Structures and spin states of bist (tridentate)-type mononuclear and triple helicate dinuclear Iron(II) complexes of Lmidazole-4-carbaldehyde azine

Yukinari Sunatsuki, Ryohei Kawamoto, Kunihiro Fujita, Hisashi Maruyama, Takayoshi Suzuki, Hiroyuki Ishida, Masaaki Kojima, Seiichiro Iijima, Naohide Matsumoto

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Abstract

Mononuclear [Fe(H2LR)2]2+ and dinuclear [Fe2(H2LR)3]4+ (R = H, 2-Me, 5-Me) complexes containing the new imidazole-4-carbaldehyde azine ligand (H2LH) and its derivatives (H2L 2-Me and H2L5-Me) prepared from the condensation reaction of 4-formylimidazole or 2-methyl- or 5-methyl-4- formylimidazole with hydrazine (2:1) were prepared, and their magnetostructural relationships were studied. In the mononuclear complexes, H2L R acts as an unsymmetrical tridentate ligand with two imidazole nitrogen atoms and one azine nitrogen atom, while in the dinuclear complexes, H2LR acts as a dinucleating ligand employing four nitrogen atoms to form a triple helicate. At room temperature, [Fe2(H 2LH)3](CIO4)4 and [Fe2(H2L2-Me)3](ClO 4)4 were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L with electron-donating methyl groups being stronger than H 2LH, with the order of the ligand field strengths being H2L2-Me > H2LH. However, in the mononuclear [Fe(H2LH)2](ClO4) 2 and [Fe(H2L2-Me)2](ClO 4)2 complexes, a different order of ligand field strengths, H 2LH > H2L2-Me, was observed because [Fe(H2LH)2](ClO4) 2 was in the LS state while [Fe(H2L2-M) 2](ClO4)2 was in the HS state at room temperature. X-ray structural studies revealed that the interligand steric repulsion between a methyl group of an H2L2-Me ligand and the other ligand in [Fe(H2L2-Me)2](ClO 4)2 is responsible for the observed change in the spin state. Two kinds of crystals, needles and blocks, were isolated for [Fe 2(H2LH)3](BF4) 4, and both exhibited a sharp spin transition, [LS-HS] [HS-HS]. The spin transition of the block crystals is more abrupt with a hysteresis, T c↑ = 190 K and Tc↓ = 183 K withΔT= 7 K.

Original languageEnglish
Pages (from-to)8784-8795
Number of pages12
JournalInorganic Chemistry
Volume48
Issue number18
DOIs
Publication statusPublished - Sep 21 2009

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Iron
Ligands
iron
ligands
Nitrogen
hydrazine
nitrogen atoms
Atoms
field strength
imidazoles
Crystals
Condensation reactions
Needles
Hysteresis
hydrazines
room temperature
needles
Derivatives
crystals

ASJC Scopus subject areas

  • Inorganic Chemistry
  • Physical and Theoretical Chemistry

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Structures and spin states of bist (tridentate)-type mononuclear and triple helicate dinuclear Iron(II) complexes of Lmidazole-4-carbaldehyde azine. / Sunatsuki, Yukinari; Kawamoto, Ryohei; Fujita, Kunihiro; Maruyama, Hisashi; Suzuki, Takayoshi; Ishida, Hiroyuki; Kojima, Masaaki; Iijima, Seiichiro; Matsumoto, Naohide.

In: Inorganic Chemistry, Vol. 48, No. 18, 21.09.2009, p. 8784-8795.

Research output: Contribution to journalArticle

Sunatsuki, Yukinari ; Kawamoto, Ryohei ; Fujita, Kunihiro ; Maruyama, Hisashi ; Suzuki, Takayoshi ; Ishida, Hiroyuki ; Kojima, Masaaki ; Iijima, Seiichiro ; Matsumoto, Naohide. / Structures and spin states of bist (tridentate)-type mononuclear and triple helicate dinuclear Iron(II) complexes of Lmidazole-4-carbaldehyde azine. In: Inorganic Chemistry. 2009 ; Vol. 48, No. 18. pp. 8784-8795.
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title = "Structures and spin states of bist (tridentate)-type mononuclear and triple helicate dinuclear Iron(II) complexes of Lmidazole-4-carbaldehyde azine",
abstract = "Mononuclear [Fe(H2LR)2]2+ and dinuclear [Fe2(H2LR)3]4+ (R = H, 2-Me, 5-Me) complexes containing the new imidazole-4-carbaldehyde azine ligand (H2LH) and its derivatives (H2L 2-Me and H2L5-Me) prepared from the condensation reaction of 4-formylimidazole or 2-methyl- or 5-methyl-4- formylimidazole with hydrazine (2:1) were prepared, and their magnetostructural relationships were studied. In the mononuclear complexes, H2L R acts as an unsymmetrical tridentate ligand with two imidazole nitrogen atoms and one azine nitrogen atom, while in the dinuclear complexes, H2LR acts as a dinucleating ligand employing four nitrogen atoms to form a triple helicate. At room temperature, [Fe2(H 2LH)3](CIO4)4 and [Fe2(H2L2-Me)3](ClO 4)4 were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L with electron-donating methyl groups being stronger than H 2LH, with the order of the ligand field strengths being H2L2-Me > H2LH. However, in the mononuclear [Fe(H2LH)2](ClO4) 2 and [Fe(H2L2-Me)2](ClO 4)2 complexes, a different order of ligand field strengths, H 2LH > H2L2-Me, was observed because [Fe(H2LH)2](ClO4) 2 was in the LS state while [Fe(H2L2-M) 2](ClO4)2 was in the HS state at room temperature. X-ray structural studies revealed that the interligand steric repulsion between a methyl group of an H2L2-Me ligand and the other ligand in [Fe(H2L2-Me)2](ClO 4)2 is responsible for the observed change in the spin state. Two kinds of crystals, needles and blocks, were isolated for [Fe 2(H2LH)3](BF4) 4, and both exhibited a sharp spin transition, [LS-HS] [HS-HS]. The spin transition of the block crystals is more abrupt with a hysteresis, T c↑ = 190 K and Tc↓ = 183 K withΔT= 7 K.",
author = "Yukinari Sunatsuki and Ryohei Kawamoto and Kunihiro Fujita and Hisashi Maruyama and Takayoshi Suzuki and Hiroyuki Ishida and Masaaki Kojima and Seiichiro Iijima and Naohide Matsumoto",
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T1 - Structures and spin states of bist (tridentate)-type mononuclear and triple helicate dinuclear Iron(II) complexes of Lmidazole-4-carbaldehyde azine

AU - Sunatsuki, Yukinari

AU - Kawamoto, Ryohei

AU - Fujita, Kunihiro

AU - Maruyama, Hisashi

AU - Suzuki, Takayoshi

AU - Ishida, Hiroyuki

AU - Kojima, Masaaki

AU - Iijima, Seiichiro

AU - Matsumoto, Naohide

PY - 2009/9/21

Y1 - 2009/9/21

N2 - Mononuclear [Fe(H2LR)2]2+ and dinuclear [Fe2(H2LR)3]4+ (R = H, 2-Me, 5-Me) complexes containing the new imidazole-4-carbaldehyde azine ligand (H2LH) and its derivatives (H2L 2-Me and H2L5-Me) prepared from the condensation reaction of 4-formylimidazole or 2-methyl- or 5-methyl-4- formylimidazole with hydrazine (2:1) were prepared, and their magnetostructural relationships were studied. In the mononuclear complexes, H2L R acts as an unsymmetrical tridentate ligand with two imidazole nitrogen atoms and one azine nitrogen atom, while in the dinuclear complexes, H2LR acts as a dinucleating ligand employing four nitrogen atoms to form a triple helicate. At room temperature, [Fe2(H 2LH)3](CIO4)4 and [Fe2(H2L2-Me)3](ClO 4)4 were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L with electron-donating methyl groups being stronger than H 2LH, with the order of the ligand field strengths being H2L2-Me > H2LH. However, in the mononuclear [Fe(H2LH)2](ClO4) 2 and [Fe(H2L2-Me)2](ClO 4)2 complexes, a different order of ligand field strengths, H 2LH > H2L2-Me, was observed because [Fe(H2LH)2](ClO4) 2 was in the LS state while [Fe(H2L2-M) 2](ClO4)2 was in the HS state at room temperature. X-ray structural studies revealed that the interligand steric repulsion between a methyl group of an H2L2-Me ligand and the other ligand in [Fe(H2L2-Me)2](ClO 4)2 is responsible for the observed change in the spin state. Two kinds of crystals, needles and blocks, were isolated for [Fe 2(H2LH)3](BF4) 4, and both exhibited a sharp spin transition, [LS-HS] [HS-HS]. The spin transition of the block crystals is more abrupt with a hysteresis, T c↑ = 190 K and Tc↓ = 183 K withΔT= 7 K.

AB - Mononuclear [Fe(H2LR)2]2+ and dinuclear [Fe2(H2LR)3]4+ (R = H, 2-Me, 5-Me) complexes containing the new imidazole-4-carbaldehyde azine ligand (H2LH) and its derivatives (H2L 2-Me and H2L5-Me) prepared from the condensation reaction of 4-formylimidazole or 2-methyl- or 5-methyl-4- formylimidazole with hydrazine (2:1) were prepared, and their magnetostructural relationships were studied. In the mononuclear complexes, H2L R acts as an unsymmetrical tridentate ligand with two imidazole nitrogen atoms and one azine nitrogen atom, while in the dinuclear complexes, H2LR acts as a dinucleating ligand employing four nitrogen atoms to form a triple helicate. At room temperature, [Fe2(H 2LH)3](CIO4)4 and [Fe2(H2L2-Me)3](ClO 4)4 were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L with electron-donating methyl groups being stronger than H 2LH, with the order of the ligand field strengths being H2L2-Me > H2LH. However, in the mononuclear [Fe(H2LH)2](ClO4) 2 and [Fe(H2L2-Me)2](ClO 4)2 complexes, a different order of ligand field strengths, H 2LH > H2L2-Me, was observed because [Fe(H2LH)2](ClO4) 2 was in the LS state while [Fe(H2L2-M) 2](ClO4)2 was in the HS state at room temperature. X-ray structural studies revealed that the interligand steric repulsion between a methyl group of an H2L2-Me ligand and the other ligand in [Fe(H2L2-Me)2](ClO 4)2 is responsible for the observed change in the spin state. Two kinds of crystals, needles and blocks, were isolated for [Fe 2(H2LH)3](BF4) 4, and both exhibited a sharp spin transition, [LS-HS] [HS-HS]. The spin transition of the block crystals is more abrupt with a hysteresis, T c↑ = 190 K and Tc↓ = 183 K withΔT= 7 K.

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