2 research outputs found

    Scan Rate Dependent Spin Crossover Iron(II) Complex with Two Different Relaxations and Thermal Hysteresis <i>fac</i>-[Fe<sup>II</sup>(HL<sup><i>n</i>‑Pr</sup>)<sub>3</sub>]Cl·PF<sub>6</sub> (HL<sup><i>n</i>‑Pr</sup> = 2‑Methylimidazol-4-yl-methylideneamino‑<i>n</i>‑propyl)

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    Solvent-free spin crossover Fe<sup>II</sup> complex <i>fac</i>-[Fe<sup>II</sup>(HL<sup><i>n</i>‑Pr</sup>)<sub>3</sub>]­Cl·PF<sub>6</sub> was prepared, where HL<sup><i>n</i>‑Pr</sup> denotes 2-methylimidazol-4-yl-methylideneamino-<i>n</i>-propyl. The magnetic susceptibility measurements at scan rate of 0.5 K min<sup>–1</sup> showed two successive spin transition processes consisting of the first spin transition <i>T</i><sub>1</sub> centered at 122 K (<i>T</i><sub>1↑</sub> = 127.1 K, <i>T</i><sub>1↓</sub> = 115.8 K) and the second spin transition <i>T</i><sub>2</sub> centered at ca. 105 K (<i>T</i><sub>2↑</sub> = 115.8 K, <i>T</i><sub>2↓</sub> = 97.2 K). The magnetic susceptibility measurements at the scan rate of 2.0, 1.0, 0.5, 0.25, and 0.1 K min<sup>–1</sup> showed two scan speed dependent spin transitions, while the Mössbauer spectra detected only the first spin transition <i>T</i><sub>1</sub>. The crystal structures were determined at 160, 143, 120, 110, 95 K in the cooling mode, and 110, 120, and 130 K in the warming mode so as to follow the spin transition process of high-spin HS → HS­(<i>T</i><sub>1</sub>) → HS­(<i>T</i><sub>2</sub>) → low-spin LS → LS­(<i>T</i><sub>2</sub>) → LS­(<i>T</i><sub>1</sub>) → HS. The crystal structures at all temperatures have a triclinic space group <i>P</i>1̅ with <i>Z</i> = 2. The complex-cation has an octahedral N<sub>6</sub> coordination geometry with three bidentate ligands and assume a <i>facial</i>-isomer with Δ- and Λ-enantimorphs. Three imidazole groups of <i>fac</i>-[Fe<sup>II</sup>(HL<sup><i>n</i>‑Pr</sup>)<sub>3</sub>]<sup>2+</sup> are hydrogen-bonded to three Cl<sup>–</sup> ions. The 3:3 NH­(imidazole)···Cl<sup>–</sup> hydrogen-bonds form a stepwise ladder assembly structure, which is maintained during the spin transition process. The spin transition process is related to the structural changes of the FeN<sub>6</sub> coordination environment, the order–disorder of PF<sub>6</sub><sup>–</sup> anion, and the conformation change of <i>n</i>-propyl groups. The Fe–N bond distance in the HS state is longer by 0.2 Å than that in the LS state. Disorder of PF<sub>6</sub><sup>–</sup> anion is not observed in the LS state but in the HS state. The conformational changes of <i>n</i>-propyl groups are found in the spin transition processes except for HS → HS­(<i>T</i><sub>1</sub>) → HS­(<i>T</i><sub>2</sub>)

    Scan Rate Dependent Spin Crossover Iron(II) Complex with Two Different Relaxations and Thermal Hysteresis <i>fac</i>-[Fe<sup>II</sup>(HL<sup><i>n</i>‑Pr</sup>)<sub>3</sub>]Cl·PF<sub>6</sub> (HL<sup><i>n</i>‑Pr</sup> = 2‑Methylimidazol-4-yl-methylideneamino‑<i>n</i>‑propyl)

    No full text
    Solvent-free spin crossover Fe<sup>II</sup> complex <i>fac</i>-[Fe<sup>II</sup>(HL<sup><i>n</i>‑Pr</sup>)<sub>3</sub>]­Cl·PF<sub>6</sub> was prepared, where HL<sup><i>n</i>‑Pr</sup> denotes 2-methylimidazol-4-yl-methylideneamino-<i>n</i>-propyl. The magnetic susceptibility measurements at scan rate of 0.5 K min<sup>–1</sup> showed two successive spin transition processes consisting of the first spin transition <i>T</i><sub>1</sub> centered at 122 K (<i>T</i><sub>1↑</sub> = 127.1 K, <i>T</i><sub>1↓</sub> = 115.8 K) and the second spin transition <i>T</i><sub>2</sub> centered at ca. 105 K (<i>T</i><sub>2↑</sub> = 115.8 K, <i>T</i><sub>2↓</sub> = 97.2 K). The magnetic susceptibility measurements at the scan rate of 2.0, 1.0, 0.5, 0.25, and 0.1 K min<sup>–1</sup> showed two scan speed dependent spin transitions, while the Mössbauer spectra detected only the first spin transition <i>T</i><sub>1</sub>. The crystal structures were determined at 160, 143, 120, 110, 95 K in the cooling mode, and 110, 120, and 130 K in the warming mode so as to follow the spin transition process of high-spin HS → HS­(<i>T</i><sub>1</sub>) → HS­(<i>T</i><sub>2</sub>) → low-spin LS → LS­(<i>T</i><sub>2</sub>) → LS­(<i>T</i><sub>1</sub>) → HS. The crystal structures at all temperatures have a triclinic space group <i>P</i>1̅ with <i>Z</i> = 2. The complex-cation has an octahedral N<sub>6</sub> coordination geometry with three bidentate ligands and assume a <i>facial</i>-isomer with Δ- and Λ-enantimorphs. Three imidazole groups of <i>fac</i>-[Fe<sup>II</sup>(HL<sup><i>n</i>‑Pr</sup>)<sub>3</sub>]<sup>2+</sup> are hydrogen-bonded to three Cl<sup>–</sup> ions. The 3:3 NH­(imidazole)···Cl<sup>–</sup> hydrogen-bonds form a stepwise ladder assembly structure, which is maintained during the spin transition process. The spin transition process is related to the structural changes of the FeN<sub>6</sub> coordination environment, the order–disorder of PF<sub>6</sub><sup>–</sup> anion, and the conformation change of <i>n</i>-propyl groups. The Fe–N bond distance in the HS state is longer by 0.2 Å than that in the LS state. Disorder of PF<sub>6</sub><sup>–</sup> anion is not observed in the LS state but in the HS state. The conformational changes of <i>n</i>-propyl groups are found in the spin transition processes except for HS → HS­(<i>T</i><sub>1</sub>) → HS­(<i>T</i><sub>2</sub>)
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