MAGNETOSTRUCTURAL J-CORRELATIONS IN Fe(III) COMPLEXES – A REVISION

Vranovičová, Beata; Boča, Roman

doi:10.2478/nbec-2013-0008

“…The J 3 interaction is the exchange coupling between the Fe2 ( S =5/2) and Fe3 ( S =5/2) metal centre bridged by −O 2− − group, and it is estimated to be −113.8 cm −1 . This is consistent with the magneto‐structural correlation established already by Boca and co‐workers, which suggests that the interaction is strongly correlated with the Fe−O−Fe angle and Fe−O distance [24a] . Here, the Fe−O distance and Fe−O−Fe angle are, respectively, 1.77 Å and 146° and it has been proven that for these distances and angles, exchange interaction will be around −125 cm −1 , and the J 3 is in agreement.…”

Section: Resultssupporting

confidence: 92%

Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

Sarkar,

Tiwari,

Samanta

et al. 2024

Angewandte Chemie

0

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A hitherto unknown series of air stable, π‐conjugated, remarkably bent tetra‐cation tetra‐radical intermolecular Fe(III) µ‐oxo tetranuclear complex, isolated from the dication diradical diiron(III) porphyrin dimers, has been synthesised and spectroscopically characterised along with single crystal X‐ray structure determination of two such molecules. These species facilitate long‐range charge/radical delocalisation through the bridge across the entire tetranuclear unit manifesting an unusually intense NIR band. Assorted spin states of Fe(III) centres are stabilised within these unique tetranuclear frameworks: terminal six‐coordinate iron centres stabilise the admixed intermediate spin states while the central five‐coordinate iron centres stabilise the high‐spin states. Variable temperature magnetic susceptibility measurements indicated strong antiferromagnetic coupling for the Fe(III)‐O‐Fe(III) unit while the exchange interactions between the Fe centres and the porphyrin π‐cation radicals are weaker as supported both by magnetic data and DFT calculations. The nature of orbital overlap between the SOMOs of Fe(III) and π* orbital of the porphyrin was found to rationalise the observed exchange coupling, establishing such a complex magnetic exchange in this tetranuclear model with a significant bioinorganic relevance.

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“…The magnetostructural correlation for iron(III) μ-O-bridged complexes was established by Gorund and Lippard in the form of an exponential function as where P is a parameter that is defined as half of the shortest superexchange pathway between two iron(III)atoms. Recently, Vranovičová and Boča have attempted to redo nonlinear regression using contemporary software as and also to reformulate this magnetostructural correlation in the form of linear equations as or by where α is the average value of Fe–O–Fe angle. In order to elucidate the applicability of such magnetostructural correlations, we compared J values for compounds 4 and 5 in Table .…”

Section: Discussionmentioning

confidence: 99%

Experimental and Theoretical Investigations of Magnetic Exchange Pathways in Structurally Diverse Iron(III) Schiff-Base Complexes

Herchel

¹

,

Němec

²

,

Machata

³

et al. 2015

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The synthesis, and the structural and magnetic properties, of the following new iron(III) Schiff base complexes with the {O',N,O″}-chelating ligand H2L (2-hydroxyphenylsalicylaldimine) are reported: K[FeL2]·H2O (1), (Pr3NH)[FeL2]·2CH3OH (2), [FeL(bpyO2) (CH3OH)][FeL2]·CH3OH (3), [Fe2L3(CH3OH)]·2CH3OH·H2O (4), and [{Fe2L2}(μ-OH)2{FeL(bpyO2)}2][BPh4]2·2H2O (5), where Pr3NH(+) represents the tripropylammonium cation and bpyO2 stands for 2,2'-bipyridine-N-dioxide. A thorough density functional theory (DFT) study of magnetic interactions (the isotropic exchange) at the B3LYP/def-TZVP level of theory was employed, and calculations have revealed superexchange pathways through intramolecular/intermolecular noncovalent contacts (π-π stacking, C-H···O and O-H···O hydrogen bonds, diamagnetic metal cations) and/or covalent bonds ((μ-O(Ph), μ-OH) or bis(μ-O(Ph)) bridging modes), which helped us to postulate trustworthy spin Hamiltonians for magnetic analysis of experimental data. Within the reported family of compounds 1-5, the mediators of the antiferromagnetic exchange can be sorted by their increasing strength as follows: π-π stacking (J(DFT) = -0.022 cm(-1)/J(mag) = -0.025(4) cm(-1) in 2) < C-H···O contacts and π-π stacking (J(DFT) = -0.19 cm(-1)/J(mag) = -0.347(9)cm(-1) in 1) < O-H···O hydrogen bonds (J(DFT) = -0.53 cm(-1)/J(mag) = -0.41(1) cm(-1) in 3) < bis(μ-O(Ph)) bridge (J(DFT) = -13.8 cm(-1)/J(mag) = -12.3(9) cm(-1) in 4) < (μ-O(Ph), μ-OH) bridge (J(DFT) = -18.0 cm(-1)/J(mag) = -17.1(2) cm(-1) in 5), where J(DFT) and J(mag) are the isotropic exchange parameters derived from DFT calculations, and analysis of the experimental magnetic data, respectively. The good agreement between theoretically calculated and experimentally derived isotropic exchange parameters suggests that this procedure is applicable also for other chemical and structural systems to interpret magnetic data properly.

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Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

Sarkar,

Tiwari,

Samanta

et al. 2024

Angew Chem Int Ed

0

View full text Add to dashboard Cite

A hitherto unknown series of air stable, π‐conjugated, remarkably bent tetra‐cation tetra‐radical intermolecular Fe(III) µ‐oxo tetranuclear complex, isolated from the dication diradical diiron(III) porphyrin dimers, has been synthesised and spectroscopically characterised along with single crystal X‐ray structure determination of two such molecules. These species facilitate long‐range charge/radical delocalisation through the bridge across the entire tetranuclear unit manifesting an unusually intense NIR band. Assorted spin states of Fe(III) centres are stabilised within these unique tetranuclear frameworks: terminal six‐coordinate iron centres stabilise the admixed intermediate spin states while the central five‐coordinate iron centres stabilise the high‐spin states. Variable temperature magnetic susceptibility measurements indicated strong antiferromagnetic coupling for the Fe(III)‐O‐Fe(III) unit while the exchange interactions between the Fe centres and the porphyrin π‐cation radicals are weaker as supported both by magnetic data and DFT calculations. The nature of orbital overlap between the SOMOs of Fe(III) and π* orbital of the porphyrin was found to rationalise the observed exchange coupling, establishing such a complex magnetic exchange in this tetranuclear model with a significant bioinorganic relevance.

show abstract

MAGNETOSTRUCTURAL J-CORRELATIONS IN Fe(III) COMPLEXES – A REVISION

Cited by 5 publications

References 8 publications

Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

Experimental and Theoretical Investigations of Magnetic Exchange Pathways in Structurally Diverse Iron(III) Schiff-Base Complexes

Unusual Stabilisation of Remarkably Bent Tetra‐Cationic Tetra‐radical Intermolecular Fe(III) μ‐Oxo Tetranuclear Complexes

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