Structures and spin states of mono- and dinuclear iron(II) complexes of imidazole-4-carbaldehyde azine and its derivatives

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

Research output: Contribution to journalArticle

40 Citations (Scopus)

Abstract

Mononuclear [Fe(H2LR)2]X2 (R = H, 2-Me, 5-Me, 2-Et-5-Me; X = ClO4, BF4) and dinuclear [Fe2(H2LR)3]X4 complexes containing imidazole-4-carbaldehyde azine (H2LH) and its derivatives prepared by condensation of 4-formylimidazole, 2-methyl- or 5-methyl-4-formylimidazole, or 2-ethyl-4-methyl-5-formylimidazole, with hydrazine in a 2:1 mole ratio in methanol, were prepared and their magnetostructural relationships were studied. In the mononuclear complexes, H2LR 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 structure. At room temperature, [Fe2(H2LH)3](ClO4)4 and [Fe2(H2L2-Me)3](ClO4)4 were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L2-Me with electron-donating methyl groups being stronger than H2LH, 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](ClO4)2 complexes, a different order of ligand field strengths, H2LH > H2L2-Me, was observed because [Fe(H2LH)2](ClO4)2 was in the LS state while [Fe(H2L2-Me)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](ClO4)2 is responsible for the observed change in the spin state. The same is true for [Fe(H2L2-Et-5-Me)2](ClO4)2, while [Fe(H2L5-Me)2](ClO4)2 does not involve such a steric congestion and stays in the LS state over the temperature range 5-300 K. Two kinds of crystals (polymorphs) were isolated for [Fe2(H2LH)3](BF4)4 and [Fe2(H2L2-Et-5-Me)3](ClO4)4, and they exhibited different magnetic behaviors.

Original languageEnglish
Pages (from-to)1871-1881
Number of pages11
JournalCoordination Chemistry Reviews
Volume254
Issue number15-16
DOIs
Publication statusPublished - Aug 2010

Fingerprint

azines
imidazoles
Iron
Ligands
Derivatives
iron
ligands
nitrogen atoms
field strength
Nitrogen
Atoms
hydrazine
congestion
Hydrazine
hydrazines
room temperature
guy wires
imidazole
perchlorate
Polymorphism

Keywords

  • Dinuclear complexes
  • Helicates
  • Iron(II) complexes
  • Spin states
  • Spin-crossover

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

Structures and spin states of mono- and dinuclear iron(II) complexes of imidazole-4-carbaldehyde azine and its derivatives. / Sunatsuki, Yukinari; Kawamoto, Ryohei; Fujita, Kunihiro; Maruyama, Hisashi; Suzuki, Takayoshi; Ishida, Hiroyuki; Kojima, Masaaki; Iijima, Seiichiro; Matsumoto, Naohide.

In: Coordination Chemistry Reviews, Vol. 254, No. 15-16, 08.2010, p. 1871-1881.

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 mono- and dinuclear iron(II) complexes of imidazole-4-carbaldehyde azine and its derivatives. In: Coordination Chemistry Reviews. 2010 ; Vol. 254, No. 15-16. pp. 1871-1881.
@article{d89359cb6cfd4c95b7148be8dbad4a2f,
title = "Structures and spin states of mono- and dinuclear iron(II) complexes of imidazole-4-carbaldehyde azine and its derivatives",
abstract = "Mononuclear [Fe(H2LR)2]X2 (R = H, 2-Me, 5-Me, 2-Et-5-Me; X = ClO4, BF4) and dinuclear [Fe2(H2LR)3]X4 complexes containing imidazole-4-carbaldehyde azine (H2LH) and its derivatives prepared by condensation of 4-formylimidazole, 2-methyl- or 5-methyl-4-formylimidazole, or 2-ethyl-4-methyl-5-formylimidazole, with hydrazine in a 2:1 mole ratio in methanol, were prepared and their magnetostructural relationships were studied. In the mononuclear complexes, H2LR 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 structure. At room temperature, [Fe2(H2LH)3](ClO4)4 and [Fe2(H2L2-Me)3](ClO4)4 were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L2-Me with electron-donating methyl groups being stronger than H2LH, 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](ClO4)2 complexes, a different order of ligand field strengths, H2LH > H2L2-Me, was observed because [Fe(H2LH)2](ClO4)2 was in the LS state while [Fe(H2L2-Me)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](ClO4)2 is responsible for the observed change in the spin state. The same is true for [Fe(H2L2-Et-5-Me)2](ClO4)2, while [Fe(H2L5-Me)2](ClO4)2 does not involve such a steric congestion and stays in the LS state over the temperature range 5-300 K. Two kinds of crystals (polymorphs) were isolated for [Fe2(H2LH)3](BF4)4 and [Fe2(H2L2-Et-5-Me)3](ClO4)4, and they exhibited different magnetic behaviors.",
keywords = "Dinuclear complexes, Helicates, Iron(II) complexes, Spin states, Spin-crossover",
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",
year = "2010",
month = "8",
doi = "10.1016/j.ccr.2009.11.016",
language = "English",
volume = "254",
pages = "1871--1881",
journal = "Coordination Chemistry Reviews",
issn = "0010-8545",
publisher = "Elsevier",
number = "15-16",

}

TY - JOUR

T1 - Structures and spin states of mono- and dinuclear iron(II) complexes of imidazole-4-carbaldehyde azine and its derivatives

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 - 2010/8

Y1 - 2010/8

N2 - Mononuclear [Fe(H2LR)2]X2 (R = H, 2-Me, 5-Me, 2-Et-5-Me; X = ClO4, BF4) and dinuclear [Fe2(H2LR)3]X4 complexes containing imidazole-4-carbaldehyde azine (H2LH) and its derivatives prepared by condensation of 4-formylimidazole, 2-methyl- or 5-methyl-4-formylimidazole, or 2-ethyl-4-methyl-5-formylimidazole, with hydrazine in a 2:1 mole ratio in methanol, were prepared and their magnetostructural relationships were studied. In the mononuclear complexes, H2LR 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 structure. At room temperature, [Fe2(H2LH)3](ClO4)4 and [Fe2(H2L2-Me)3](ClO4)4 were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L2-Me with electron-donating methyl groups being stronger than H2LH, 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](ClO4)2 complexes, a different order of ligand field strengths, H2LH > H2L2-Me, was observed because [Fe(H2LH)2](ClO4)2 was in the LS state while [Fe(H2L2-Me)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](ClO4)2 is responsible for the observed change in the spin state. The same is true for [Fe(H2L2-Et-5-Me)2](ClO4)2, while [Fe(H2L5-Me)2](ClO4)2 does not involve such a steric congestion and stays in the LS state over the temperature range 5-300 K. Two kinds of crystals (polymorphs) were isolated for [Fe2(H2LH)3](BF4)4 and [Fe2(H2L2-Et-5-Me)3](ClO4)4, and they exhibited different magnetic behaviors.

AB - Mononuclear [Fe(H2LR)2]X2 (R = H, 2-Me, 5-Me, 2-Et-5-Me; X = ClO4, BF4) and dinuclear [Fe2(H2LR)3]X4 complexes containing imidazole-4-carbaldehyde azine (H2LH) and its derivatives prepared by condensation of 4-formylimidazole, 2-methyl- or 5-methyl-4-formylimidazole, or 2-ethyl-4-methyl-5-formylimidazole, with hydrazine in a 2:1 mole ratio in methanol, were prepared and their magnetostructural relationships were studied. In the mononuclear complexes, H2LR 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 structure. At room temperature, [Fe2(H2LH)3](ClO4)4 and [Fe2(H2L2-Me)3](ClO4)4 were in the high-spin (HS) and low-spin (LS) states, respectively. The results are in accordance with the ligand field strength of H2L2-Me with electron-donating methyl groups being stronger than H2LH, 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](ClO4)2 complexes, a different order of ligand field strengths, H2LH > H2L2-Me, was observed because [Fe(H2LH)2](ClO4)2 was in the LS state while [Fe(H2L2-Me)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](ClO4)2 is responsible for the observed change in the spin state. The same is true for [Fe(H2L2-Et-5-Me)2](ClO4)2, while [Fe(H2L5-Me)2](ClO4)2 does not involve such a steric congestion and stays in the LS state over the temperature range 5-300 K. Two kinds of crystals (polymorphs) were isolated for [Fe2(H2LH)3](BF4)4 and [Fe2(H2L2-Et-5-Me)3](ClO4)4, and they exhibited different magnetic behaviors.

KW - Dinuclear complexes

KW - Helicates

KW - Iron(II) complexes

KW - Spin states

KW - Spin-crossover

UR - http://www.scopus.com/inward/record.url?scp=77953127739&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=77953127739&partnerID=8YFLogxK

U2 - 10.1016/j.ccr.2009.11.016

DO - 10.1016/j.ccr.2009.11.016

M3 - Article

AN - SCOPUS:77953127739

VL - 254

SP - 1871

EP - 1881

JO - Coordination Chemistry Reviews

JF - Coordination Chemistry Reviews

SN - 0010-8545

IS - 15-16

ER -