1
|
Electrocatalytic Conversion of Small Molecules Utilizing Concerted Proton-electron Transfer Mediators. Chimia (Aarau) 2024; 78:251-255. [PMID: 38676619 DOI: 10.2533/chimia.2024.251] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2024] [Accepted: 02/19/2024] [Indexed: 04/29/2024] Open
Abstract
Activation of small molecules such as CO2, N2 or organic substrates and their subsequent transformation into complex value-added chemicals by electrocatalysis, utilizing renewable energy sources under ambient conditions, has gained considerable interest in the last few years. However, activation of these chemically inert molecules is hindered by their intrinsically high activation energy barrier presupposing the development of tailored catalytic systems, often precluding selective transformation to the desired target products. Recent studies have shown that the utilization of concerted proton-electron transfer (CPET) mediators (med-H) may facilitate these challenging electrocatalytic reactions.
Collapse
|
2
|
Gauging Iron-Sulfur Cubane Reactivity from Covalency: Trends with Oxidation State. JACS AU 2024; 4:1315-1322. [PMID: 38665672 PMCID: PMC11040707 DOI: 10.1021/jacsau.4c00213] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/07/2024] [Revised: 04/03/2024] [Accepted: 04/03/2024] [Indexed: 04/28/2024]
Abstract
We investigated room-temperature metal and ligand K-edge X-ray absorption (XAS) spectra of a complete redox series of cubane-type iron-sulfur clusters. The Fe K-edge position provides a qualitative but convenient alternative to the traditional spectroscopic descriptors used to identify oxidation states in these systems, which we demonstrate by providing a calibration curve based on two analytic methods. Furthermore, high energy resolution fluorescence detected XAS (HERFD-XAS) at the S K-edge was used to measure Fe-S bond covalencies and record their variation with the average valence of the Fe atoms. While the Fe-S(thiolate) covalency evolves linearly, gaining 11 ± 0.4% per bond and hole, the Fe-S(μ3) covalency evolves asystematically, reflecting changes in the magnetic exchange mechanism. A strong discontinuity manifested for superoxidation to the all-ferric state, distinguishing its electronic structure and its potential (bio)chemical role from those of its redox congeners. We highlight the functional implications of these trends for the reactivity of iron-sulfur cubanes.
Collapse
|
3
|
Understanding the Synergy between Fe and Mo Sites in the Nitrate Reduction Reaction on a Bio-Inspired Bimetallic MXene Electrocatalyst. Angew Chem Int Ed Engl 2023:e202313746. [PMID: 37907396 DOI: 10.1002/anie.202313746] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2023] [Revised: 10/17/2023] [Accepted: 10/31/2023] [Indexed: 11/02/2023]
Abstract
Mo- and Fe-containing enzymes catalyze the reduction of nitrate and nitrite ions in nature. Inspired by this activity, we study here the nitrate reduction reaction (NO3 RR) catalyzed by an Fe-substituted two-dimensional molybdenum carbide of the MXene family, viz., Mo2 CTx : Fe (Tx are oxo, hydroxy and fluoro surface termination groups). Mo2 CTx : Fe contains isolated Fe sites in Mo positions of the host MXene (Mo2 CTx ) and features a Faradaic efficiency (FE) and an NH3 yield rate of 41 % and 3.2 μmol h-1 mg-1 , respectively, for the reduction of NO3 - to NH4 + in acidic media and 70 % and 12.9 μmol h-1 mg-1 in neutral media. Regardless of the media, Mo2 CTx : Fe outperforms monometallic Mo2 CTx owing to a more facile reductive defunctionalization of Tx groups, as evidenced by in situ X-ray absorption spectroscopy (Mo K-edge). After surface reduction, a Tx vacancy site binds a nitrate ion that subsequently fills the vacancy site with O* via oxygen transfer. Density function theory calculations provide further evidence that Fe sites promote the formation of surface O vacancies, which are identified as active sites and that function in NO3 RR in close analogy to the prevailing mechanism of the natural Mo-based nitrate reductase enzymes.
Collapse
|
4
|
Mixed-metal Ionothermal Synthesis of Metallophthalocyanine Covalent Organic Frameworks for CO 2 Capture and Conversion. Angew Chem Int Ed Engl 2023; 62:e202309775. [PMID: 37533138 DOI: 10.1002/anie.202309775] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2023] [Revised: 07/29/2023] [Accepted: 08/02/2023] [Indexed: 08/04/2023]
Abstract
Phthalocyanines (PCs) are intriguing building blocks owing to their stability, physicochemical and catalytic properties. Although PC-based polymers have been reported before, many suffer from relatively low stability, crystallinity, and low surface areas. Utilizing a mixed-metal salt ionothermal approach, we report the synthesis of a series of metallophthalocyanine-based covalent organic frameworks (COFs) starting from 1,2,4,5-tetracyanobenzene and 2,3,6,7-tetracyanoanthracene to form the corresponding COFs named M-pPPCs and M-anPPCs, respectively. The obtained COFs followed the Irving-Williams series in their metal contents, surface areas, and pore volume and featured excellent CO2 uptake capacities up to 7.6 mmol g-1 at 273 K, 1.1 bar. We also investigated the growth of the Co-pPPC and Co-anPPC on a highly conductive carbon nanofiber and demonstrated their high catalytic activity in the electrochemical CO2 reduction, which showed Faradaic efficiencies towards CO up to 74 % at -0.64 V vs. RHE.
Collapse
|
5
|
Molecular Bio-inspired Strategies for the Design of Electrocatalytic Systems. Chimia (Aarau) 2023; 77:478-483. [PMID: 38047788 DOI: 10.2533/chimia.2023.478] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2023] [Accepted: 06/14/2023] [Indexed: 12/05/2023] Open
Abstract
This perspective article delves into the realm of bio-inspired catalysis, highlighting the valuable insights gleaned from enzymatic systems for the design of advanced electrocatalysts. We focus here on three key aspects to mimic: the structure of enzymatic active sites, the essential functions to enable catalytic activity as well as key elementary steps of reaction mechanisms employed by enzymes to ensure maximum efficiency and selectivity. Our research group's contributions to these areas are highlighted, including the synthesis and catalytic activity of cobalt(III) pyridinethiolate complexes, the exploration of bimetallic sites mimicking biological carbon dioxide reductases and of all-ferrous Fe4S4 clusters as mimics of FeP active sites, and the integration of concerted proton-electron transfer (CPET) mediators for the generation of metal hydride species. We emphasize the potential of these bio-inspired approaches in advancing electrocatalyst design and their relevance to molecular catalysis.
Collapse
|
6
|
Co-Electrospun Poly(ε-Caprolactone)/Zein Articular Cartilage Scaffolds. Bioengineering (Basel) 2023; 10:771. [PMID: 37508797 PMCID: PMC10376865 DOI: 10.3390/bioengineering10070771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2023] [Revised: 06/19/2023] [Accepted: 06/21/2023] [Indexed: 07/30/2023] Open
Abstract
Osteoarthritis scaffold-based grafts fail because of poor integration with the surrounding soft tissue and inadequate tribological properties. To circumvent this, we propose electrospun poly(ε-caprolactone)/zein-based scaffolds owing to their biomimetic capabilities. The scaffold surfaces were characterized using Fourier-transform infrared spectroscopy, X-ray photoelectron spectroscopy, static water contact angles, and profilometry. Scaffold biocompatibility properties were assessed by measuring protein adsorption (Bicinchoninic Acid Assay), cell spreading (stained F-actin), and metabolic activity (PrestoBlue™ Cell Viability Reagent) of primary bovine chondrocytes. The data show that zein surface segregation in the membranes not only completely changed the hydrophobic behavior of the materials, but also increased the cell yield and metabolic activity on the scaffolds. The surface segregation is verified by the infrared peak at 1658 cm-1, along with the presence and increase in N1 content in the survey XPS. This observation could explain the decrease in the water contact angles from 125° to approximately 60° in zein-comprised materials and the decrease in the protein adsorption of both bovine serum albumin and synovial fluid by half. Surface nano roughness in the PCL/zein samples additionally benefited the radial spreading of bovine chondrocytes. This study showed that co-electrospun PCL/zein scaffolds have promising surface and biocompatibility properties for use in articular-tissue-engineering applications.
Collapse
|
7
|
Probing the Role of Environmental and Sample Characteristics in Gap Mode Tip-Enhanced Raman Spectroscopy. Anal Chem 2023. [PMID: 37260258 DOI: 10.1021/acs.analchem.3c00410] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Tip-enhanced Raman spectroscopy (TERS) has emerged as a powerful analytical tool for nondestructive and label-free molecular characterization at the nanoscale. However, the influence of environmental factors and sample characteristics on the occurrence of spurious signals, enhancement of TERS signals, and longevity of TERS probes is not well understood yet. Herein, we present a detailed investigation of the influence of oxygen, humidity, and atmospheric carbon contaminants on scanning tunneling microscopy-TERS (STM-TERS) measurements of self-assembled monolayer systems in ambient and inert environments. Our results reveal a consistent increase of TERS signals, significant reduction of spurious signals, and drastically improved longevity of TERS probes in the inert environment. Additionally, sample characteristics such as molecular packing, chemisorption behavior, and hydrophilicity are found to have a direct impact on signal enhancement in the TERS measurements of molecular self-assembled monolayers (SAMs). The novel insights gained in this study are expected to pave the way for a more robust data analysis and improved experimental design in the future gap mode STM- and atomic force microscopy-TERS (AFM-TERS) studies.
Collapse
|
8
|
Copper(II) defect-cubane water oxidation electrocatalysts: from molecular tetramers to oxidic nanostructures. Chem Commun (Camb) 2023; 59:5866-5869. [PMID: 37089062 PMCID: PMC10174076 DOI: 10.1039/d3cc01005h] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
We report on the synthesis and spectroscopic evidence for a sequence of structural transformations of a new defect-cubane type copper complex, [Cu4(pyalk)4(OAc)4](ClO4)(HNEt3), which acts as a pre-catalyst for water oxidation. In situ and post-catalytic studies showed that the tetrameric complex undergoes a structural transformation into dimeric and monomeric species, induced by water molecules and carbonate anions, respectively. Further, the observed electrocatalytic water oxidation activity has been confirmed to arise from in situ-generated Cu(II) oxidic nanostructures at the electrode interface.
Collapse
|
9
|
Electrocatalyst Microenvironment Engineering for Enhanced Product Selectivity in Carbon Dioxide and Nitrogen Reduction Reactions. ACS Catal 2023; 13:5375-5396. [PMID: 37123597 PMCID: PMC10127282 DOI: 10.1021/acscatal.3c00201] [Citation(s) in RCA: 10] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2023] [Revised: 03/23/2023] [Indexed: 04/08/2023]
Abstract
Carbon and nitrogen fixation strategies are regarded as alternative routes to produce valuable chemicals used as energy carriers and fertilizers that are traditionally obtained from unsustainable and energy-intensive coal gasification (CO and CH4), Fischer-Tropsch (C2H4), and Haber-Bosch (NH3) processes. Recently, the electrocatalytic CO2 reduction reaction (CO2RR) and N2 reduction reaction (NRR) have received tremendous attention, with the merits of being both efficient strategies to store renewable electricity while providing alternative preparation routes to fossil-fuel-driven reactions. To date, the development of the CO2RR and NRR processes is primarily hindered by the competitive hydrogen evolution reaction (HER); however, the corresponding strategies for inhibiting this undesired side reaction are still quite limited. Considering such complex reactions involve three gas-liquid-solid phases and successive proton-coupled electron transfers, it appears meaningful to review the current strategies for improving product selectivity in light of their respective reaction mechanisms, kinetics, and thermodynamics. By examining the developments and understanding in catalyst design, electrolyte engineering, and three-phase interface modulation, we discuss three key strategies for improving product selectivity for the CO2RR and NRR: (i) targeting molecularly defined active sites, (ii) increasing the local reactant concentration at the active sites, and (iii) stabilizing and confining product intermediates.
Collapse
|
10
|
Molybdenum(IV) -Diketonate Complexes as Highly Active Catalysts for Allylic Substitution Reactions. Chem Commun (Camb) 2023; 59:4636-4639. [PMID: 36987978 PMCID: PMC10101048 DOI: 10.1039/d3cc00572k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/15/2023]
Abstract
The synthesis and characterization of a series of Mo(IV) bis--diketonate (Rdiket, R = Me, tBu, Ph) dichloride (RMoIVCl2) and bistriflate (RMoIV(OTf)2) complexes are reported. All complexes are characterized in solid...
Collapse
|
11
|
A Germapyramidane Switches Between 3D Cluster and 2D Cyclic Structures in Single-Electron Steps. Angew Chem Int Ed Engl 2022; 61:e202211749. [PMID: 36152009 PMCID: PMC9828763 DOI: 10.1002/anie.202211749] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2022] [Indexed: 01/12/2023]
Abstract
Reaction of the imidazolium-substituted iphosphate-diide, (Ipr)2 C2 P2 (IDP), with GeCl2 ⋅ dioxane and KBArF24 [(BarF24 )- =tetrakis[(3,5-trifluoromethyl)phenyl]borate)] afforded the dicationic spherical-aromatic nido-cluster [Ge(η4 -IDP)]2+ ([1]2+ ) (Ipr=1,3-bis(2,6-diisopropylphenyl)imidazolium-2-ylidene). This complex is a rare heavy analogue of the elusive pyramidane [C(η4 -C4 H4 )]. [1]2+ undergoes two reversible one-electron reductions, which yield the radical cation [2]⋅+ and the neutral GeII species 3. Both [2]⋅+ and 3 rearrange in solution forming the 2D aromatic and planar imidazolium-substituted digermolide [4]2+ and germole-diide 5, respectively. Both planar species can be oxidized back to [1]2+ using AgSbF6 . These redox-isomerizations correspond to the fundamental transformation of a 3D aromatic cluster into a 2D aromatic ring compound upon reduction and vice versa. The mechanism of these reactions was elucidated using DFT calculations and cyclic voltammetry experiments.
Collapse
|
12
|
A Germapyramidane Switches Between 3D Cluster and 2D Cyclic Structures in Single Electron Steps. Angew Chem Int Ed Engl 2022. [DOI: 10.1002/ange.202211749] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
13
|
Electrocatalytic metal hydride generation using CPET mediators. Nature 2022; 607:499-506. [PMID: 35859199 DOI: 10.1038/s41586-022-04874-z] [Citation(s) in RCA: 21] [Impact Index Per Article: 10.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2021] [Accepted: 05/16/2022] [Indexed: 11/09/2022]
Abstract
Transition metal hydrides (M-H) are ubiquitous intermediates in a wide range of enzymatic processes and catalytic reactions, playing a central role in H+/H2 interconversion1, the reduction of CO2 to formic acid (HCOOH)2 and in hydrogenation reactions. The facile formation of M-H is a critical challenge to address to further improve the energy efficiency of these reactions. Specifically, the easy electrochemical generation of M-H using mild proton sources is key to enable high selectivity versus competitive CO and H2 formation in the CO2 electroreduction to HCOOH, the highest value-added CO2 reduction product3. Here we introduce a strategy for electrocatalytic M-H generation using concerted proton-electron transfer (CPET) mediators. As a proof of principle, the combination of a series of CPET mediators with the CO2 electroreduction catalyst [MnI(bpy)(CO)3Br] (bpy = 2,2'-bipyridine) was investigated, probing the reversal of the product selectivity from CO to HCOOH to evaluate the efficiency of the manganese hydride (Mn-H) generation step. We demonstrate the formation of the Mn-H species by in situ spectroscopic techniques and determine the thermodynamic boundary conditions for this mechanism to occur. A synthetic iron-sulfur cluster is identified as the best CPET mediator for the system, enabling the preparation of a benchmark catalytic system for HCOOH generation.
Collapse
|
14
|
Visualizing Surface Phase Separation in PS-PMMA Polymer Blends at the Nanoscale. ACS APPLIED MATERIALS & INTERFACES 2022; 14:24938-24945. [PMID: 35590476 DOI: 10.1021/acsami.2c03857] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Phase-separated polymer blend films are an important class of functional materials with numerous technological applications in solar cells, catalysis, and biotechnology. These technologies are underpinned by the precise control of phase separation at the nanometer length-scales, which is highly challenging to visualize using conventional analytical tools. Herein, we introduce tip-enhanced Raman spectroscopy (TERS), in combination with atomic force microscopy (AFM), confocal Raman spectroscopy, and X-ray photoelectron spectroscopy (XPS), as a sensitive nanoanalytical method to determine lateral and vertical phase-separation in polystyrene (PS)-poly(methyl methacrylate) (PMMA) polymer blend films. Correlative topographical, molecular, and elemental information reveals a vertical phase separation of the polymers within the top ca. 20 nm of the blend surface in addition to the lateral phase separation in the bulk. Furthermore, complementary TERS and XPS measurements reveal the presence of PMMA within 9.2 nm of the surface and PS at the subsurface of the polymer blend. This fundamental work establishes TERS as a powerful analytical tool for surface characterization of this important class of polymers at nanometer length scales.
Collapse
|
15
|
Design of 4‐Coordinate Ti Imido Aryloxide on the Surface of Silica for Catalytic Oxo/Imido Heterometathesis. Helv Chim Acta 2022. [DOI: 10.1002/hlca.202200030] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
16
|
Highly Dispersed Silica-Supported Iridium and Iridium-Aluminium Catalysts for Methane Activation Prepared via Surface Organometallic Chemistry. Chem Commun (Camb) 2022; 58:8214-8217. [DOI: 10.1039/d2cc02139k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The grafting of an iridium-aluminium precursor onto silica followed by thermal treatment under H2 yields small (<2 nm), narrowly distributed nanoparticles used as catalysts for methane H/D exchange. This Ir-Al/SiO2...
Collapse
|
17
|
Unexpected Disparity in Photoinduced Reactions of C 60 and C 70 in Water with the Generation of O 2 •- or 1O 2. JACS AU 2021; 1:1601-1611. [PMID: 34723263 PMCID: PMC8549049 DOI: 10.1021/jacsau.1c00239] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/28/2021] [Indexed: 06/01/2023]
Abstract
Well-defined fullerene-PEG conjugates, C60-PEG (1) and two C70-PEG (2 and 3 with the addition sites on ab-[6,6] and cc-[6,6]-junctions), were prepared from their corresponding Prato monoadduct precursors. The resulting highly water-soluble fullerene-PEG conjugates 1-3 were evaluated for their DNA-cleaving activities and reactive oxygen species (ROS) generation under visible light irradiation. Unexpectedly, photoinduced cleavage of DNA by C60-PEG 1 was much higher than that by C70-PEG 2 and 3 with higher absorption intensity, especially in the presence of an electron donor (NADH). The preference of photoinduced ROS generation from fullerene-PEG conjugates 1-3 via the type II (energy transfer) or the type I (electron transfer) photoreaction was found to be dependent on the fullerene core (between C60 and C70) and functionalization pattern of C70 (between 2 and 3). This was clearly supported by the electron transfer rate obtained from cyclic voltammetry data and computationally estimated relative rate of each step of the type II and the type I reactions, with the finding that type II energy transfer reactions occurred in the inverted Marcus regime while type I electron transfer reactions proceeded in the normal Marcus regime. This finding on the disparity in the pathways of photoinduced reactions (type I versus type II) provides insights into the behavior of photosensitizers in water and the design of photodynamic therapy drugs.
Collapse
|
18
|
Abstract
Global societal challenges emphasize the importance of collaboration between scientists and policy-makers, while the participation of a diverse group of professionals, including early-career scientists, is critical towards a sustainable future. The European Young Chemists' Network (EYCN) has been actively working with the European Chemical Society (EuChemS) to create a platform for early-career chemists in policy advice. This article comments on the possible roles of scientists in policy-making and provides an overview of relevant initiatives and platforms at the European level that could facilitate involvement. Opportunities for participation in policy advice from the perspective of early-career chemists are discussed and examples of impact are provided, hoping to stimulate further discussions and engagement in policy-making.
Collapse
|
19
|
Frontispiece: Dinitrogen Fixation: Rationalizing Strategies Utilizing Molecular Complexes. Chemistry 2021. [DOI: 10.1002/chem.202181261] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
20
|
Abstract
Dinitrogen (N2 ) is the most abundant gas in Earth's atmosphere, but its inertness hinders its use as a nitrogen source in the biosphere and in industry. Efficient catalysts are hence required to ov. ercome the high kinetic barriers associated to N2 transformation. In that respect, molecular complexes have demonstrated strong potential to mediate N2 functionalization reactions under mild conditions while providing a straightforward understanding of the reaction mechanisms. This Review emphasizes the strategies for N2 reduction and functionalization using molecular transition metal and actinide complexes according to their proposed reaction mechanisms, distinguishing complexes inducing cleavage of the N≡N bond before (dissociative mechanism) or concomitantly with functionalization (associative mechanism). We present here the main examples of stoichiometric and catalytic N2 functionalization reactions following these strategies.
Collapse
|
21
|
Synthesis and Characterization of Ion Pairs between Alkaline Metal Ions and Anionic Anti-Aromatic and Aromatic Hydrocarbons with π-Conjugated Central Seven- and Eight-Membered Rings. Molecules 2020; 25:molecules25204742. [PMID: 33076581 PMCID: PMC7594067 DOI: 10.3390/molecules25204742] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Revised: 10/02/2020] [Accepted: 10/04/2020] [Indexed: 11/29/2022] Open
Abstract
The synthesis, isolation and full characterization of ion pairs between alkaline metal ions (Li+, Na+, K+) and mono-anions and dianions obtained from 5H-dibenzo[a,d]cycloheptenyl (C15H11 = trop) is reported. According to Nuclear Magnetic Resonance (NMR) spectroscopy, single crystal X-ray analysis and Density Functional Theory (DFT) calculations, the trop‒ and trop2−• anions show anti-aromatic properties which are dependent on the counter cation M+ and solvent molecules serving as co-ligands. For comparison, the disodium and dipotassium salt of the dianion of dibenzo[a,e]cyclooctatetraene (C16H12 = dbcot) were prepared, which show classical aromatic character. A d8-Rh(I) complex of trop− was prepared and the structure shows a distortion of the C15H11 ligand into a conjugated 10π -benzo pentadienide unit—to which the Rh(I) center is coordinated—and an aromatic 6π electron benzo group which is non-coordinated. Electron transfer reactions between neutral and anionic trop and dbcot species show that the anti-aromatic compounds obtained from trop are significantly stronger reductants.
Collapse
|
22
|
Abstract
This account reviews our recent research activities in the field of CO₂ reduction. We discuss here the potential of the bio-inspired approach for the design of electrocatalytic systems for small molecule transformation. Exploiting the billion years of evolution of natural systems, we illustrate the potential of bio-inspired strategies across multiple scales to design catalytic systems. We demonstrate in particular how the shape of biological systems as well as enzymatic active sites and their environment can constitute effective sources of inspiration for the design of electrocatalysts with improved performances.
Collapse
|
23
|
Electroreduction of CO
2
to Formate with Low Overpotential using Cobalt Pyridine Thiolate Complexes. Angew Chem Int Ed Engl 2020. [DOI: 10.1002/ange.202006269] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
|
24
|
Electroreduction of CO 2 to Formate with Low Overpotential using Cobalt Pyridine Thiolate Complexes. Angew Chem Int Ed Engl 2020; 59:15726-15733. [PMID: 32673413 DOI: 10.1002/anie.202006269] [Citation(s) in RCA: 25] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2020] [Indexed: 11/11/2022]
Abstract
Electrocatalytic CO2 reduction to value-added products provides a viable alternative to the use of carbon sources derived from fossil fuels. Carrying out these transformations at reasonable energetic costs, for example, with low overpotential, remains a challenge. Molecular catalysts allow fine control of activity and selectivity via tuning of their coordination sphere and ligand set. Herein we investigate a series of cobalt(III) pyridine-thiolate complexes as electrocatalysts for CO2 reduction. The effect of the ligands and proton sources on activity was examined. We identified bipyridine bis(2-pyridinethiolato) cobalt(III) hexaflurophosphate as a highly selective catalyst for formate production operating at a low overpotential of 110 mV with a turnover frequency (TOF) of 10 s-1 . Electrokinetic analysis coupled with density functional theory (DFT) computations established the mechanistic pathway, highlighting the role of metal hydride intermediates. The catalysts deactivate via the formation of stable cobalt carbonyl complexes, but the active species could be regenerated upon oxidation and release of coordinated CO ligands.
Collapse
|
25
|
The Young Faculty Meeting 2020 – Beyond Research: Components to Success. Chimia (Aarau) 2020. [DOI: 10.2533/chimia.2020.631] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022] Open
|
26
|
A bioinspired molybdenum-copper molecular catalyst for CO 2 electroreduction. Chem Sci 2020; 11:5503-5510. [PMID: 32874493 PMCID: PMC7448372 DOI: 10.1039/d0sc01045f] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2020] [Accepted: 05/08/2020] [Indexed: 11/21/2022] Open
Abstract
A bimetallic Mo–Cu complex inspired by the active site of the carbon monoxide dehydrogenase enzyme mediates the electroreduction of carbon dioxide to formic acid.
Non-noble metal molecular catalysts mediating the electrocatalytic reduction of carbon dioxide are still scarce. This work reports the electrochemical reduction of CO2 to formate catalyzed by the bimetallic complex [(bdt)MoVI(O)S2CuICN]2– (bdt = benzenedithiolate), a mimic of the active site of the Mo–Cu carbon monoxide dehydrogenase enzyme (CODH2). Infrared spectroelectrochemical (IR-SEC) studies coupled with density functional theory (DFT) computations revealed that the complex is only a pre-catalyst, the active catalyst being generated upon reduction in the presence of CO2. We found that the two-electron reduction of [(bdt)MoVI(O)S2CuICN]2– triggers the transfer of the oxo moiety to CO2 forming CO32– and the complex [(bdt)MoIVS2CuICN]2– and that a further one-electron reduction is needed to generate the active catalyst. Its protonation yields a reactive MoVH hydride intermediate which reacts with CO2 to produce formate. These findings are particularly relevant to the design of catalysts from metal oxo precursors.
Collapse
|
27
|
A Heterogeneous Recyclable Rhodium‐based Catalyst for the Reduction of Pyridine Dinucleotides and Flavins. ChemCatChem 2020. [DOI: 10.1002/cctc.201901726] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
|
28
|
Carbon-Nanotube-Supported Copper Polyphthalocyanine for Efficient and Selective Electrocatalytic CO 2 Reduction to CO. CHEMSUSCHEM 2020; 13:173-179. [PMID: 31622012 DOI: 10.1002/cssc.201902859] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/16/2019] [Indexed: 06/10/2023]
Abstract
Electroreduction of CO2 to CO is one of the simplest ways to valorise CO2 as a source of carbon. Herein, a cheap, robust, Cu-based hybrid catalyst consisting of a polymer of Cu phthalocyanine coated on carbon nanotubes, which proved to be selective for CO production (80 % faradaic yield) at relatively low overpotentials, was developed. Polymerisation of Cu phthalocyanine was shown to have a drastic effect on the selectivity of the reaction because molecular Cu phthalocyanine was instead selective for proton reduction under the same conditions. Although the material only showed isolated Cu sites in phthalocyanine-like CuN4 coordination, in situ and operando X-ray absorption spectroscopy showed that, under operating conditions, the Cu atoms were fully converted to Cu nanoparticles, which were likely the catalytically active species. Interestingly, this restructuring of the metal sites was reversible.
Collapse
|
29
|
Bio-inspired hydrophobicity promotes CO 2 reduction on a Cu surface. NATURE MATERIALS 2019; 18:1222-1227. [PMID: 31384032 DOI: 10.1038/s41563-019-0445-x] [Citation(s) in RCA: 263] [Impact Index Per Article: 52.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 06/24/2019] [Indexed: 05/03/2023]
Abstract
The aqueous electrocatalytic reduction of CO2 into alcohol and hydrocarbon fuels presents a sustainable route towards energy-rich chemical feedstocks. Cu is the only material able to catalyse the substantial formation of multicarbon products (C2/C3), but competing proton reduction to hydrogen is an ever-present drain on selectivity. Here, a superhydrophobic surface was generated by 1-octadecanethiol treatment of hierarchically structured Cu dendrites, inspired by the structure of gas-trapping cuticles on subaquatic spiders. The hydrophobic electrode attained a 56% Faradaic efficiency for ethylene and 17% for ethanol production at neutral pH, compared to 9% and 4% on a hydrophilic, wettable equivalent. These observations are assigned to trapped gases at the hydrophobic Cu surface, which increase the concentration of CO2 at the electrode-solution interface and consequently increase CO2 reduction selectivity. Hydrophobicity is thus proposed as a governing factor in CO2 reduction selectivity and can help explain trends seen on previously reported electrocatalysts.
Collapse
|
30
|
Molecular and Silica‐Supported Mo and W d
0
Imido‐Methoxybenzylidene Complexes: Structure and Metathesis Activity. Helv Chim Acta 2019. [DOI: 10.1002/hlca.201900190] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
|
31
|
Electroreduction of CO
2
on Single‐Site Copper‐Nitrogen‐Doped Carbon Material: Selective Formation of Ethanol and Reversible Restructuration of the Metal Sites. Angew Chem Int Ed Engl 2019. [DOI: 10.1002/ange.201907994] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
|
32
|
Electroreduction of CO
2
on Single‐Site Copper‐Nitrogen‐Doped Carbon Material: Selective Formation of Ethanol and Reversible Restructuration of the Metal Sites. Angew Chem Int Ed Engl 2019; 58:15098-15103. [DOI: 10.1002/anie.201907994] [Citation(s) in RCA: 215] [Impact Index Per Article: 43.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2019] [Revised: 08/02/2019] [Indexed: 12/18/2022]
|
33
|
Copper-Substituted NiTiO 3 Ilmenite-Type Materials for Oxygen Evolution Reaction. ACS APPLIED MATERIALS & INTERFACES 2019; 11:31038-31048. [PMID: 31379151 DOI: 10.1021/acsami.9b08535] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Single Ni1-xCuxTiO3 (0.05 ≤ x ≤ 0.2) Ilmenite-type phases were successfully prepared through a solid-state reaction route using divalent metal nitrates as precursors and characterized. Their electrocatalytic performance for oxygen evolution reaction (OER) in alkaline media is presented. The Cu content was determined (0.05 ≤ x ≤ 0.2) by X-ray diffraction. A thorough powder neutron diffraction study was carried out to identify the subtle changes caused by copper substitution in the structure of NiTiO3. The evolution of the optical and magnetic properties with the Cu content was also investigated on the raw micrometer-sized particles. A reduction in particle size down to ≈15 nm was achieved by ball-milling the raw powder prepared by the solid-state reaction. The best catalytic activity for OER was obtained for nanometer-sized particles of Ni0.8Cu0.2TiO3 drop-casted on the Cu plate. For this electrode, a current density of 10 mA cm-2 for oxygen production was generated at 345 and 470 mV applied overpotentials with 1 and 0.1 M NaOH solutions as electrolytes, respectively. The catalyst retained this OER activity at 10 mA cm-2 for long-term electrolysis with a faradic efficiency of 90% for O2 production in a 0.1 M NaOH electrolyte.
Collapse
|
34
|
A reactive coordinatively saturated Mo(iii) complex: exploiting the hemi-lability of tris( tert-butoxy)silanolate ligands. Chem Sci 2019; 10:6362-6367. [PMID: 31341592 PMCID: PMC6601292 DOI: 10.1039/c9sc01955c] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2019] [Accepted: 05/13/2019] [Indexed: 12/15/2022] Open
Abstract
Hemilabile tris(tert-butoxy)silanolate ligands allow stabilizing a mononuclear octahedral Mo(iii) complex without quenching its reactivity towards small molecules (N2, CO2, N2O).
Coordinatively unsaturated Mo(iii) complexes have been identified as highly reactive species able to activate dinitrogen without the need for a sacrificial reducing agent. Here, we report a coordinatively saturated octahedral Mo(iii) complex stabilized by κ2-tris(tert-butoxy)silanolate ligands, which is yet highly reactive towards dinitrogen and small molecules. The combined high stability and activity are ascribed to the dual binding mode of the tris(tert-butoxy)silanolate ligands that allow unlocking a coordination site in the presence of reactive small molecules to promote their activation at low temperatures.
Collapse
|
35
|
Zn-Cu Alloy Nanofoams as Efficient Catalysts for the Reduction of CO 2 to Syngas Mixtures with a Potential-Independent H 2 /CO Ratio. CHEMSUSCHEM 2019; 12:511-517. [PMID: 30637969 DOI: 10.1002/cssc.201802287] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/05/2018] [Revised: 11/13/2018] [Indexed: 06/09/2023]
Abstract
Alloying strategies are commonly used to design electrocatalysts that take on properties of their constituent elements. Herein, such a strategy is used to develop Zn-Cu alloyed electrodes with unique hierarchical porosity and tunable selectivity for CO2 versus H+ reduction. By varying the Zn/Cu ratio, tailored syngas mixtures are obtained without the production of other gaseous products, which is attributed to preferential CO- and H2 -forming pathways on the alloys. The syngas ratios are also significantly less sensitive to the applied potential in the alloys relative to pure metal equivalents; an essential quality when coupling electrocatalysis with renewable power sources that have fluctuating intensity. As such, industrially relevant syngas ratios are achieved at large currents (-60 mA) for extensive operating times (>9 h), demonstrating the potential of this strategy for fossil-free fuel production.
Collapse
|
36
|
Low-Coordinated Titanium(III) Alkyl-Molecular and Surface-Complexes: Detailed Structure from Advanced EPR Spectroscopy. Angew Chem Int Ed Engl 2018. [DOI: 10.1002/ange.201806497] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
37
|
Low-Coordinated Titanium(III) Alkyl-Molecular and Surface-Complexes: Detailed Structure from Advanced EPR Spectroscopy. Angew Chem Int Ed Engl 2018; 57:14533-14537. [DOI: 10.1002/anie.201806497] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2018] [Indexed: 11/10/2022]
|
38
|
Bridging the Gap between Industrial and Well‐Defined Supported Catalysts. Angew Chem Int Ed Engl 2018; 57:6398-6440. [DOI: 10.1002/anie.201702387] [Citation(s) in RCA: 152] [Impact Index Per Article: 25.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2017] [Indexed: 12/22/2022]
|
39
|
|
40
|
|
41
|
Silica-supported isolated molybdenum di-oxo species: formation and activation with organosilicon agent for olefin metathesis. Chem Commun (Camb) 2018; 54:3989-3992. [DOI: 10.1039/c8cc01876f] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
A well-defined silica-supported molybdenum dioxo species, (SiO)2Mo(O)2, prepared via Surface Organometallic Chemistry, is highly active in metathesis upon reaction with organosilicon reducing agent.
Collapse
|
42
|
Site-isolated manganese carbonyl on bipyridine-functionalities of periodic mesoporous organosilicas: efficient CO 2 photoreduction and detection of key reaction intermediates. Chem Sci 2017; 8:8204-8213. [PMID: 29568468 PMCID: PMC5857931 DOI: 10.1039/c7sc03512h] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2017] [Accepted: 10/08/2017] [Indexed: 01/30/2023] Open
Abstract
Well-defined and fully characterized supported CO2 reduction catalysts are developed through the immobilization of an earth abundant Mn complex on bpy-PMO (bpy = bipyridine; PMO = Periodic Mesoporous Organosilica) platform materials. The resulting isolated Mn-carbonyl centers coordinated to bipyridine functionalities of bpy-PMO catalyze the photoreduction of CO2 into CO and HCOOH with up to ca. 720 TON in the presence of BIH (1,3-dimethyl-2-phenyl-2,3-dihydro-1H-benzoimidazole), used as the electron donor. A broad range of photochemical conditions (varying solvents, sacrificial electron donors, photosensitizer type and concentration, catalyst loading as well as the Mn loading within the PMO) are investigated, demonstrating high activity even for simple organic dyes and Zn-porphyrin as photosensitizers. Spectroscopic and catalytic data also indicate that site isolation of the Mn complex in the PMO framework probably inhibits bimolecular processes such as dimerisation and disproportionation and thus allows the spectroscopic observation of key reaction intermediates, namely the two meridional isomers of the carbonyl complexes and the bipyridine radical anion species.
Collapse
|
43
|
|
44
|
Synthesis, Characterization, and DFT Analysis of Bis-Terpyridyl-Based Molecular Cobalt Complexes. Inorg Chem 2017; 56:5930-5940. [DOI: 10.1021/acs.inorgchem.7b00595] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
|
45
|
A Dendritic Nanostructured Copper Oxide Electrocatalyst for the Oxygen Evolution Reaction. Angew Chem Int Ed Engl 2017. [DOI: 10.1002/ange.201700388] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
|
46
|
A Dendritic Nanostructured Copper Oxide Electrocatalyst for the Oxygen Evolution Reaction. Angew Chem Int Ed Engl 2017; 56:4792-4796. [DOI: 10.1002/anie.201700388] [Citation(s) in RCA: 169] [Impact Index Per Article: 24.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 03/05/2017] [Indexed: 11/09/2022]
|
47
|
Magnetic Memory from Site Isolated Dy(III) on Silica Materials. ACS CENTRAL SCIENCE 2017; 3:244-249. [PMID: 28386602 PMCID: PMC5364447 DOI: 10.1021/acscentsci.7b00035] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/21/2017] [Indexed: 05/26/2023]
Abstract
Achieving magnetic remanence at single isolated metal sites dispersed at the surface of a solid matrix has been envisioned as a key step toward information storage and processing in the smallest unit of matter. Here, we show that isolated Dy(III) sites distributed at the surface of silica nanoparticles, prepared with a simple and scalable two-step process, show magnetic remanence and display a hysteresis loop open at liquid 4He temperature, in contrast to the molecular precursor which does not display any magnetic memory. This singular behavior is achieved through the controlled grafting of a tailored Dy(III) siloxide complex on partially dehydroxylated silica nanoparticles followed by thermal annealing. This approach allows control of the density and the structure of isolated, "bare" Dy(III) sites bound to the silica surface. During the process, all organic fragments are removed, leaving the surface as the sole ligand, promoting magnetic remanence.
Collapse
|
48
|
|
49
|
Low Temperature Activation of Supported Metathesis Catalysts by Organosilicon Reducing Agents. ACS CENTRAL SCIENCE 2016; 2:569-76. [PMID: 27610418 PMCID: PMC4999968 DOI: 10.1021/acscentsci.6b00176] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Indexed: 05/26/2023]
Abstract
Alkene metathesis is a widely and increasingly used reaction in academia and industry because of its efficiency in terms of atom economy and its wide applicability. This reaction is notably responsible for the production of several million tons of propene annually. Such industrial processes rely on inexpensive silica-supported tungsten oxide catalysts, which operate at high temperatures (>350 °C), in contrast with the mild room temperature reaction conditions typically used with the corresponding molecular alkene metathesis homogeneous catalysts. This large difference in the temperature requirements is generally thought to arise from the difficulty in generating active sites (carbenes or metallacyclobutanes) in the classical metal oxide catalysts and prevents broader applicability, notably with functionalized substrates. We report here a low temperature activation process of well-defined metal oxo surface species using organosilicon reductants, which generate a large amount of active species at only 70 °C (0.6 active sites/W). This high activity at low temperature broadens the scope of these catalysts to functionalized substrates. This activation process can also be applied to classical industrial catalysts. We provide evidence for the formation of a metallacyclopentane intermediate and propose how the active species are formed.
Collapse
|
50
|
Highly Active Subnanometer Au Particles Supported on TiO2 for Photocatalytic Hydrogen Evolution from a Well-Defined Organogold Precursor, [Au5(mesityl)5]. Inorg Chem 2016; 55:4026-33. [DOI: 10.1021/acs.inorgchem.6b00341] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
|