Spin-Singlet Transition in the Magnetic Hybrid Compound from a Spin-Crossover Fe(III) Cation and π-Radical Anion

Takahashi, Kazuyuki; Sakurai, Takahiro; Zhang, Wei Min; Okubo, Susumu; Ohta, H.; Yamamoto, Takashi; Einaga, Yasuaki; Mori, H.

doi:10.3390/inorganics5030054

Cited by 7 publications

(6 citation statements)

References 53 publications

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“…The isomer shift of 3 is similar to those of the simulated HS spectra reported in the literature. Note that the quadrupole splitting of 3 is the largest among those of the HS spectra in the related compounds and corresponds to that of the [Ni(nmt) 2 ] compound having the significantly distorted coordination octahedron (mnt = maleonitriledithiolate) [33]. This suggests that the compound 3 might have a distorted coordination sphere due to some crystal packing effect.…”

Section: Mössbauer Spectroscopy For 1 Andmentioning

confidence: 96%

“…We focused on the [Fe(qsal) 2 ] compounds showing a cooperative SCO transition probably due to strong π-stacking interactions and developed SCO conductors and magnets by combining the [Fe(qsal) 2 ] cation with redox active functional anions [22,23]. A number of multifunctional materials from the [Fe(qsal) 2 ] cation have been reported to date [24][25][26][27][28][29][30][31][32][33]. Recently, heteroleptic Fe(III) compounds [34][35][36][37] as well as Fe(II) compounds [38][39][40][41][42][43][44] from the qsal and its derivatives, were also reported.…”

Section: Introductionmentioning

confidence: 99%

“…Therefore, non-solvate [Fe(qsal) 2 ] compounds seem to be favorable for the elucidation of the SCO mechanism. Meanwhile, structure-characterized non-solvate [Fe(qsal) 2 ] compounds were rare [11,13,15,24,33].…”

Section: Introductionmentioning

confidence: 99%

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High-Temperature Cooperative Spin Crossover Transitions and Single-Crystal Reflection Spectra of [FeIII(qsal)2](CH3OSO3) and Related Compounds

Takahashi

Yamamoto

et al. 2019

Crystals

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New Fe(III) compounds from qsal ligand, [Fe(qsal)2](CH3OSO3) (1) and [Fe(qsal)2](CH3SO3)·CH3OH (3), along with known compound, [Fe(qsal)2](CF3SO3) (2), were obtained as large well-shaped crystals (Hqsal = N-(8-quinolyl)salicylaldimine). The compounds 1 and 2 were in the low-spin (LS) state at 300 K and exhibited a cooperative spin crossover (SCO) transition with a thermal hysteresis loop at higher temperatures, whereas 3 was in the high-spin (HS) state below 300 K. The optical conductivity spectra for 1 and 3 were calculated from the single-crystal reflection spectra, which were, to the best of our knowledge, the first optical conductivity spectra of SCO compounds. The absorption bands for the LS and HS [Fe(qsal)2] cations were assigned by time-dependent density functional theory calculations. The crystal structures of 1 and 2 consisted of a common one-dimensional (1D) array of the [Fe(qsal)2] cation, whereas that of 3 had an unusual 1D arrangement by π-stacking interactions which has never been reported. The crystal structures in the high-temperature phases for 1 and 2 indicate that large structural changes were triggered by the motion of counter anions. The comparison of the crystal structures of the known [Fe(qsal)2] compounds suggests the significant role of a large non-spherical counter-anion or solvate molecule for the total lattice energy gain in the crystal of a charged complex.

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Section: Mössbauer Spectroscopy For 1 Andmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

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High-Temperature Cooperative Spin Crossover Transitions and Single-Crystal Reflection Spectra of [FeIII(qsal)2](CH3OSO3) and Related Compounds

Takahashi

Yamamoto

et al. 2019

Crystals

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“…They clarify the crystal structures and magnetic properties of the SCO-POM hybrids and find that the hydrogen bonding interactions between the Fe(II) cation and POM anion strongly influenced the spin state of the Fe(II) cation. Similarly, Takahashi and co-workers [21] report the crystal structures and physical properties of a new hybrid compound from a well-known Fe(III) SCO complex cation with a π-radical anion. They reveal that the coordination distortion induced by strong π-stacking interactions between an Fe(III) cation and a π-radical anion may suppress the occurrence of SCO.…”

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confidence: 94%

Spin-Crossover Complexes

Takahashi

2018

Inorganics

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Spin-crossover (SCO) is a spin-state switching phenomenon between a high-spin (HS) and low-spin (LS) electronic configurations in a transition metal center. The SCO phenomenon is widely recognized as an example of molecular bistability. The SCO compounds most widely studied are six-coordinate first-row transition metal complexes with d 4 -d 7 configurations. A relative small enthalpy variation between LS and HS states can be realized by coopetition between ligand field stabilization (LFS) and spin pairing energies, which is illustrated by the Tanabe-Sugano diagrams in common coordination chemistry textbooks. Since an entropy variation in spin multiplicity from LS to HS is always positive, an increase in temperature can induce the transformation in Gibbs free energy from a positive to a negative sign, at which point SCO conversion occurs from the LS to HS state.Cambi and co-workers' pioneering work on the anomalous magnetic behaviors of mononuclear Fe(III) dithiocarbamate complexes [1] was first recognized as SCO phenomena in the early 1930s. However, progress on SCO complexes awaited the dissemination of ligand field theory into coordination chemistry. The concept of controlling LFS energies by substitution with different field strength ligands resulted in the corroboration of SCO phenomena in some Co(II) and Fe(II) complexes in the early 1960s. Moreover, subsequent findings that pressure [2] and light [3] can induce an SCO phenomenon may attract attention to SCO complexes. In the 1990s the demonstration of device applications using the SCO complex [4] illuminated the potential of SCO complexes in future practical applications in memory, display, and sensing devices. Figure 1 shows the number of published articles per year whose titles or topics contain the words "spin-crossover," "spin equilibrium," or their derivatives. Studies concerning SCO complexes have apparently increased since the 1980s; moreover, the number has more rapidly developed after the 2000s. The fundamentals and applications of SCO complexes have attracted growing interest not only in inorganic coordination chemistry but also in a wide range of relevant research fields.

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“…While the distortion is most prevalent in [Fe(bpp) 2 ] 2+ chemistry, it also occurs in high-spin iron(II) complexes of other tris -heterocyclic ligands, − and in related complexes of high-spin iron(III), − manganese(II), − cobalt(II), − and zinc(II). − In high-spin iron(II) complexes, the distortion electronically resembles a Jahn–Teller distortion of a 5 E ground state (in D 2d symmetry), which is favored in complexes of tridentate ligands with a narrow bite angle. , However, distortion also occurs in complexes with an orbital singlet ground state. In that case, the absence of a ligand field stabilization energy makes their coordination geometry more susceptible to deformations induced by crystal packing.…”

Section: Introductionmentioning

confidence: 99%

A Survey of the Angular Distortion Landscape in the Coordination Geometries of High-Spin Iron(II) 2,6-Bis(pyrazolyl)pyridine Complexes

Capel Berdiell,

Michaels,

Munro

et al. 2024

Inorg. Chem.

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Reaction of 2,4,6-trifluoropyridine with sodium 3,4dimethoxybenzenethiolate and 2 equiv of sodium pyrazolate in tetrahydrofuran at room temperature affords 4-(3,4-dimethoxyphenylsulfanyl)-2,6-di(pyrazol-1-yl)pyridine (L), in 30% yield. The iron(II) complexes [FeL 2 ][BF 4 ] 2 (1a) and [FeL 2 ][ClO 4 ] 2 (1b) are high-spin with a highly distorted six-coordinate geometry. This structural deviation from ideal D 2d symmetry is common in highspin [Fe(bpp) 2 ] 2+ (bpp = di{pyrazol-1-yl}pyridine) derivatives, which are important in spin-crossover materials research. The magnitude of the distortion in 1a and 1b is the largest yet discovered for a mononuclear complex. Gas-phase DFT calculations at the ω-B97X-D/6-311G** level of theory identified four minimum or local minimum structural pathways across the distortion landscape, all of which are observed experimentally in different complexes. Small distortions from D 2d symmetry are energetically favorable in complexes with electron-donating ligand substituents, including sulfanyl groups, which also have smaller energy penalties associated with the lowest energy distortion pathway. Natural population analysis showed that these differences reflect greater changes to the Fe−N{pyridyl} σ-bonding as the distortion proceeds, in the presence of more electron-rich pyridyl donors. The results imply that [Fe(bpp) 2 ] 2+ derivatives with electron-donating pyridyl substituents are more likely to undergo cooperative spin transitions in the solid state. The high-spin salt [Fe(bpp) 2 ][CF 3 SO 3 ] 2 , which also has a strong angular distortion, is also briefly described and included in the analysis.

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Spin-Singlet Transition in the Magnetic Hybrid Compound from a Spin-Crossover Fe(III) Cation and π-Radical Anion

Cited by 7 publications

References 53 publications

High-Temperature Cooperative Spin Crossover Transitions and Single-Crystal Reflection Spectra of [FeIII(qsal)2](CH3OSO3) and Related Compounds

High-Temperature Cooperative Spin Crossover Transitions and Single-Crystal Reflection Spectra of [FeIII(qsal)2](CH3OSO3) and Related Compounds

Spin-Crossover Complexes

A Survey of the Angular Distortion Landscape in the Coordination Geometries of High-Spin Iron(II) 2,6-Bis(pyrazolyl)pyridine Complexes

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