Examination of the Magneto-Structural Effects of Hangman Groups on Ferric Porphyrins by EPR

Nehrkorn, Joscha; Bonke, Shannon A.; Aliabadi, Azar; Schwalbe, Matthias; Schnegg, Alexander

doi:10.1021/acs.inorgchem.9b02348

Cited by 4 publications

(6 citation statements)

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“… a Brackett et al for ferrihemoglobin-F. b Nehrkorn et al for FeTPPCl c Behere et al for FeTPPBr. d Hu et al for Imidazole complexes of FeOEP. e GS stands for ground-state electronic term.…”

Section: Resultsmentioning

confidence: 99%

“…the triplet ( S = 1), quintet ( S = 2), and singlet ( S = 0) states, dictate the overall magnetochemical behavior of these complexes. The square planar iron(II)–porphyrin as an isolated molecule exhibits a triplet ground state. − The addition of various ligands to the axial coordination sites of the metal center provides a route to manipulate the magneto-chemistry of the metalloporphyrin complexes. − The change in the ligand environment by such means triggers an alteration in the fundamental magnetic properties like the spin state of the complex, crystal field splitting, and so on. On the other hand, the strong chemisorption of the molecule on the substrate induces a set of modifications to the molecular structure that pave the path for manipulating the magnetic state of the molecule.…”

Section: Introductionmentioning

confidence: 99%

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Can Iron–Porphyrins Behave as Single-Molecule Magnets?

Mukhopadhyaya,

Ali

2024

J. Phys. Chem. A

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The study of magnetic properties, especially the magnetic anisotropy of iron−porphyrin complexes employing multiconfigurational methods, is quite challenging due to many strongly correlated electrons in nearly degenerate orbitals. However, a prerequisite for observing the magnetic anisotropy and slow magnetization relaxation, the zero-field splitting parameter, D, was experimentally observed decades ago for halide-based axially ligated penta-coordinate Fe(III)− porphyrins. In these complexes, the signs of D were reported mostly as positive; in a few cases, inconclusive signs of the D parameter were also mentioned. However, no ab initio calculations have been reported to shed light on this. Deciphering the electronic structure of these penta-coordinated complexes employing the complete active space self-consistent field method and N-electron valence second-order perturbation theory, we confirm the positive D values. However, a negative D value is highly desired to observe the single-molecule magnet properties without an external magnetic field, which we observed in the Fe(II)−porphyrin complexes with axial imidazole ligands instead of halide ligands. The detailed analysis of the multireference wave functions unravels the role of axial ligands in determining the sign and magnitude of the D parameters.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Can Iron–Porphyrins Behave as Single-Molecule Magnets?

Mukhopadhyaya,

Ali

2024

J. Phys. Chem. A

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“…[ 270 ] Because EPR is sensitive to unpaired electrons only, most atoms are “transparent” to EPR; however, many transition metals ions are EPR active. Depending on the type of EPR, conditions, and sample properties, the paramagnetic species separation distances, local coordination structure, charge assignment, and spin quantity [ 274 ] can be determined. Hyperfine interactions between the unpaired electron and local nuclei can give rise to the splitting of EPR resonance signals, indicating the type of local nucleus.…”

Section: Advanced Characterizationmentioning

confidence: 99%

“…The former is EPR‐silent and is indeed the complex they obtained. Meanwhile, from EPR, model SACs consisting of ferric porphyrins with hangman groups showed an elongated FeCl bond length compared to the non‐hangman equivalent, [ 274 ] suggesting future insights could be obtained from hangman groups that form DACs.…”

Section: Advanced Characterizationmentioning

confidence: 99%

Dual‐Metal Atom Electrocatalysts: Theory, Synthesis, Characterization, and Applications

Pedersen

Barrio

et al. 2021

Advanced Energy Materials

112

106

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a required reduction in emissions per unit production of 75% by 2050 in order to have a 50% chance of limiting global mean temperature rise by 2 °C compared to pre-industrial levels. [1,2] Improvements in the field of electrocatalysts, especially in relation to electrolyzers and fuel cells, will help these devices become part of the solution to the looming sustainable energy and chemical production needs. [3] For these devices to be entirely renewable, H 2 (and O 2 ) needs to be produced by water splitting in electrolyzers through H 2 and O 2 evolution (green hydrogen production), rather than from methane reforming (grey hydrogen production). [4,5] H 2 can then be used in electrochemical O 2 reduction in fuel cells to produce electricity. [6,7] Meanwhile, electrochemical reduction of N 2 to NH 3 can provide a sustainable means to a critical fertilization source for the agricultural industry and a carrier for H 2 . [8] Moreover, a way of producing value-added products and a "circular economy" for industry from CO 2 emissions is via the electrocatalytically driven CO 2 reduction, which converts CO 2 to essential feedstocks, such as ethylene or ethanol for the chemical industry. [9] Low-temperature fuel cells and electrolyzers typically utilize catalysts based on platinum group metal (PGM) nanoparticles, [10] which limits device commercialization due to increasing global demand, low uptake of recycling, and high cost of PGMs. [11] Consequently, many researchers have turned their attention to reducing PGM loading or entirely replacing them with lower-cost earth-abundant metals, such as Fe, Cu, Ni, Co, Mn, and, most recently, Sn. [12] Regardless of the catalyst composition, improvements in the electrochemical activity have been highly sought after with two general options available; increasing the number of accessible catalytic sites and/or increasing the intrinsic activity of the catalytic sites. [13] Many different catalyst designs have been explored in order to raise the activity, such as alloying [14] or nanostructuring. [15] While increasing the density of catalytic sites improves activity, this method becomes physically limited when catalyst loading affects charge and mass transport. [13] Thus, improving the activity per catalytic site (intrinsic activity) through controlling local geometry and electronic structure has garnered research attention, with successful methods including shrinking the catalytic site down to atomic scale, as well as locally introducing light heteroatoms or hosting the catalytic site at edges. [10,[16][17][18] Electrochemical clean energy conversion and the production of sustainable chemicals are critical in the journey to realizing a truly sustainable society. To progress electrochemical storage and conversion devices to commercialization, improving the electrocatalyst performance and cost are of utmost importance. Research into dual-metal atom catalysts (DACs) is rising in prominence due to the advantages of these sites over single-metal atom catalysts (SACs), such as breaking scaling ...

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“…There is still a limited understanding of how ZFS para- meters relate to the geometric and electronic structures of transition metals compounds, including how metal-ligand bonding affects ZFS. 56,57 However studies from Neese and coworkers have revealed a correlation between the increase of D with the spectrochemical series showing a decrease of the ligand field strength. 57 Looking at our zero-field splitting values for the S = 5/2 spin system, from the simulated EPR spectra it may be qualitatively predicted that compared to the iron(III)-2-aminophenolate species (1 Ox and 2 Ox ), the binding of dioxygen changes the coordination geometry and decreases the |D| value.…”

Section: Reactions Of Iron(ii)-2-aminophenolate Complexes With Omentioning

confidence: 99%