EPR spectra and structures of spin-variable iron(III) complexes

Муравьев, В. И.

doi:10.1134/s1070328411100071

Cited by 6 publications

(4 citation statements)

References 7 publications

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“…By 1 H NMR, Fe( tbu dhbpy)Cl exhibits paramagnetic broadening and shifts in N , N -DMF- d 7 . A μ eff value of 5.90(7) Bohr magnetons is obtained in N , N -DMF- d 7 , using the Evans method for determining paramagnetic susceptibility, consistent with high spin Fe(III) (S = 5/2). , An X-band EPR spectrum also gives a rhombic signal at g = 4.2 with no low spin impurities, consistent with results obtained by the Evans method. , Three characteristic absorbances with λ max at 320, 446, and 542 nm are observed by UV–vis in N , N -DMF (Figure S2). These absorbances are assigned to a single ligand π–π* and two phenolate to Fe(III) ligand-to-metal charge transfers with molar absorptivities of 17200, 3120, and 2330 M –1 s –1 , respectively.…”

Section: Methodssupporting

confidence: 79%

“…56,57 An X-band EPR spectrum also gives a rhombic signal at g = 4.2 with no low spin impurities, consistent with results obtained by the Evans method. 58,59 Three characteristic absorbances with λ max at 320, 446, and 542 nm are observed by UV−vis in N,N-DMF (Figure S2). These absorbances are assigned to a single ligand π−π* and two phenolate to Fe(III) ligand-to-metal charge transfers with molar absorptivities of 17200, 3120, and 2330 M −1 s −1 , respectively.…”

Section: ■ Introductionmentioning

confidence: 99%

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Electrocatalytic Reduction of CO₂ to Formate by an Iron Schiff Base Complex

et al. 2018

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The synthesis, structural characterization, and reactivity of an iron(III) chloride compound of 6,6'-di(3,5-di-tert-butyl-2-hydroxybenzene)-2,2'-bipyridine (Fe(dhbpy)Cl), under electrochemically reducing conditions is reported. In the presence of carbon dioxide (CO) under anhydrous conditions in N,N-dimethylformamide (DMF), this complex mediates the 2e reductive disproportionation of two equivalents of CO to carbon monoxide (CO) and carbonate (CO). Upon addition of phenol (PhOH) as a proton source under CO saturation, catalytic current is observed; product analysis from controlled potential electrolysis experiments shows the majority product is formate (68 ± 4% Faradaic efficiency), with H as a minor product (30 ± 10% Faradaic efficiency) and minimal CO (1.1 ± 0.3% Faradaic efficiency). On the basis of data obtained from cyclic voltammetry and infrared spectroelectrochemistry (IR-SEC), the release of CO from intermediate Fe carbonyl species is extremely slow and undergoes competitive degradation, limiting the activity and lifetime of this catalyst. Mechanistic studies also indicate the phenolate moieties coordinated to Fe are sensitive to protonation in the reduced state, suggesting the possibility of cooperative pendent proton interactions being involved in CO reduction.

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Section: Methodssupporting

confidence: 79%

Section: ■ Introductionmentioning

confidence: 99%

Electrocatalytic Reduction of CO₂ to Formate by an Iron Schiff Base Complex

et al. 2018

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“…38 Using the obtained theoretical equation for D, 38 the energy gaps between the ground-state and excited terms and SOC of Fe 3+ ion equal ζ Fe = 397 cm −1 . Murav'ev 39 on the example of similar HS iron(III) complexes estimated that the D-parameter should be in the following range: 0.01 cm −1 < |D| < 0.04 cm −1 . D values evaluated by him agree with our experimental EPR data (g = 2.1, |D| = 0.043 cm −1 ) obtained for the liquid-crystalline HS iron(III) complex with Schiff-based ligands.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Detailed EPR Study of Spin Crossover Dendrimeric Iron(III) Complex

et al. 2013

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The unusual magnetic behavior of the first dendritic Fe(3+) complex with general formula [Fe(L)2](+)Cl(-)·H2O based on a branched Schiff base has been investigated by electron paramagnetic resonance (EPR) and Mössbauer spectroscopy. EPR displays that complex consists of the three types of magnetically active iron centers: one S = 1/2 low-spin (LS) and two S = 5/2 high-spin (HS) centers with strong low-symmetry and weak distorted octahedral crystal fields. Analysis of the magnetic behavior reflected by I versus T (where I is the EPR lines integrated intensity of the spectrum) demonstrates that the dendritic Fe(3+) complex has sufficiently different behavior in three temperature intervals. The first (4.2-50 K) interval corresponds to the antiferromagnetic exchange interactions between LS-LS, LS-HS, and HS-HS centers. The appearance of a presumable magnetoelectric effect is registered in the second (50-200 K) temperature interval, whereas a spin transition process between LS and HS centers occurs in the third (200-330 K) one. The coexistence of the magnetic ordering, presumable magnetoelectric effect, and spin crossover in one and the same material has been detected for the first time. The Mössbauer spectroscopy data completely confirm the EPR results.

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“…In this situation the states of the three spin doublets of the S = 5/2 multiplet of the iron(III) ion are mixed giving rise to many "forbidden" transitions. [39][40][41] Indeed, as we have shown in the HF-ESR experiment, increasing the energy of the microwave quantum by at least one order of magnitude drastically simplifies the spectra and enables an accurate determination of the parameters of the spin-Hamiltonian (3). Similar rather uncommon ESR behaviour of the [Fe(DMSO) 6 ](NO 3 ) 3 complex with the axial ZFS parameter D ≈ 0.2 cm −1 was described by Solano-Peralta and co-authors.…”

Section: Discussionmentioning

confidence: 99%