Cobalt Corroles Research Articles

Regulating Steric Effect of Cobalt Corroles for Promoted Oxygen Electrocatalysis

Regulating Steric Effect of Cobalt Corroles for Promoted Oxygen Electrocatalysis

CoCorrole-Functionalized PCN-222 for Carbon Monoxide Selective Adsorption.

The high risk of CO poisoning justifies the need for indoor air quality control and warning systems based on the detection of low concentrations (ppm-ppb) of CO. Cobalt corrole complexes selectively bind CO vs. O2, CO2, N2, opening new fields of applications. By combining the CO chemisorption properties of cobalt corroles with the known sorption capacity of MOFs, we hope to obtain high performance sensing materials for CO detection. In addition, the exposed metal sites of MOFs lead to CO2 physisorption, allowing the co-detection of CO and CO2. In this work, PCN-222, a stable Zr-based MOF made from Ni(TCPP) with natural vacancies, has been used as a porous matrix for the grafting of electron-poor metallocorroles. The materials were characterized by powder XRD, SEM and optical microscopy, BET analyses and gas adsorption measurements at 298 K. No degradation of the crystalline structure of PCN-222 was observed. At 1 atm, the adsorbed CO(g) volumes measured for the best materials were 12.15 cm3 g-1 and 14.01 cm3 g-1 for CoCorr2@PCN-222 and CoCorr3@PCN-222 respectively, and both materials exhibited high CO chemisorption and selectivity against O2, N2, and CO2 at low pressure due to the highest energy of the chemisorption process vs physisorption.

A photoelectrochemical immunosensor based on cobalt corrole sensitized carbon nitride for human norovirus detection

Norovirus (NoV) stands as the prevailing etiological agent behind childhood gastroenteritis and foodborne illness, garnering significant attention due to its high infectivity pathogenicity. Protruding domain within the capsid protein (VP1) emerges as the primary antigenicity determinant and a hypervariable region, presenting a potential target site for detecting NoV infection. Herein, a label-free photoelectrochemical (PEC) immunosensor was proposed to achieve high sensitivity toward VP1, utilizing Co-Corrole sensitized carbon nitride (Co-Corrole/CN). Co-Corrole combines with CN through covalent bonds, and the strong binding effect accelerates the directional transport of electrons from CN to Co-Corrole. Co-Corrole acts as a photosensitizer, enhancing light harvesting in the visible region. The well-defined interfacial contact in Co-Corrole/CN heterojunction facilitates the electron-hole pairs separation and transfer. The strong light utilization and efficient carrier migration improve the PEC performance to amplify the photocurrent. This developed immunosensor platform demonstrated a wide range (0.75 pg mL–1-150 ng mL–1) with a notably low limit of detection (0.25 pg mL–1), exhibiting excellent stability and selectivity for other viruses. Moreover, this sensor detected clinical samples with remarkable accuracy and practicability. This research develops a facile and label-free diagnostic analytical technology for highly sensitive detection of NoV VP1 and offers promising prospects for improved diagnostic capability.

Electrocatalytic Hydrogen Evolution Reaction of Cobalt Triaryl Corrole Bearing Nitro Group

The use of non–precious metals for electrocatalytic hydrogen reaction (HER) is particularly important for energy conservation and environmental protection. In this work, three new cobalt corroles containing o−, m−, and p−nitrobenzyl (1, 2, 3) at the meso 10−position of the corrole macrocycle were synthesized, and their electrocatalytic hydrogen evolution reaction in organic and neutral aqueous systems was also investigated. The results show that these three cobalt corroles have significant catalytic HER activity in both systems, and the catalytic efficiency follows 1 > 3 > 2, which indicates that the position of the nitro group can affect the catalytic property of the complexes. In the organic phase, when using trifluoroacetic acid or p−toluenesulfonic acid as the proton source, the electrocatalytic HER may undergo an EECC (E: electron transfer, C: proton coupling) pathway. In a neutral aqueous system, the HER turnover frequency value of 1 is up to 137.4 h−1 at 938 mV overpotential.

Electrocatalytic Properties of meso‐ Perfluorinated Metallo Corroles for the Reduction of CO2

Corrole, a contracted tetrapyrrolic macrocycle has been also used to design molecular for the CO2 reduction. The electrochemical activity towards CO2 reduction can rival those of their porphyrin analogues. However, the catalytic activity of the metallocorrole is initiated at the corresponding MII/I couple. Accordingly, a catalytic current in presence of CO2 with cobalt corrole appears when the CoI species is generated. We have designed an electron deficient A2B corrole holding two ‐CF3 groups and a benzonitrile in the meso positions and its cobalt complex (1). We reasoned that these groups could shuffle the redox potentials to reach the M(I) oxidation states at more positive values thereby lowering the overpotential for the catalytic CO2 reduction. Our results clearly show that catalyst 1 when adsorbed on a carbon electrode, shows the most favourable catalytic performance for CO production, achieving an efficiency of 85% with a current density of ‐1.5 mA cm‐2 at ‐1.0 V vs NHE. The current densities of controlled potential electrolysis with increasing amount of KHCO3, were found to increase more than one order of magnitude with the formation of MeOH.

Electrocatalytic hydrogen evolution by cobalt(Ⅲ) triphenyl corrole bearing different number of trifluoromethyl groups

Hydrogen production from electrolyzing water is known as the most promising hydrogen production method. To further understand the effect of steric hindrance and electron-withdrawing groups on catalysts, four cobalt triphenyl corroles bearing different number of ortho-trifluoromethyls (1, 2, 3, 4) had been synthesized and used as hydrogen evolution electrocatalysts. These cobalt corroles showed effective electrocatalytic hydrogen evolution activity in organic medium and neutral aqueous medium, with turnover frequency ranging from 100 s−1 to 220 s−1 using 32 equivalents of trifluoroacetic acid proton source in DMF. The electrocatalytic HER goes via competitive ECEC or EECC pathway depending on the used proton source. The electrocatalytic HER activity varies obviously with the number of the peripheral ortho- groups. This work is helpful for the design of new metal corrole HER electrocatalyst.

Structurally influenced optical nonlinearities and ultrafast dynamics in β-acroleyl- and β-dicyanobutadienyl-appended cobalt corroles.

The strong two-photon induced nonlinear absorption and self-focusing type positive nonlinear refraction are pronounced by the structural engineering in β-functionalized cobalt corroles.

Exploring the role of polymer interactions during water electrolysis under basic conditions with bifunctional cobalt corroles

Cobalt corroles modified with aminoalkyl chains show increased catalytic performance for bifunctional water splitting at pH 14 when immobilized.

Electrochemistry of and Electrocatalysis by Low-Symmetry N4 Macrocycles

The introduction of efficient and affordable catalysts for three seemingly simple electrochemical reactions could improve very much the sustainability of our energy supply: reduction of protons to hydrogen gas (the hydrogen evolution reaction, HER), water oxidation, and selective reduction of oxygen to water (the oxygen reduction reaction, ORR).1–6 Platinum group metals (PGM) are outstanding catalysts for all these reactions, but being rare and expensive prevents their utility for large scale operations.7 Within the search for catalysts based on earth abundant 1st row transition metals, we now introduce two different molecular catalysts: Co(III) complexes of corroles, with very different in size meso-C substituents (C6F5 >> CF3 >> H), as well by newly synthesized and fully characterized Co(II), Cu(II) and Ni(II) monoazaporphyrins (MAzP) with meso-CF3 substituents. All the catalyst were adsorbed on carbon supports with very different porosity (Vulcan << BP2000). The corrole-modified electrodes were studied as ORR catalysts, revealing that the onset potential of the best performing cobalt corrole is approaching that of Pt and with low percentage formation of undesired hydrogen peroxide. Testing that complex as a cathode for an anion exchange membrane fuel cell (AEMFC) revealed high power density relative to other molecular catalysts and excellent stability over 12 hours.Metal complexes of a novel MAzP with CF3 on the three meso-C positions were studied as catalysts for HER in PBS buffer (pH=7.4), as well as for water oxidation and ORR at pH 13. The cobalt complex performed best in all processes. Compared to cobalt porphyrins with either three or four CF3 groups on the meso-C positions, Co-MAzP performed better for water oxidation. For HER catalysis, it has the same onset potential and current as the tetra-CF3 cobalt porphyrin and more current than the tris-CF3 analogue. In ORR catalysis, Co-MAzP performs with the lowest onset potential, but less H2O2 is formed via catalysis by the other porphyrins.(1) Meng, J.; Lei, H.; Li, X.; Qi, J.; Zhang, W.; Cao, R. Attaching Cobalt Corroles onto Carbon Nanotubes: Verification of Four-Electron Oxygen Reduction by Mononuclear Cobalt Complexes with Significantly Improved Efficiency. ACS catalysis. 2019, pp 4551–4560.(2) Beyene, B. B.; Hung, C.-H. Recent Progress on Metalloporphyrin-Based Hydrogen Evolution Catalysis. Coord. Chem. Rev. 2020, 410, 213234.(3) Mondal, B.; Chattopadhyay, S.; Dey, S.; Mahammed, A.; Mittra, K.; Rana, A.; Gross, Z.; Dey, A. Elucidation of Factors That Govern the 2e–/2H+ vs 4e–/4H+ Selectivity of Water Oxidation by a Cobalt Corrole. J. Am. Chem. Soc. 2020, 142 (50), 21040–21049.(4) Cui, X.; Cui, Y.; Chen, M.; Xiong, R.; Huang, Y.; Liu, X. Enhancing Electrochemical Hydrogen Evolution Performance of CoMoO4-Based Microrod Arrays in Neutral Media through Alkaline Activation. ACS Appl. Mater. Interfaces 2020, 12 (27), 30905–30914.(5) Fornaciari, J. C.; Weng, L.-C.; Alia, S. M.; Zhan, C.; Pham, T. A.; Bell, A. T.; Ogitsu, T.; Danilovic, N.; Weber, A. Z. Mechanistic Understanding of PH Effects on the Oxygen Evolution Reaction. Electrochim. Acta 2022, 405, 139810.(6) Yao, B.; He, Y.; Wang, S.; Sun, H.; Liu, X. Recent Advances in Porphyrin-Based Systems for Electrochemical Oxygen Evolution Reaction. International journal of molecular sciences. 2022, p 6036.(7) Mehta, V.; Cooper, J. S. Review and Analysis of PEM Fuel Cell Design and Manufacturing. Journal of power sources. 2003, pp 32–53.

Effect of Apical Ligands, Substituents and Oxidation States on the Electronic Structure of Co(III) Corrolates

AbstractCobalt(III) corroles are the most commonly studied types of metallocorroles, yet the details of their electronic structure, ground spin states and place of redox events are not always straightforward. Corroles are redox active, potentially non‐innocent ligands, and it has been found through various experimental and computational techniques, that the innocent or non‐innocent behavior is modulated by the apical ligands bound to the cobalt center. In this work, we aim to analyze the effect of corrole substituents and number and type of apical ligands on the electronic structure of cobalt corroles through density functional and wavefunction theories, and to determine the relative energies between closed‐ and open‐shell states. We further perform preliminary analyses on the place of electron abstraction upon oxidation and on the effect of the corrole and apical ligands on the cobalt ligand field splittings. We find that both ligand field and electron‐donating or withdrawing effects determine the relative energies of open‐shell and closed shell singlet states.

Electrocatalytic Hydrogen Evolution of Transition Metal (Fe, Co and Cu)–Corrole Complexes Bearing an Imidazole Group

The study of the hydrogen evolution reaction (HER) by non-noble transition metals is of great significance for the production of hydrogen energy. In this work, a new 5,15-bis-(pentafluorophenyl)-10-[4-(1H-imidazole) phenyl]-corrole and its metal complexes (metal = Co, Cu, Fe) were synthesized and used for electrocatalyzed HER in DMF organic solvent and aqueous media. The prepared cobalt corrole showed the best catalytic performance in both media. Its turnover frequency (TOF) and catalytic efficiency (C.E) could reach 265 s−1 and 1.04 when TsOH was used as the proton source in a DMF solvent. In aqueous media, its TOF could also reach 405 h−1. The catalytic HER may go through an EECEC or ECEC (E: electron transfer, C: chemical step) pathway for these catalysts, depending on the acidity and concentration of the proton source. The present work successfully demonstrates that imidazole at a meso-phenyl group may improve the electrocatalytic HER activity of transition metal corroles.

Tuning ORR selectivity of π-conjugated cobalt corroles from 2e- to 4e-

Efficient oxygen reduction reaction (ORR) is crucial for the performance of fuel cells and other electrochemical devices. Seeking for stable and electrochemically selective 2e- and 4e- ORR electrocatalyst is yet a challenge, making the design extremely important and outmost of interest. In this study, we demonstrate a method to tune ORR selectivity by adjusting the local cobalt density through oligo-/polymerization of π-conjugated cobalt(III) A2B and A3-corroles to linear and two-dimensional matrix structures. These heterogeneous catalysts exhibit remarkable physicochemical properties, fast charge transfer kinetics, electrochemical reversibility, and high durability. Unselective three-electron transfer kinetics with n = 2.5–2.9 in between −0.20 V and +0.40 V vs. RHE are detected with the π-conjugated cobalt(III) A2B- corrole polymers. Highly selective four-electron kinetics with n = 3.7 in between −0.20 V and +0.40 V vs. RHE are detected by employing the cobalt A3-corrole oligomers during the ORR catalysis.

Hydrogen evolution activity of cobalt corroles

An electrochemical study of a series of bis-pyridine ligated A2B type cobalt corroles has been carried out. The impact of substituting with electron withdrawing or donating groups on the overall oxidation or reduction potential was assessed through the use of cyclic voltametric (CV) experiments. DFT methods have also been used to assess the influence of meso-substituents and to structurally optimize the geometries of the complexes to help our understanding of the sometimes-subtle structural characteristics found in the macromolecular systems. A novel penta-coordinated triphenylphosphine ligated corrole i.e., [10-(2,6-difluorophenyl)-5,15-bis(4-nitrophenyl)corrolato]cobalt(III) was also synthesised and characterized using different spectroscopic techniques and X-ray diffraction methods. The hydrogen evolution reaction (HER) capability of the two complexes herein were assessed through CV. The complexes do not show activity toward the HER; rather they supply ligands for the process. The meso-substituents have significant effect on the overall activity of Co macrocycles.

Panchromatic and Perturbed Absorption Spectral Features and Multiredox Properties of Dicyanovinyl- and Dicyanobutadienyl-Appended Cobalt Corroles.

Four new β-functionalized π-extended cobalt corroles with one and two dicyanovinyl (DCV) or dicyanobutadienyl (DCBD) moieties at the 3- and 3,17-positions have been synthesized and characterized by various spectroscopic techniques. Interestingly, the synthesized DCV- and DCBD-appended cobalt corroles displayed panchromatic and near-infrared absorption in the range 300-1100 nm in CH2Cl2 and pyridine solvents. (MN)2-(Cor)Co and A2MN2-(Cor)Co exhibited 8-9 times enhancement in the molar absorptivity of the Q band compared to the parent corrole ((Cor)Co). The unique absorption spectral features of these β-functionalized cobalt corroles are splitting, broadening, and red-shifting in the Soret and Q bands. One DCV unit brings a 30-46 nm red shift, whereas one DCBD unit brings a 40-75 nm red shift in the Q band compared to the corresponding precursors. This is rare that the intensity of the longest Q band is greater than or equal to the Soret-like bands. These corrole derivatives exhibit UV-vis spectral features similar to those of chlorophyll a. A 220 mV positive shift per DCV group and 160 mV positive shift per DCBD group were observed in the first oxidation potentials compared to (Cor)Co in the desired direction for the utility of these cobalt complexes in electrocatalysis. DFT studies revealed that HOMO and LUMO were stabilized after appending DCV and DCBD groups on the corrole macrocycle and exhibited a "push-pull" behavior leading to promising material applications in nonlinear optics (NLO) and catalysis.

A One‐Pot Three‐In‐One Synthetic Strategy to Immobilize Cobalt Corroles on Carbon Nanotubes for Oxygen Electrocatalysis

AbstractMolecular electrocatalysis requires the immobilization of molecular catalysts on electrode materials for practical uses. Direct adsorption of catalyst molecules on electrode materials is simple, but grafting molecules through chemical bonds can significantly improve electrocatalytic efficiency and durability. However, designing and synthesizing catalyst molecules to simultaneously improve catalytic activities and realize easy grafting on electrodes is challenging. The study herein reports on a one‐pot strategy to graft Co corroles on pyridine‐modified carbon nanotubes (CNTs) for oxygen electrocatalysis. By modifying CNTs with pyridines, the resulting pyridine‐modified CNTs can function as platforms to grab in situ generated Co corroles through the axial pyridine ligation on Co. Such an immobilization strategy combines three effects for the regulation of electrocatalysis, including the axial ligand effect, the electron transfer effect, and the chemical bond effect. The resulting hybrid materials show high efficiency for oxygen electrocatalysis, and the Zn–air battery assembled using these materials displays comparable performance as the Pt/Ir‐based battery. Moreover, the electrocatalytic efficiency of these hybrid materials can be systematically tuned by using different pyridines, highlighting the controllable feature of this strategy. Therefore, this work is significant to present a one‐pot three‐in‐one strategy to immobilize catalyst molecules on CNTs for electrocatalysis.

A Cobalt(III) Corrole with a Tethered Imidazole for Boosted Electrocatalytic Oxygen Reduction Reaction

Comprehensive SummaryDeveloping electrocatalysts with high activity and selectivity for the oxygen reduction reaction (ORR) is vital to promote the performance of the next‐generation energy technologies, which depend on the efficiency of the catalytic reduction of dioxygen. In the structure of cytochrome c oxidases (CcOs), a histidine imidazole residue binding to the axial position of Fe plays a crucial role in facilitating the selective reduction of O2 to water. Inspired by nature, we herein report on the synthesis of CoIII corrole 1 tethered with an imidazole ligand as well as its electrocatalytic ORR and O2 binding features. As compared to the imidazolium‐free analogue, complex 1 displayed remarkably boosted activity for the selective four‐electron/four‐proton (4e‐/4H+) ORR with a half‐wave potential of E1/2 = 0.82 V versus reversible hydrogen electrode (RHE) in 0.1 mol/L KOH solutions. Importantly, we demonstrate that the tethered axial imidazole ligand improves the O2 binding ability of 1 thermodynamically and dynamically, which is crucial to boost electrocatalytic ORR performance. This work presents an example to improve electrocatalytic ORR activity and selectivity of Co corroles by introducing an axial imidazole ligand to enhance the O2 binding and activation.

A Bifunctional Electrocatalyst for OER and ORR based on a Cobalt(II) Triazole Pyridine Bis-[Cobalt(III) Corrole] Complex.

As alternative energy sources are essential to reach a climate-neutral economy, hydrogen peroxide (H2O2) as futuristic energy carrier gains enormous awareness. However, seeking for stable and electrochemically selective H2O2 ORR electrocatalyst is yet a challenge, making the design of-ideally-bifunctional catalysts extremely important and outmost of interest. In this study, we explore the application of a trimetallic cobalt(II) triazole pyridine bis-[cobalt(III) corrole] complex CoIITP[CoIIIC]2 3 in OER and ORR catalysis due to its remarkable physicochemical properties, fast charge transfer kinetics, electrochemical reversibility, and durability. With nearly 100 % selective catalytic activity towards the two-electron transfer generated H2O2, an ORR onset potential of 0.8 V vs RHE and a cycling stability of 50 000 cycles are detected. Similarly, promising results are obtained when applied in OER catalysis. A relatively low overpotential at 10 mA cm-2 of 412 mV, Faraday efficiency 98 % for oxygen, an outstanding Tafel slope of 64 mV dec-1 combined with superior stability.

A Bifunctional Electrocatalyst for OER and ORR based on a Cobalt(II) Triazole Pyridine Bis-[Cobalt(III) Corrole] Complex.

As alternative energy sources are essential to reach a climate-neutral economy, hydrogen peroxide (H2 O2 ) as futuristic energy carrier gains enormous awareness. However, seeking for stable and electrochemically selective H2 O2 ORR electrocatalyst is yet a challenge, making the design of-ideally-bifunctional catalysts extremely important and outmost of interest. In this study, we explore the application of a trimetallic cobalt(II) triazole pyridine bis-[cobalt(III) corrole] complex CoII TP[CoIII C]2 3 in OER and ORR catalysis due to its remarkable physicochemical properties, fast charge transfer kinetics, electrochemical reversibility, and durability. With nearly 100 % selective catalytic activity towards the two-electron transfer generated H2 O2 , an ORR onset potential of 0.8 V vs RHE and a cycling stability of 50 000 cycles are detected. Similarly, promising results are obtained when applied in OER catalysis. A relatively low overpotential at 10 mA cm-2 of 412 mV, Faraday efficiency 98 % for oxygen, an outstanding Tafel slope of 64 mV dec-1 combined with superior stability.

Altering the Site of Electron Abstraction in Cobalt Corroles via meso-Trifluoromethyl Substituents

A mono-DMSO cobalt meso-CF3 corrole, formulated as (CF3)3CorCo(DMSO), where (CF3)3Cor is the trianion of 5,10,15-tris(trifluoromethyl)corrole, was synthesized and characterized as to its spectral and electrochemical properties in nonaqueous media with a focus on its coordination chemistry and electronic structure. Cyclic voltammetric measurements showed more facile reductions and difficult oxidations compared to the cobalt triarylcorrole possessing p-CF3Ph units at the meso-positions, a result consistent with the enhanced inductive effect of the electron-withdrawing trifluoromethyl substituents linked directly at the meso-carbon atoms of the macrocycle. The effects of DMSO, pyridine, and cyanide anions (CN-) on the electrochemistry and spectral properties of the compound were investigated, and it was found that only two molar equivalents are needed to form the bis-CN adduct, which exhibited two 1-electron oxidations at 0.27 and 0.95 V vs saturated calomel electrode (SCE) in CH2Cl2/0.1 M TBAP. The sites of electron transfer in the first oxidation and reduction were investigated by spectroelectrochemistry and confirmed that the first electron addition affords a Cor3-CoII complex under all solution conditions independent of the initial coordination and/or electronic configuration (i.e., innocent Cor3-CoIII or noninnocent Cor•2-CoII). In contrast, data for the first oxidation suggests that the site of electron abstraction (ligand or metal) depended upon coordination of the neutral and in situ generated complexes under the various solution conditions, leading to a Co(IV)-corrole3- product for both the bis-pyridine and bis-cyanide adducts.

Electrocatalytic Hydrogen Evolution of the Cobalt Triaryl Corroles Bearing Hydroxyl Groups

AbstractThree isomeric A2B‐type new cobalt triaryl corroles bearing hydroxyphenyl substituents have been prepared and well characterized. Their activity and stability in the electrocatalytic hydrogen evolution reaction (HER) have been investigated. The results showed that the hydroxyl position of the phenyl group had significant influence on electrocatalytic HER. The ortho‐hydroxyphenyl substituted cobalt corrole (1) core displays the best HER activity using TsOH proton source, and the turnover frequency (TOF) and catalytic efficiency (C.E) reach 318.68 s−1 and 1.13, respectively. Moreover, a turnover number (TON) of 1447.39 and Faraday efficiency (FE) of 98.7 % have been observed in aqueous medium. The catalytic pathway is via EECEC, EECC or ECEC pathways depending on the acidity of acid proton source (E: electron transfer step, C: chemical step, in this case protonation). The catalytic HER performance of these cobalt corroles follows an order of o‐hydroxyl &gt; p‐hydroxyl &gt; m‐hydroxyl isomer, showing the o‐ and p‐hydroxyl of the phenyl groups are more efficient in accelerating proton relay.