Spin crossover in iron(III) complexes

Harding, David J.; Harding, Phimphaka; Phonsri, Wasinee

doi:10.1016/j.ccr.2016.01.006

Cited by 262 publications

(226 citation statements)

References 165 publications

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“…Expanded chelate ring sizes should also promote the high spin states of complexes, by increasing the ligand conformational strain associated with the more compact low-spin form [71,72] [75,76], for example, although that remains to be confirmed by a solution-phase study. It is harder to elucidate trends from those compounds in the solid state, since their SCO is often very gradual and can be influenced by the salicyl ligand conformation in the crystal [68].…”

Section: Influence Of Chelate and Macrocycle Ring Size On Metal Ion Smentioning

confidence: 99%

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

2016

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Abstract:The relationship between chemical structure and spin state in a transition metal complex has an important bearing on mechanistic bioinorganic chemistry, catalysis by base metals, and the design of spin crossover materials. The latter provide an ideal testbed for this question, since small changes in spin state energetics can be easily detected from shifts in the spin crossover equilibrium temperature. Published structure-function relationships relating ligand design and spin state from the spin crossover literature give varied results. A sterically crowded ligand sphere favors the expanded metal-ligand bonds associated with the high-spin state. However, steric clashes at the molecular periphery can stabilize either the high-spin or the low-spin state in a predictable way, depending on their effect on ligand conformation. In the absence of steric influences, the picture is less clear since electron-withdrawing ligand substituents are reported to favor the low-spin or the high-spin state in different series of compounds. A recent study has shed light on this conundrum, showing that the electronic influence of a substituent on a coordinated metal ion depends on its position on the ligand framework. Finally, hydrogen bonding to complexes containing peripheral N-H groups consistently stabilizes the low-spin state, where this has been quantified.

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Section: Influence Of Chelate and Macrocycle Ring Size On Metal Ion Smentioning

confidence: 99%

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

2016

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“…Fe(III) complexes often exhibit faster relaxation than Fe(II) complexes, due to smaller iron-ligand distance change upon spin crossover [60]. Most of the Fe(III) complexes studied by photomagnetism are based of tridentate ligands, derived from salicylaldehyde and amines [61]. The studies performed so far do not show any particular trend in the sense that these tridentate-based Fe(III) complexes do not belong to any specific T 0 line [22f, 62].…”

Section: Iv4-cautions With the Databasementioning

confidence: 99%

A critical review of the T(LIESST) temperature in spin crossover materials − What it is and what it is not

Chastanet¹,

Desplanches²,

Baldé³

et al. 2018

Chem.Sq.

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Light-Induced Excited Spin-State Trapping has been studied since 1982 in solution and 1984 in solid state as it offers a reversible way of photoswitching the electronic configuration of spin crossover systems. Since then, the lifetime of the photo-induced state was deeply investigated through kinetics measurements. In 1998, a fast and easy way to record the limit temperature above which the photo-induced state is erased, denoted T(LIESST), was introduced. This procedure has been widely used in the spin crossover community due to its easiness and its efficiency to provide detailed information on the photo-induced state. Correlations between T(LIESST) and structural parameters have been proposed for instance. However, it intrinsically contains drawbacks that can lead to misinterpretation of behaviours and can lead to an over-estimation of its scope. This review aims to present and discuss not only the correct way to measure T(LIESST) but also the essential contributions it has brought and the limits not to be exceeded in its interpretation.

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“…Iron(II) (3d 6 ) coordination compounds attract a great deal of attention in various SCO complexes, because SCO takes place between dia-and paramagnetic states to show drastic change in magnetic and chromic properties. The six-nitrogen donor structures (i.e., Fe II N 6 ) have been studied extensively, and in particular diimines like 2-pyridylmethyleneimine and bipyridyl derivatives [8][9][10][11][12][13] and triimines like 2,6-bis(azaaryl)pyridine derivatives and tripodal tris(azaaryl) compounds [14][15][16][17][18][19] are the most popular ligands for this purpose.…”

Section: Introductionmentioning

confidence: 99%

“…Spin-crossover (SCO) is a reversible transition between low-spin (LS) and high-spin (HS) states by external stimuli like heat, light, pressure, or magnetic field [1][2][3][4][5][6][7]. Iron(II) (3d 6 ) coordination compounds attract a great deal of attention in various SCO complexes, because SCO takes place between dia-and paramagnetic states to show drastic change in magnetic and chromic properties.…”

Section: Introductionmentioning

confidence: 99%

Pybox-Iron(II) Spin-Crossover Complexes with Substituent Effects from the 4-Position of the Pyridine Ring (Pybox = 2,6-Bis(oxazolin-2-yl)pyridine)

Kimura

Ishida

2017

Inorganics

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Spin-crossover (SCO) behavior of a series of [Fe(X-pybox) 2 ](ClO 4 ) 2 was investigated, where X-pybox stands for 4-X-substituted 2,6-bis(oxazolin-2-yl)pyridine with X = H, Cl, Ph, CH 3 O, and CH 3 S. We confirmed that the mother compound [Fe(H-pybox) 2 ](ClO 4 ) 2 underwent SCO above room temperature. After X was introduced, the SCO temperatures (T 1/2 ) were modulated as 310, 230, and 330 K for X = Cl, Ph, and CH 3 S, respectively. The CH 3 O derivative possessed the high-spin state down to 2 K. Crystallographic analysis for X = H, Cl, CH 3 O, and CH 3 S was successful, being consistent with the results of the magnetic study. Distorted coordination structures stabilize the HS (high-spin) state, and the highest degree of the coordination structure distortion is found in the CH 3 O derivative. A plot of T 1/2 against the Hammett substituent constant σ p showed a positive relation. Solution susceptometry was also performed to remove intermolecular interaction and rigid crystal lattice effects, and the T 1/2 's were determined as 260, 270, 240, 170, and 210 K for X = H, Cl, Ph, CH 3 O, and CH 3 S, respectively, in acetone. The substituent effect on T 1/2 became very distinct, and it is clarified that electron-donating groups stabilize the HS state.

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Spin crossover in iron(III) complexes

Cited by 262 publications

References 165 publications

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

The Effect of Ligand Design on Metal Ion Spin State—Lessons from Spin Crossover Complexes

A critical review of the T(LIESST) temperature in spin crossover materials − What it is and what it is not

Pybox-Iron(II) Spin-Crossover Complexes with Substituent Effects from the 4-Position of the Pyridine Ring (Pybox = 2,6-Bis(oxazolin-2-yl)pyridine)

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