Homochiral <i>versus</i> racemic polymorphs of spin-crossover iron(<scp>ii</scp>) complexes with reversible LIESST effect

Ma, Tingting; Sun, Xiao-Peng; Yao, Zi‐Shuo; Tao, Jun

doi:10.1039/c9qi01590f

Cited by 22 publications

(29 citation statements)

References 68 publications

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“…This yielded new insights into the effect of remote substituents − and chelate ligand bite angle , on a complex’s ligand field, and it also illustrated how this can be perturbed by crystal packing in the solid state . Another goal was a chiral ligand system, to allow optical isomers of a complex to be distinguished by their spin state. , Our first attempt toward that aim involved homoleptic iron(II) complexes of the chiral 2,6- bis (oxazolinyl)pyridine (PyBox) ligand system ( L 2 R, Chart ). Homochiral [Fe(( R )- L 2 Ph) 2 ] 2+ and heterochiral [Fe(( R )- L 2 Ph)(( S )- L 2 Ph)] 2+ exhibit SCO with midpoint temperatures ( T 1/2 ) of 244 and 278 K respectively, in CD 3 CN solution.…”

Section: Introductionmentioning

confidence: 99%

Spin-States of Diastereomeric Iron(II) Complexes of 2,6-Bis(thiazolin-2-yl)pyridine (ThioPyBox) Ligands and a Comparison with the Corresponding PyBox Derivatives

et al. 2021

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This report investigates homoleptic iron(II) complexes of thiazolinyl analogues of chiral PyBox tridentate ligands: 2,6-bis(4-phenyl-4,5-dihydrothiazol-2-yl)pyridine (L 1 Ph), 2,6-bis(4-isopropyl-4,5-dihydrothiazol-2-yl)pyridine (L 1 iPr), and 2,6-bis(4tert-butyl-4,5-dihydrothiazol-2-yl)pyridine (L 1 t-Bu). Crystallographic data imply the larger and more flexible thiazolinyl rings reduce steric clashes between the R substituents in homochiral [Fe((R)-L 1 R) 2 ] 2+ or [Fe((S)-L 1 R) 2 ] 2+ (R = Ph, iPr, or t-Bu), compared to their PyBox (L 2 R) analogues. Conversely, the larger heterocyclic S atoms are in close contact with the R substituents in heterochiraland [Fe(L 1 iPr) 2 ] 2+ exhibit spin-crossover equilibria in CD 3 CN, centered at 344 ± 6 K and 277 ± 1 K respectively, while their heterochiral congeners are essentially low-spin within the liquid range of the solvent. These data imply that the diastereomers of [Fe(L 1 Ph) 2 ] 2+ and [Fe(L 1 iPr) 2 ] 2+ show a greater difference in their spin-state behaviors than was previous found for [Fe(L 2 Ph) 2 ] 2+ . Gas-phase DFT calculations (B86PW91/def2-SVP) of the [Fe(L 1 R) 2 ] 2+ and [Fe(L 2 R) 2 ] 2+ complexes reproduce most of the observed trends, but they overstabilize the high-spin state of SCO-active [Fe(L 1 iPr) 2 ] 2+ by ca. 1.5 kcal mol −1 . This might reflect the influence of intramolecular dispersion interactions on the spin states of these compounds. Attempts to model this with the dispersion-corrected functionals B97-D2 or PBE-D3 were less successful than our original protocol, confirming that the spin states of sterically hindered molecules are a challenging computational problem.

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Section: Introductionmentioning

confidence: 99%

Spin-States of Diastereomeric Iron(II) Complexes of 2,6-Bis(thiazolin-2-yl)pyridine (ThioPyBox) Ligands and a Comparison with the Corresponding PyBox Derivatives

et al. 2021

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“…31 The chirality of such compounds is another attractive feature, since chiral-at-molecule SCO complexes are still quite rare. 28–30,32 Such compounds have potential for switchable ferroelectric or chiroptical properties in the solid state. 33,34…”

Section: Introductionmentioning

confidence: 99%

Heteroleptic iron(ii) complexes of chiral 2,6-bis(oxazolin-2-yl)-pyridine (PyBox) and 2,6-bis(thiazolin-2-yl)pyridine ligands – the interplay of two different ligands on the metal ion spin sate

et al. 2022

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Complexation of Fe[ClO4]2·6H2O by 1 equiv 2,6-bis((4S)-4-phenyl-4,5-dihydrooxazol-2-yl)pyridine ((S)-L1Ph) and 2,6-bis((4R)-4-phenyl-4,5-dihydrothiazol-2-yl)pyridine ((R)-L2Ph) cleanly affords [Fe((S)-L1Ph)((R)-L2Ph)][ClO4]2; [Fe((R)-L1iPr)((S)-L2iPr)][ClO4]2 (L1iPr = 2,6-bis(4-isopropyl-4,5-dihydrooxazol-2-yl)pyridine; L2iPr = 2,6-bis(4-isopropyl-4,5-dihydrothiazol-2-yl)pyridine) was prepared by a similar route. The compounds exhibit...

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“…The development of molecular materials with switchable physical properties is a burgeoning field in materials science. − One fascinating material is spin-crossover (SCO) compounds, whose spin multiplicity can be tuned by physical or chemical external stimuli. For example, the electron configuration of the Fe II SCO complex can be interconverted between t 2g 6 e g 0 (low spin, LS) and t 2g 4 e g 2 (high spin, HS), introducing a diamagnetic-to-paramagnetic transition of the materials in response to external stimuli. − The magnetic bistability is important for molecular memory media and switches. , In addition to the magnetic switching, variation of the spin state is usually accompanied by a color change, suggesting a displaying role of the SCO materials. − A recent demonstration performed by Real and co-workers shows that a meltable Fe II complex can manifest distinct color variation from homogeneous green to dark green-violet in response to a thermally controlled HS-to-LS transition …”

Section: Introductionmentioning

confidence: 99%

Reverse Hofmann-Type Spin-Crossover Compound Showing a Multichannel Controllable Color Change in an Ambient Environment

et al. 2021

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Materials that demonstrate a multichannel controllable color change in response to external stimuli are fascinating for their potential applications in sensoring and displaying devices. Herein we report a FeII spin-crossover (SCO) compound that exhibits both solvatochromism and thermochromism under an ambient environment. This Hofmann-type compound possesses two different pores where the solvent guests can be removed in a two-step process. Because the loss of solvent guests modifies the spin state of magnetic centers, an unusual yellow–red–yellow two-step color change of crystals was detected. Moreover, because of the strong cooperativity of the spin centers, a dramatic red-to-yellow color change of crystals in response to a minute thermal perturbation around 303 K is triggered by an abrupt spin transition of the metal centers. The multichannel controllable dramatic color change demonstrated in the present compound highlights the sensoring and displaying roles of SCO materials.

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Homochiral versus racemic polymorphs of spin-crossover iron(ii) complexes with reversible LIESST effect

Abstract: Homochiral and racemic polymorphs show different spin-crossover behaviours due to different intermolecular interactions, and reversible LIESST effects can be realized on homochiral complexes.

Cited by 22 publications

References 68 publications

Spin-States of Diastereomeric Iron(II) Complexes of 2,6-Bis(thiazolin-2-yl)pyridine (ThioPyBox) Ligands and a Comparison with the Corresponding PyBox Derivatives

Spin-States of Diastereomeric Iron(II) Complexes of 2,6-Bis(thiazolin-2-yl)pyridine (ThioPyBox) Ligands and a Comparison with the Corresponding PyBox Derivatives

Heteroleptic iron(ii) complexes of chiral 2,6-bis(oxazolin-2-yl)-pyridine (PyBox) and 2,6-bis(thiazolin-2-yl)pyridine ligands – the interplay of two different ligands on the metal ion spin sate

Reverse Hofmann-Type Spin-Crossover Compound Showing a Multichannel Controllable Color Change in an Ambient Environment

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