Electrochemical Epoxidation Catalyzed by Manganese Salen Complex and Carbonate with Boron-Doped Diamond Electrode
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2023-02-14 |
| Journal | Molecules |
| Authors | Pijush Kanti Roy, Keisuke Amanai, Ryosuke Shimizu, Masahito Kodera, Takuya Kurahashi |
| Institutions | Doshisha University, University of Nagasaki |
| Citations | 7 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Electrochemical Epoxidation Using BDD Electrodes
Section titled âTechnical Documentation & Analysis: Electrochemical Epoxidation Using BDD ElectrodesâExecutive Summary
Section titled âExecutive SummaryâThis research validates the critical role of Boron-Doped Diamond (BDD) electrodes in highly selective electro-organic synthesis. The key findings directly support 6CCVDâs expertise in providing high-performance BDD materials for advanced electrochemical applications.
- BDD Superiority Confirmed: BDD was proven to be the optimal anode material for electrochemical epoxidation, achieving an 18.5% epoxide yield for trans-$\beta$-methylstyrene, significantly outperforming traditional electrodes like Platinum, Glassy Carbon, and Graphite (< 2.2%).
- Selective Oxidant Generation: The high overpotential of BDD for water oxidation is essential, enabling the selective in situ generation of percarbonate ions ($\text{CO}_4^{2-}$) from sodium carbonate electrolyte, which acts as the clean oxygen source.
- Elimination of Side Products: By using carbonate/BDD instead of chloride/Pt systems, the method successfully avoids unwanted allylic halogenation (chlorination), leading to cleaner product streams.
- Catalyst Optimization: The study confirmed that Jacobsenâs catalyst $\text{Mn}(\text{L}1\text{-}t\text{-}\text{Bu})$ provides the highest yield (74.1% in conventional $\text{NaOCl}$ system; 18.5% electrochemically), highlighting the synergy between the catalyst and the BDD-generated oxidant.
- Optimal Operating Parameters: The reaction requires precise control, with optimal conditions identified as $2.50 \text{ V}$ vs. $\text{Ag}/\text{AgCl}$ and a low bath temperature of $-5 \text{ °C}$.
- Application Potential: This work establishes BDD as a promising tool for the clean, efficient, and scalable electrochemical synthesis of epoxides, essential precursors for epoxy resins and pharmaceuticals.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the electrochemical epoxidation of trans-$\beta$-methylstyrene catalyzed by $\text{Mn}^{\text{III}}(\text{L}1\text{-}t\text{-}\text{Bu})$ using various anodes.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Anode Material | Boron-Doped Diamond (BDD) | N/A | Highest yield achieved |
| BDD Epoxide Yield | 18.5 | % | trans-$\beta$-methylstyrene (30 min) |
| Platinum Epoxide Yield | 1.8 | % | trans-$\beta$-methylstyrene (30 min) |
| Glassy Carbon Yield | 2.2 | % | trans-$\beta$-methylstyrene (30 min) |
| Graphite Yield | 1.8 | % | trans-$\beta$-methylstyrene (30 min) |
| Anode Surface Area | 3 | $\text{cm}^2$ | BDD plate dimension used |
| Optimal Applied Voltage | 2.50 | V | vs. $\text{Ag}/\text{AgCl}$ reference electrode |
| Optimal Bath Temperature | -5 | °C | Required for maximizing yield |
| Electrolyte | $1 \text{ M } \text{Na}_2\text{CO}_3$ | M | Aqueous phase concentration |
| Solvent System | $\text{CH}_2\text{Cl}_2 / 1 \text{ M } \text{Na}_2\text{CO}_3$ aq. (1:9) | N/A | Optimal biphasic system |
| Cyclooctene Yield (90 min) | 6.8 | % | Electrochemical generation ($\text{Mn}(\text{L}1\text{-}\text{Ome})$) |
| BDD Overpotential Advantage | Higher | N/A | Overpotential for water oxidation compared to Pt/Graphite |
Key Methodologies
Section titled âKey MethodologiesâThe electrochemical epoxidation relied on the unique properties of the BDD anode to facilitate the desired reaction pathway in a biphasic system.
- Electrode Configuration: An undivided $5 \text{ mL}$ cell was used, featuring a BDD plate ($3 \text{ cm}^2$) as the working anode and a Platinum (Pt) plate as the cathode.
- Biphasic Solvent System: The reaction was conducted in a water-dichloromethane biphasic system (1:9 ratio, organic:aqueous). This separation is critical: the BDD anode contacts the aqueous phase ($1 \text{ M } \text{Na}_2\text{CO}_3$) for oxidant generation, while the catalyst and alkene substrate reside in the organic phase ($\text{CH}_2\text{Cl}_2$).
- Oxidant Generation: Electrolysis of the aqueous $1 \text{ M } \text{Na}_2\text{CO}_3$ solution at the BDD anode ($2.50 \text{ V}$ vs. $\text{Ag}/\text{AgCl}$) generates percarbonate ions ($\text{CO}_4^{2-}$), which migrate to the organic phase to drive the epoxidation catalyzed by the Manganese Salen complex.
- Temperature Control: Low temperatures (optimal $-5 \text{ °C}$) were maintained using an alcohol bath and cooling system to suppress unwanted side reactions and maximize epoxide yield.
- Catalyst Loading: Reactions typically used a 5:1 substrate-to-catalyst ratio (0.25 mmol substrate, 0.05 mmol catalyst).
- BDD Mechanism Advantage: The high overpotential of BDD prevents the competing oxidation of water to $\text{O}_2$, ensuring that the electrical energy is efficiently channeled into the desired percarbonate generation pathway.
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThis research highlights the necessity of high-quality, specialized Boron-Doped Diamond (BDD) electrodes. 6CCVD is uniquely positioned to supply and customize the required materials for replicating, scaling, and extending this electrocatalytic synthesis.
| Applicable Materials | 6CCVD Specification | Relevance to Epoxidation Research |
|---|---|---|
| Boron-Doped Diamond (BDD) | High-Purity MPCVD BDD Wafers/Plates | Essential for achieving the high overpotential required to selectively generate percarbonate ($\text{CO}_4^{2-}$) and avoid $\text{O}_2$ evolution, directly leading to the 18.5% yield advantage. |
| Custom Dimensions | Plates/Wafers up to 125 mm | The paper used a $3 \text{ cm}^2$ BDD plate. 6CCVD provides custom-sized BDD electrodes, precision laser-cut to any required geometry for R&D or pilot-scale reactors. |
| Doping Control | Controlled Boron Concentration | We offer BDD with tailored boron doping levels. Controlling the doping density is critical for optimizing conductivity and maximizing the electrochemical efficiency for specific reactions like carbonate oxidation. |
| Surface Finish | Polishing to Ra < 5 nm (PCD) | Highly polished BDD surfaces ensure maximum stability and reproducibility of the electrochemical interface, minimizing fouling and maximizing catalyst lifetime. |
| Metalization Potential | Internal Metalization (Au, Pt, Ti, W) | For future integration into microfluidic or flow reactors, 6CCVD can deposit custom metal contacts (e.g., Ti/Pt/Au) onto the BDD surface, enabling complex electrode designs and arrays. |
Customization Potential
Section titled âCustomization PotentialâThe successful replication and scale-up of this electrochemical epoxidation process depend on reliable BDD supply. 6CCVD offers:
- Custom Electrode Fabrication: We can supply BDD plates or wafers in dimensions far exceeding the $3 \text{ cm}^2$ used in the study, up to $125 \text{ mm}$ diameter, suitable for scaling up the reaction volume.
- Integrated Systems: Our capabilities include patterning and metalizing BDD surfaces, allowing researchers to transition from simple plate electrodes to sophisticated microelectrode arrays for enhanced mass transport control in biphasic systems.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house team of PhD material scientists and electrochemists specializes in optimizing diamond properties for demanding applications. We offer comprehensive engineering support for:
- Material Selection: Assistance in selecting the optimal BDD doping level and thickness (SCD or PCD) for similar electrochemical epoxidation projects or other electro-organic synthesis applications requiring high overpotential anodes.
- Process Optimization: Consultation on integrating BDD into flow cells and optimizing electrode geometry to improve current density and yield stability over prolonged reaction times.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Epoxides are essential precursors for epoxy resins and other chemical products. In this study, we investigated whether electrochemically oxidizing carbonate ions could produce percarbonate to promote an epoxidation reaction in the presence of appropriate metal catalysts, although Tanaka and co-workers had already completed a separate study in which the electrochemical oxidation of chloride ions was used to produce hypochlorite ions for electrochemical epoxidation. We found that epoxides could be obtained from styrene derivatives in the presence of metal complexes, including manganese(III) and oxidovanadium(IV) porphyrin complexes and manganese salen complexes, using a boron-doped diamond as the anode. After considering various complexes as potential catalysts, we found that manganese salen complexes showed better performance in terms of epoxide yield. Furthermore, the substituent effect of the manganese salen complex was also investigated, and it was found that the highest epoxide yields were obtained when Jacobsenâs catalyst was used. Although there is still room for improving the yields, this study has shown that the in situ electrochemical generation of percarbonate ions is a promising method for the electrochemical epoxidation of alkenes.
Tech Support
Section titled âTech SupportâOriginal Source
Section titled âOriginal SourceâReferences
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