Syntheses, structures, magnetic and spectroscopic properties of bis(pentane-2,4-dionato)chromium(iii) complexes incorporating 3- or 4-pyridyl-substituted nitronyl and imino nitroxides

Atsushi Iino, Takayoshi Suzuki, Sumio Kaizaki

Research output: Contribution to journalArticle

Abstract

Preparation and characterization by X-ray analysis and 2H NMR spectra have been described for twelve chromium(iii)–nitroxide complexes of cis-[Cr(acac)2Cl(L)] and cis- and trans-[Cr(acac)2(L)2]PF6 with monodentate coordination through the pyridyl-N atom in the nitroxides, where acac = pentane-2,4-dionate and L = 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl 3-oxide (NIT3py or NIT4py) and 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl (IM3py or IM4py). An intramolecular magnetic interaction between CrIII and the nitroxide was found to be weakly antiferrromagnetic and ferromagnetic, respectively, in the NIT3py or IM3py complexes and the NIT4py or IM4py complexes. The difference in sign of these magnetic interaction constants between the 3- and 4-pyridyl-substituted nitroxides can be interpreted by a spin polarization mechanism for the π-electron system including the nitroxide SOMO π* and CrIII dπ orbitals. The inherently weak magnetic interactions and absence of an intensity enhancement of the spin-forbidden d–d transition band in these nitroxides complexes are in contrast to our previous results for the chelated NIT2py [4,4,5,5-tetramethyl-2-(2-pyridyl)imidazolin-1-oxyl 3-oxide] and IM2py [4,4,5,5-tetramethyl-2-(2-pyridyl)imidazolin-1-oxyl] complexes. This may be accounted for by the difference in the mechanism of magnetic interactions; spin-polarization mechanism and exchange mechanism, respectively.

Original languageEnglish
Pages (from-to)4604-4611
Number of pages8
JournalJournal of the Chemical Society. Dalton Transactions
Volume3
Issue number24
DOIs
Publication statusPublished - Dec 2 2003
Externally publishedYes

Fingerprint

Spin polarization
Magnetic structure
Chromium
Oxides
X ray analysis
Nuclear magnetic resonance
Atoms
Electrons
pentane

Keywords

  • Chromium
  • Magnetic properties
  • Nmr spectroscopy
  • Radicals
  • X-ray diffraction
  • X-ray powder diffraction

ASJC Scopus subject areas

  • Chemistry(all)

Cite this

@article{4ee124424741417da1ab69f82d33e321,
title = "Syntheses, structures, magnetic and spectroscopic properties of bis(pentane-2,4-dionato)chromium(iii) complexes incorporating 3- or 4-pyridyl-substituted nitronyl and imino nitroxides",
abstract = "Preparation and characterization by X-ray analysis and 2H NMR spectra have been described for twelve chromium(iii)–nitroxide complexes of cis-[Cr(acac)2Cl(L)] and cis- and trans-[Cr(acac)2(L)2]PF6 with monodentate coordination through the pyridyl-N atom in the nitroxides, where acac = pentane-2,4-dionate and L = 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl 3-oxide (NIT3py or NIT4py) and 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl (IM3py or IM4py). An intramolecular magnetic interaction between CrIII and the nitroxide was found to be weakly antiferrromagnetic and ferromagnetic, respectively, in the NIT3py or IM3py complexes and the NIT4py or IM4py complexes. The difference in sign of these magnetic interaction constants between the 3- and 4-pyridyl-substituted nitroxides can be interpreted by a spin polarization mechanism for the π-electron system including the nitroxide SOMO π* and CrIII dπ orbitals. The inherently weak magnetic interactions and absence of an intensity enhancement of the spin-forbidden d–d transition band in these nitroxides complexes are in contrast to our previous results for the chelated NIT2py [4,4,5,5-tetramethyl-2-(2-pyridyl)imidazolin-1-oxyl 3-oxide] and IM2py [4,4,5,5-tetramethyl-2-(2-pyridyl)imidazolin-1-oxyl] complexes. This may be accounted for by the difference in the mechanism of magnetic interactions; spin-polarization mechanism and exchange mechanism, respectively.",
keywords = "Chromium, Magnetic properties, Nmr spectroscopy, Radicals, X-ray diffraction, X-ray powder diffraction",
author = "Atsushi Iino and Takayoshi Suzuki and Sumio Kaizaki",
year = "2003",
month = "12",
day = "2",
doi = "10.1039/b310571g",
language = "English",
volume = "3",
pages = "4604--4611",
journal = "Dalton Transactions",
issn = "1477-9226",
publisher = "Royal Society of Chemistry",
number = "24",

}

TY - JOUR

T1 - Syntheses, structures, magnetic and spectroscopic properties of bis(pentane-2,4-dionato)chromium(iii) complexes incorporating 3- or 4-pyridyl-substituted nitronyl and imino nitroxides

AU - Iino, Atsushi

AU - Suzuki, Takayoshi

AU - Kaizaki, Sumio

PY - 2003/12/2

Y1 - 2003/12/2

N2 - Preparation and characterization by X-ray analysis and 2H NMR spectra have been described for twelve chromium(iii)–nitroxide complexes of cis-[Cr(acac)2Cl(L)] and cis- and trans-[Cr(acac)2(L)2]PF6 with monodentate coordination through the pyridyl-N atom in the nitroxides, where acac = pentane-2,4-dionate and L = 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl 3-oxide (NIT3py or NIT4py) and 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl (IM3py or IM4py). An intramolecular magnetic interaction between CrIII and the nitroxide was found to be weakly antiferrromagnetic and ferromagnetic, respectively, in the NIT3py or IM3py complexes and the NIT4py or IM4py complexes. The difference in sign of these magnetic interaction constants between the 3- and 4-pyridyl-substituted nitroxides can be interpreted by a spin polarization mechanism for the π-electron system including the nitroxide SOMO π* and CrIII dπ orbitals. The inherently weak magnetic interactions and absence of an intensity enhancement of the spin-forbidden d–d transition band in these nitroxides complexes are in contrast to our previous results for the chelated NIT2py [4,4,5,5-tetramethyl-2-(2-pyridyl)imidazolin-1-oxyl 3-oxide] and IM2py [4,4,5,5-tetramethyl-2-(2-pyridyl)imidazolin-1-oxyl] complexes. This may be accounted for by the difference in the mechanism of magnetic interactions; spin-polarization mechanism and exchange mechanism, respectively.

AB - Preparation and characterization by X-ray analysis and 2H NMR spectra have been described for twelve chromium(iii)–nitroxide complexes of cis-[Cr(acac)2Cl(L)] and cis- and trans-[Cr(acac)2(L)2]PF6 with monodentate coordination through the pyridyl-N atom in the nitroxides, where acac = pentane-2,4-dionate and L = 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl 3-oxide (NIT3py or NIT4py) and 4,4,5,5-tetramethyl-2-(3- or 4-pyridyl)imidazolin-1-oxyl (IM3py or IM4py). An intramolecular magnetic interaction between CrIII and the nitroxide was found to be weakly antiferrromagnetic and ferromagnetic, respectively, in the NIT3py or IM3py complexes and the NIT4py or IM4py complexes. The difference in sign of these magnetic interaction constants between the 3- and 4-pyridyl-substituted nitroxides can be interpreted by a spin polarization mechanism for the π-electron system including the nitroxide SOMO π* and CrIII dπ orbitals. The inherently weak magnetic interactions and absence of an intensity enhancement of the spin-forbidden d–d transition band in these nitroxides complexes are in contrast to our previous results for the chelated NIT2py [4,4,5,5-tetramethyl-2-(2-pyridyl)imidazolin-1-oxyl 3-oxide] and IM2py [4,4,5,5-tetramethyl-2-(2-pyridyl)imidazolin-1-oxyl] complexes. This may be accounted for by the difference in the mechanism of magnetic interactions; spin-polarization mechanism and exchange mechanism, respectively.

KW - Chromium

KW - Magnetic properties

KW - Nmr spectroscopy

KW - Radicals

KW - X-ray diffraction

KW - X-ray powder diffraction

UR - http://www.scopus.com/inward/record.url?scp=85034337342&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85034337342&partnerID=8YFLogxK

U2 - 10.1039/b310571g

DO - 10.1039/b310571g

M3 - Article

AN - SCOPUS:85034337342

VL - 3

SP - 4604

EP - 4611

JO - Dalton Transactions

JF - Dalton Transactions

SN - 1477-9226

IS - 24

ER -