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Bhunia S, Ghatak A, Rana A, Dey A. Amine Groups in the Second Sphere of Iron Porphyrins Allow for Higher and Selective 4e -/4H + Oxygen Reduction Rates at Lower Overpotentials. J Am Chem Soc 2023; 145:3812-3825. [PMID: 36744304 DOI: 10.1021/jacs.2c13552] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Iron porphyrins with one or four tertiary amine groups in their second sphere are used to investigate the electrochemical O2 reduction reaction (ORR) in organic (homogeneous) and aqueous (heterogeneous) conditions. Both of these complexes show selective 4e-/4H+ reduction of oxygen to water at rates that are 2-3 orders of magnitude higher than those of iron tetraphenylporphyrin lacking these amines in the second sphere. In organic solvents, these amines get protonated, which leads to the lowering of overpotentials, and the rate of the ORR is enhanced almost 75,000 times relative to rates expected from the established scaling relationship for the ORR by iron porphyrins. In the aqueous medium, the same trend of higher ORR rates at a lower overpotential is observed. In situ resonance Raman data under heterogeneous aqueous conditions show that the presence of one amine group in the second sphere leads to a cleavage of the O-O bond in a FeIII-OOH intermediate as the rate-determining step (rds). The presence of four such amine groups enhances the rate of O-O bond cleavage such that this intermediate is no longer observed during the ORR; rather, the proton-coupled reduction of the FeIII-O2- intermediate with a H/D isotope effect of 10.6 is the rds. These data clearly demonstrate changes in the rds of the electrochemical ORR depending on the nature of second-sphere residues and explain their deviation from linear scaling relationships.
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Affiliation(s)
- Sarmistha Bhunia
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, West Bengal700032, India
| | - Arnab Ghatak
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, West Bengal700032, India
| | - Atanu Rana
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, West Bengal700032, India
| | - Abhishek Dey
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A & 2B Raja S. C. Mullick Road, Jadavpur, Kolkata, West Bengal700032, India
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2
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Pattanayak S, Loewen ND, Berben LA. Using Substituted [Fe 4N(CO) 12] - as a Platform To Probe the Effect of Cation and Lewis Acid Location on Redox Potential. Inorg Chem 2023; 62:1919-1925. [PMID: 36006454 DOI: 10.1021/acs.inorgchem.2c01556] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
The impact of cationic and Lewis acidic functional groups installed in the primary or secondary coordination sphere (PCS or SCS) of an (electro)catalyst is known to vary depending on the precise positioning of those groups. However, it is difficult to systematically probe the effect of that position. In this report, we probe the effect of the functional group position and identity on the observed reduction potentials (Ep,c) using substituted iron clusters, [Fe4N(CO)11R]n, where R = NO+, PPh2-CH2CH2-9BBN, (MePTA+)2, (MePTA+)4, and H+ and n = 0, -1, +1, or +3 (9-BBN is 9-borabicyclo(3.3.1)nonane; MePTA+ is 1-methyl-1-azonia-3,5-diaza-7-phosphaadamantane). The cationic NO+ and H+ ligands cause anodic shifts of 700 and 320 mV, respectively, in Ep,c relative to unsubstituted [Fe4N(CO)12]-. Infrared absorption band data, νCO, suggests that some of the 700 mV shift by NO+ results from electronic changes to the cluster core. This contrasts with the effects of cationic MePTA+ and H+ which cause primarily electrostatic effects on Ep,c. Lewis acidic 9-BBN in the SCS had almost no effect on Ep,c.
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Affiliation(s)
- Santanu Pattanayak
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Natalia D Loewen
- Department of Chemistry, University of California, Davis, California 95616, United States
| | - Louise A Berben
- Department of Chemistry, University of California, Davis, California 95616, United States
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3
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CO2 Electroreduction on Carbon-Based Electrodes Functionalized with Molecular Organometallic Complexes—A Mini Review. Catalysts 2022. [DOI: 10.3390/catal12111448] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Heterogeneous electrochemical CO2 reduction has potential advantages with respect to the homogeneous counterpart due to the easier recovery of products and catalysts, the relatively small amounts of catalyst necessary for efficient electrolysis, the longer lifetime of the catalysts, and the elimination of solubility problems. Unfortunately, several disadvantages are also present, including the difficulty of designing the optimized and best-performing catalysts by the appropriate choice of the ligands as well as a larger heterogeneity in the nature of the catalytic site that introduces differences in the mechanistic pathway and in electrogenerated products. The advantages of homogeneous and heterogeneous systems can be preserved by anchoring intact organometallic molecules on the electrode surface with the aim of increasing the dispersion of active components at a molecular level and facilitating the electron transfer to the electrocatalyst. Electrode functionalization can be obtained by non-covalent or covalent interactions and by direct electropolymerization on the electrode surface. A critical overview covering the very recent literature on CO2 electroreduction by intact organometallic complexes attached to the electrode is summarized herein, and particular attention is given to their catalytic performances. We hope this mini review can provide new insights into the development of more efficient CO2 electrocatalysts for real-life applications.
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4
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Donohoe C, Schaberle FA, Rodrigues FMS, Gonçalves NPF, Kingsbury CJ, Pereira MM, Senge MO, Gomes-da-Silva LC, Arnaut LG. Unraveling the Pivotal Role of Atropisomerism for Cellular Internalization. J Am Chem Soc 2022; 144:15252-15265. [PMID: 35960892 PMCID: PMC9446767 DOI: 10.1021/jacs.2c05844] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The intrinsic challenge of large molecules to cross the cell membrane and reach intracellular targets is a major obstacle for the development of new medicines. We report how rotation along a single C-C bond, between atropisomers of a drug in clinical trials, improves cell uptake and therapeutic efficacy. The atropisomers of redaporfin (a fluorinated sulfonamide bacteriochlorin photosensitizer of 1135 Da) are separable and display orders of magnitude differences in photodynamic efficacy that are directly related to their differential cellular uptake. We show that redaporfin atropisomer uptake is passive and only marginally affected by ATP depletion, plasma proteins, or formulation in micelles. The α4 atropisomer, where meso-phenyl sulfonamide substituents are on the same side of the tetrapyrrole macrocycle, exhibits the highest cellular uptake and phototoxicity. This is the most amphipathic atropisomer with a conformation that optimizes hydrogen bonding (H-bonding) with polar head groups of membrane phospholipids. Consequently, α4 binds to the phospholipids on the surface of the membrane, flips into the membrane to adopt the orientation of a surfactant, and eventually diffuses to the interior of the cell (bind-flip mechanism). We observed increased α4 internalization by cells of the tumor microenvironment in vivo and correlated this to the response of photodynamic therapy when tumor illumination was performed 24 h after α4 administration. These results show that properly orientated aryl sulfonamide groups can be incorporated into drug design as efficient cell-penetrating motifs in vivo and reveal the unexpected biological consequences of atropisomerism.
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Affiliation(s)
- Claire Donohoe
- CQC, Coimbra Chemistry Center, University of Coimbra, Rua Larga, Coimbra 3004-535, Portugal.,Medicinal Chemistry, Trinity Translational Medicine Institute, Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, Ireland
| | - Fábio A Schaberle
- CQC, Coimbra Chemistry Center, University of Coimbra, Rua Larga, Coimbra 3004-535, Portugal
| | - Fábio M S Rodrigues
- CQC, Coimbra Chemistry Center, University of Coimbra, Rua Larga, Coimbra 3004-535, Portugal
| | - Nuno P F Gonçalves
- Luzitin SA, Ed. Bluepharma, S. Martinho do Bispo, Coimbra 3045-016, Portugal
| | - Christopher J Kingsbury
- School of Chemistry, Chair of Organic Chemistry, Trinity Biomedical Sciences Institute, Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, Dublin 2, Ireland
| | - Mariette M Pereira
- CQC, Coimbra Chemistry Center, University of Coimbra, Rua Larga, Coimbra 3004-535, Portugal
| | - Mathias O Senge
- Medicinal Chemistry, Trinity Translational Medicine Institute, Trinity Centre for Health Sciences, St. James's Hospital, Trinity College Dublin, The University of Dublin, Dublin 8, Ireland.,Institute for Advanced Study (TUM-IAS), Technical University of Munich, Lichtenbergstrasse 2a, Garching 85748, Germany
| | - Lígia C Gomes-da-Silva
- CQC, Coimbra Chemistry Center, University of Coimbra, Rua Larga, Coimbra 3004-535, Portugal
| | - Luis G Arnaut
- CQC, Coimbra Chemistry Center, University of Coimbra, Rua Larga, Coimbra 3004-535, Portugal
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5
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Weberg AB, Murphy RP, Tomson NC. Oriented internal electrostatic fields: an emerging design element in coordination chemistry and catalysis. Chem Sci 2022; 13:5432-5446. [PMID: 35694353 PMCID: PMC9116365 DOI: 10.1039/d2sc01715f] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2022] [Accepted: 04/19/2022] [Indexed: 11/21/2022] Open
Abstract
The power of oriented electrostatic fields (ESFs) to influence chemical bonding and reactivity is a phenomenon of rapidly growing interest. The presence of strong ESFs has recently been implicated as one of the most significant contributors to the activity of select enzymes, wherein alignment of a substrate's changing dipole moment with a strong, local electrostatic field has been shown to be responsible for the majority of the enzymatic rate enhancement. Outside of enzymology, researchers have studied the impacts of "internal" electrostatic fields via the addition of ionic salts to reactions and the incorporation of charged functional groups into organic molecules (both experimentally and computationally), and "externally" via the implementation of bulk fields between electrode plates. Incorporation of charged moieties into homogeneous inorganic complexes to generate internal ESFs represents an area of high potential for novel catalyst design. This field has only begun to materialize within the past 10 years but could be an area of significant impact moving forward, since it provides a means for tuning the properties of molecular complexes via a method that is orthogonal to traditional strategies, thereby providing possibilities for improved catalytic conditions and novel reactivity. In this perspective, we highlight recent developments in this area and offer insights, obtained from our own research, on the challenges and future directions of this emerging field of research.
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Affiliation(s)
- Alexander B Weberg
- R, oy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S. 34th Street Philadelphia Pennsylvania 19104 USA
| | - Ryan P Murphy
- R, oy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S. 34th Street Philadelphia Pennsylvania 19104 USA
| | - Neil C Tomson
- R, oy and Diana Vagelos Laboratories, Department of Chemistry, University of Pennsylvania 231 S. 34th Street Philadelphia Pennsylvania 19104 USA
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6
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Sharma VK, Stark M, Fridman N, Assaraf YG, Gross Z. Doubly Stimulated Corrole for Organelle-Selective Antitumor Cytotoxicity. J Med Chem 2022; 65:6100-6115. [PMID: 35434997 DOI: 10.1021/acs.jmedchem.1c02085] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Balancing between safety and efficacy of cancer chemotherapeutics is achievable by relying on internal and/or external stimuli for selective and on-demand antitumor cytotoxicity. We now introduce the difluorophosphorus(V) corrole PC-Im, a theranostic agent with a pH-sensitive N-methylimidazole moiety. Structure/activity relationships, via comparison with the permanently charged PC-ImM+ and the lipophilic PC, uncovered the exceptional features of PC-Im: nanoparticular and monomeric at neutral and low pH, respectively, 10-fold increased light-induced singlet oxygen production at acidic pH, internalization into malignant cells within minutes, and selective accumulation within lysosomes. Submillimolar PC-Im concentrations are tolerable in the dark, while illumination induces nanomolar cytotoxic effects due to a multiplicity of cellular deleterious events: endoplasmic reticulum fragmentation, lysosome fusion and exocytosis, calcium leakage, mitochondrial fission, and swelling. PC-Im emerges as an antitumor agent, whose potency is triggered by endogenous and exogenous stimuli, assuring its cytotoxicity will occur selectively upon lysosomal accumulation and solely upon light activation.
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Affiliation(s)
- Vinay K Sharma
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Michal Stark
- The Fred Wyszkowski Cancer Research Laboratory, Department of Biology, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Natalia Fridman
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Yehuda G Assaraf
- The Fred Wyszkowski Cancer Research Laboratory, Department of Biology, Technion-Israel Institute of Technology, Haifa 3200003, Israel
| | - Zeev Gross
- Schulich Faculty of Chemistry, Technion-Israel Institute of Technology, Haifa 3200003, Israel
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7
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Kelty ML, McNeece AJ, Kurutz JW, Filatov AS, Anderson JS. Electrostatic vs. inductive effects in phosphine ligand donor properties and reactivity. Chem Sci 2022; 13:4377-4387. [PMID: 35509471 PMCID: PMC9007067 DOI: 10.1039/d1sc04277g] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 03/15/2022] [Indexed: 11/21/2022] Open
Abstract
Enhanced rates and selectivity in enzymes are enabled in part by precisely tuned electric fields within active sites. Analogously, the use of charged groups to leverage electrostatics in molecular systems is a promising strategy to tune reactivity. However, separation of the through space and through bond effects of charged functional groups is a long standing challenge that limits the rational application of electric fields in molecular systems. To address this challenge we developed a method using the phosphorus selenium coupling value (J P-Se) of anionic phosphine selenides to quantify the electrostatic contribution of the borate moiety to donor strength. In this analysis we report the synthesis of a novel anionic phosphine, PPh2CH2BF3K, the corresponding tetraphenyl phosphonium and tetraethyl ammonium selenides [PPh4][SePPh2CH2BF3] and [TEA][SePPh2CH2BF3], and the Rh carbonyl complex [PPh4][Rh(acac)(CO)(PPh2(CH2BF3))]. Solvent-dependent changes in J P-Se were fit using Coulomb's law and support up to an 80% electrostatic contribution to the increase in donor strength of [PPh4][SePPh2CH2BF3] relative to SePPh2Et, while controls with [TEA][SePPh2CH2BF3] exclude convoluting ion pairing effects. Calculations using explicit solvation or point charges effectively replicate the experimental data. This J P-Se method was extended to [PPh4][SePPh2(2-BF3Ph)] and likewise estimates up to a 70% electrostatic contribution to the increase in donor strength relative to SePPh3. The use of PPh2CH2BF3K also accelerates C-F oxidative addition reactivity with Ni(COD)2 by an order of magnitude in comparison to the comparatively donating neutral phosphines PEt3 and PCy3. This enhanced reactivity prompted the investigation of catalytic fluoroarene C-F borylation, with improved yields observed for less fluorinated arenes. These results demonstrate that covalently bound charged functionalities can exert a significant electrostatic influence under common solution phase reaction conditions and experimentally validate theoretical predictions regarding electrostatic effects in reactivity.
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Affiliation(s)
- Margaret L Kelty
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Andrew J McNeece
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Josh W Kurutz
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - Alexander S Filatov
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
| | - John S Anderson
- Department of Chemistry, University of Chicago 929 E 57th St Chicago IL 60637 USA
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8
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Bhunia S, Ghatak A, Dey A. Second Sphere Effects on Oxygen Reduction and Peroxide Activation by Mononuclear Iron Porphyrins and Related Systems. Chem Rev 2022; 122:12370-12426. [PMID: 35404575 DOI: 10.1021/acs.chemrev.1c01021] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Activation and reduction of O2 and H2O2 by synthetic and biosynthetic iron porphyrin models have proved to be a versatile platform for evaluating second-sphere effects deemed important in naturally occurring heme active sites. Advances in synthetic techniques have made it possible to install different functional groups around the porphyrin ligand, recreating artificial analogues of the proximal and distal sites encountered in the heme proteins. Using judicious choices of these substituents, several of the elegant second-sphere effects that are proposed to be important in the reactivity of key heme proteins have been evaluated under controlled environments, adding fundamental insight into the roles played by these weak interactions in nature. This review presents a detailed description of these efforts and how these have not only demystified these second-sphere effects but also how the knowledge obtained resulted in functional mimics of these heme enzymes.
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Affiliation(s)
- Sarmistha Bhunia
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
| | - Arnab Ghatak
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
| | - Abhishek Dey
- School of Chemical Science, Indian Association for the Cultivation of Science, 2A Raja SC Mullick Road, Kolkata 700032, India
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9
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Norvaiša K, Maguire S, Donohoe C, O'Brien JE, Twamley B, Gomes-da-Silva LC, Senge MO. Steric Repulsion Induced Conformational Switch in Supramolecular Structures. Chemistry 2021; 28:e202103879. [PMID: 34792217 PMCID: PMC9299809 DOI: 10.1002/chem.202103879] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2021] [Indexed: 11/24/2022]
Abstract
Inspired by the rigidified architecture of ‘picket‐fence’ systems, we propose a strategy utilizing strain to impose intramolecular tension in already peripherally overcrowded structures leading to selective atropisomeric conversion. Employing this approach, tuneable shape‐persistent porphyrin conformations were acquired exhibiting distinctive supramolecular nanostructures based on the orientation of the peripheral groups. The intrinsic assemblies driven by non‐covalent bonding interactions form supramolecular polymers while encapsulating small molecules in parallel channels or solvent‐accessible voids. The developed molecular strain engineering methodologies combined with synthetic approaches have allowed the introduction of the pivalate units creating a highly strained molecular skeleton. Changes in the absorption spectrum indicated the presence of severe steric repulsions between the peripheral groups which were confirmed by single crystal X‐ray analysis. To release the steric strain introduced by the peripheral units, thermal equilibration strategies were used to selectively convert the most abundant atropisomer to the desirable minor one.
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Affiliation(s)
- Karolis Norvaiša
- School of Chemistry, Chair of Organic Chemistry Trinity Biomedical Sciences Institute Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, D02 R590, Dublin 2, Ireland
| | - Sophie Maguire
- School of Chemistry, Chair of Organic Chemistry Trinity Biomedical Sciences Institute Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, D02 R590, Dublin 2, Ireland
| | - Claire Donohoe
- School of Chemistry, Chair of Organic Chemistry Trinity Biomedical Sciences Institute Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, D02 R590, Dublin 2, Ireland.,CQC, Coimbra Chemistry Center Department of Chemistry, University of Coimbra, 3000-435, Coimbra, Portugal
| | - John E O'Brien
- School of Chemistry Trinity College Dublin, The University of Dublin, D02 PN40, Dublin 2, Ireland
| | - Brendan Twamley
- School of Chemistry Trinity College Dublin, The University of Dublin, D02 PN40, Dublin 2, Ireland
| | - Ligia C Gomes-da-Silva
- CQC, Coimbra Chemistry Center Department of Chemistry, University of Coimbra, 3000-435, Coimbra, Portugal
| | - Mathias O Senge
- School of Chemistry, Chair of Organic Chemistry Trinity Biomedical Sciences Institute Trinity College Dublin, The University of Dublin, 152-160 Pearse Street, D02 R590, Dublin 2, Ireland.,Institute for Advanced Study (TUM-IAS) Focus Group - Molecular and Interfacial Engineering of Organic Nanosystems, Technical University of Munich, Lichtenbergstrasse 2a, D-85748, Garching, Germany
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10
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Tantillo DJ, Laconsay CJ. Melding of Experiment and Theory Illuminates Mechanisms of Metal-Catalyzed Rearrangements: Computational Approaches and Caveats. SYNTHESIS-STUTTGART 2021. [DOI: 10.1055/s-0040-1720451] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
Abstract
AbstractThis review summarizes approaches and caveats in computational modeling of transition-metal-catalyzed sigmatropic rearrangements involving carbene transfer. We highlight contemporary examples of combined synthetic and theoretical investigations that showcase the synergy achievable by integrating experiment and theory.1 Introduction2 Mechanistic Models3 Theoretical Approaches and Caveats3.1 Recommended Computational Tools3.2 Choice of Functional and Basis Set3.3 Conformations and Ligand-Binding Modes3.4 Solvation4 Synergy of Experiment and Theory – Case Studies4.1 Metal-Bound or Free Ylides?4.2 Conformations and Ligand-Binding Modes of Paddlewheel Complexes4.3 No Metal, Just Light4.4 How To ‘Cope’ with Nonstatistical Dynamic Effects5 Outlook
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11
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Léonard NG, Dhaoui R, Chantarojsiri T, Yang JY. Electric Fields in Catalysis: From Enzymes to Molecular Catalysts. ACS Catal 2021; 11:10923-10932. [DOI: 10.1021/acscatal.1c02084] [Citation(s) in RCA: 26] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Affiliation(s)
- Nadia G. Léonard
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Rakia Dhaoui
- Department of Chemistry, University of California, Irvine, California 92697, United States
| | - Teera Chantarojsiri
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Mahidol University, Bangkok, 10400, Thailand
| | - Jenny Y. Yang
- Department of Chemistry, University of California, Irvine, California 92697, United States
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12
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Martin DJ, Mayer JM. Oriented Electrostatic Effects on O 2 and CO 2 Reduction by a Polycationic Iron Porphyrin. J Am Chem Soc 2021; 143:11423-11434. [PMID: 34292718 DOI: 10.1021/jacs.1c03132] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Next-generation energy technologies require improved methods for rapid and efficient chemical-to-electrical energy transformations. One new approach has been to include atomically positioned, electrostatic motifs in molecular catalysts to stabilize high-energy, charged intermediates. For example, an iron porphyrin bearing four cationic, o-N,N,N-trimethylanilinium groups (o-[N(CH3)3]+) has recently been used to catalyze the complex, multistep O2 and CO2 reduction reactions (ORR and CO2RR) with fast rates and at low overpotentials. The success of this catalyst is attributed, at least in part, to specific charge-charge interactions between the atomically positioned o-[N(CH3)3]+ groups and the bound substrate. However, by nature of the mono-ortho substitution pattern, there are four possible atropisomers of this metalloporphyrin and thus four unique electrostatic environments. This work reports that each of the four individual atropisomers catalyzes both the ORR and CO2RR with fast rates and low overpotentials. The maximum turnover frequencies vary among the atropisomers, by a factor of 60 for the ORR and a factor of 5 for CO2RR. For the ORR, the αβαβ isomer is the fastest and has the highest overpotential, while for the CO2RR the αααα isomer is the fastest and has the highest overpotential. The role of charge positioning is complex and can affect more than a single step such as CO2 binding. These data offer a first-of-a-kind perspective on atomically positioned charge and highlight the significance of high charge density, rather than orientation, on the thermodynamics and kinetics of multistep molecular electrochemical transformations.
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Affiliation(s)
- Daniel J Martin
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
| | - James M Mayer
- Department of Chemistry, Yale University, New Haven, Connecticut 06520-8107, United States
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