Synthesis, magnetic properties, and electronic spectra of mixed ligand bis(β-diketonato)chromium(III) complexes with a chelated nitronyl nitroxide radical: X-ray structure of [Cr(dpm)2(NIT2py)]PF6

Yasunori Tsukahara, Atsushi Iino, Takafumi Yoshida, Takayoshi Suzuki, Sumio Kaizaki

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Abstract

A new series of nine nitronyl nitroxide Cr(III) complexes with various β-diketonates, [Cr(β-diketonato)2(NIT2py)]PF6, have been synthesized where NIT2py is 2-(2′-(pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide- 1-oxyl, and their structures, magnetic and optical properties have been examined. X-Ray analysis of [Cr(dpm)2(NIT2py)]PF6 (monoclinic, space group P21/a, a = 13.960(4), b = 31.19(1), c = 13.940(4), Z = 4) demonstrated that NIT2py coordinated to Cr(III) as a bidentate six-membered chelate. Variable-temperature magnetic susceptibility measurements indicated the antiferromagnetic interaction between Cr(III) and NIT2py with a variety of the magnetic coupling constant J values for these complexes. From the variable temperature or solvent dependent UV-vis spectra and MCD, and/or the resonance Raman spectra of the bis(β-diketonato)(NIT2py) Cr(III) complexes, the absorption components centered around 13.3 × 103 cm-1 were assigned to the formally spin-forbidden d-d transition within the t2g subshell associated with the intensity enhancement and the newly appeared vibronic bands around (16.0-18.0) × 103 cm-1 were due to the metal-ligand charge transfer [t2g-SOMO(φ*) MLCT] transitions. The change of their spectroscopic characteristics with varying the β-diketonato ligands is discussed in connection with the antiferromagnetic coupling constant J values on the basis of the exchange mechanism along with the coligand effect. The luminescence spectra which show a large Stokes shift suggest the antiferromagnetic interaction in the lowest excited states originates from the 2E or 2T1 level of the Cr(III) moiety.

Original languageEnglish
Pages (from-to)181-187
Number of pages7
JournalJournal of the Chemical Society, Dalton Transactions
Issue number2
Publication statusPublished - 2002
Externally publishedYes

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Chromium
Magnetic properties
Ligands
X rays
Magnetic couplings
X ray analysis
Magnetic susceptibility
Excited states
Oxides
Charge transfer
Raman scattering
Luminescence
Optical properties
Metals
Temperature
nitroxyl

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{e4493b7614ef4f4cb614cc81cbc5e13a,
title = "Synthesis, magnetic properties, and electronic spectra of mixed ligand bis(β-diketonato)chromium(III) complexes with a chelated nitronyl nitroxide radical: X-ray structure of [Cr(dpm)2(NIT2py)]PF6",
abstract = "A new series of nine nitronyl nitroxide Cr(III) complexes with various β-diketonates, [Cr(β-diketonato)2(NIT2py)]PF6, have been synthesized where NIT2py is 2-(2′-(pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide- 1-oxyl, and their structures, magnetic and optical properties have been examined. X-Ray analysis of [Cr(dpm)2(NIT2py)]PF6 (monoclinic, space group P21/a, a = 13.960(4), b = 31.19(1), c = 13.940(4), Z = 4) demonstrated that NIT2py coordinated to Cr(III) as a bidentate six-membered chelate. Variable-temperature magnetic susceptibility measurements indicated the antiferromagnetic interaction between Cr(III) and NIT2py with a variety of the magnetic coupling constant J values for these complexes. From the variable temperature or solvent dependent UV-vis spectra and MCD, and/or the resonance Raman spectra of the bis(β-diketonato)(NIT2py) Cr(III) complexes, the absorption components centered around 13.3 × 103 cm-1 were assigned to the formally spin-forbidden d-d transition within the t2g subshell associated with the intensity enhancement and the newly appeared vibronic bands around (16.0-18.0) × 103 cm-1 were due to the metal-ligand charge transfer [t2g-SOMO(φ*) MLCT] transitions. The change of their spectroscopic characteristics with varying the β-diketonato ligands is discussed in connection with the antiferromagnetic coupling constant J values on the basis of the exchange mechanism along with the coligand effect. The luminescence spectra which show a large Stokes shift suggest the antiferromagnetic interaction in the lowest excited states originates from the 2E or 2T1 level of the Cr(III) moiety.",
author = "Yasunori Tsukahara and Atsushi Iino and Takafumi Yoshida and Takayoshi Suzuki and Sumio Kaizaki",
year = "2002",
language = "English",
pages = "181--187",
journal = "Dalton Transactions",
issn = "1477-9226",
publisher = "Royal Society of Chemistry",
number = "2",

}

TY - JOUR

T1 - Synthesis, magnetic properties, and electronic spectra of mixed ligand bis(β-diketonato)chromium(III) complexes with a chelated nitronyl nitroxide radical

T2 - X-ray structure of [Cr(dpm)2(NIT2py)]PF6

AU - Tsukahara, Yasunori

AU - Iino, Atsushi

AU - Yoshida, Takafumi

AU - Suzuki, Takayoshi

AU - Kaizaki, Sumio

PY - 2002

Y1 - 2002

N2 - A new series of nine nitronyl nitroxide Cr(III) complexes with various β-diketonates, [Cr(β-diketonato)2(NIT2py)]PF6, have been synthesized where NIT2py is 2-(2′-(pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide- 1-oxyl, and their structures, magnetic and optical properties have been examined. X-Ray analysis of [Cr(dpm)2(NIT2py)]PF6 (monoclinic, space group P21/a, a = 13.960(4), b = 31.19(1), c = 13.940(4), Z = 4) demonstrated that NIT2py coordinated to Cr(III) as a bidentate six-membered chelate. Variable-temperature magnetic susceptibility measurements indicated the antiferromagnetic interaction between Cr(III) and NIT2py with a variety of the magnetic coupling constant J values for these complexes. From the variable temperature or solvent dependent UV-vis spectra and MCD, and/or the resonance Raman spectra of the bis(β-diketonato)(NIT2py) Cr(III) complexes, the absorption components centered around 13.3 × 103 cm-1 were assigned to the formally spin-forbidden d-d transition within the t2g subshell associated with the intensity enhancement and the newly appeared vibronic bands around (16.0-18.0) × 103 cm-1 were due to the metal-ligand charge transfer [t2g-SOMO(φ*) MLCT] transitions. The change of their spectroscopic characteristics with varying the β-diketonato ligands is discussed in connection with the antiferromagnetic coupling constant J values on the basis of the exchange mechanism along with the coligand effect. The luminescence spectra which show a large Stokes shift suggest the antiferromagnetic interaction in the lowest excited states originates from the 2E or 2T1 level of the Cr(III) moiety.

AB - A new series of nine nitronyl nitroxide Cr(III) complexes with various β-diketonates, [Cr(β-diketonato)2(NIT2py)]PF6, have been synthesized where NIT2py is 2-(2′-(pyridyl)-4,4,5,5-tetramethyl-4,5-dihydro-1H-imidazolyl-3-oxide- 1-oxyl, and their structures, magnetic and optical properties have been examined. X-Ray analysis of [Cr(dpm)2(NIT2py)]PF6 (monoclinic, space group P21/a, a = 13.960(4), b = 31.19(1), c = 13.940(4), Z = 4) demonstrated that NIT2py coordinated to Cr(III) as a bidentate six-membered chelate. Variable-temperature magnetic susceptibility measurements indicated the antiferromagnetic interaction between Cr(III) and NIT2py with a variety of the magnetic coupling constant J values for these complexes. From the variable temperature or solvent dependent UV-vis spectra and MCD, and/or the resonance Raman spectra of the bis(β-diketonato)(NIT2py) Cr(III) complexes, the absorption components centered around 13.3 × 103 cm-1 were assigned to the formally spin-forbidden d-d transition within the t2g subshell associated with the intensity enhancement and the newly appeared vibronic bands around (16.0-18.0) × 103 cm-1 were due to the metal-ligand charge transfer [t2g-SOMO(φ*) MLCT] transitions. The change of their spectroscopic characteristics with varying the β-diketonato ligands is discussed in connection with the antiferromagnetic coupling constant J values on the basis of the exchange mechanism along with the coligand effect. The luminescence spectra which show a large Stokes shift suggest the antiferromagnetic interaction in the lowest excited states originates from the 2E or 2T1 level of the Cr(III) moiety.

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