighting an operational η as low as 40 mV. This study provides valuable insights into optimizing WOR catalysis through molecular design and environmental tuning.

Nickel Nanocluster-Stabilized Unsaturated Ni-N3 Atomic Sites for Efficient CO2-to-CO Electrolysis at Industrial-Level Current.

Unsaturated Ni single atom catalysts (SACs), Ni-Nx (x=1,2,3), have been investigated to break the conventional Ni-N4 structural limitation and provide more unoccupied 3d orbitals for CO2RR intermediates adsorption, but their intrinsically low structural stability has seriously hindered their applications. Here, we developed a strategy by integrating Ni nanoclusters to stabilize unsaturated Ni-N3 atomic sites for efficient CO2 electroreduction to CO at industrial-level current. DFTcalculations revealed that the incorporation of Ni nanocluster effectively stabilizes the unsaturated Ni-N3 atomic sites and modulates their electronic structure to enhance the adsorption of the key intermediate *COOH during CO2RR. Guided by these insights, we prepared an optimal composite catalyst, Ni6@Ni-N3, which features a Ni6N6 nanocluster surrounded by six Ni-N3 single atoms sites, through low-temperature pyrolysis. As a result, Ni6@Ni-N3 demonstrated a remarkably high CO Faradaic efficiency (FECO) of 99.7% and a turnover frequency (TOF) of 83984.2 h-1 at 500 mA cm-2 under -1.15 VRHE, much better than the conventionalNi-N4 . XAS analyses of Ni6@Ni-N3 before and after long-term CO2RR testing confirmed the excellent stability of its coordinative environment. This work highlights a generalizable approach for stabilizing unsaturated single-atom catalysts, paving the way for their application in high-performance CO2RR.

Discovery of highly active kynureninases for cancer immunotherapy through protein language model.

Tailor-made enzymes empower a wide range of versatile applications, although searching for the desirable enzymes often requires high throughput screening and thus poses significant challenges. In this study, we employed homology searches and protein language models to discover and prioritize enzymes by their kinetic parameters. We aimed to discover kynureninases as a potentially versatile therapeutic enzyme, which hydrolyses L-kynurenine, a potent immunosuppressive metabolite, to overcome the immunosuppressive tumor microenvironment in anticancer therapy. Subsequently, we experimentally validated the efficacy of four top-ranked kynureninases under in vitro and in vivo conditions. Our findings revealed a catalytically most active one with a nearly twofold increase in turnover number over the prior best and a 3.4-fold reduction in tumor weight in mouse model comparisons. Consequently, our approach holds promise for the targeted quantitative enzyme discovery and selection suitable for specific applications with higher accuracy, significantly broadening the scope of enzyme utilization. A web-executable version of our workflow is available at seekrank.steineggerlab.com and our code is available as free open-source software at github.com/steineggerlab/SeekRank.

Generating Strong Metal-Support Interaction and Oxygen Vacancies in Cu/MgAlOx Catalysts by CO2 Treatment for Enhanced CO2 Hydrogenation to Methanol.

Strong metal-support interactions (SMSIs) are essential for optimizing the performance of supported metal catalysts by tuning the metal-oxide interface structures. This study explores the hydrogenation of CO2 to methanol over Cu-supported catalysts, focusing on the synergistic effects of strong metal-support interaction (SMSI) and oxygen vacancies introduced by the CO2 treatment to the catalysts on the catalytic performance. Cu nanoparticles were immobilized on Mg-Al layered double oxide (LDO) supports and modified with nitrate ions to promote oxygen vacancy generation. Further calcination in a 15% CO2/85% N2 atmosphere at various temperatures not only resulted in the formation of SMSI and electronic metal-support interaction (EMSI) between Cu and MgO, but also generated abundant oxygen vacancies on MgO. The optimized 7.5%Cu/MA-C700 catalyst (Cu supported on MgAl-LDO treated in CO2 at 700 °C) exhibited significantly higher methanol production and turnover frequency compared to the air-calcined counterparts. In situ FTIR studies further revealed that oxygen vacancies led to the formation of more monodentate formate species, thus enhancing methanol production. This research provides a novel approach to engineering the catalyst interface structure and the interaction between the active metal and the support, particularly for the irreducible metal oxide support, for efficient hydrogenation of CO2 to methanol.

Screened Ni3 single-cluster catalyst supported on graphidyne for high-performance electrocatalytic NO reduction to NH3: A computational study.

Electrocatalytic NO reduction (NORR) to NH3 represents a promising approach for converting hazardous NO waste gases into high-value NH3 products under ambient conditions. However, exploring stable, low-cost, and highly efficient catalysts to enhance the NO-to-NH3 conversion process remains a significant challenge. Herein, through systematic computational studies based on density functional theory (DFT), we rationally designed transition metal triatomic cluster supported on graphdiyne (TM3/GDY) as potential single-cluster catalysts for high-performance NORR. The results indicated that the GDY support is incredibly effective at immobilizing these triatomic metal clusters, preventing metal aggregation and dissolution. Furthermore, the TM3/GDY systems exhibit tunable reactivity for NO activation due to the synergistic effect of triple-metal sites. Among all examined candidates, Ni3/GDY demonstrates the highest NORR catalytic performance with a record low limiting potential of -0.05V. Notably, NO adsorption strength was identified as an effective descriptor to rationalize the NORR activity trend, which is highly dependent on the amount of the carrying charges on the anchored TM3 clusters. Additionally, the hydrogenation steps during NORR are kinetically feasible on Ni3/GDY with a small kinetic barrier of 0.34V for the rate-determining step, corresponding to an outstanding turnover frequency (3.03×10-25)s-1 per site at 300K for NH3 generation, implying an ultra-fast reaction rate. Our work not only identified promising NORR catalysts but also provided valuable insights for rationally designing atomically precise novel catalysts for the resource utilization of small molecules.

Facile access to chiral anti-1,2-diol derivatives via Ir-catalyzed asymmetric hydrogenation of α-alkoxy-β-ketoesters.

The iridium-catalyzed asymmetric hydrogenation of α-alkoxy-β-ketoesters via dynamic kinetic resolution has been achieved with high efficiency and enantioselectivity. This strategy allows for the synthesis of differentiated anti-1,2-diol derivatives in high yields, exhibiting excellent enantio- and diastereoselectivity (up to 99% yield, 99% ee, and 99 : 1 dr). Additionally, high turnover number (TON) experiments (up to 1000 TON) and gram-scale synthesis of a key fragment of the potential drug Tesaglitazar were successfully performed, highlighting the protocol's potential for broader applications.

Enhancing activity and selectivity of palladium catalysts in ketone α-arylation by tailoring the imine chelate of pyridinium amidate (PYA) ligands.

Even though α-arylation of ketones is attractive for direct C-H functionalization of organic substrates, the method largely relies on phosphine-ligated palladium complexes. Only recently, efforts have focused on developing nitrogen-based ligands as a more sustainable alternative to phosphines, with pyridine-functionalized pyridinium amidate (pyr-PYA) N,N'-bidentate ligands displaying good selectivity and activity. Here, we report on a second generation set of catalyst precursors that feature a 5-membered N-heterocycle instead of a pyridine as chelating unit of the PYA ligand to provide less steric congestion for the rate-limiting transmetalation of the enolate. To this end, new heterocycle-functionalized PYA palladium(ii) complexes containing an oxazole (5b), N-phenyl-triazole (5c), N-methyl pyrazole (5d), N-phenyl-pyrazole, (5e), N-xylyl-pyrazole (5f), and N-isopropyl-pyrazole (5g) were synthesized compared to the parent pyr-PYA complex 5a. Less packing of the palladium coordination sphere was evidenced from solid state X-ray diffraction analysis. While the catalytic activity of the oxazole system was lower, all other complexes showed higher activity. In particular, complex 5g comprised of an electron-donating and sterically demanding iPr-pyrazole chelating PYA ligand is remarkably stable towards air and moisture and shows outstanding catalytic activity with complete selectivity (>99% yield) and turnover frequencies up to 1200 h-1, surpassing that of parent 5a by one order of magnitude and rivalling the most active phosphine-based palladium systems. Kinetic studies demonstrate a first order rate-dependence on palladium and the substrate. Some deviation of linearity together with poisoning experiments suggest a mixed homogeneous/heterogeneous pathway, though the reproducible kinetics of in situ catalyst recycling experiments strongly point to a molecularly defined active species, demonstrating the high potential of PYA-based ligands.

High‐Efficiency Hydrogen Production From Hydrazine Borane Using Cu/MIL‐53(Al) Nanocatalysts: Synthesis, Characterization, and Performance Evaluation Nanocatalysts Supported on MIL‐53(Al)

AbstractThis work highlights the novelty of investigating hydrogen production from hydrazine borane (HB) using copper (Cu). This first‐row transition metal is abundant yet underexplored as a catalyst compared to precious metals. We focus on The synthesis of Cu nanoparticles supported on MIL‐53(Al) (Cu/MIL‐53(Al)) through an impregnation‐reduction method and evaluate their performance in HB hydrolysis. Advanced characterization techniques, including X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), and TEM‐energy‐dispersive X‐ray spectroscopy (TEM‐EDX), reveal an average Cu nanoparticle size of 3.94 ± 0.32 nm. Notably, the turnover frequency (TOF) for hydrogen production with Cu/MIL‐53(Al) at 298 K was 966 h⁻¹ (16.1 min⁻¹), representing the highest TOF reported for Cu‐based systems in HB hydrolysis. Furthermore, we calculated the activation energy (Ea#), activation enthalpy (ΔH#), and activation entropy (ΔS#) for the Cu/MIL‐53(Al) catalyst as 83.77 kJ mol⁻¹, 81.15 kJ mol⁻¹, and 48.56 J mol⁻¹ K⁻¹, respectively, using the Arrhenius and Eyring‐Polanyi equations. These findings underscore the potential of Cu/MIL‐53(Al) as an efficient and cost‐effective catalyst for hydrogen production, significantly advancing sustainable hydrogen energy technologies.

Double reactive oxygen species system photoinduced by Cu8 NCs: synergistic catalysis of phenylacetylene self-coupling reaction.

Atomically precise nanoclusters (NCs) can serve as an excellent platform for a comprehensive understanding of structure-property relationships. Herein, three structurally similar Cu8 NCs (Cu8-1, Cu8-2 and Cu8-3) have been prepared for the photocatalytic phenylacetylene self-coupling reaction. It was found that Cu8-1 NC achieved the highest turnover number (TON) of 524.4, significantly higher than those of most reported catalysts. Herein, we propose a reasonable two-channel ROS participation mechanism by free radical scavenging and electron paramagnetic resonance (EPR) trapping experiments. This study provides a feasible strategy for exploring the photoinduced oxidative coupling of phenylacetylene, and provides a way for designing photocatalysts.

Nickel(II)-hydrazineylpyridine catalyzed regioselective synthesis of α-benzyl substituted β-hydroxy ketones via a Fenton free radical reaction.

Ni(II)-hydrazineylpyridine (Ni(II)-PyH)-catalyzed regioselective synthesis of α-benzyl substituted β-hydroxy ketones from α,β-unsaturated ketones and alcohols is reported via a Fenton free-radical reaction. This protocol enables facile access to desired products in good to excellent yields in 12 h using toluene solvent at room temperature to 100 °C. The structural analysis of the products was confirmed by 1H, 13C-NMR, GC-MS, and HRMS data. Hydrogen peroxide used in the reaction facilitates Ni-catalyst oxidation state variations by a disproportionate reaction, which makes the catalyst recyclable up to 4 catalytic cycles without loss of activity. The method has high functional group tolerance with both aliphatic and aromatic ketones and alcohols. The catalyst structure was fully characterized using IR, UV, EPR and XPS analyses. The thermal stability of the catalyst was up to 290 °C, which was confirmed via a TGA study. The green metrics of the reaction showed 90%atom economy with a turnover frequency of 165.