Geometric structure, electronic structure, and spin transition of several FeII spin-crossover molecules

Tuấn, Nguyễn Anh

doi:10.1063/1.3670044

Cited by 4 publications

(3 citation statements)

References 16 publications

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“…Molecule (1) has stepwise spin transition with no thermal hysteresis, 11) while molecule (7) has abrupt spin transition with T ↑ = 314 K and T ↓ = 244 K resulting in wide thermal hysteresis ¦T SCO = 70 K. 12) Moreover, our previous study showed that ¦T SCO increased with ¦U of Fe II SCO complexes. 10) These results allow us to predict that designed Fe II (LX 2 ) molecules (2)(6) with ¦E in the range of [0.404, 0.443] eV should be SCO complexes with thermal hysteresis ¦T SCO in the range from 0 to 70 K. Our results clearly demonstrate that ¦E and ¦U of Fe II (LX 2 ) molecules can be tailored by variation in the axial ligand X, and the pK a constant of X is a key parameter for determining ¦E and ¦U, and thus ¦T SCO of Fe II (LX 2 ) complexes.…”

Section: Resultsmentioning

confidence: 99%

“…8,9) Our previous study demonstrated that ¦T SCO increased with the spin-state electrostaticenergy difference (¦U ) of Fe II SCO complexes. 10) In this paper, (6), and Him (7), in which molecules (1) and (7) have been synthesized. 1113) Their geometric structure, electronic structure, and magnetic properties have been examined in order to determine the role of ligands in tailoring SCO behavior of Fe II complexes.…”

Section: Introductionmentioning

confidence: 99%

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Ligand-Driven Spin-Crossover Behavior of Fe<sup>II</sup> Molecules

et al. 2016

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In order to explore a way to tailor thermal hysteresis behavior of spin-crossover (SCO) complexes, a series of seven Fe II (LX 2 ) complexes with different ligand configurations has been designed or reconstructed. These Fe II (LX 2 ) complexes differ in axial ligands X = Py, CNPY, NC 5 H 4 CH 3 , NC 5 H 4 OCH 3 , NC 5 H 4 Cl, X = NC 5 H 4 Br, and Him. Geometric structure, electronic structure, and magnetic properties of Fe II (LX 2 ) complexes have been investigated using density-functional theory with full geometry optimization. Our calculated results show that the spinstate electrostatic-energy difference (¦U ) of these Fe II SCO complexes can be tailored by adjusting the pK a constant of axial ligands X. The increase of ¦U of these Fe II SCO complexes from ¹12.18 eV to 6.64 eV results from the increase of pK a constant of axial ligands X from 1.10 to 7.00. The role of axial ligands X in determining SCO behavior of Fe II SCO complexes has been revealed. In addition, our previous study (N. A. Tuan: J. Appl. Phys. 111 (2012) 07D101) demonstrated that thermal hysteresis of spin-crossover increased with the ¦U of Fe II SCO complexes. These results would give some hints into how thermal hysteresis can be tailored in Fe II SCO complexes.

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Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Ligand-Driven Spin-Crossover Behavior of Fe<sup>II</sup> Molecules

et al. 2016

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“…The change in spin state is associated with a change in magnetization, unit-cell volume and color; this is why materials undergoing a spin crossover transition have attracted wide interest for many potential applications, e.g. information storage, optical devices and displays (Le ´tard et al, 2003;Ksenofontov et al, 2004;Tuan, 2012;Brooker, 2015;Kahn et al, 1992;Kahn & Martinez, 1998). Recently, spin-crossover materials have been discussed as solid-state materials for caloric applications (Vallone et al, 2019;Sandeman, 2016;Romanini et al, 2021;von Ranke, 2017;Reis, 2020), as the spin crossover transition is susceptible to pressure (P).…”

Section: Introductionmentioning

confidence: 99%

Structural insight into the cooperativity of spin crossover compounds

Shahed

Sharma

Angst

et al. 2023

Acta Crystallogr Sect B

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Spin-crossover (SCO) compounds are promising materials for a wide variety of industrial applications. However, the fundamental understanding of their nature of transition and its effect on the physical properties are still being fervently explored; the microscopic knowledge of their transition is essential for tailoring their properties. Here an attempt is made to correlate the changes in macroscopic physical properties with microscopic structural changes in the orthorhombic and monoclinic polymorphs of the SCO compound Fe(PM-Bia)2(NCS)2 (PM = N-2′-pyridylmethylene and Bia = 4-aminobiphenyl) by employing single-crystal X-ray diffraction, magnetization and DSC measurements. The dependence of macroscopic properties on cooperativity, highlighting the role of hydrogen bonding, π–π and van der Waals interactions is discussed. Values of entropy, enthalpy and cooperativity are calculated numerically based on the Slichter–Drickamer model. The particle size dependence of the magnetic properties is probed along with the thermal exchange and the kinetic behavior of the two polymorphs based on the dependence of magnetization on temperature scan rate and a theoretical model is proposed for the calculation of the non-equilibrium spin-phase fraction. Also a scan-rate-dependent two-step behavior observed for the orthorhombic polymorph, which is absent for the monoclinic polymorph, is reported. Moreover, it is found that the radiation dose from synchrotron radiation affects the spin-crossover process and shifts the transition region to lower temperatures, implying that the spin crossover can be tuned with radiation damage.

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Mechanochemical Synthesis of 3d Transition‐Metal–1,2,4‐Triazole Complexes as Precursors for Microwave‐Assisted and Thermal Conversion to Coordination Polymers with a High Influence on the Dielectric Properties

Brede

Heine

Sextl

et al. 2016

Chemistry A European J

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The complexes [MCl2 (TzH)4] (M=Mn (1), Fe (2); TzH=1,2,4-1H-triazole) and [ZnCl2 (TzH)2] (3) have been obtained by mechanochemical reactions of the corresponding divalent metal chloride and 1,2,4-1H-triazole. They were successfully used as precursors for the formation of coordination polymers either by a microwave-assisted reaction or by thermal conversion. For manganese, the conversion directly yielded 1∞ [MnCl2 TzH] (4), whereas for the iron-containing precursor, 1∞ [FeCl2 TzH] (6), was formed via the intermediate coordination polymer 1∞ [FeCl(TzH)2]Cl (5). For cobalt, the isotypic polymer 1∞ [CoCl(TzH)2]Cl (7) was obtained, but exclusively by a microwave-induced reaction directly from CoCl2 . The crystal structures were resolved from single crystals and powders. The dielectric properties were determined and revealed large differences in permittivity between the precursor complexes and the rigid chain-like coordination polymers. Whereas the monomeric complexes exhibit very different dielectric behaviour, depending on the transition metal, from "low-k" to "high-k" with the permittivity ranging from 4.3 to >100 for frequencies of up to 1000 Hz, the coordination polymers and complexes with strong intermolecular interactions are all close to "low-k" materials with very low dielectric constants up to 50 °C. Therefore, the conversion procedures can be used to deliberately influence the dielectric properties from complex to polymer and for different 3d transition-metal ions.

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Geometric structure, electronic structure, and spin transition of several FeII spin-crossover molecules

Abstract: Articles you may be interested inHysteresis and change of transition temperature in thin films of Fe{[Me2Pyrz]3BH}2, a new sublimable spincrossover molecule Assessment of density functional theory for iron(II) molecules across the spin-crossover transition

Cited by 4 publications

References 16 publications

Ligand-Driven Spin-Crossover Behavior of Fe<sup>II</sup> Molecules

Ligand-Driven Spin-Crossover Behavior of Fe<sup>II</sup> Molecules

Structural insight into the cooperativity of spin crossover compounds

Mechanochemical Synthesis of 3d Transition‐Metal–1,2,4‐Triazole Complexes as Precursors for Microwave‐Assisted and Thermal Conversion to Coordination Polymers with a High Influence on the Dielectric Properties

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