Understanding of cooperative effects in molecule-based spin transition materials

Fang, Yan; Meng, Yin-Shan; Oshio, Hiroki; Liu, Tao

doi:10.1016/j.ccr.2023.215483

Cited by 15 publications

(2 citation statements)

References 203 publications

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“…[1,2] They have been extensively investigated in the past years since the switch from low (LS) to high (HS) spin state can be reversibly controlled by external stimuli, like temperature, light, pressure, etc., [3][4][5] thus holding promises for application in information processing and data storage devices or molecular switches. [6][7][8][9][10] Special interest has been focussed on compounds that show spin modulation upon light irradiation, with the so-called LIESST (Light-Induced Excited Spin State Trapping) effect at cryogenic temperatures, mostly studied in iron(II) complexes, [10][11][12] and upon application of external pressure, since it favours a LS configuration increasing the SCO transition temperature. [13] Another factor that shows an impact on the SCO properties in the solid state is the crystal packing, as given by the change of counterions, substituents on the donor ligands and/or the presence of crystallization solvent, since it changes the asset of iron(II) centres in the crystal structure.…”

Section: Introductionmentioning

confidence: 99%

Role of Alkylated 2,6‐bis(tetrazol‐5‐yl)pyridyl Ligands and Iron(II) Salts in Selecting Spin Crossover Complexes

Mazzoni,

Baratti,

Rustichelli

et al. 2024

Eur J Inorg Chem

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The substituents in 2,6‐bis(2‐R‐2H‐tetrazol‐5‐yl)pyridyl neutral ligands R2btp (R = Me, tBu) revealed a prominent effect when reacting with iron(II) salts, in combination with the nature of the anion. According to metal:ligand molar ratio, reaction of R2btp with FeCl2 led to isolate [FeII(R2btp‐k3N,N’,N”)2](FeIIICl4)2, R = Me (1a) and tBu (2a), where the octahedral iron(II) centres bring two tridentate ligands in mer coordination mode, but also [FeII(tBu2btp‐k3N,N’,N”)(tBu2btp‐kN)2(H2O‐kO)](FeIIICl4)2 (2b), where one ligand is tridentate, while the other two coordinate the iron(II) through one tetrazolyl nitrogen atom, and the octahedral sphere is completed by one water molecule. In all cases, half of the iron ions are oxidised to iron(III) forming the paramagnetic tetrachloroferrato counterions. Reaction of tBu2btp with Fe(ClO4)2×6H2O led to the octahedral [FeII(tBu2btp‐k3N,N’,N”)2](ClO4)2∙4DCM (4a∙4DCM), which shows solvent‐dependent spin crossover behaviour: while 4a∙4DCM is blocked in the high spin state, its unsolvated form, 4a, undergoes spin transition to low spin in two subsequent steps at 206 K, with opening of a 23‐K hysteresis (T1/2¯ = 194 K, T1/2 = 217 K), and at 136 K (T1/2¯ = 135 K, T1/2 = 137 K). The magnetic profile changes to an incomplete spin transition when the sample absorbs water molecules yielding 4a×1.5H2O.

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Section: Introductionmentioning

confidence: 99%

Role of Alkylated 2,6‐bis(tetrazol‐5‐yl)pyridyl Ligands and Iron(II) Salts in Selecting Spin Crossover Complexes

Mazzoni,

Baratti,

Rustichelli

et al. 2024

Eur J Inorg Chem

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“…The electronic configuration shifts between low-temperature (LT; LS-Co(III)/LS-Fe(II)) and high-temperature (HT; HS-Co(II)/LS-Fe(III)) phases (LS and HS: low- and high-spin, respectively; Scheme ). Subsequently, numerous molecular PBAs featuring metal complexes with various numbers of nuclei have been reported. − These PBAs frequently face stimulus-responsiveness-associated challenges, including thermally driven intramolecular electron transfer or spin crossover, often resulting in gradual or incomplete phase transitions upon cocrystallization with different molecules or the loss of cocrystallized solvent molecules. − For example, intermolecular interactions influence spin-crossover complexes, causing gradual, incomplete changes in their spin states. Hence, changes in intermolecular interactions owing to the removal of crystallized solvent molecules or cocrystallization with other molecules influence the switching behaviors of external-stimulus-responsive metal complexes, including electron-transfer and/or spin-crossover systems. − Despite the existence of numerous examples of hydrogen-bonded spin-crossover complexes, − materials exhibiting abrupt supramolecular-assembly-induced phase transitions with components individually nonresponsive to external stimuli remain relatively rare.…”

mentioning

confidence: 99%

Assembling Smallest Prussian Blue Analogs Using Chiral Hydrogen Bond-Donating Unit toward Complete Phase Transition

Fukushima,

Sekine,

Zhang

et al. 2024

J. Am. Chem. Soc.

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Exploring methods for assembling functional materials at the molecular level may yield functional expressions derived from the assembly method. This study developed novel switchable molecular assemblies characterized by abrupt, complete phase transitions promoted via hydrogen bonding with a chiral carboxylic acid. These assemblies were prepared by aggregating discrete molecules that are unresponsive to external stimuli. Furthermore, enantiopure hydrogen-bond donor (HBD) molecules provide switchable compounds with cooperative and abrupt phase transitions, whereas the racemic mixture of the HBD provides a hydrogenbonded one-dimensional compound with a broad and incomplete phase transition when structural disordering is observed. This study presents a novel strategy for observing metal-to-metal electron-transfer-coupled spin transitions via hydrogen-bond formation.

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A Multiferroic Spin‐Crossover Molecular Crystal

Ai,

Hu,

Weng

et al. 2024

Advanced Materials

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Spin‐crossover (SCO) ferroelectrics with dual‐function switches have attracted great attention for significant magnetoelectric application prospects. However, the multiferroic crystals with SCO features have rarely been reported. Herein, a molecular multiferroic Fe(II) crystalline complex [FeII(C8‐F‐pbh)2] (1‐F, C8‐F‐pbh = (1Z,N'E)‐3‐F‐4‐(octyloxy)‐N’‐(pyridin‐2‐ylmethylene)‐benzo‐hydrazonate) showing the coexistence of ferroelectricity, ferroelasticity, and SCO behavior is presented for the first time. By H/F substitution, the low phase transition temperature (270 K) of the non‐fluorinated parent compound is significantly increased to 318 K in 1‐F, which exhibits a spatial symmetry breaking 222F2 type ferroelectric phase transition with clear room‐temperature ferroelectricity. Besides, 1‐F also displays a spin transition between high‐ and low‐spin states, accompanied by the d‐orbital breaking within the t2g4eg2 and t2g6eg° configuration change of octahedrally coordinated FeII center. Moreover, the 222F2 type ferroelectric phase transition is also a ferroelastic one, verified by the ferroelectric domains reversal and the evolution of ferroelastic domains. To the knowledge, 1‐F is the first multiferroic SCO molecular crystal. This unprecedented finding sheds light on the exploration of molecular multistability materials for future smart devices.

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Understanding of cooperative effects in molecule-based spin transition materials

Cited by 15 publications

References 203 publications

Role of Alkylated 2,6‐bis(tetrazol‐5‐yl)pyridyl Ligands and Iron(II) Salts in Selecting Spin Crossover Complexes

Role of Alkylated 2,6‐bis(tetrazol‐5‐yl)pyridyl Ligands and Iron(II) Salts in Selecting Spin Crossover Complexes

Assembling Smallest Prussian Blue Analogs Using Chiral Hydrogen Bond-Donating Unit toward Complete Phase Transition

A Multiferroic Spin‐Crossover Molecular Crystal

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