Name: [(dpephos)(bcp)cu]pf6: a general and broadly applicable copper-based photoredox catalyst
Uploaded: 2019-05-21T14:45:00.000+00:00
Duration: 9 min 12 s
Description: Watch this Scientific Journal Video about [DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst at JoVE.com

This work was supported by the Universit&#233; libre de Bruxelles (ULB), the F&#233;d&#233;ration Wallonie-Bruxelles (ARC Consolidator 2014-2019), Innoviris (project PhotoCop), and the COST action CM1202. H.B. acknowledges the Fonds pour la formation &#224; la Recherche dans l&#8217;Industrie et dans l&#8217;Agriculture (F.R.I.A.) for graduate fellowship. C.T. acknowledges the Fonds de la Recherche Scientifique (FNRS) for research fellowship.

1. Synthesis of [(DPEPhos)(bcp)Cu]PF6
<ol>
	<li>Add 3.73 g (10.00 mmol) of tetrakisacetonitrile copper(I) hexafluorophosphate and 5.39 g (10.00 mmol) of DPEPhos to a 2 L round bottom flask equipped with a magnetic stir bar.</li>
	<li>Fit the round bottom flask with a three neck vacuum adapter connected to a vacuum line and an argon line.</li>
	<li>Evacuate the flask under vacuum and backfill with argon three times. Replace the three neck vacuum adapter by a rubber septum. 
	NOTE: The reaction can be performed under air with slightly reduced efficiency (see discussion section for details).</li>
	<li>Add 800 mL of dry dichloromethane. 
	NOTE: Dichloromethane is freshly distilled from CaH2. The reaction can also be performed in regular dichloromethane (99.8%) with similar efficiency (see discussion section for details).</li>
	<li>Stir the reaction mixture for 2 h in the dark (reaction flask covered with aluminum foil) at room temperature (23-25 &#186;C)&#160;under an argon atmosphere.</li>
	<li>Add 3.60 g (10.00 mmol) of bcp to a 500 mL round bottom flask equipped with a magnetic stir bar.</li>
	<li>Fit the round bottom flask with a three neck vacuum adapter connected to a vacuum line and an argon line.</li>
	<li>Evacuate the flask under vacuum and backfill with argon three times. Replace the three neck vacuum adapter by a rubber septum.</li>
	<li>Add 200 mL of dry dichloromethane and gently stir the suspension until complete dissolution of the bcp.</li>
	<li>Add the solution of bcp in dichloromethane to the reaction mixture using a cannula.</li>
	<li>Stir for an additional hour in the dark (reaction flask covered with aluminum foil) at room temperature (23-25&#160;&#186;C) under an argon atmosphere.</li>
	<li>Filter the mixture through a pad of Celite, wash with ca. 100 mL of dichloromethane and concentrate the filtrate to ca. 50-100 mL under reduced pressure.</li>
	<li>Add the concentrate dropwise to 1 L of diethyl ether using an addition funnel and with vigorous stirring to induce precipitation of the desired complex.</li>
	<li>Collect the precipitate by filtration through a fritted glass (pore size 3) and wash the precipitate with ca. 100 mL of diethyl ether.</li>
	<li>Dry the bright yellow precipitate under vacuum at room temperature (23-25&#160;&#186;C) for 5 h to recover 10.1 g (91% yield) of the copper complex. 
	NOTE: A 75% yield was obtained when the reaction was performed under air using distilled dichloromethane; a 89% yield was obtained when the reaction was performed under argon using regular dichloromethane; when performing the reaction under air with regular dichloromethane, the reaction was found to be less efficient and led to much lower purity (ca 70%, as estimated by 1H NMR with an internal standard).</li>
	<li>Characterize [(DPEPhos)(bcp)Cu]PF6 as previously reported31.</li>
</ol>
2. Direct arylation of N-methylpyrrole with 4-iodobenzonitrile
<ol>
	<li>Add 55 mg (0.05 mmol) of [(DPEPhos)(bcp)Cu]PF6, 59 mg (0.25 mmol) of dicyclohexylisobutylamine (Cy2NiBu), 138 mg (1.0 mmol) of K2CO3 and 114 mg (0.50 mmol) of 4-iodobenzonitrile to an oven-dried 10 mL vial.</li>
	<li>Add a magnetic stir bar, seal the vial with a rubber septum, evacuate the vial under vacuum and backfill with argon three times.</li>
	<li>Add 5 mL of acetonitrile and 890 &#956;L (10.00 mmol) of N-methylpyrrole. Replace the rubber septum by a screw cap. 
	NOTE: Acetonitrile is freshly distilled from CaH2 and degassed using freeze-pump-thaw cycles prior to use to ensure high yields and reproducibility.</li>
	<li>Stir the reaction mixture for 3 days at room temperature (23-25&#160;&#186;C) in a photoreactor under 420 nm wavelength irradiation. 
	NOTE: As an alternative to the use of a photoreactor, the reaction can also be conveniently performed using blue LEDs strips or a photochemistry device with a blue LED lamp (440 nm, 34 W). These experimental setups are shown in Figure 3 (see Representative results) and a discussion on their respective results is provided in the &#34;Discussion&#34;&#160;section.</li>
	<li>Filter the reaction mixture through a pad of Celite, wash with ca. 5 mL of diethyl ether and concentrate the filtrate under reduced pressure.</li>
	<li>Purify the crude residue by flash column chromatography over silica gel (eluent system petroleum ether/EtOAc: 90/10).</li>
	<li>Dry the pure compound under vacuum at room temperature (23-25&#160;&#186;C) for 3 h to recover 65 mg (72% yield) of the desired C2-arylated pyrrole. 
	NOTE: The use of blue LEDs strips afforded a 76% yield (69 mg) while the use of a photochemistry device with a blue LED lamp (440 nm, 34 W) afforded an 86% yield (78 mg).</li>
	<li>Characterize the pure compound as previously reported32.</li>
</ol>
3. Cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide to luotonin A
<ol>
	<li>Add 37 mg (0.09 mmol) of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide, 9 mg (9.0 &#956;mol) of [(DPEPhos)(bcp)Cu]PF6, 11 mg (0.04 mmol) of Cy2NiBu and 25 mg (0.18 mmol) of K2CO3 to an oven-dried 7 mL vial equipped with a magnetic stir bar.</li>
	<li>Seal the vial with a rubber septum, evacuate the vial under vacuum and backfill with argon three times.</li>
	<li>Add 2 mL of acetonitrile. Replace the rubber septum by a screw cap. 
	NOTE: Acetonitrile is distilled from CaH2 and degassed using freeze-pump-thaw cycles prior to use to ensure high yields and reproducibility.</li>
	<li>Stir the reaction mixture for 5 days at&#160;room temperature (23-25&#160;&#186;C) in a photoreactor under 420 nm wavelength irradiation.</li>
	<li>Filter the reaction mixture through a pad of Celite, wash with ca. 2 mL of dichloromethane and concentrate the filtrate under reduced pressure.</li>
	<li>Purify the crude residue by flash column chromatography over silica gel (eluent system: petroleum ether/EtOAc 60:40).</li>
	<li>Dry the pure compound under vacuum at room temperature (23-25&#160;&#186;C) for 3 h to recover 20 mg (79% yield) of the desired luotonin A.</li>
	<li>Characterize the desired luotonin A as previously reported29.</li>
</ol>

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The authors have nothing to disclose.

Synthesis of [(DPEPhos)(bcp)Cu]PF6 
The synthesis of [(DPEPhos)(bcp)Cu]PF6 is typically performed using dry dichloromethane (distilled prior to use) and under argon to ensure the highest yield, purity and good reproducibility. As mentioned in the protocol, the synthesis of [(DPEPhos)(bcp)Cu]PF6 can be performed with regular dichloromethane (99.8%) and/or under air with variable efficiencies. Indeed, while the use of regular dichloromethane under argon afforded the sa...

Radical transformations have been known for decades to provide remarkably efficient pathways in synthetic chemistry which are often complementary to transformations based on cationic, anionic or pericyclic processes1. While particularly promising for various types of transformations, radical-based chemistry has however long been underexploited, mainly because of the need for highly toxic reagents which considerably limits its attractiveness. Moreover, radical processes have long been considered as transformations associated with poor levels of control in terms of regio- and/or stereoselectivity, or leading to extensive dimerization and/or polymerization issues.
Alternative strategies have recently been developed in order to facilitate the generation and better control the reactivity of radical species. Among them, photoredox catalysis has become one of the most powerful methods as it allows the convenient generation of radical species using a light-responsive compound, namely the photoredox catalyst, and visible light irradiation2,3. Visible light itself is indeed able to promote population of the excited state of the photoredox catalyst which becomes, consequently, both a stronger reductant and oxidant than in its corresponding ground state. These enhanced redox properties make single-electron transfer processes, not feasible in the ground state, possible under mild conditions from the excited state. Over the past decade, visible light photoredox catalysis has become an attractive and powerful technique in organic synthesis and has allowed the development of numerous remarkably efficient and selective transformations based on radical intermediates generated under sustainable, mild and user-friendly conditions.
While most photoredox processes reported to date are dominated by the use of iridium- and ruthenium-based photoredox catalysts, as well as by some organic dyes such as pyrylium and acridinium derivatives4, cheaper alternatives are still highly demanded for the development of complementary processes of interest for industrial applications. In this regard, the use of copper-based photoredox catalysts appears particularly appealing as they are not only cheaper but also provide opportunities to activate a broader and/or different range of substrates, which therefore opens new perspectives in photoredox catalysis5,6,7,8. Despite some promising early works reported by the Kutal9, Mitani10&#160;and Sauvage11&#160;groups, photoactivatable copper complexes have, however, only been scarcely used in photoredox catalysis, most probably because of their short-lived excited states compared to their ruthenium- and iridium-based congeners. More recently, recent remarkable contributions by Peters and Fu12,13,14,15, Reiser16,17,18,19,20&#160;and other groups21,22,23,24,25&#160;have clearly brought attention back to copper-based photoredox catalysts and demonstrated their unique potential.
As part of our recent interest in copper-catalyzed radical processes26,27, we recently reported a general and broadly applicable copper-based photoredox catalyst, [(DPEPhos)(bcp)Cu]PF6 (DPEPhos: bis[(2-diphenylphosphino)phenyl] ether; bcp: bathocuproine), which turned out to be particularly efficient for the activation of organic halides under visible light irradiation (Figure 1A)28,29,30. Upon irradiation with visible light and in the presence of an amine as sacrificial reductant, a wide range of unactivated aryl and alkyl halides was shown to be easily activated by catalytic amounts of [(DPEPhos)(bcp)Cu]PF6 and therefore to participate in various radical transformations including reductions, cyclizations and direct arylation of several electron-rich (hetero)arenes. Furthermore, [(DPEPhos)(bcp)Cu]PF6 has also proven successful at promoting photoinduced radical domino cyclizations of ynamides and cyanamides, providing an efficient and straightforward access to complex tri-, tetra- and pentacyclic nitrogen heterocycles at the core structures of various natural products. This strategy permitted the efficient synthesis of rosettacin, luotonin A, and deoxyvasicinone, natural products that exhibit anticancer, antimicrobial, anti-inflammatory and antidepressant activities. These transformations are illustrated in Figure 1C. From a mechanistic standpoint, the photoinduced activation of organic halides with [(DPEPhos)(bcp)Cu]PF6 proceeds through a rare Cu(I)/Cu(I)*/Cu(0) catalytic cycle, which has been confirmed by extensive mechanistic and photophysical studies. In particular, excitation of the ground state [(DPEPhos)(bcp)Cu]PF6 [Cu(I)] upon irradiation by visible light leads to the formation of the corresponding excited complex [(DPEPhos)(bcp)Cu]PF6* [Cu(I)*] which is then reduced by the sacrificial amine to generate the corresponding [(DPEPhos)(bcp)Cu]PF6 [Cu(0)] species. This Cu(0) intermediate is reductive&#160;enough to reduce the carbon&#8211;halogen bond of various organic halides to generate the corresponding radicals, which can then participate in the aforementioned transformations, together with regeneration of the starting catalyst (Figure 1B).
In the following section, we first describe the protocol to synthesize the photoactivatable [(DPEPhos)(bcp)Cu]PF6 (whose NMR and spectroscopic characterizations are presented in the representative results section). The synthesis is straightforward and particularly convenient, and simply requires addition of 1 equivalent of DPEPhos and 1 equivalent of bcp to a solution of tetrakisacetonitrile copper(I) hexafluorophosphate in dichloromethane. The desired [(DPEPhos)(bcp)Cu]PF6 is then isolated by precipitation from diethyl ether and can be easily obtained on a multigram scale (Figure 2A). Importantly, the isolated copper complex is not particularly sensitive to oxygen and moisture and can therefore be conveniently handled with no specific precautions other than being stored away from light.
Secondly, we describe the protocols to activate organic halides using [(DPEPhos)(bcp)Cu]PF6 under visible light irradiation by focusing on two different transformations. The first reaction is the direct arylation of N-methylpyrrole with 4-iodobenzonitrile using catalytic amounts of [(DPEPhos)(bcp)Cu]PF6 as photoredox catalyst, dicyclohexylisobutylamine as the sacrificial reductant and potassium carbonate as the base under irradiation at 420 nm (Figure 2B). The second reaction is the radical cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide, using the same catalyst and sacrificial reductant, whose cyclization directly leads to luotonin A, a natural product displaying interesting anticancer activities (Figure 2C). Detailed protocols are provided for both transformations.

<table><tbody><tr><td>&lt;strong&gt;Material&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Bathocuproine (bcp)</td><td>Acros</td><td>161340010</td><td></td></tr><tr><td>Acetonitrile, 99.9+</td><td>Acros</td><td>326811000</td><td></td></tr><tr><td>Celite 545</td><td>Acros</td><td>349670025</td><td></td></tr><tr><td>Bis[(2-diphenylphosphino)phenyl] ether (DPEphos)</td><td>Acros</td><td>383370050</td><td></td></tr><tr><td>Calcium hydride</td><td>Acros</td><td>C/1620/48</td><td></td></tr><tr><td>Dichloromethane, 99.8%</td><td>Fisher Chemical</td><td>D/1852/25</td><td></td></tr><tr><td>Dietyl ether, &gt;= 99%</td><td>Fisher Chemical</td><td>D/2400/MS21</td><td></td></tr><tr><td>Ethyl acetate</td><td>Fisher Chemical</td><td>E/0900/25</td><td></td></tr><tr><td>N-Methylpyrrole, 99%</td><td>Sigma Aldrich</td><td>M78801</td><td></td></tr><tr><td>4-Iodobenzonitrile, 98%</td><td>Combi-Blocks</td><td>OR-3151</td><td></td></tr><tr><td>Petroleum ether (40-60 &amp;deg;)</td><td>Fisher Chemical</td><td>P/1760/25</td><td></td></tr><tr><td>Potassium carbonate, anhydrous</td><td>Fisher Chemical</td><td>P/4120/60</td><td></td></tr><tr><td>Tetrakisacetonitrile copper(I) hexafluorophosphate, 97%</td><td>Sigma Aldrich</td><td>346276</td><td></td></tr><tr><td>&lt;strong&gt;Equipment&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>&lt;sup&gt;1&lt;/sup&gt;H and &lt;sup&gt;13&lt;/sup&gt;C NMR spectrometer</td><td>Bruker</td><td>Avance 300 Spectrometer</td><td></td></tr><tr><td>&lt;sup&gt;1&lt;/sup&gt;H and &lt;sup&gt;13&lt;/sup&gt;C NMR spectrometer</td><td>Varian</td><td>VNMRS 400 Spectrometer</td><td></td></tr><tr><td>420 nm light tubes</td><td>Luzchem</td><td>LZC-420</td><td></td></tr><tr><td>Blue LEDs lamp</td><td>Kessil</td><td>H150-Blue</td><td></td></tr><tr><td>Blue LEDs strips</td><td>Eglo</td><td>92065</td><td></td></tr><tr><td>Photochemistry Device PhotoRedOx Box</td><td>Hepatochem</td><td>HCK1006-01-016</td><td></td></tr><tr><td>Photoreactor</td><td>Luzchem</td><td>CCP-4V</td><td></td></tr><tr><td>Spectrofluorimeter</td><td>Shimadzu</td><td>RF-5301PC</td><td></td></tr><tr><td>UV/Vis spectrometer</td><td>Perkin Elmer</td><td>Lambda 40</td><td></td></tr></tbody></table>

[(dpephos)(bcp)cu]pf6: a general and broadly applicable copper-based photoredox catalyst

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the activation of a broad variety of organic halides, including unactivated ones. These can then participate in various radical transformations such as reduction and cyclization reactions, as well as in the direct arylation of several (hetero)arenes. These transformations provide a straightforward access to a range of small molecules of interest in synthetic chemistry, as well as to biologically active natural products. Altogether, [(DPEPhos)(bcp)Cu]PF6 acts as a convenient photoredox catalyst which appears to be an attractive, cheap and complementary alternative to the state-of-the-art iridium- and ruthenium-based photoredox catalysts. Here, we report a detailed protocol for the synthesis of [(DPEPhos)(bcp)Cu]PF6, as well as NMR and spectroscopic characterizations, and we illustrate its use in synthetic chemistry for the direct arylation of (hetero)arenes and radical cyclization of organic halides. In particular, the direct arylation of N-methylpyrrole with 4-iodobenzonitrile to afford&#160;4-(1-methyl-1H-pyrrol-2-yl)benzonitrile and the radical cyclization of N-benzoyl-N-[(2-iodoquinolin-3-yl)methyl]cyanamide to afford natural product luotonin A are detailed. The scope and limitations of this copper-based photoredox catalyst are also briefly discussed.

Synthesis of [(DPEPhos)(bcp)Cu]PF6 
As shown by the protocol described in the above section, the synthesis of [(DPEPhos)(bcp)Cu]PF6 is particularly convenient and can be easily performed on a multigram scale. The 1H and 13C NMR spectra indicate formation of the pure complex (Figure 4A,B). The spectroscopic data correspond to those previously reported31.
...

Watch this Scientific Journal Video about [DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst at JoVE.com

[DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Detailed and general protocols are presented for the synthesis of [(DPEPhos)(bcp)Cu]PF6, a general copper-based photoredox catalyst, and for its use in synthetic chemistry for the direct arylation of C-H bonds in (hetero)arenes and radical cyclization of organic halides.

[(DPEPhos)(bcp)Cu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Our group recently reported the use of [(DPEPhos)(bcp)Cu]PF6 as a general copper-based photoredox catalyst which proved efficient to promote the ...

-dpephos-bcp-cupf6-general-broadly-applicable-copper-based-photoredox

Universidad de Cartagena UDEC

Research

JoVE Journal

Chemistry

9.1K Views.  Université libre de Bruxelles (ULB). Detailed and general protocols are presented for the synthesis of [(DPEPhos)(bcp)Cu]PF6, a general copper-based photoredox catalyst, and for its use in synthetic chemistry for the direct arylation of C-H bonds in (hetero)arenes and radical cyclization of organic halides.

Video: [DPEPhosbcpCu]PF6: A General and Broadly Applicable Copper-Based Photoredox Catalyst

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium Under Mild Reaction Conditions

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family of easy accessible, very cheap, and air stable, but highly active and universally applicable C-C cross-coupling catalysts with an excellent functional group tolerance. Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1), the least stable complex within this series towards protons; e.g. in the form of water, allows an eased nanoparticle formation and hence, proved to be the most active Heck catalyst within this series at 100 &#176;C and is a very rare example of an effective and versatile catalyst system that efficiently operates under mild reaction conditions. Rapid and complete catalyst degradation under work-up conditions into phosphonates, piperidinium salts and other, palladium-containing decomposition products assure an easy separation of the coupling products from catalyst and ligands. The facile, cheap, and rapid synthesis of 1,1',1"-(phosphinetriyl)tripiperidine and 1 respectively, the simple and convenient use as well as its excellent catalytic performance in the Heck reaction at 100 &#176;C make 1 to one of the most attractive and greenest Heck catalysts available.
We provide here the visualized protocols for the ligand and catalyst syntheses as well as the reaction protocol for Heck reactions performed at 10 mmol scale at 100 &#176;C and show that this catalyst is suitable for its use in organic syntheses.

Mizoroki-Heck Cross-coupling Reactions Catalyzed by Dichloro{bis[1,1',1''-phosphinetriyltripiperidine]}palladium Under Mild Reaction Conditions

Dichloro{bis[1,1',1''-(phosphinetriyl)tripiperidine]}palladium [(P(NC5H10)3)2Pd(Cl)2] (1) is an easy accessible, cheap, and air stable, but highly active Heck catalyst with an excellent functional group tolerance that efficiently operates under mild reaction conditions to give the coupling products in very high yields.

Dichloro-bis(aminophosphine) complexes of palladium with the general formula of [(P{(NC5H10)3-n(C6H11)n})2Pd(Cl)2] (where n = 0-2), belong to a new family ...

HKUST-1 as a Heterogeneous Catalyst for the Synthesis of Vanillin

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately 200 different odorant compounds in addition to vanillin. The natural extraction of vanillin (from the orchid Vanilla planifolia, Vanilla tahitiensis and Vanilla pompon) represents only 1% of the worldwide production and since this process is expensive and very long, the rest of the production of vanillin is synthesized. Many biotechnological approaches can be used for the synthesis of vanillin from lignin, phenolic stilbenes, isoeugenol, eugenol, guaicol, etc., with the disadvantage of harming the environment since these processes use strong oxidizing agents and toxic solvents. Thus, eco-friendly alternatives on the production of vanillin are very desirable and thus, under current investigation. Porous coordination polymers (PCPs) are a new class of highly crystalline materials that recently have been used for catalysis. HKUST-1 (Cu3(BTC)2(H2O)3, BTC = 1,3,5-benzene-tricarboxylate) is a very well known PCP which has been extensively studied as a heterogeneous catalyst. Here, we report a synthetic strategy for the production of vanillin by the oxidation of trans-ferulic acid using HKUST-1 as a catalyst.

The conversion of trans-ferulic acid to vanillin was achieved by heterogeneous catalysis. HKUST-1 was employed in this synthesis and the essential step in the catalytic process was the generation of unsaturated metal sites. Thus, when the catalyst was activated under vacuum, full vanillin conversion (yield of 95%) was obtained.

Vanillin (4-hydoxy-3-methoxybenzaldehyde) is the main component of the extract of vanilla bean. The natural vanilla scent is a mixture of approximately ...

Synthesis and Testing of Supported Pt-Cu Solid Solution Nanoparticle Catalysts for Propane Dehydrogenation

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are demonstrated here. The catalyst forms a substitutional solid solution structure, with a small and uniform particle size around 2 nm. This is realized by careful control over the impregnation, calcination, and reduction steps during catalyst preparation and is identified by advanced in situ synchrotron techniques. The catalyst propane dehydrogenation performance continuously improves with increasing Cu:Pt atomic ratio.

A convenient method for the synthesis of 2 nm supported bimetallic nanoparticle Pt-Cu catalysts for propane dehydrogenation is reported here. In situ synchrotron X-ray techniques allow for the determination of the catalyst structure, which is typically unobtainable using laboratory instruments.

A convenient method for the synthesis of bimetallic Pt-Cu catalysts and performance tests for propane dehydrogenation and characterization are ...

Preparation of Polyoxometalate-based Photo-responsive Membranes for the Photo-activation of Manganese Oxide Catalysts

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic polymers, with the aim of photo-activating oxygen-evolving manganese oxide catalysts, which are important components in artificial photosynthesis. The cross-linking technique was applied to obtain a self-standing membrane with a high PW12O403- content. Incorporation and structure retention of PW12O403- within the polymer matrix were confirmed by FT-IR and micro-Raman spectroscopy, and optical characteristics were investigated by UV-Vis spectroscopy, which revealed successful construction of the metal-to-metal charge transfer (MMCT) unit. After deposition of MnOx oxygen evolving catalysts, photocurrent measurements under visible light irradiation verified the sequential charge transfer, Mn &#8594; MMCT unit &#8594; electrode, and&#160;the photocurrent intensity was consistent with the redox potential of the donor metal (Ce or Co). This method provides a new strategy for preparing integrated systems involving catalysts and photon-absorption parts for use with photo-functional materials.

Here, we present a protocol to prepare charge transfer chromophores based on a polyoxometalate/polymer composite membrane.

This paper presents a method to prepare charge-transfer chromophores using polyoxotungstate (PW12O403-), transition metal ions (Ce3+ or Co2+), and organic ...

A Complete Method for Evaluating the Performance of Photocatalysts for the Degradation of Antibiotics in Environmental Remediation

Various antibiotics such as tetracycline, aureomycin, amoxicillin, and levofloxacin are found in large quantities in groundwater and soil systems, potentially leading to the development of resistant and multi-drug resistant bacteria, posing a threat to humans, animals, and environmental systems. Photocatalytic technology has attracted keen interest due to its rapid and stable treatment and direct use of solar energy. However, most studies evaluating the performance of semiconductor catalysts for the photocatalytic degradation of organic pollutants in water are currently incomplete. In this paper, a complete experimental protocol is designed to comprehensively evaluate the photocatalytic performance of semiconductor catalysts. Herein, rhombic dodecahedral silver phosphate was prepared by a simple solvent phase synthesis method at room temperature and atmospheric pressure. BrSubphthalocyanine/Ag3PO4 heterojunction materials were prepared by the solvothermal method. The catalytic performance of as-prepared materials for the degradation of tetracycline was evaluated by studying different influencing factors such as catalyst dosage, temperature, pH, and anions at atmospheric pressure using a 300 W xenon lamp as a simulated solar light source and a light intensity of 350 mW/cm2. Compared with the first cycle, the constructed BrSubphthalocyanine/Ag3PO4 maintained 82.0% of the original photocatalytic activity after five photocatalytic cycles, while the pristine Ag3PO4 maintained only 28.6%. The stability of silver phosphate samples was further tested by a five-cycle experiment. This paper provides a complete process for evaluating the catalytic performance of semiconductor catalysts in the laboratory for the development of semiconductor catalysts with potential for practical applications.

Presented here is a protocol to explore a universal set of experimental procedures for comprehensive laboratory evaluation of photocatalysts in the field of environmental purification, using the example of photocatalytic removal of antibiotic organic pollutant molecules from water by phthalocyanine sensitized silver phosphate composites.

Various antibiotics such as tetracycline, aureomycin, amoxicillin, and levofloxacin are found in large quantities in groundwater and soil systems, ...

Environment

Design, Synthesis, and Photochemical Properties of Clickable Caged Compounds

Caged compounds enable the photo-mediated manipulation of the cell physiology with high spatiotemporal resolution. However, the limited structural diversity of currently available caging groups and the difficulties in synthetic modification without sacrificing their photolysis efficiencies are obstacles to expanding the repertoire of caged compounds for live cell applications. As the chemical modification of coumarin-type photo-caging groups is a promising approach for the preparation of caged compounds with diverse physical and chemical properties, we report a method for the synthesis of clickable caged compounds that can be modified easily with various functional units via the copper(I)-catalyzed Huisgen cyclization. The modular platform molecule contains a (6-bromo-7-hydroxycoumarin-4-yl)methyl (Bhc) group as a photo-caging group, which exhibits a high photolysis efficiency compared to those of the conventional 2-nitrobenzyls. General procedures for the preparation of clickable caged compounds containing amines, alcohols, and carboxylates are presented. Additional properties such as the water solubility and cell targeting ability can be readily incorporated into clickable caged compounds. Furthermore, the physical and photochemical properties, including the photolysis quantum yield, were measured and were found to be superior to those of the corresponding Bhc caged compounds. The described protocol could therefore be considered a potential solution for the lack of structural diversity in the available caged compounds.

A protocol for the synthesis and measurement of the photochemical properties of modular caged compounds with clickable moieties is presented.

Caged compounds enable the photo-mediated manipulation of the cell physiology with high spatiotemporal resolution. However, the limited structural ...

Cercosporin-Photocatalyzed [4+1]- and [4+2]-Annulations of Azoalkenes Under Mild Conditions

The interest on nitrogen-containing heterocycles has expanded rapidly in the synthetic community since they are important motifs for new drugs. Traditionally, they were synthesized through thermal cycloaddition reactions, whereas today, photocatalysis is preferred due to the mild and efficient conditions. With this focus, a new photocatalytic method for the synthesis of nitrogen-containing heterocycles is highly desired. Here, we report a protocol for the biosynthesis of cercosporin, which could function as a metal-free photocatalyst. We then illustrate cercosporin-photocatalyzed protocols for the synthesis of nitrogen-containing heterocycles 1,2,3-thiadiazoles through annulation of azoalkenes with KSCN, and synthesis of 1,4,5,6-tetrahydropyridazines [4+2] through cyclodimerization of azoalkenes under mild conditions, respectively. As a result, there is a new bridge between the microbial fermentation method and organic synthesis in a mild, cost-effective, environmentally friendly and sustainable manner.

New routes for the synthesis of nitrogen-containing heterocycles utilizing cercosporin as a metal-free photocatalyst were developed.

The interest on nitrogen-containing heterocycles has expanded rapidly in the synthetic community since they are important motifs for new drugs. ...

Self-Assembly of Hybrid Lipid Membranes Doped with Hydrophobic Organic Molecules at the Water/Air Interface

Because of their unique properties, including an ultrathin thickness (3-4 nm), ultrahigh resistivity, fluidity and self-assembly ability, lipid bilayers can be readily functionalized and have been used in various applications such as bio-sensors and bio-devices. In this study, we introduced a planar organic molecule: copper (II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc) to dope lipid membranes. The CuPc/lipid hybrid membrane forms at the water/air interface by self-assembly. In this membrane, the hydrophobic CuPc molecules are located between the hydrophobic tails of lipid molecules, forming a lipid/CuPc/lipid sandwich structure. Interestingly, an air-stable hybrid lipid bilayer can be readily formed by transferring the hybrid membrane onto a Si substrate. We report a straightforward method for incorporating nanomaterials into a lipid bilayer system, which represents a new methodology for the fabrication of biosensors and biodevices.

We report a protocol for producing a hybrid lipid membrane at the water/air interface by doping the lipid bilayer with copper (II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc) molecules. The resulting hybrid lipid membrane has a lipid/CuPc/lipid sandwich structure. This protocol can also be applied to the formation of other functional nanomaterials.

Because of their unique properties, including an ultrathin thickness (3-4 nm), ultrahigh resistivity, fluidity and self-assembly ability, lipid bilayers ...

Quantifying the Binding Interactions Between Cu(II) and Peptide Residues in the Presence and Absence of Chromophores

Copper(II) is an essential metal in biological systems, conferring unique chemical properties to the biomolecules with which it interacts. It has been reported to directly bind to a variety of peptides and play both necessary and pathological roles ranging from mediating structure to electron transfer properties to imparting catalytic function. Quantifying the binding affinity and thermodynamics of these Cu(II)-peptide complexes in vitro provides insight into the thermodynamic driving force of binding, potential competitions between different metal ions for the peptide or between different peptides for Cu(II), and the prevalence of the Cu(II)-peptide complex in vivo. However, quantifying the binding thermodynamics can be challenging due to a myriad of factors, including accounting for all competing equilibria within a titration experiment, especially in cases where there are a lack of discrete spectroscopic handles representing the peptide, the d-block metal ion, and their interactions.
Here, a robust set of experiments is provided for the accurate quantification of Cu(II)-peptide thermodynamics. This article focuses on the use of electronic absorption spectroscopy in the presence and absence of chromophoric ligands to provide the needed spectroscopic handle on Cu(II) and the use of label-free isothermal titration calorimetry. In both experimental techniques, a process is described to account for all competing equilibria. While the focus of this article is on Cu(II), the described set of experiments can apply beyond Cu(II)-peptide interactions, and provide a framework for accurate quantification of other metal-peptide systems under physiologically relevant conditions.

Quantifying the Binding Interactions Between CuII and Peptide Residues in the Presence and Absence of Chromophores

This article focuses on the use of electronic absorption spectroscopy and isothermal titration calorimetry to probe and quantify the thermodynamics of Cu(II) binding to peptides and proteins.

Copper(II) is an essential metal in biological systems, conferring unique chemical properties to the biomolecules with which it interacts. It has been ...

Biochemistry

Structure Of Ferrocene

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University&#160;
In 1951, Kealy and Pauson reported to Nature the synthesis of a new organometallic compound, ferrocene.1&#160;In their original report, Pauson suggested a structure for ferrocene in which the iron is singly bonded (sigma bonds) to one carbon atom of each cyclopentadiene ligand (Figure 1, Structure I).1,2,3&#160;This initial report led to wide-spread interest in the structure of ferrocene, and many leading scientists participated in the structure elucidation of this interesting new molecule. Wilkinson and Woodward were quick to suggest an alternative formulization where the iron is &#34;sandwiched&#34; between two cyclopentadiene ligands, with equal binding to all 10 carbon atoms (Figure 1, Structure II).4&#160;Here, we will synthesize ferrocene and decide, based on experimental data (IR and 1H NMR), which of these structures is observed. In addition, we will study the electrochemistry of ferrocene by collecting a cyclic voltammogram. In the course of this experiment, we introduce the 18-electron rule and discuss valence electron counting for transition metal complexes.
<img alt="Figure 1" src="/files/ftp_upload/10347/10347fig1v2.jpg" /> 
Figure 1. Two proposed structures of ferrocene.

Structure Determination of Ferrocene-an Organometallic Complex

Source: Tamara M. Powers, Department of Chemistry, Texas A&#38;M University&#160;
In 1951, Kealy and Pauson reported to Nature the synthesis of a new ...

[(DPEPhos)(bcp)Cu]PF₆: A General and Broadly Applicable Copper-Based Photoredox Catalyst

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