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12 pages, 3861 KiB

Open AccessArticle

Electrochemical Iodination through the In Situ Generation of Iodinating Agents: A Promising Green Approach

by Letizia Sorti, Fiammetta Vitulano, Elia Cappellini, Fulvio Uggeri, Carlo Francesco Morelli, Guido Sello, Alessandro Minguzzi and Alberto Vertova

Molecules 2023, 28(14), 5555; https://doi.org/10.3390/molecules28145555 - 20 Jul 2023

Viewed by 1115

Abstract

The synthesis of iodinated compounds using cheap, simple, and green strategies is of fundamental importance. Iodination reactions are mainly used to synthesize useful intermediates, especially in the pharmaceutical field, where they are employed for the production of contrast media or of iodinated active [...] Read more.

The synthesis of iodinated compounds using cheap, simple, and green strategies is of fundamental importance. Iodination reactions are mainly used to synthesize useful intermediates, especially in the pharmaceutical field, where they are employed for the production of contrast media or of iodinated active pharmaceutical ingredients. Traditional synthetic methods suffer from the use of erosive, toxic, or hazardous reactants. Approaches which involve the use of molecular iodine as an iodinating agent require the addition of an oxidizing agent, which is often difficult to handle. Electrochemistry can offer a valid and green alternative by avoiding the addition of such oxidizing agents, transforming the iodine source in the active species through the use of electrons as the main reactants. Herein, we report the electrochemical iodination with the generation of iodinating species in situ in water by using iodides as the source of iodine atoms. First of all, the electrochemical behavior of iodide and iodine in water on carbonaceous anodes was studied and, after selecting the suitable potential, in situ electrochemical iodination was successfully applied to 5-hydroxyisophthalic acid and 5-sulfosalicylic acid, comparing the iodinating power of I₂ and iodonium species. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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13 pages, 2801 KiB

Open AccessArticle

The Role of Water Content of Deep Eutectic Solvent Ethaline in the Anodic Process of Gold Electrode

by Jie-Du Wu, Yu Ding, Feng Zhu, Yu Gu, Wei-Wei Wang, Lan Sun, Bing-Wei Mao and Jia-Wei Yan

Molecules 2023, 28(5), 2300; https://doi.org/10.3390/molecules28052300 - 01 Mar 2023

Cited by 1 | Viewed by 1809

Abstract

Traditional coupling of ligands for gold wet etching makes large-scale applications problematic. Deep eutectic solvents (DESs) are a new class of environment-friendly solvents, which could possibly overcome the shortcomings. In this work, the effect of water content on the Au anodic process in [...] Read more.

Traditional coupling of ligands for gold wet etching makes large-scale applications problematic. Deep eutectic solvents (DESs) are a new class of environment-friendly solvents, which could possibly overcome the shortcomings. In this work, the effect of water content on the Au anodic process in DES ethaline was investigated by combining linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). Meanwhile, we employed atomic force microscopy (AFM) to image the evolution of the surface morphology of the Au electrode during its dissolution and passivation process. The obtained AFM data help to explain the observations about the effect of water content on the Au anodic process from the microscopic perspective. High water contents make the occurrence of anodic dissolution of gold at higher potential, but enhances the rate of the electron transfer and gold dissolution. AFM results reveal the occurrence of massive exfoliation, which confirms that the gold dissolution reaction is more violent in ethaline with higher water contents. In addition, AFM results illustrate that the passive film and its average roughness could be tailored by changing the water content of ethaline. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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15 pages, 4059 KiB

Open AccessArticle

Inducible Nitric Oxide Synthase Embedded in Alginate/Polyethyleneimine Hydrogel as a New Platform to Explore NO-Driven Modulation of Biological Function

by Shaimaa Maher, Lauren A. Smith, Celine A. El-Khoury, Haitham Kalil, Khalid Sossey-Alaoui and Mekki Bayachou

Molecules 2023, 28(4), 1612; https://doi.org/10.3390/molecules28041612 - 07 Feb 2023

Cited by 4 | Viewed by 1454

Abstract

Nitric oxide (NO), a small free radical molecule, turned out to be pervasive in biology and was shown to have a substantial influence on a range of biological activities, including cell growth and apoptosis. This molecule is involved in signaling and affects a [...] Read more.

Nitric oxide (NO), a small free radical molecule, turned out to be pervasive in biology and was shown to have a substantial influence on a range of biological activities, including cell growth and apoptosis. This molecule is involved in signaling and affects a number of physiologic functions. In recent decades, several processes related to cancer, such as angiogenesis, programmed cell death, infiltration, cell cycle progression, and metastasis, have been linked with nitric oxide. In addition, other parallel work showed that NO also has the potential to operate as an anti-cancer agent. As a result, it has gained attention in cancer-related therapeutics. The nitric oxide synthase enzyme family (NOS) is required for the biosynthesis of nitric oxide. It is becoming increasingly popular to develop NO-releasing materials as strong tumoricidal therapies that can deliver sustained high concentrations of nitric oxide to tumor sites. In this paper, we developed NO-releasing materials based on sodium alginate hydrogel. In this regard, alginate hydrogel discs were modified by adsorbing layers of polyethyleneimine and iNOS-oxygenase. These NO-releasing hydrogel discs were prepared using the layer-by-layer film building technique. The iNOS-oxygenase is adsorbed on the positively charged polyethyleneimine (PEI) matrix layer, which was formed on a negatively charged sodium alginate hydrogel. We show that nitric oxide is produced by enzymes contained within the hydrogel material when it is exposed to a solution containing all the components necessary for the NOS reaction. The electrostatic chemical adsorption of the layer-by-layer process was confirmed by FTIR measurements as well as scanning electron microscopy. We then tested the biocompatibility of the resulting modified sodium alginate hydrogel discs. We showed that this NOS-PEI-modified hydrogel is overall compatible with cell growth. We characterized the NOS/hydrogel films and examined their functional features in terms of NO release profiles. However, during the first 24 h of activity, these films show an increase in NO release flux, followed by a gradual drop and then a period of stable NO release. These findings show the inherent potential of using this system as a platform for NO-driven modulation of biological functions, including carcinogenesis. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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13 pages, 2427 KiB

Open AccessFeature PaperArticle

Electrochemical Characterization and CO₂ Reduction Reaction of a Family of Pyridazine-Bridged Dinuclear Mn(I) Carbonyl Complexes

by Jacopo Isopi, Elsa Quartapelle Procopio, Lorenzo Veronese, Marco Malferrari, Giovanni Valenti, Monica Panigati, Francesco Paolucci and Massimo Marcaccio

Molecules 2023, 28(3), 1138; https://doi.org/10.3390/molecules28031138 - 23 Jan 2023

Cited by 1 | Viewed by 1439

Abstract

Three recently synthesized neutral dinuclear carbonyl manganese complexes with the pyridazine bridging ligand, of general formula [Mn₂(μ-ER)₂(CO)₆(μ-pydz)] (pydz = pyridazine; E = O or S; R = methyl or phenyl), have been investigated by cyclic voltammetry in [...] Read more.

Three recently synthesized neutral dinuclear carbonyl manganese complexes with the pyridazine bridging ligand, of general formula [Mn₂(μ-ER)₂(CO)₆(μ-pydz)] (pydz = pyridazine; E = O or S; R = methyl or phenyl), have been investigated by cyclic voltammetry in dimethylformamide and acetonitrile both under an inert argon atmosphere and in the presence of carbon dioxide. This family of Mn(I) compounds behaves interestingly at negative potentials in the presence of CO₂. Based on this behavior, which is herein discussed, a rather efficient catalytic mechanism for the CO₂ reduction reaction toward the generation of CO has been hypothesized. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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12 pages, 3404 KiB

Open AccessArticle

Enhanced Catalytic Activity of TEMPO-Mediated Aerobic Oxidation of Alcohols via Redox-Active Metal–Organic Framework Nodes

by Bing Wang, Junjie Zhang, Yun Xue, Yuliang Chong, Dongdong Zhao, Hu Cheng, Liangliang Tian and Jinliang Zhuang

Molecules 2023, 28(2), 593; https://doi.org/10.3390/molecules28020593 - 06 Jan 2023

Cited by 2 | Viewed by 1449

Abstract

Metal–organic frameworks (MOFs) are outstanding platforms for heterogeneous catalysis due to their tunable pore size, huge surface area, large porosity, and potential active sites. The design and synthesis of MOF/organocatalyst co-catalytic systems have attracted considerable interest owing to their high catalytic activity, low [...] Read more.

Metal–organic frameworks (MOFs) are outstanding platforms for heterogeneous catalysis due to their tunable pore size, huge surface area, large porosity, and potential active sites. The design and synthesis of MOF/organocatalyst co-catalytic systems have attracted considerable interest owing to their high catalytic activity, low toxicity, and mild reaction conditions. Herein, we reported the synthesis of a bifunctional TEMPO-IsoNTA organocatalyst featuring a pyridyl group as an anchoring site and a TEMPO radical as a catalytic active site. By using the topologically isomorphic structures of MIL-101(Fe) and MIL-101(Cr) as co-catalysts, these MOF/TEMPO-IsoNTA systems enable the efficient aerobic oxidation of various alcohols to their corresponding aldehydes or ketones under mild conditions. Notably, the MIL-101(Fe)/TEMPO-IsoNTA system exhibits superior catalytic activity, thanks to their redox-active Fe^III-oxo nodes, which facilitate the regeneration of TEMPO-IsoNTA. Our research not only solves the problem of potential heavy metal contamination in the TEMPO-based homogeneous catalytic system, but also enriches the understanding of synergism of MOFs/organocatalysts. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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11 pages, 1681 KiB

Open AccessArticle

Multiple Pulse Amperometry—An Antifouling Approach for Nitrite Determination Using Carbon Fiber Microelectrodes

by Douglas P. M. Saraiva, Daniel V. Braga, Bruna Bossard and Mauro Bertotti

Molecules 2023, 28(1), 387; https://doi.org/10.3390/molecules28010387 - 02 Jan 2023

Cited by 4 | Viewed by 1304

Abstract

Nitrite is a ubiquitous pollutant in modern society. Developing new strategies for its determination is very important, and electroanalytical methods present outstanding performance on this task. However, the use of bare electrodes is not recommended because of their predisposition to poisoning and passivation. [...] Read more.

Nitrite is a ubiquitous pollutant in modern society. Developing new strategies for its determination is very important, and electroanalytical methods present outstanding performance on this task. However, the use of bare electrodes is not recommended because of their predisposition to poisoning and passivation. We herein report a procedure to overcome these limitations on carbon fiber microelectrodes through pulsed amperometry. A three-pulse amperometry approach was used to reduce the current decay from 47% (after 20 min under constant potential) to virtually 0%. Repeatability and reproducibility were found to have an RSD lower than 0.5% and 7%, respectively. Tap water and synthetic inorganic saliva samples were fortified with nitrite, and the results obtained with the proposed sensor were in good agreement with the amount added. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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13 pages, 2111 KiB

Open AccessArticle

Electrochemical Sensor Based on Multi-Walled Carbon Nanotubes and N-Doped TiO₂ Nanoparticles for Voltametric Simultaneous Determination of Benserazide and Levodopa

by Elisangela Pacheco da Silva, Mayara da Silva Araujo, Marcos H. Kunita, Roberto Matos and Roberta Antigo Medeiros

Molecules 2022, 27(23), 8614; https://doi.org/10.3390/molecules27238614 - 06 Dec 2022

Cited by 2 | Viewed by 1292

Abstract

An electrochemical sensor for simultaneous determination of Benserazide (BEZ) and levodopa (L-dopa) was successfully developed using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotube and nitrogen-doped titanium dioxide nanoparticles (GCE/MWCNT/N-TiO₂). Cyclic voltammetry and square wave voltammetry were employed to [...] Read more.

An electrochemical sensor for simultaneous determination of Benserazide (BEZ) and levodopa (L-dopa) was successfully developed using a glassy carbon electrode (GCE) modified with multi-walled carbon nanotube and nitrogen-doped titanium dioxide nanoparticles (GCE/MWCNT/N-TiO₂). Cyclic voltammetry and square wave voltammetry were employed to investigate the electrochemical behavior of different working electrodes and analytes. In comparison with unmodified GCE, the modified electrode exhibited better electrocatalytic activity towards BEZ and L-dopa and was efficient in providing a satisfactory separation for oxidation peaks, with a potential difference of 140 mV clearly allows the simultaneous determination of these compounds. Under the optimized conditions, linear ranges of 2.0–20.0 and 2.0–70.0 μmol L⁻¹ were obtained for BEZ and L-dopa, respectively, with a limit of detection of 1.6 µmol L⁻¹ for BEZ and 2.0 µmol L⁻¹ for L-dopa. The method was applied in simultaneous determination of the analytes in pharmaceutical samples, and the accuracy was attested by comparison with HPLC-DAD as the reference method, with a relative error lower than 4.0%. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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9 pages, 2146 KiB

Open AccessArticle

Electrochemical Enzyme Sensor Based on the Two-Dimensional Metal–Organic Layers Supported Horseradish Peroxidase

by Yu Xiong, Chao Wang, YuanFei Wu, Chunhua Luo, Dongping Zhan and Shizhen Wang

Molecules 2022, 27(23), 8599; https://doi.org/10.3390/molecules27238599 - 06 Dec 2022

Cited by 3 | Viewed by 1293

Abstract

Metal–organic frames (MOFs) have recently been used to support redox enzymes for highly sensitive and selective chemical sensors for small biomolecules such as oxygen (O₂), hydrogen peroxide (H₂O₂), etc. However, most MOFs are insulative and their three-dimensional [...] Read more.

Metal–organic frames (MOFs) have recently been used to support redox enzymes for highly sensitive and selective chemical sensors for small biomolecules such as oxygen (O₂), hydrogen peroxide (H₂O₂), etc. However, most MOFs are insulative and their three-dimensional (3D) porous structures hinder the electron transfer pathway between the current collector and the redox enzyme molecules. In order to facilitate electron transfer, here we adopt two-dimensional (2D) metal–organic layers (MOLs) to support the HRP molecules in the detection of H₂O₂. The correlation between the current response and the H₂O₂ concentration presents a linear range from 7.5 μM to 1500 μM with a detection limit of 0.87 μM (S/N = 3). The sensitivity, reproducibility, and stability of the enzyme sensor are promoted due to the facilitated electron transfer. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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15 pages, 3966 KiB

Open AccessArticle

Self-Assembled Monolayers of Molecular Conductors with Terpyridine-Metal Redox Switching Elements: A Combined AFM, STM and Electrochemical Study

by Jana Kocábová, František Vavrek, Štěpánka Nováková Lachmanová, Jakub Šebera, Michal Valášek and Magdaléna Hromadová

Molecules 2022, 27(23), 8320; https://doi.org/10.3390/molecules27238320 - 29 Nov 2022

Viewed by 1693

Abstract

Self-assembled monolayers (SAMs) of terpyridine-based transition metal (ruthenium and osmium) complexes, anchored to gold substrate via tripodal anchoring groups, have been investigated as possible redox switching elements for molecular electronics. An electrochemical study was complemented by atomic force microscopy (AFM) and scanning tunneling [...] Read more.

Self-assembled monolayers (SAMs) of terpyridine-based transition metal (ruthenium and osmium) complexes, anchored to gold substrate via tripodal anchoring groups, have been investigated as possible redox switching elements for molecular electronics. An electrochemical study was complemented by atomic force microscopy (AFM) and scanning tunneling microscopy (STM) methods. STM was used for determination of the SAM conductance values, and computation of the attenuation factor β from tunneling current–distance curves. We have shown that SAMs of Os-tripod molecules contain larger adlayer structures compared with SAMs of Ru-tripod molecules, which are characterized by a large number of almost evenly distributed small islands. Furthermore, upon cyclic voltammetric experimentation, Os-tripod films rearrange to form a smaller number of even larger islands, reminiscent of the Ostwald ripening process. Os-tripod SAMs displayed a higher surface concentration of molecules and lower conductance compared with Ru-tripod SAMs. The attenuation factor of Os-tripod films changed dramatically, upon electrochemical cycling, to a higher value. These observations are in accordance with previously reported electron transfer kinetics studies. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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13 pages, 1826 KiB

Open AccessArticle

Electrochemical-Induced Cascade Reaction of 2-Formyl Benzonitrile with Anilines: Synthesis of N-Aryl Isoindolinones

by Valerio Morlacci, Tonino Caruso, Marco Chiarini, Antonio Arcadi, Massimiliano Aschi and Laura Palombi

Molecules 2022, 27(23), 8199; https://doi.org/10.3390/molecules27238199 - 24 Nov 2022

Cited by 4 | Viewed by 1310

Abstract

An electrochemical initiated tandem reaction of anilines with 2-formyl benzonitrile has been developed. Thus, unprecedented 3-N-aryl substituted isoindolinones have been conveniently achieved by constant current electrolysis in a divided cell using catalytic amount of electricity and supporting electrolyte and a Pt-cathode [...] Read more.

An electrochemical initiated tandem reaction of anilines with 2-formyl benzonitrile has been developed. Thus, unprecedented 3-N-aryl substituted isoindolinones have been conveniently achieved by constant current electrolysis in a divided cell using catalytic amount of electricity and supporting electrolyte and a Pt-cathode as working electrode. The origin of the electrochemical activation as well as the mechanism of the subsequent chemical cascade reactions have been investigated by DFT calculations. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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17 pages, 3604 KiB

Open AccessArticle

Thermodynamics and Kinetics of Electron Transfer of Electrode-Immobilized Small Laccase from Streptomyces coelicolor

by Giulia Di Rocco, Gianantonio Battistuzzi, Antonio Ranieri, Carlo Augusto Bortolotti, Marco Borsari and Marco Sola

Molecules 2022, 27(22), 8079; https://doi.org/10.3390/molecules27228079 - 21 Nov 2022

Cited by 3 | Viewed by 1231

Abstract

The thermodynamic and kinetic properties for heterogeneous electron transfer (ET) were measured for the electrode-immobilized small laccase (SLAC) from Streptomyces coelicolor subjected to different electrostatic and covalent protein-electrode linkages, using cyclic voltammetry. Once immobilized electrostatically onto a gold electrode using mixed carboxyl- and [...] Read more.

The thermodynamic and kinetic properties for heterogeneous electron transfer (ET) were measured for the electrode-immobilized small laccase (SLAC) from Streptomyces coelicolor subjected to different electrostatic and covalent protein-electrode linkages, using cyclic voltammetry. Once immobilized electrostatically onto a gold electrode using mixed carboxyl- and hydroxy-terminated alkane-thiolate SAMs or covalently exploiting the same SAM subjected to N-hydroxysuccinimide+1-Ethyl-3-(3-dimethylaminopropyl)carbodiimide (NHS-EDC) chemistry, the SLAC-electrode electron flow occurs through the T1 center. The E°′ values (from +0.2 to +0.1 V vs. SHE at pH 7.0) are lower by more than 0.2 V compared to the protein either in solution or immobilized with different anchoring strategies using uncharged SAMs. For the present electrostatic and covalent binding, this effect can, respectively, be ascribed to the negative charge of the SAM surfaces and to deletion of the positive charge of Lys/Arg residues due to amide bond formation which both selectively stabilize the more positively charged oxidized SLAC. Observation of enthalpy/entropy compensation within the series indicates that the immobilized proteins experience different reduction-induced solvent reorganization effects. The E°′ values for the covalently attached SLAC are sensitive to three acid base equilibria, with apparent pK_a values of pK_a1ox = 5.1, pK_a1red = 7.5, pK_a2ox = 8.4, pK_a2red = 10.9, pK_a2ox = 8.9, pK_a2red = 11.3 possibly involving one residue close to the T1 center and two residues (Lys and/or Arg) along with moderate protein unfolding, respectively. Therefore, the E°′ value of immobilized SLAC turns out to be particularly sensitive to the anchoring mode and medium conditions. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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11 pages, 2588 KiB

Open AccessArticle

Electrochemistry of Tetrathiafulvalene Ligands Assembled on the Surface of Gold Nanoparticles

by Jiří Janoušek, Jiří Rybáček, Miloš Buděšínský, Lubomír Pospíšil, Irena G. Stará and Ivo Starý

Molecules 2022, 27(21), 7639; https://doi.org/10.3390/molecules27217639 - 07 Nov 2022

Cited by 1 | Viewed by 1642

Abstract

The synthesis of a tetrathiafulvalene (TTF) derivative, S-[4-({4-[(2,2′-bi-1,3-dithiol-4-ylmethoxy)methyl] phenyl}ethynyl)phenyl] ethanethioate, suitable for the modification of gold nanoparticles (AuNPs), is described in this article. The TTF ligand was self-assembled on the AuNP surface through ligand exchange, starting from dodecanethiol-stabilized AuNPs. The resulting modified [...] Read more.

The synthesis of a tetrathiafulvalene (TTF) derivative, S-[4-({4-[(2,2′-bi-1,3-dithiol-4-ylmethoxy)methyl] phenyl}ethynyl)phenyl] ethanethioate, suitable for the modification of gold nanoparticles (AuNPs), is described in this article. The TTF ligand was self-assembled on the AuNP surface through ligand exchange, starting from dodecanethiol-stabilized AuNPs. The resulting modified AuNPs were characterized by TEM, UV-Vis spectroscopy, and electrochemistry. The most suitable electrochemical method was the phase-sensitive AC voltammetry at very low frequencies of the sine-wave perturbation. The results indicate a diminishing electronic communication between the two equivalent redox centers of TTF and also intermolecular donor–acceptor interactions manifested by an additional oxidation wave upon attachment of the ligand to AuNPs. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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14 pages, 3481 KiB

Open AccessArticle

Copper-Catalyzed Homocoupling of Boronic Acids: A Focus on B-to-Cu and Cu-to-Cu Transmetalations

by Aude Salamé, Jordan Rio, Ilaria Ciofini, Lionel Perrin, Laurence Grimaud and Pierre-Adrien Payard

Molecules 2022, 27(21), 7517; https://doi.org/10.3390/molecules27217517 - 03 Nov 2022

Cited by 2 | Viewed by 2198

Abstract

Controlling and understanding the Cu-catalyzed homocoupling reaction is crucial to prompt the development of efficient Cu-catalyzed cross-coupling reactions. The presence of a coordinating base (hydroxide and methoxide) enables the B-to-Cu(II) transmetalation from aryl boronic acid to Cu^IICl₂ in methanol, through [...] Read more.

Controlling and understanding the Cu-catalyzed homocoupling reaction is crucial to prompt the development of efficient Cu-catalyzed cross-coupling reactions. The presence of a coordinating base (hydroxide and methoxide) enables the B-to-Cu(II) transmetalation from aryl boronic acid to Cu^IICl₂ in methanol, through the formation of mixed Cu-(μ-OH)-B intermediates. A second B-to-Cu transmetalation to form bis-aryl Cu(II) complexes is disfavored. Instead, organocopper(II) dimers undergo a coupled transmetalation-electron transfer (TET) allowing the formation of bis-organocopper(III) complexes readily promoting reductive elimination. Based on this mechanism some guidelines are suggested to control the undesired formation of homocoupling product in Cu-catalyzed cross-coupling reactions. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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14 pages, 3721 KiB

Open AccessArticle

Electrocatalytic Behavior of an Amide Functionalized Mn(II) Coordination Polymer on ORR, OER and HER

by Anup Paul, Kristina Radinović, Susanta Hazra, Dušan Mladenović, Biljana Šljukić, Rais Ahmad Khan, Maria Fátima C. Guedes da Silva and Armando J. L. Pombeiro

Molecules 2022, 27(21), 7323; https://doi.org/10.3390/molecules27217323 - 28 Oct 2022

Cited by 2 | Viewed by 1699

Abstract

The new 3D coordination polymer (CP) [Mn(L)(HCOO)]_n (Mn-CP) [L = 4-(pyridin-4-ylcarbamoyl)benzoate] was synthesised via a hydrothermal reaction using the pyridyl amide functionalized benzoic acid HL. It was characterized by elemental, FT-IR spectroscopy, single-crystal and powder X-ray diffraction (PXRD) analyses. Its [...] Read more.

The new 3D coordination polymer (CP) [Mn(L)(HCOO)]_n (Mn-CP) [L = 4-(pyridin-4-ylcarbamoyl)benzoate] was synthesised via a hydrothermal reaction using the pyridyl amide functionalized benzoic acid HL. It was characterized by elemental, FT-IR spectroscopy, single-crystal and powder X-ray diffraction (PXRD) analyses. Its structural features were disclosed by single-crystal X-ray diffraction analysis, which revealed a 3D structure with the monoclinic space group P21/c. Its performance as an electrocatalyst for oxygen reduction (ORR), oxygen evolution (OER), and hydrogen evolution (HER) reactions was tested in both acidic (0.5 M H₂SO₄) and alkaline (0.1 M KOH) media. A distinct reduction peak was observed at 0.53 V vs. RHE in 0.1 M KOH, which corresponds to the oxygen reduction, thus clearly demonstrating the material’s activity for the ORR. Tafel analysis revealed a Tafel slope of 101 mV dec⁻¹ with mixed kinetics of 2e⁻ and 4e⁻ pathways indicated by the Koutecky–Levich analysis. Conversely, the ORR peak was not present in 0.5 M H₂SO₄ indicating no activity of Mn-CP for this reaction in acidic media. In addition, Mn-CP demonstrated a noteworthy activity toward OER and HER in acidic media, in contrast to what was observed in 0.1 M KOH. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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6 pages, 1603 KiB

Open AccessCommunication

First Example of a Heptazine-Porphyrin Dyad; Synthesis and Spectroscopic Properties

by Frédérique Brégier, Vincent Sol, Yves Champavier, Laurent Galmiche, Clémence Allain and Pierre Audebert

Molecules 2022, 27(19), 6698; https://doi.org/10.3390/molecules27196698 - 08 Oct 2022

Cited by 2 | Viewed by 1233

Abstract

We have prepared the first example of a porphyrin linked to an heptazine photoactive antenna. The two entities, linked with an alkyl spacer, demonstrate the activity of both active moieties. While they behave electrochemically independantly, on the other hand the spectroscopy shows the [...] Read more.

We have prepared the first example of a porphyrin linked to an heptazine photoactive antenna. The two entities, linked with an alkyl spacer, demonstrate the activity of both active moieties. While they behave electrochemically independantly, on the other hand the spectroscopy shows the existence of energy transfer between both partners. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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15 pages, 3017 KiB

Open AccessArticle

Synthesis, Electrochemical and Fluorescence Properties of the First Fluorescent Member of the Ferrocifen Family and of Its Oxidized Derivatives

by Charles Fayolle, Pascal Pigeon, Nathalie Fischer-Durand, Michèle Salmain, Olivier Buriez, Anne Vessières and Eric Labbé

Molecules 2022, 27(19), 6690; https://doi.org/10.3390/molecules27196690 - 08 Oct 2022

Viewed by 1412

Abstract

The first fluorescent ferrociphenol derivative (P797) has been synthesized via McMurry cross-coupling followed by copper-catalyzed [3 + 2] azide-alkyne cycloaddition of the fluorescent group coumarin. Cyclic voltammograms of P797 exhibit either a monoelectronic oxidation wave ascribed to the ferrocene Fe(II) → Fe(III) conversion [...] Read more.

The first fluorescent ferrociphenol derivative (P797) has been synthesized via McMurry cross-coupling followed by copper-catalyzed [3 + 2] azide-alkyne cycloaddition of the fluorescent group coumarin. Cyclic voltammograms of P797 exhibit either a monoelectronic oxidation wave ascribed to the ferrocene Fe(II) → Fe(III) conversion or a three-electron oxidation process in the presence of a base, leading to a Fe(III) quinone methide adduct. This general sequence is consistent with those previously described for non-fluorescent ferrociphenols. Furthermore, the fluorescence properties of P797 and its oxidized intermediates appear to strongly depend on the redox state of the ferrocene group. Indeed, electrochemical generation of Fe(III) (ferrocenium) states markedly increases the fluorescence emission intensity. In contrast, the emission of the Fe(II) (ferrocene) states is partially quenched by photoinduced electron transfer (PET) from the Fe(II) donor to the coumarin acceptor and by concentration-dependent self-quenching. Owing to its switchable fluorescence properties, complex P797 could represent an innovative and useful tool to study the biodistribution and the redox state of ferrocifens in cancer cells. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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21 pages, 5560 KiB

Open AccessArticle

Electrochemical Properties of a Rhodium(III) Mono-Terpyridyl Complex and Use as a Catalyst for Light-Driven Hydrogen Evolution in Water

by Fakourou Camara, Thomas Gavaggio, Baptiste Dautreppe, Jérôme Chauvin, Jacques Pécaut, Dmitry Aldakov, Marie-Noëlle Collomb and Jérôme Fortage

Molecules 2022, 27(19), 6614; https://doi.org/10.3390/molecules27196614 - 05 Oct 2022

Cited by 4 | Viewed by 1738

Abstract

Molecular hydrogen (H₂) is considered one of the most promising fuels to decarbonize the industrial and transportation sectors, and its photocatalytic production from molecular catalysts is a research field that is still abounding. The search for new molecular catalysts for H [...] Read more.

Molecular hydrogen (H₂) is considered one of the most promising fuels to decarbonize the industrial and transportation sectors, and its photocatalytic production from molecular catalysts is a research field that is still abounding. The search for new molecular catalysts for H₂ production with simple and easily synthesized ligands is still ongoing, and the terpyridine ligand with its particular electronic and coordination properties, is a good candidate to design new catalysts meeting these requirements. Herein, we have isolated the new mono-terpyridyl rhodium complex, [Rh^III(tpy)(CH₃CN)Cl₂](CF₃SO₃) (Rh-tpy), and shown that it can act as a catalyst for the light-induced proton reduction into H₂ in water in the presence of the [Ru(bpy)₃]Cl₂ (Ru) photosensitizer and ascorbate as sacrificial electron donor. Under photocatalytic conditions, in acetate buffer at pH 4.5 with 0.1 M of ascorbate and 530 μM of Ru, the Rh-tpy catalyst produces H₂ with turnover number versus catalyst (TON_Cat*) of 300 at a Rh concentration of 10 μM, and up to 1000 at a concentration of 1 μM. The photocatalytic performance of Ru/Rh-tpy/HA^–/H₂A has been also compared with that obtained with the bis-dimethyl-bipyridyl complex [Rh^III(dmbpy)₂Cl₂]⁺ (Rh2) as a catalyst in the same experimental conditions. The investigation of the electrochemical properties of Rh-tpy in DMF solvent reveals that the two-electrons reduced state of the complex, the square-planar [Rh^I(tpy)Cl] (Rh^I-tpy), is quantitatively electrogenerated by bulk electrolysis. This complex is stable for hours under an inert atmosphere owing to the π-acceptor property of the terpyridine ligand that stabilizes the low oxidation states of the rhodium, making this catalyst less prone to degrade during photocatalysis. The π-acceptor property of terpyridine also confers to the Rh-tpy catalyst a moderately negative reduction potential (Ep_c(Rh^III/Rh^I) = −0.83 V vs. SCE in DMF), making possible its reduction by the reduced state of Ru, [Ru^II(bpy)(bpy^•−)]⁺ (Ru⁻) (E_1/2(Ru^II/Ru⁻) = −1.50 V vs. SCE) generated by a reductive quenching of the Ru excited state (*Ru) by ascorbate during photocatalysis. A Stern–Volmer plot and transient absorption spectroscopy confirmed that the first step of the photocatalytic process is the reductive quenching of *Ru by ascorbate. The resulting reduced Ru species (Ru⁻) were then able to activate the Rh^III-tpy H₂-evolving catalyst by reduction generating Rh^I-tpy, which can react with a proton on a sub-nanosecond time scale to form a Rh^III(H)-tpy hydride, the key intermediate for H₂ evolution. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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12 pages, 2076 KiB

Open AccessFeature PaperArticle

Electrochemical Properties of Carbon Fibers from Felts

by Guilhem Pignol, Patricia Bassil, Jean-Marie Fontmorin, Didier Floner, Florence Geneste and Philippe Hapiot

Molecules 2022, 27(19), 6584; https://doi.org/10.3390/molecules27196584 - 04 Oct 2022

Cited by 3 | Viewed by 1672

Abstract

Electrochemical behaviors of individual carbon fibers coming from carbon felts were investigated using two different redox couples, 1,1′-dimethanolferrocene and potassium ferrocyanide. Electrochemical responses were examined after different oxidation treatments, then simulated and interpreted using the Kissa 1D software and existing models. Our experiments [...] Read more.

Electrochemical behaviors of individual carbon fibers coming from carbon felts were investigated using two different redox couples, 1,1′-dimethanolferrocene and potassium ferrocyanide. Electrochemical responses were examined after different oxidation treatments, then simulated and interpreted using the Kissa 1D software and existing models. Our experiments indicate that a crude carbon fiber behaves as an assembly of sites with different electrochemical reactivities. In such case, the Butler–Volmer law is not appropriate to describe the electron transfer kinetics because of the large created overpotential. Oxidation of the fiber erases the effect by increasing the kinetics of the electron transfer probably by a homogenization and increase of the reactivity on all the fiber. Additionally, analysis of the signal shows the large influence of the convection that affects the electrochemical response even at moderate scan rates (typically below 0.1–0.2 V s⁻¹). Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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20 pages, 11633 KiB

Open AccessArticle

Visible Light Photoelectrochemical Sensor for Dopamine: Determination Using Iron Vanadate Modified Electrode

by Luan Pereira Camargo, Marcelo Rodrigues da Silva Pelissari, Paulo Rogério Catarini da Silva, Augusto Batagin-Neto, Roberta Antigo Medeiros, Marcos Antônio Dias and Luiz Henrique Dall’Antonia

Molecules 2022, 27(19), 6410; https://doi.org/10.3390/molecules27196410 - 28 Sep 2022

Cited by 4 | Viewed by 2159

Abstract

This study reports a facile approach for constructing low-cost and remarkable electroactivity iron vanadate (Fe-V-O) semiconductor material to be used as a photoelectrochemical sensor for dopamine detection. The structure and morphology of the iron vanadate obtained by the Successive Ionic Adsorption and Reaction [...] Read more.

This study reports a facile approach for constructing low-cost and remarkable electroactivity iron vanadate (Fe-V-O) semiconductor material to be used as a photoelectrochemical sensor for dopamine detection. The structure and morphology of the iron vanadate obtained by the Successive Ionic Adsorption and Reaction process were critically characterized, and the photoelectrochemical characterization showed a high photoelectroactivity of the photoanode in visible light irradiation. Under best conditions, dopamine was detected by chronoamperometry at +0.35 V vs. Ag/AgCl, achieving two linear response ranges (between 1.21 and 30.32 μmol L⁻¹, and between 30.32 and 72.77 μmol L⁻¹). The limits of detection and quantification were 0.34 and 1.12 μmol L⁻¹, respectively. Besides, the accuracy of the proposed electrode was assessed by determining dopamine in artificial cerebrospinal fluid, obtaining recovery values ranging from 98.7 to 102.4%. The selectivity was also evaluated by dopamine detection against several interferent species, demonstrating good precision and promising application for the proposed method. Furthermore, DFT-based electronic structure calculations were also conducted to help the interpretation. The dominant dopamine species were determined according to the experimental conditions, and their interaction with the iron vanadate photoanode was proposed. The improved light-induced DOP detection was likewise evaluated regarding the charge transfer process. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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17 pages, 2003 KiB

Open AccessFeature PaperArticle

Direct Electrooxidative Selenylation/Cyclization of Alkynes: Access to Functionalized Benzo[b]furans

by Balati Hasimujiang, Shengsheng Lin, Chengwei Zheng, Yong Zeng and Zhixiong Ruan

Molecules 2022, 27(19), 6314; https://doi.org/10.3390/molecules27196314 - 25 Sep 2022

Cited by 8 | Viewed by 1510

Abstract

A mild, practical, metal and oxidant-free methodology for the synthesis of various C-3 selenylated benzo[b]furan derivatives was developed through the intramolecular cyclization of alkynes promoted with diselenides via electrooxidation. A wide range of selenium-substituted benzo[b]furan derivatives were obtained in [...] Read more.

A mild, practical, metal and oxidant-free methodology for the synthesis of various C-3 selenylated benzo[b]furan derivatives was developed through the intramolecular cyclization of alkynes promoted with diselenides via electrooxidation. A wide range of selenium-substituted benzo[b]furan derivatives were obtained in good to excellent yields with high regioselectivity under constant current in an undivided cell equipped with carbon and platinum plates as the anode and cathode, respectively. Moreover, the convergent approach exhibited good functional group tolerance and could be easily scaled up with good efficiency, providing rapid access to a diverse range of selenylated benzo[b]furans derivatives from simple, readily available starting materials. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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18 pages, 4302 KiB

Open AccessArticle

Electrochemical Investigation of Iron-Catalyzed Atom Transfer Radical Polymerization

by Gianluca Gazzola, Sebastiano Pasinato, Marco Fantin, Niccolò Braidi, Cristina Tubaro, Christian Durante and Abdirisak Ahmed Isse

Molecules 2022, 27(19), 6312; https://doi.org/10.3390/molecules27196312 - 24 Sep 2022

Cited by 2 | Viewed by 1823

Abstract

Use of iron-based catalysts in atom transfer radical polymerization (ATRP) is very interesting because of the abundance of the metal and its biocompatibility. Although the mechanism of action is not well understood yet, iron halide salts are usually used as catalysts, often in [...] Read more.

Use of iron-based catalysts in atom transfer radical polymerization (ATRP) is very interesting because of the abundance of the metal and its biocompatibility. Although the mechanism of action is not well understood yet, iron halide salts are usually used as catalysts, often in the presence of nitrogen or phosphorous ligands (L). In this study, electrochemically mediated ATRP (eATRP) of methyl methacrylate (MMA) catalyzed by FeCl₃, both in the absence and presence of additional ligands, was investigated in dimethylformamide. The electrochemical behavior of FeCl₃ and FeCl₃/L was deeply investigated showing the speciation of Fe(III) and Fe(II) and the role played by added ligands. It is shown that amine ligands form stable iron complexes, whereas phosphines act as reducing agents. eATRP of MMA catalyzed by FeCl₃ was investigated in different conditions. In particular, the effects of temperature, catalyst concentration, catalyst-to-initiator ratio, halide ion excess and added ligands were investigated. In general, polymerization was moderately fast but difficult to control. Surprisingly, the best results were obtained with FeCl₃ without any other ligand. Electrogenerated Fe(II) effectively activates the dormant chains but deactivation of the propagating radicals by Fe(III) species is less efficient, resulting in dispersity > 1.5, unless a high concentration of FeCl₃ is used. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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15 pages, 2592 KiB

Open AccessArticle

Electrocatalytic Depolymerization of Self-Immolative Poly(Dithiothreitol) Derivatives

by Magnus Hansen-Felby, Steen U. Pedersen and Kim Daasbjerg

Molecules 2022, 27(19), 6292; https://doi.org/10.3390/molecules27196292 - 23 Sep 2022

Cited by 1 | Viewed by 1346

Abstract

We report the use of electrogenerated anthraquinone radical anion (AQ•⁻) to trigger fast catalytic depolymerization of polymers derived from poly(dithiothreitol) (pDTT)—a self-immolative polymer (SIP) with a backbone of dithiothreitols connected with disulfide bonds and end-capped via disulfide bonds to pyridyl groups. [...] Read more.

We report the use of electrogenerated anthraquinone radical anion (AQ•⁻) to trigger fast catalytic depolymerization of polymers derived from poly(dithiothreitol) (pDTT)—a self-immolative polymer (SIP) with a backbone of dithiothreitols connected with disulfide bonds and end-capped via disulfide bonds to pyridyl groups. The pDTT derivatives studied include polymers with simple thiohexyl end-caps or modified with AQ or methyl groups by Steglich esterification. All polymers were shown to be depolymerized using catalytic amounts of electrons delivered by AQ•⁻. For pDTT, as little as 0.2 electrons per polymer chain was needed to achieve complete depolymerization. We hypothesize that the reaction proceeds with AQ•⁻ as an electron carrier (either molecularly or as a pendant group), which transfers an electron to a disulfide bond in the polymer in a dissociative manner, generating a thiyl radical and a thiolate. The rapid and catalytic depolymerization is driven by thiyl radicals attacking other disulfide bonds internally or between pDTT chains in a chain reaction. Electrochemical triggering works as a general method for initiating depolymerization of pDTT derivatives and may likely also be used for depolymerization of other disulfide polymers. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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16 pages, 4550 KiB

Open AccessArticle

Helical versus Flat Bis-Ferrocenyl End-Capped Peptides: The Influence of the Molecular Skeleton on Redox Properties

by Saverio Santi, Barbara Biondi, Roberta Cardena, Annalisa Bisello, Renato Schiesari, Silvia Tomelleri, Marco Crisma and Fernando Formaggio

Molecules 2022, 27(18), 6128; https://doi.org/10.3390/molecules27186128 - 19 Sep 2022

Cited by 2 | Viewed by 1484

Abstract

Despite the fact that peptide conjugates with a pendant ferrocenyl (Fc) have been widely investigated, bis-ferrocenyl end-capped peptides are rarely synthetized. In this paper, in addition to the full characterization of the Fc-CO-[_L-Dap(Boc)]_n-NH-Fc series, we report a comparison of [...] Read more.

Despite the fact that peptide conjugates with a pendant ferrocenyl (Fc) have been widely investigated, bis-ferrocenyl end-capped peptides are rarely synthetized. In this paper, in addition to the full characterization of the Fc-CO-[_L-Dap(Boc)]_n-NH-Fc series, we report a comparison of the three series of bis-ferrocenyl homopeptides synthesized to date, to gain insights into the influence of α-amino isobutyric (Aib), 2,3-diamino propionic (Dap) and C^α,β-didehydroalanine (ΔAla) amino acids on the peptide secondary structure and on the ferrocene redox properties. The results obtained by 2D NMR analysis and X-ray crystal structures, and further supported by electrochemical data, evidence different behaviors depending on the nature of the amino acid; that is, the formation of 3₁₀-helices or fully extended (2.0₅-helix) structures. In these foldamers, the orientation of the carbonyl groups in the peptide helix yields a macrodipole with the positive pole on the N-terminal amino acid and the negative pole on the C-terminal amino acid, so that oxidation of the Fc moieties takes place more or less easily depending on the orientation of the macrodipole moment as the peptide chain grows. Conversely, the fully extended conformation adopted by ΔAla flat peptides neither generates a macrodipole nor affects Fc oxidation. The utilization as electrochemical and optical (Circular Dichroism) probes of the two terminal Fc groups, bound to the same peptide chain, makes it possible to study the end-to-end effects of the positive charges produced by single and double oxidations, and to evidence the presence “exciton-coupled” CD among the two intramolecularly interacting Fc groups of the _L-Dap(Boc) series. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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11 pages, 4241 KiB

Open AccessArticle

Adsorption and Electropolymerization of p-Aminophenol Reduces Reproducibility of Electrochemical Immunoassays

by Grace Buckey, Olivia E. Owens, Ainslee W. Gabriel, Claudia M. Downing, Margaret C. Calhoun and David E. Cliffel

Molecules 2022, 27(18), 6046; https://doi.org/10.3390/molecules27186046 - 16 Sep 2022

Cited by 2 | Viewed by 2163

Abstract

This paper investigates the electrochemical behavior of p-aminophenol (PAP) on commercially available carbon screen-printed electrodes (CSPEs) and gold screen-printed electrodes (GSPEs) at neutral and basic pHs for the development of inexpensive immunoassays. The electrochemical oxidative signal from PAP results from its adsorption [...] Read more.

This paper investigates the electrochemical behavior of p-aminophenol (PAP) on commercially available carbon screen-printed electrodes (CSPEs) and gold screen-printed electrodes (GSPEs) at neutral and basic pHs for the development of inexpensive immunoassays. The electrochemical oxidative signal from PAP results from its adsorption to the electrode. The formation of self-assembled monolayers on gold electrodes prevented PAP adsorption but also reduced its oxidative current, confirming that adsorption increases signal production. On bare electrodes, PAP adsorption results in oxidative current variability depending on the electroactive surface area of the screen-printed electrode. This variability could not be remedied by cleaning and reusing the same GSPE. Decreasing the PAP concentration to 3.8 μM greatly improved the consistency of the measurements, suggesting that the adsorption of PAP is concentration-dependent. Multiple PAP oxidations on the same electrode caused polymerization, limiting PAP in continuous monitoring applications. Infrared and Raman spectroscopy allow the distinction between adsorbed PAP and electropolymerized PAP on the surface of a gold wafer. The results from this study suggest that the use of PAP production in immunoassays with SPEs must be fine-tuned, and electrodes must be cleaned or disposed of between measurements. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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7 pages, 1019 KiB

Open AccessArticle

Investigating Localized Electrochemical of Ferrocenyl-Imidazolium in Ionic Liquid Using Scanning Electrochemical Microscopy Configuration

by Thuan-Nguyen Pham-Truong and Jalal Ghilane

Molecules 2022, 27(18), 6004; https://doi.org/10.3390/molecules27186004 - 15 Sep 2022

Cited by 1 | Viewed by 1056

Abstract

In the present work, the localized electrochemical behavior of redox molecule in ionic liquid has been investigated using scanning electrochemical microscopy. The electrochemical response of ferrocenyl-imidazolium redox mediator was studied by recording approach curves over a conducting and insulating substrate in an undiluted [...] Read more.

In the present work, the localized electrochemical behavior of redox molecule in ionic liquid has been investigated using scanning electrochemical microscopy. The electrochemical response of ferrocenyl-imidazolium redox mediator was studied by recording approach curves over a conducting and insulating substrate in an undiluted ionic liquid. The SECM approach curve over the conducting substrate displays a positive feedback, as observed in classical solvent. However, in the case of the insulating substrate, the approach curve reveals different shapes, depending on the used approach speed. In this configuration, low approach speed is necessary to reach the expected negative feedback. Interestingly, at a very close distance between the UME and the insulating substrate, a thin film behavior is revealed. In addition, the approach curves on both insulator and conducting substrates can be reconstructed from punctual responses at different distance tip-substrate. The latter match perfectly with the expected theoretical curves over conducting and insulating under diffusion control. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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11 pages, 4465 KiB

Open AccessArticle

Interfacial Characterization of Polypyrrole/AuNP Composites towards Electrocatalysis of Ascorbic Acid Oxidation

by Camila Pesqueira, Bruna M. Hryniewicz, Larissa Bach-Toledo, Luciane Novaes Tenório, Luís F. Marchesi, Talita Mazon and Marcio Vidotti

Molecules 2022, 27(18), 5776; https://doi.org/10.3390/molecules27185776 - 07 Sep 2022

Cited by 4 | Viewed by 1689

Abstract

Polypyrrole (PPy) is an interesting conducting polymer due to its good environmental stability, high conductivity, and biocompatibility. The association between PPy and metallic nanoparticles has been widely studied since it enhances electrochemical properties. In this context, gold ions are reduced to gold nanoparticles [...] Read more.

Polypyrrole (PPy) is an interesting conducting polymer due to its good environmental stability, high conductivity, and biocompatibility. The association between PPy and metallic nanoparticles has been widely studied since it enhances electrochemical properties. In this context, gold ions are reduced to gold nanoparticles (AuNPs) directly on the polymer surface as PPy can be oxidized to an overoxidized state. This work proposes the PPy electrochemical synthesis followed by the direct reduction of gold on its surface in a fast reaction. The modified electrodes were characterized by electronic microscopic and infrared spectroscopy. The effect of reduction time on the electrochemical properties was evaluated by the electrocatalytic properties of the obtained material from the oxidation of ascorbic acid (AA) and electrochemical impedance spectroscopy studies. The presence of AuNPs improved the AA electrocatalysis by reducing oxidation potential and lowering charge transfer resistance. EIS data were fitted using a transmission line model. The results indicated an increase in the electronic transport of the polymeric film in the presence of AuNPs. However, PPy overoxidation occurs when the AuNPs’ deposition is higher than 30 s. In PPy/AuNPs 15 s, smaller and less agglomerated particles were formed with fewer PPy overoxidized, confirming the observed electrocatalytic behavior. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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17 pages, 1887 KiB

Open AccessArticle

Hydrogen-Chlorate Electric Power Source: Feasibility of the Device, Discharge Characteristics and Modes of Operation

by Dmitry V. Konev, Olga I. Istakova, Evgeny A. Ruban, Artem T. Glazkov and Mikhail A. Vorotyntsev

Molecules 2022, 27(17), 5638; https://doi.org/10.3390/molecules27175638 - 01 Sep 2022

Cited by 1 | Viewed by 2106

Abstract

A power source based on the current-generating reaction of aqueous chlorate-to-chloride reduction by molecular hydrogen would provide as much as 1150 Wh per 1 L of reagent storage (for a combination of 700 atm compressed hydrogen and saturated aqueous solution of lithium chlorate) [...] Read more.

A power source based on the current-generating reaction of aqueous chlorate-to-chloride reduction by molecular hydrogen would provide as much as 1150 Wh per 1 L of reagent storage (for a combination of 700 atm compressed hydrogen and saturated aqueous solution of lithium chlorate) at room temperature, but direct electroreduction of chlorate only proceeds with unacceptably high overvoltages, even for the most catalytically active electrodes. In the present study, we experimentally demonstrated that this process can be performed via redox-mediator catalysis by intermediate products of chlorate reduction, owing to their participation in homogeneous com- and disproportionation reactions. A series of current–voltage and discharge characteristics were measured for hydrogen-chlorate membrane–electrode assembly (MEA) cells at various concentrations of chlorate and sulfuric acid under operando spectrophotometric monitoring of the electrolyte composition during the discharge. We established that chlorine dioxide (ClO₂) is the key intermediate product; its fraction in the electrolyte solution increases progressively, up to its maximum, equal to 0.4–0.6 of the initial amount of chlorate anions, whereas the ClO₂ amount decreases gradually to a zero value in the later stage. In most discharge experiments, the Faradaic yield exceeded 90% (maximal value: 99%), providing approximately 48% chemical energy storage-to-electricity conversion efficiency at maximal power of the discharge (max value: 402 mW/cm²). These results support prospect of a hydrogen-chlorate flow current generator as a highly specific energy-capacity source for airless media. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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14 pages, 1700 KiB

Open AccessArticle

Weak Coordinating Character of Organosulfonates in Oriented Silica Films: An Efficient Approach for Immobilizing Cationic Metal-Transition Complexes

by Samuel Ahoulou, Clara Richart, Cédric Carteret, Sébastien Pillet, Neus Vilà and Alain Walcarius

Molecules 2022, 27(17), 5444; https://doi.org/10.3390/molecules27175444 - 25 Aug 2022

Cited by 2 | Viewed by 1327

Abstract

Iron (II) tris(2,2′-bipyridine) complexes, [Fe(bpy)₃]²⁺, have been synthesized and immobilized in organosulfonate-functionalized nanostructured silica thin films taking advantage of the stabilization of [Fe(H₂O)₆]²⁺ species by hydrogen bonds to the anionic sulfonate moieties grafted to [...] Read more.

Iron (II) tris(2,2′-bipyridine) complexes, [Fe(bpy)₃]²⁺, have been synthesized and immobilized in organosulfonate-functionalized nanostructured silica thin films taking advantage of the stabilization of [Fe(H₂O)₆]²⁺ species by hydrogen bonds to the anionic sulfonate moieties grafted to the silica nanopores. In a first step, thiol-based silica films have been electrochemically generated on indium tin oxide (ITO) substrates by co-condensation of 3-mercaptopropyltrimethoxysilane (MPTMS) and tetraethoxysilane (TEOS). Secondly, the thiol function has been modified to sulfonate by chemical oxidation using hydrogen peroxide in acidic medium as an oxidizing agent. The immobilization of [Fe(bpy)₃]²⁺ complexes has been performed in situ in two consecutive steps: (i) impregnation of the sulfonate functionalized silica films in an aqueous solution of iron (II) sulfate heptahydrate; (ii) dipping of the iron-containing mesostructures in a solution of bipyridine ligands in acetonitrile. The in situ formation of the [Fe(bpy)₃]²⁺ complex is evidenced by its characteristic optical absorption spectrum, and elemental composition analysis using X-ray photoelectron spectroscopy. The measured optical and electrochemical properties of immobilized [Fe(bpy)₃]²⁺ complexes are not altered by confinement in the nanostructured silica thin film. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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15 pages, 3666 KiB

Open AccessArticle

Electrochemical Bottom-Up Synthesis of Chiral Carbon Dots from L-Proline and Their Application as Nano-Organocatalysts in a Stereoselective Aldol Reaction

by Martina Bortolami, Ingrid Izabela Bogles, Cecilia Bombelli, Fabiana Pandolfi, Marta Feroci and Fabrizio Vetica

Molecules 2022, 27(16), 5150; https://doi.org/10.3390/molecules27165150 - 12 Aug 2022

Cited by 11 | Viewed by 2555

Abstract

Chirality is undoubtedly a fundamental property of nature since the different interactions of optically active molecules in a chiral environment are essential for numerous applications. Thus, in the field of asymmetric synthesis, the search for efficient, sustainable, cost-effective and recyclable chiral catalysts is [...] Read more.

Chirality is undoubtedly a fundamental property of nature since the different interactions of optically active molecules in a chiral environment are essential for numerous applications. Thus, in the field of asymmetric synthesis, the search for efficient, sustainable, cost-effective and recyclable chiral catalysts is still the main challenge in organic chemistry. The field of carbon dots (CDs) has experienced tremendous development in the last 15 years, including their applications as achiral catalysts. Thus, understanding the implications of chirality in CDs chemistry could be of utmost importance to achieving sustainable and biocompatible chiral nanocatalysts. An efficient and cost-effective electrochemical synthetic methodology for the synthesis of L-Proline-based chiral carbon dots (CCDs) and EtOH-derived L-Proline-based chiral carbon dots (CCDs) is herein reported. The electrochemical set-up and reaction conditions have been thoroughly optimised and their effects on CCDs size, photoluminescence, as well as catalytic activity have been investigated. The obtained CCDs have been successfully employed to catalyze an asymmetric aldol reaction, showing excellent results in terms of yield, diastereo- and enantioselectivity. Moreover, the sustainable nature of the CCDs was demonstrated by recycling the catalysts for up to 3 cycles without any loss of reactivity or stereoselectivity. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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15 pages, 2560 KiB

Open AccessArticle

Electrochemical Site-Selective Alkylation of Azobenzenes with (Thio)Xanthenes

by Qiang Zhong, Hui Gao, Pei-Long Wang, Chao Zhou, Tao Miao and Hongji Li

Molecules 2022, 27(15), 4967; https://doi.org/10.3390/molecules27154967 - 04 Aug 2022

Cited by 4 | Viewed by 1536

Abstract

Herein, we first report an electrochemical methodology for the site-selective alkylation of azobenzenes with (thio)xanthenes in the absence of any transition metal catalyst or external oxidant. A variety of groups are compatible with this electrochemical alkylation, which furnishes the products in moderate to [...] Read more.

Herein, we first report an electrochemical methodology for the site-selective alkylation of azobenzenes with (thio)xanthenes in the absence of any transition metal catalyst or external oxidant. A variety of groups are compatible with this electrochemical alkylation, which furnishes the products in moderate to good yields. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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13 pages, 3490 KiB

Open AccessFeature PaperArticle

Zero-Biased Photoelectrochemical Detection of Cardiac Biomarker Myoglobin Based on CdSeS/ZnS Quantum Dots and Barium Titanate Perovskite

by Fernanda M. R. Lima, Alan S. de Menezes, Adeilton P. Maciel, Francisco S. M. Sinfrônio, Lauro T. Kubota, Flávio S. Damos and Rita C. S. Luz

Molecules 2022, 27(15), 4778; https://doi.org/10.3390/molecules27154778 - 26 Jul 2022

Cited by 2 | Viewed by 1639

Abstract

Cardiovascular diseases are considered one of the leading causes of premature mortality of patients worldwide. Therefore, rapid diagnosis of these diseases is crucial to ensure the patient’s survival. During a heart attack or severe muscle damage, myoglobin is rapidly released in the body [...] Read more.

Cardiovascular diseases are considered one of the leading causes of premature mortality of patients worldwide. Therefore, rapid diagnosis of these diseases is crucial to ensure the patient’s survival. During a heart attack or severe muscle damage, myoglobin is rapidly released in the body to constitute itself as a precise biomarker of acute myocardial infarction. Thus, we described the photoelectrochemical immunosensor development to detect myoglobin. It was based on fluorine-doped tin oxide modified with CdSeS/ZnSe quantum dots and barium titanate (BTO), designated as CdSeS/ZnSQDS/BTO. It was characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDX), transmission electron microscopy (TEM), X-ray diffraction (XRD), electrochemical impedance spectroscopy (EIS), and amperometry. The anodic photocurrent at the potential of 0 V (vs. Ag/AgCl) and pH 7.4 was found linearly related to the myoglobin (Mb) concentration from 0.01 to 1000 ng mL⁻¹. Furthermore, the immunosensor showed an average recovery rate of 95.7–110.7% for the determination of myoglobin. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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17 pages, 4966 KiB

Open AccessArticle

A New Supramolecular Tetraruthenated Cobalt (II) Porphyrazine Displaying Outstanding Electrocatalytical Performance in Oxygen Evolution Reaction

by Hiago N. Silva, Sérgio Hiroshi Toma, Artur Luís Hennemann, Josué M. Gonçalves, Marcelo Nakamura, Koiti Araki, Marcos Makoto Toyama and Henrique Eisi Toma

Molecules 2022, 27(14), 4598; https://doi.org/10.3390/molecules27144598 - 19 Jul 2022

Cited by 3 | Viewed by 1528

Abstract

A new supramolecular electrocatalyst for Oxygen Evolution Reaction (OER) was synthesized from a central multibridging cobalt tetrapyridylporphyrazine (CoTPyPz) species by attaching four [Ru(bpy)₂Cl]⁺ groups. Both CoTPyPz and the tetraruthenated cobalt porphyrazine species, TRuCoTPyPz, form very homogenous molecular films just by [...] Read more.

A new supramolecular electrocatalyst for Oxygen Evolution Reaction (OER) was synthesized from a central multibridging cobalt tetrapyridylporphyrazine (CoTPyPz) species by attaching four [Ru(bpy)₂Cl]⁺ groups. Both CoTPyPz and the tetraruthenated cobalt porphyrazine species, TRuCoTPyPz, form very homogenous molecular films just by dropcasting their methanol solutions onto GCE electrodes. Such films exhibited low overpotentials for O₂ evolution, e.g., 560 e 340 mV, respectively, displaying high stability, typically exceeding 15 h. The kinetic parameters obtained from the Tafel plots showed that the peripheral complexes are very important for the electrocatalytic activity. Hyperspectral Raman images taken along the electrochemical process demonstrated that the cobalt center is the primary active catalyst site, but its performance is enhanced by the ruthenium complexes, which act as electron-donating groups, in the supramolecular system. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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Graphical abstract

13 pages, 3439 KiB

Open AccessArticle

On the Dynamics of the Carbon–Bromine Bond Dissociation in the 1-Bromo-2-Methylnaphthalene Radical Anion

by Marco Bonechi, Walter Giurlani, Massimo Innocenti, Dario Pasini, Suryakant Mishra, Roberto Giovanardi and Claudio Fontanesi

Molecules 2022, 27(14), 4539; https://doi.org/10.3390/molecules27144539 - 15 Jul 2022

Cited by 1 | Viewed by 1443

Abstract

This paper studies the mechanism of electrochemically induced carbon–bromine dissociation in 1-Br-2-methylnaphalene in the reduction regime. In particular, the bond dissociation of the relevant radical anion is disassembled at a molecular level, exploiting quantum mechanical calculations including steady-state, equilibrium and dissociation dynamics via [...] Read more.

This paper studies the mechanism of electrochemically induced carbon–bromine dissociation in 1-Br-2-methylnaphalene in the reduction regime. In particular, the bond dissociation of the relevant radical anion is disassembled at a molecular level, exploiting quantum mechanical calculations including steady-state, equilibrium and dissociation dynamics via dynamic reaction coordinate (DRC) calculations. DRC is a molecular-dynamic-based calculation relying on an ab initio potential surface. This is to achieve a detailed picture of the dissociation process in an elementary molecular detail. From a thermodynamic point of view, all the reaction paths examined are energetically feasible. The obtained results suggest that the carbon halogen bond dissociates following the first electron uptake follow a stepwise mechanism. Indeed, the formation of the bromide anion and an organic radical occurs. The latter reacts to form a binaphthalene intrinsically chiral dimer. This paper is respectfully dedicated to Professors Anny Jutand and Christian Amatore for their outstanding contribution in the field of electrochemical catalysis and electrosynthesis. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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Review

Jump to: Research

32 pages, 13655 KiB

Open AccessReview

Hard Carbons as Anodes in Sodium-Ion Batteries: Sodium Storage Mechanism and Optimization Strategies

by Liyang Liu, Ye Tian, Abubakar Abdussalam, Muhammad Rehan Hasan Shah Gilani, Wei Zhang and Guobao Xu

Molecules 2022, 27(19), 6516; https://doi.org/10.3390/molecules27196516 - 02 Oct 2022

Cited by 10 | Viewed by 6227

Abstract

Sodium-ion batteries (SIBs) are regarded as promising alternatives to lithium-ion batteries (LIBs) in the field of energy, especially in large-scale energy storage systems. Tremendous effort has been put into the electrode research of SIBs, and hard carbon (HC) stands out among the anode [...] Read more.

Sodium-ion batteries (SIBs) are regarded as promising alternatives to lithium-ion batteries (LIBs) in the field of energy, especially in large-scale energy storage systems. Tremendous effort has been put into the electrode research of SIBs, and hard carbon (HC) stands out among the anode materials due to its advantages in cost, resource, industrial processes, and safety. However, different from the application of graphite in LIBs, HC, as a disordered carbon material, leaves more to be completely comprehended about its sodium storage mechanism, and there is still plenty of room for improvement in its capacity, rate performance and cycling performance. This paper reviews the research reports on HC materials in recent years, especially the research process of the sodium storage mechanism and the modification and optimization of HC materials. Finally, the review summarizes the sterling achievements and the challenges on the basis of recent progress, as well as the prospects on the development of HC anode materials in SIBs. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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31 pages, 18429 KiB

Open AccessReview

Electrochemical and Spectroscopic Characterization of Oxidized Intermediate Forms of Vitamin E

by Richard D. Webster

Molecules 2022, 27(19), 6194; https://doi.org/10.3390/molecules27196194 - 21 Sep 2022

Cited by 4 | Viewed by 1827

Abstract

Vitamin E, a collection of lipophilic phenolic compounds based on chroman-6-ol, has a rich and fascinating oxidative chemistry involving a range of intermediate forms, some of which are proposed to be important in its biological functions. In this review, the available electrochemical and [...] Read more.

Vitamin E, a collection of lipophilic phenolic compounds based on chroman-6-ol, has a rich and fascinating oxidative chemistry involving a range of intermediate forms, some of which are proposed to be important in its biological functions. In this review, the available electrochemical and spectroscopic data on these oxidized intermediates are summarized, along with a discussion on how their lifetimes and chemical stability are either typical of similar phenolic and chroman-6-ol derived compounds, or atypical and unique to the specific oxidized isomeric form of vitamin E. The overall electrochemical oxidation mechanism for vitamin E can be summarized as involving the loss of two-electrons and one-proton, although the electron transfer and chemical steps can be controlled to progress along different pathways to prolong the lifetimes of discreet intermediates by modifying the experimental conditions (applied electrochemical potential, aqueous or non-aqueous solvent, and pH). Depending on the environment, the electrochemical reactions can involve single electron transfer (SET), proton-coupled electron transfer (PCET), as well as homogeneous disproportionation and comproportionation steps. The intermediate species produced via chemical or electrochemical oxidation include phenolates, phenol cation radicals, phenoxyl neutral radicals, dications, diamagnetic cations (phenoxeniums) and para–quinone methides. The cation radicals of all the tocopherols are atypically long-lived compared to the cation radicals of other phenols, due to their relatively weak acidity. The diamagnetic cation derived from α–tocopherol is exceptionally long-lived compared to the diamagnetic cations from the other β–, γ– and δ–isomers of vitamin E and compared with other phenoxenium cations derived from phenolic compounds. In contrast, the lifetime of the phenoxyl radical derived from α–tocopherol, which is considered to be critical in biological reactions, is typical for what is expected for a compound with its structural features. Over longer times via hydrolysis reactions, hydroxy para–quinone hemiketals and quinones can be formed from the oxidized intermediates, which can themselves undergo reduction processes to form intermediate anion radicals and dianions. Methods for generating the oxidized intermediates by chemical, photochemical and electrochemical methods are discussed, along with a summary of how the final products vary depending on the method used for oxidation. Since the intermediates mainly only survive in solution, they are most often monitored using UV-vis spectroscopy, FTIR or Raman spectroscopies, and EPR spectroscopy, with the spectroscopic techniques sometimes combined with fast photoinitiated excitation and time-resolved spectroscopy for detection of short-lived species. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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19 pages, 5180 KiB

Open AccessReview

Formate Dehydrogenase Mimics as Catalysts for Carbon Dioxide Reduction

by Thibault Fogeron, Yun Li and Marc Fontecave

Molecules 2022, 27(18), 5989; https://doi.org/10.3390/molecules27185989 - 14 Sep 2022

Cited by 3 | Viewed by 2373

Abstract

Formate dehydrogenases (FDH) reversibly catalyze the interconversion of CO₂ to formate. They belong to the family of molybdenum and tungsten-dependent oxidoreductases. For several decades, scientists have been synthesizing structural and functional model complexes inspired by these enzymes. These studies not only allow [...] Read more.

Formate dehydrogenases (FDH) reversibly catalyze the interconversion of CO₂ to formate. They belong to the family of molybdenum and tungsten-dependent oxidoreductases. For several decades, scientists have been synthesizing structural and functional model complexes inspired by these enzymes. These studies not only allow for finding certain efficient catalysts but also in some cases to better understand the functioning of the enzymes. However, FDH models for catalytic CO₂ reduction are less studied compared to the oxygen atom transfer (OAT) reaction. Herein, we present recent results of structural and functional models of FDH. Full article

(This article belongs to the Special Issue Electrochemistry and Organometallic Catalysis: Themed Issue in Honor of the Great Contribution of Prof. Dr. Christian Amatore and Prof. Dr. Anny Jutand)

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