Spin crossover in homoleptic Fe(II) imidazolylimine complexes

Scott, Hayley S.; Staniland, Robert W.; Kruger, Paul E.

doi:10.1016/j.ccr.2018.02.001

Cited by 91 publications

(66 citation statements)

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“…The structure of 1 is comprised of three bidentate L1 ligands coordinated to an octahedral Fe II centre via imidazole and imine nitrogen atoms. The nature of the coordination of the unsymmetrical ligands gives the mer isomer, which is relatively rare for mononuclear Fe II imidazolylimine‐based complexes . The Fe‐N coordination bond distances indicate that the Fe II centre is in the LS state at 120 K, with an average length of 1.991(2) Å.…”

Section: Figurementioning

confidence: 99%

“…Complex 1 is only the third structurally characterised example to show mer ‐substitution about the Fe II centre with the remaining twenty seven examples being the fac ‐isomer. The three complexes with mer ‐configuration all show similar SCO properties with T 1/2 values ranging from 105–184 K . The complexes with fac ‐configuration show extremely diverse SCO behaviour, which includes abrupt or gradual; complete or incomplete, and; with or without hysteretic crossover.…”

Section: Figurementioning

confidence: 99%

“…[4] We recently compiled as urvey of homoleptic imidazolylimine-coordinated Fe II complexesa nd showedthem to be amenable to study the intricacies of SCO behaviour. [5] Thisi s, in part, due to the ligand field afforded by the bidentate N imine and N imidazole coordinating group, which falls within an optimal range to thermally access SCO. [6] This, and their facile synthesis, renders Fe II -imidazolylimine complexes ar ichs eam to be exploredi nt he pursuit of new molecular SCO materials.…”

mentioning

confidence: 99%

“…The natureo f the coordination of the unsymmetrical ligandsg ives the mer isomer,w hich is relativelyr are for mononuclear Fe II imidazolylimine-based complexes. [5] The Fe-N coordination bond distances indicate that the Fe II centre is in the LS state at 120 K, with an average length of 1.991(2) .T he octahedral distortion parameter, S,( defined as the sum of deviations from 908 of the 12 Fe-N cis angles) [9] is equal to 688 (S is equal to 0f or an ideal octahedron and increases with the deformation). Two crystallographically independent ClO 4 À anionsa re presenti n the asymmetricu nit.…”

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confidence: 99%

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Solvent Dependent Spin‐Crossover and Photomagnetic Properties in an Imidazolylimine Fe^II Complex

Archer

Scott

Polson

et al. 2019

Chemistry An Asian Journal

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The synthesis and physico‐chemical characterization of an FeII complex [Fe(L1)3](ClO4)2⋅CH3CN⋅0.5H2O, 1, incorporating a bidentate imidazolylimine‐based ligand are reported. Complex 1 crystallises as the mer‐isomer and the crystal lattice is replete with hydrogen bonding interactions between ClO4− anions, solvent molecules and imidazole N‐H groups. Variable‐temperature structural, magnetic, photomagnetic and optical reflectivity techniques have been deployed to fully characterise the spin‐crossover (SCO) behaviour in 1 along with its desolvated phase, 1⋅desolv. Variable‐temperature (1.8–300 K) magnetic‐susceptibility measurements reveal a broad two‐step full SCO for 1 (T1/2=158 and 184 K) and photomagnetic experiments at 10 K under white‐light irradiation revealed complete photo‐induced SCO. 1⋅desolv displays considerably different magnetic behaviour with sharp single‐step SCO accompanied by a thermal hysteresis (T1/2↑=105 K, T1/2↓=95 K) in addition to full photo‐induced SCO at lower temperatures.

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Section: Figurementioning

confidence: 99%

Section: Figurementioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Solvent Dependent Spin‐Crossover and Photomagnetic Properties in an Imidazolylimine Fe^II Complex

Archer

Scott

Polson

et al. 2019

Chemistry An Asian Journal

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“…In the overwhelming majority of the complexes, changing spin multiplicity is accompanied by an abrupt change in the magnetic and optical properties. Monographs, numerous reviews and scientific papers are devoted to the investigation of this phenomenon.…”

Section: Introductionmentioning

confidence: 99%

Studies on Sulfate Iron(II) Complex With Tris(pyrazol‐1‐yl)methane Exhibiting Spin Crossover in Aqueous Solutions

et al. 2019

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Using the methods of UV‐, VIS‐ and near‐IR spectrometry, potentiometry, static magnetic susceptibility and cyclic voltammetry, an iron(II) complex with tris(pyrazol‐1‐yl)methane (L) having the composition of [FeL2]SO4 is studied in aqueous solution. In the solid state this compound exhibits spin crossover 1A1 ↔ 5T2. The protonation constants of L (log K1H=2.53, log K2H=1.80) and stability constants of the complex (log β(FeL2+) ≈ 4, log β(FeL22+)=8.62) at t = 25° C, I=0.05 M have been determined. The studies on μeff(T) of [FeL2]SO4 in solution in the temperature range from 280 to 355 K have shown that the value of μeff exhibits an increase with increasing temperature. This indicates that with increasing temperature a transition occurs from the low spin (LS) state of the complex to the high spin (HS) state thereof.

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Deciphering the Influence of Meridional versus Facial Isomers in Spin Crossover Complexes

Lathion

Guénée

Besnard

et al. 2018

Chemistry A European J

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Chelate coordination of non-symmetrical didentate pyrazine-benzimidazole (L1) or pyridine-benzimidazole (L2) N-donor ligands around divalent iron in acetonitrile produces stable homoleptic triple-helical spin crossover [Fe(Lk) ] complexes existing as mixtures of meridional (C -symmetry) and facial (C -symmetry) isomers in slow exchange on the NMR timescale. The speciation deviates from the expected statistical ratio mer/fac=3:1, a trend assigned to the thermodynamic trans-influence, combined with solvation effects. Consequently, the observed spin state Fe ↔Fe equilibria occurring in [Fe(Lk) ] refer to mixtures of complexes in solution, an issue usually not considered in this field, but which limits rational structure-properties correlations. Taking advantage of the selective and quantitative formation of isostructural facial isomers in non-constrained related spin crossover d-f helicates (HHH)-[LnFe(Lk) ] (Ln is a trivalent lanthanide, Lk=L5, L6), we propose a novel strategy for assigning pertinent thermodynamic driving forces to each spin crossover triple-helical isomer. The different enthalpic contributions to the spin state equilibrium found in mer-[Fe(Lk) ] and fac-[Fe(Lk) ] reflect the Fe-N bond strengths dictated by the trans-influence, whereas a concomitant solvent-based entropic contribution reinforces the latter effect and results in systematic shifts of the spin crossover transitions toward higher temperature in the facial isomers.

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Spin crossover in homoleptic Fe(II) imidazolylimine complexes

Cited by 91 publications

References 100 publications

Solvent Dependent Spin‐Crossover and Photomagnetic Properties in an Imidazolylimine Fe^II Complex

Solvent Dependent Spin‐Crossover and Photomagnetic Properties in an Imidazolylimine Fe^II Complex

Studies on Sulfate Iron(II) Complex With Tris(pyrazol‐1‐yl)methane Exhibiting Spin Crossover in Aqueous Solutions

Deciphering the Influence of Meridional versus Facial Isomers in Spin Crossover Complexes

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Spin crossover in homoleptic Fe(II) imidazolylimine complexes

Cited by 91 publications

References 100 publications

Solvent Dependent Spin‐Crossover and Photomagnetic Properties in an Imidazolylimine FeII Complex

Solvent Dependent Spin‐Crossover and Photomagnetic Properties in an Imidazolylimine FeII Complex

Studies on Sulfate Iron(II) Complex With Tris(pyrazol‐1‐yl)methane Exhibiting Spin Crossover in Aqueous Solutions

Deciphering the Influence of Meridional versus Facial Isomers in Spin Crossover Complexes

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Solvent Dependent Spin‐Crossover and Photomagnetic Properties in an Imidazolylimine Fe^II Complex

Solvent Dependent Spin‐Crossover and Photomagnetic Properties in an Imidazolylimine Fe^II Complex