Single‐Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2–3/2 Spin Admixture

Viciano‐Chumillas, Marta; Blondin, Geneviève; Clémancey, Martin; Krzystek, J.; Ozerov, Mykhaylo; Armentano, Donatella; Schnegg, Alexander; Lohmiller, Thomas; Telser, Joshua; Lloret, Francesc; Cano, Joan

doi:10.1002/chem.202003052

Cited by 12 publications

(19 citation statements)

References 107 publications

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“…Observation of the spin-crossover phenomenon along with the slow magnetic relaxation at a high blocking temperature is highly anticipated for potential use as molecular qubits and logic devices. , This will revolutionize the field of quantum devices for high-density data storage and fast processing of information. Mononuclear 3d transition-metal complexes hold promise in this direction with both evident properties of magnetism and spin-crossover at the molecular level. , Ligand field in 3d-transition-metal complexes could play a central role in controlling the magnetic anisotropy and the SCO behavior of the molecule. , Thus, understanding the ligand-field-derived modulation of anisotropy in conjunction with the SCO property can help in designing molecules with both properties.…”

Section: Introductionmentioning

confidence: 99%

“…Mononuclear 3d transition-metal complexes hold promise in this direction with both evident properties of magnetism and spin-crossover at the molecular level. 36,37 Ligand field in 3d-transition-metal complexes could play a central role in controlling the magnetic anisotropy and the SCO behavior of the molecule. 38,39 Thus, understanding the ligand-field-derived modulation of anisotropy in conjunction with the SCO property can help in designing molecules with both properties.…”

Section: Introductionmentioning

confidence: 99%

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First-Principles Investigations of Magnetic Anisotropy and Spin-Crossover Behavior of Fe(III)–TBP Complexes

Khurana¹,

Gupta²,

Ali³

2021

J. Phys. Chem. A

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With the ongoing effort to obtain mononuclear 3d-transitionmetal complexes that manifest slow relaxation of magnetization and, hence, can behave as single-molecule magnets (SMMs), we have modeled 14 Fe(III) complexes based on an experimentally synthesized (PMe 3 ) 2 FeCl 3 complex [J. Am. Chem. Soc. 2017, 139 (46), 16474−16477], by varying the axial ligands with group XV elements (N, P, and As) and equatorial halide ligands from F, Cl, Br, and I. Out of these, nine complexes possess large zero field splitting (ZFS) parameter D in the range of −40 to −60 cm −1 . The first-principles investigation of the ground-spin state applying density functional theory (DFT) and wave function-based multiconfigurations methods, e.g., SA-CASSCF/NEVPT2, are found to be quite consistent except for few delicate cases with near-degenerate spin states. In such cases, the hybrid B3LYP functional is found to be biased toward high-spin (HS) state. Altering the percentage of exact exchange admixed in the B3LYP functional leads to intermediate-spin (IS) ground state consistent with the multireference calculations. The origin of large zero field splitting (ZFS) in the Fe(III)-based trigonal bipyramidal (TBP) complexes is investigated. Furthermore, a number of complexes are identified with very small ΔG HS−IS adia. values indicating the possible spin-crossover phenomenon between the bistable spin states.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

First-Principles Investigations of Magnetic Anisotropy and Spin-Crossover Behavior of Fe(III)–TBP Complexes

Khurana¹,

Gupta²,

Ali³

2021

J. Phys. Chem. A

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“…The present approach resembles Maltempo’s model used to explain the magnetism of high-spin iron(III) porphyrins . However, in the present case, the unusual magnetic properties of 1 do not originate from the interaction of two states with different spin but rather from the coupling of three different S = 1 states.…”

Section: Resultsmentioning

confidence: 67%

Experimental and Theoretical Evidence for an Unusual Almost Triply Degenerate Electronic Ground State of Ferrous Tetraphenylporphyrin

et al. 2021

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Iron porphyrins exhibit unrivalled catalytic activity for electrochemical CO2-to-CO conversion. Despite intensive experimental and computational studies in the last 4 decades, the exact nature of the prototypical square-planar [FeII(TPP)] complex (1; TPP2– = tetraphenylporphyrinate dianion) remained highly debated. Specifically, its intermediate-spin (S = 1) ground state was contradictorily assigned to either a nondegenerate 3A2g state with a (d xy )2(d z 2 )2(d xz,yz )2 configuration or a degenerate 3Eg θ state with a (d xy )2(d xz,yz )3(d z 2 )1/(d z 2 )2(d xy )1(d xz,yz )3 configuration. To address this question, we present herein a comprehensive, spectroscopy-based theoretical and experimental electronic-structure investigation on complex 1. Highly correlated wave-function-based computations predicted that 3A2g and 3Eg θ are well-isolated from other triplet states by ca. 4000 cm–1, whereas their splitting ΔA–E is on par with the effective spin–orbit coupling (SOC) constant of iron(II) (≈400 cm–1). Therfore, we invoked an effective Hamiltonian (EH) operating on the nine magnetic sublevels arising from SOC between the 3A2g and 3Eg θ states. This approach enabled us to successfully simulate all spectroscopic data of 1 obtained by variable-temperature and variable-field magnetization, applied-field 57Fe Mössbauer, and terahertz electron paramagnetic resonance measurements. Remarkably, the EH contains only three adjustable parameters, namely, the energy gap without SOC, ΔA–E, an angle θ that describes the mixing of (d xy )2(d xz,yz )3(d z 2 )1 and (d z 2 )2(d xy )1(d xz,yz )3 configurations, and the ⟨r d –3⟩ expectation value of the iron d orbitals that is necessary to estimate the 57Fe magnetic hyperfine coupling tensor. The EH simulations revealed that the triplet ground state of 1 is genuinely multiconfigurational with substantial parentages of both 3A2g (<88%) and 3Eg (>12%), owing to their accidental near-triple degeneracy with ΔA–E = +950 cm–1. As a consequence of this peculiar electronic structure, 1 exhibits a huge effective magnetic moment (4.2 μB at 300 K), large temperature-independent paramagnetism, a large and positive axial zero-field splitting, strong easy-plane magnetization (g ⊥ ≈ 3 and g ∥ ≈ 1.7) and a large and positive internal field at the 57Fe nucleus aligned in the xy plane. Further in-depth analyses suggested that g ⊥ ≫ g ∥ is a general spectroscopic signature of near-triple orbital degeneracy with more than half-filled pseudodegenerate orbital sets. Implications of the unusual electronic structure of 1 for CO2 reduction are discussed.

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“…Specifically, forty of the early LUMOs and also HOMOs, including also those more diffuse d orbitals that constitute a double d shell, were tested for expanding the active space. 65 However, this methodology, which allowed improving the estimation of D in a high-spin d 5 iron(III) complex with large zfs, 66 does not report any advance here. Thus, values of D in these new 80 calculations, ranging from −57.9 to −56.2 cm −1 , were similar to that found from the original active space, the changes being not significant.…”

Section: Dalton Transactions Papermentioning

confidence: 87%

Field-induced mononuclear cobalt(ii) single-molecule magnet (SMM) based on a benzothiadiazole-ortho-vanillin ligand

et al. 2022

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Single‐Ion Magnetic Behaviour in an Iron(III) Porphyrin Complex: A Dichotomy Between High Spin and 5/2–3/2 Spin Admixture

Cited by 12 publications

References 107 publications

First-Principles Investigations of Magnetic Anisotropy and Spin-Crossover Behavior of Fe(III)–TBP Complexes

First-Principles Investigations of Magnetic Anisotropy and Spin-Crossover Behavior of Fe(III)–TBP Complexes

Experimental and Theoretical Evidence for an Unusual Almost Triply Degenerate Electronic Ground State of Ferrous Tetraphenylporphyrin

Field-induced mononuclear cobalt(ii) single-molecule magnet (SMM) based on a benzothiadiazole-ortho-vanillin ligand

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